beverages

Article
Influences of Fermentation Conditions on the Chemical
Composition of Red Dragon Fruit (Hylocereus polyrhizus) Wine
Truong Bao Ngoc 1 , Pham Van Thinh 2 , Dang Thuy Mui 2 , Le Hanh Uyen 1 , Nguyen Ngoc Kim Ngan 1 ,
Ngo Thi Kim Tran 1 , Pham Hoang Tien Khang 1 , Le Quang Huy 3 , Truong Ngoc Minh 4,5, *
and Nguyen Quang Trung 6,7, *

1 Faculty of Food Science and Technology, Ho Chi Minh City University of Industry and Trade,
Ho Chi Minh City 700000, Vietnam; truongbaongoc2710@gmail.com (T.B.N.);
lehanhuyen15072002@gmail.com (L.H.U.); nngan8458@gmail.com (N.N.K.N.);
mk.ngothikimtran@gmail.com (N.T.K.T.); khangpht9@gmail.com (P.H.T.K.)
2 Faculty of Tourism and Culinary, Ho Chi Minh City University of Industry and Trade,
Ho Chi Minh City 700000, Vietnam; thinhpv@huit.edu.vn (P.V.T.); dangthuymui@gmail.com (D.T.M.)
3 Caty Foods Joint Stock Company, 104 Chu Van An, Ward 26, Binh Thanh District,
Ho Chi Minh City 700000, Vietnam; lequanghuy05@gmail.com
4 Center for High Technology Research and Development, Vietnam Academy of Science and Technology,
18 Hoang Quoc Viet Street, Cau Giay, Hanoi 100000, Vietnam
5 Vicomi Tam An Investment and Commercial Company Limited, 140 Nghia Dung Street, Phuc Xa Ward,
Ba Dinh District, Hanoi 111000, Vietnam
6 Institute of Environmental Science and Public Health, 18 Hoang Quoc Viet Street, Cau Giay,
Hanoi 100000, Vietnam
7 Hera USA Corporation, 10333 Harwin Drive, Suite 261, Houston, TX 77036, USA
* Correspondence: minhtn689@gmail.com (T.N.M.); nqtrung79@gmail.com (N.Q.T.)

Abstract: Red dragon fruit (Hylocereus polyrhizus), recognized globally for its substantial nutrient
content and health benefits, has been extensively studied; studies have particularly focused on the
fruit, while the composition of the stem remains less explored. This research focuses on optimizing
Citation: Ngoc, T.B.; Thinh, P.V.; Mui, fermentation parameters for red dragon fruit wine, specifically examining yeast-strain selection,
D.T.; Uyen, L.H.; Ngan, N.N.K.; Tran, juice-to-water dilution ratios, and yeast concentrations. Saccharomyces cerevisiae RV002 emerged as
N.T.K.; Khang, P.H.T.; Huy, L.Q.; the optimal strain due to its robust performance and adaptability under adverse conditions. The
Minh, T.N.; Trung, N.Q. Influences of study identified a 50% dilution ratio as ideal for maximizing clarity and the sensory attributes of the
Fermentation Conditions on the
wine, whereas dilution ratios exceeding 90% significantly reduced ethanol content below acceptable
Chemical Composition of Red Dragon
commercial standards. An optimal yeast concentration of 1 g/L was found to balance microbial
Fruit (Hylocereus polyrhizus) Wine.
suppression and alcohol yield effectively; deviations from this concentration led to microbial con-
Beverages 2024, 10, 61. https://
tamination or impaired fermentation dynamics. Fermentation markedly altered the biochemical
doi.org/10.3390/beverages10030061
properties of Hylocereus polyrhizus, reducing sugar and vitamin C levels while increasing polyphe-
Academic Editor: Panagiotis nol content and antioxidant activity, thereby enhancing potential health benefits. These findings
Kandylis
underscore the transformative effects of microbial activity on the substrate’s chemical landscape
Received: 18 May 2024 and highlight the potential of tailored fermentation strategies to enhance the utility and value of
Revised: 26 June 2024 underutilized fruits in sustainable agricultural practices.
Accepted: 4 July 2024
Published: 11 July 2024 Keywords: Saccharomyces cerevisiae; dragon fruit wine; fermentation optimization; nutrient composition;
wine quality; commercial yeast strains

Copyright: © 2024 by the authors.

Licensee MDPI, Basel, Switzerland.
1. Introduction
This article is an open access article
distributed under the terms and
Over the past decade, the global wine industry has seen a surge in innovative ap-
conditions of the Creative Commons proaches to diversifying wine sources beyond traditional grapes [1]. Notably, dragon fruit
Attribution (CC BY) license (https:// (Hylocereus spp.), a vibrant and nutrient-rich fruit, has entered the scene as a novel ingre-
creativecommons.org/licenses/by/ dient for wine production [2]. Originating from the Americas and cultivated extensively
4.0/). in Southeast Asia, particularly in Vietnam, where annual agricultural outputs reach about

Beverages 2024, 10, 61. https://doi.org/10.3390/beverages10030061 https://www.mdpi.com/journal/beverages

Beverages 2024, 10, 61 2 of 19

1.4 million tons, dragon fruit is valued not only for its rich content of vitamins, minerals,
and antioxidants, but also for its potential uses in creating high-value products such as
wine [3,4]. The launch of red dragon fruit wine over a decade ago was a pivotal moment
in the beverage industry. This not only diversified the wine market but also attracted
consumers with its vibrant color and distinctive taste [5]. The wine’s unique health benefits,
derived from the dragon fruit’s rich nutritional profile, including antioxidants, vitamins,
and minerals, added to its allure [6,7]. Moreover, its exotic appeal, rooted in the fruit’s trop-
ical origin, offered a novel experience that resonated with consumers seeking alternatives
to traditional grape wines, enhancing its market presence [8].
The production of dragon fruit wine represents a crucial strategy through which to
enhance the agricultural value of this crop, especially given the fruit’s limited fresh storage
life of up to 14 days at 10 ◦ C and only 5 days at room temperature [9]. Fermentation into
wine not only extends the usability of dragon fruit, but also adds economic value, turning
a perishable product into a more stable and internationally marketable commodity [2,8,10].
However, the fermentation process is an ecologically complex activity, heavily reliant on the
effective role of yeasts, particularly Saccharomyces cerevisiae, which catalyzes the conversion
of fruit juice into an alcoholic beverage through biochemical transformation [2].
The process of fermenting red dragon fruit wine is influenced by various factors that
are crucial to ensuring the production of high-quality wine. These factors include the
specific yeast strain used, the fermentation protocol, and the fruit’s unique characteristics,
such as pH levels, soluble solids content, and sugar concentration [11]. Notably, recent
advancements have highlighted the importance of selecting optimal yeast strains and
adjusting fermentation conditions to enhance the organoleptic qualities of fruit wines.
Research has shown that the right combination of yeast variety, fermentation conditions,
and post-harvest treatments significantly affects the chemical composition and overall
sensory profile of the wine, making these aspects vital for producing premium-quality
fruit wine [12].
Moreover, fermentation is not just a simple conversion of sugars into alcohol; it
involves a complex set of biochemical reactions that are sensitive to the ecological conditions
within the fermentation vessel [13]. These include the interactions between different yeast
strains and how they manage nutrient competition, sugar metabolism, and stress from
by-products like ethanol [14]. Understanding and controlling these interactions are key to
preventing common issues such as excessive haze, which can be mitigated by managing
polyphenol and protein interactions within the wine. Such knowledge is essential not
only for enhancing the clarity and taste of the wine but also for extending its shelf life and
improving its marketability. Therefore, a deep dive into the fermentation process, backed
by rigorous scientific research, is indispensable for innovating and refining the production
of red dragon fruit wine [15].
This research aims to systematically evaluate the factors that influence the fermenta-
tion of red dragon fruit wine and to assess their impact on both the chemical composition
and the sensory qualities of the final product. After the fermentation protocol had been
optimized to enhance wine production from red dragon fruit, the biochemical compo-
sition of Hylocereus polyrhizus before and after fermentation was meticulously analyzed.
The study particularly focuses on three critical variables: the dilution ratio of dragon
fruit juice to water, the yeast strain employed, and the yeast concentration. The current
fermentation-dilution ratio is 50%, as higher dilution ratios reduce the amount of reduc-
ing sugars, affecting yeast growth and fermentation efficiency. The yeast strain used is
Saccharomyces cerevisiae, specifically Angel RV002, which is known for its high citric-acid
resistance, and Fermentis yeast, which is known for its tolerance to hypertonic environ-
ments and cold conditions [16]. While these strains exhibit robust fermentation capabilities,
challenges include their cost and need for precise management to prevent by-product
formation. Previous investigations into fermentation have explored various aspects, but the
distinct properties of dragon fruit and its significance in Vietnamese agriculture warrant a
specialized examination. This study underscores the importance of optimizing these fer-
Beverages 2024, 10, x FOR PEER REVIEW 3 of 20

Beverages 2024, 10, 61 3 of 19

properties of dragon fruit and its significance in Vietnamese agriculture warrant a special-
ized examination. This study underscores the importance of optimizing these fermenta-
tion parameters to improve wine quality, providing valuable insights for enhancing the
mentation parameters to improve wine quality, providing valuable insights for enhancing
commercial viability of dragon fruit wine [16–20]. The importance of this research lies in
the commercial viability of dragon fruit wine [16–20]. The importance of this research lies
its potential to furnish a scientific foundation for refining the processes of dragon fruit
in its potential to furnish a scientific foundation for refining the processes of dragon fruit
wine production, thus elevating the fruit’s commercial value and supporting sustainable
wine production, thus elevating the fruit’s commercial value and supporting sustainable
agricultural practices. By exploring and optimizing key fermentation parameters, this
agricultural practices. By exploring and optimizing key fermentation parameters, this
study
studycontributes
contributesto the broader
to the knowledge
broader basebase
knowledge regarding fruit fruit
regarding winewine
production, provid-
production, pro-
ing novel insights into the use of non-traditional fruits in winemaking and addressing
viding novel insights into the use of non-traditional fruits in winemaking and addressing
challenges
challenges related
relatedtotopost-harvest
post-harvestlosses.
losses.

2. 2.
Materials and
Materials Methods
and Methods
2.1.
2.1. Materials
Materials
One
One hundred
hundred kilograms
kilograms ofof red
red dragon
dragon fruit,encompassing
fruit, encompassing four
four varieties,
varieties, RedRed Pulp
Pulp
Dragon
Dragon Fruit,Pink
Fruit, Pink Purple
Purple PulpDragon
Pulp Dragon Fruit,White
Fruit, White PulpRed
Pulp RedSkin
SkinDragon
DragonFruit,
Fruit,and
and
Yellow
Yellow Skin
Skin White
White Pulp
Pulp Dragon
Dragon Fruit,
Fruit, were
were sourced
sourced from
from Binh
Binh Thuan,
Thuan, with
with equal
equal masses
masses
ofof
2525
kgkgofofeach
each variety.Each
variety. Each fruit
fruit ofof the
the Red
Red Pulp
Pulp variety,which
variety, whichwaswasselected
selected based
based onon
the national standard TCVN 7523:2014 CODEX STAN 237-2003
the national standard TCVN 7523:2014 CODEX STAN 237-2003 [21], weighed between 301 [21], weighed between
to301
400to 400 g (Figure
g (Figure 1). common
1). Three Three common
types of types
yeastofavailable
yeast available in the Vietnamese
in the Vietnamese market market
were
used: Angel yeast from Angel Food Yeast Co., Ltd., (Yichang, China); Saigon Saigon
were used: Angel yeast from Angel Food Yeast Co., Ltd., (Yichang, China); yeast
yeast from
from Saigon
Saigon Food Co.,
Food Yeast YeastLtd.,
Co., (Ho
Ltd., Chi
(Ho Minh
Chi MinhCity,City, Vietnam);
Vietnam); andand Fermentis
Fermentis yeast
yeast from
from
Lesaffre
Lesaffre Yeast
Yeast Co.,Ltd.,
Co., Ltd.,(Lille,
(Lille,France).
France).

(a) (b) (c) (d)

Hylocereus polyrhizus Hylocereus megalanthus Hylocereus undatus Hylocereus undatus costaricensis
Figure 1. 1.
Figure Varieties of of
Varieties Hylocereus used
Hylocereus inin
used fermentation studies.
fermentation studies.

2.2.
2.2. Experimental
Experimental Methods
Methods
2.2.1. Sample Preparation
2.2.1. Sample Preparation
The
The fruits
fruits were
were first
first processed
processed byby washing
washing them
them with
with a saline
a saline solution
solution consisting
consisting ofof
0.9% sodium chloride in water. They were then peeled and juiced using
0.9% sodium chloride in water. They were then peeled and juiced using a slow juicer. The a slow juicer. The
resulting juice was filtered through a cloth filter and diluted to initial concentrations ofof
resulting juice was filtered through a cloth filter and diluted to initial concentrations
50%,
50%, 60%,
60%, 70%,
70%, 80%,
80%, andand 90%.
90%. The
The pHpH was
was adjusted
adjusted toto
4.54.5 using
using citric
citric acid
acid andsodium
and sodium
carbonate (Na
carbonate (Na2CO 2 3). 3Citric acid was used in a 1% solution, with approximately 1010
CO ). Citric acid was used in a 1% solution, with approximately mLmL
added per liter of juice to lower the pH. If necessary, a 0.5% sodium
added per liter of juice to lower the pH. If necessary, a 0.5% sodium carbonate solution carbonate solution
was
was used
used toto increase
increase thethe pH,
pH, with
with about
about 5 mL
5 mL per
per liter
liter ofof juice.
juice. TheThe soluble
soluble solids
solids content
content
was set to 24 ◦ Bx by adding refined sucrose from Khanh Hoa Sugar Company (Khanh Hoa,
was set to 24°Bx by adding refined sucrose from Khanh Hoa Sugar Company (Khanh Hoa,
Vietnam), which had a purity >99.5%, moisture content <0.05%, and reducing sugars <0.1%.
Vietnam), which had a purity >99.5%, moisture content <0.05%, and reducing sugars
Additionally, a pectinase enzyme from Novoferin 14 at a concentration of 0.1% and sodium
<0.1%. Additionally, a pectinase enzyme from Novoferin 14 at a concentration of 0.1% and
metabisulfite (Na2 S2 O5 ) at 0.05 g/L were added. The mixture was left at room temperature
sodium metabisulfite (Na2S2O5) at 0.05 g/L were added. The mixture was left at room tem-
for one day to stabilize before fermentation.
perature for one day to stabilize before fermentation.
Yeast Strains and Fermentation Setup
Commercial yeast strains of Saccharomyces cerevisiae were used, specifically Angel yeast,
Saigon yeast, and Fermentis yeast. The fermentation trials were set up in a fully randomized
design with three replicates. Each fermentation batch was 10 L, with a yeast dosage of
10 g per batch. The fermentation process was maintained at a constant temperature of
Beverages 2024, 10, 61 4 of 19

25 ◦ C. Samples of 250 mL were withdrawn daily for analysis, ensuring sufficient volume
for experimental purposes, and were well mixed prior to sampling to maintain uniformity.
There were three yeast treatments: Angel yeast, Fermentis yeast, and Saigon yeast,
each tested at different dilutions. Angel yeast was supplemented at 10 g with 100 mL water
per 10 L batch, Fermentis yeast at 20 g with 200 mL water, and Saigon yeast at 200 g with
2000 mL water. The fermentation trials included five dilution ratios of dragon fruit juice to
water: 50%, 60%, 70%, 80%, and 90%, each with three replicates, for a total of 45 treatments.
Yeast-cell counting was conducted using a hemocytometer. The sample was diluted
in a ratio of 5:4:1 and thoroughly mixed, and 10 µL was placed onto the hemocytometer
grid. The chamber was filled by capillary action and examined under a microscope at
40× magnification using an Optika B-352A microscope (Ponteranica, Italy) to count the
cells in five large square grids. This ratio refers to 50 µL water, 40 µL fermentation broth,
and 10 µL methylene blue. Regarding the colony-forming units (CFU) per gram, Angel
yeast had approximately 5 × 109 CFU/g, Fermentis yeast had 6 × 109 CFU/g, and Saigon
yeast had 7 × 109 CFU/g. This quantification is crucial, as the amount of fermentation
inoculum directly relates to the number of active yeast cells, impacting fermentation efficacy
and outcomes.

2.2.2. Chemicals and Equipment

For the study, a range of high-purity chemicals was utilized to ensure the accuracy
and repeatability of the results. These included Folin reagent (sodium 3,4-dioxo-3,4-
dihydronaphthalene-1-sulfonate) at 1 N concentration (Darmstadt, Germany), methanol
with 98% purity (Xilong, China), and sulfuric acid graded at ≥98.08% (Duc Giang Chem-
icals Group JSC, Ha Noi, Vietnam). Additional substances included 3,5-dinitrosalicylic
acid (Shanghai Zhanyun Chemical, Shanghai, China) and sodium carbonate (TangShang,
China). The experimental procedures were supported by sophisticated laboratory equip-
ment, including a PhotoLab 6100 VIS spectrometer (WTW, Oberbayern, Germany) for
precise absorbance measurements across a wide spectral range.
The chemicals were sourced primarily from established suppliers in China and Viet-
nam, guaranteeing their quality and consistency for use in biochemical analyses and
fermentation processes. Additionally, the experimental procedures were supported by
advanced weighing scales and electronic scales from Sartorius (Goettingen, Germany), a
manufacturer known for their accuracy. The fermentation processes were monitored using
a 14 L thermostatic tank from Memmert, which allowed precise temperature control.

2.2.3. Methods
Vitamin C Determination: The total ascorbic acid content was measured using a UV-VIS
spectrophotometer (WTW—A xylem brand, Weilheim, Germany). Thirty grams of the
sample were weighed into a 50 mL Falcon tube, centrifuged at 1970× g for 15 min; next,
the supernatant was collected. Then, 0.23 mL of 3% bromine was pipetted into 4 mL of the
sample solution, and this step was followed by the addition of 0.13 mL of 10% thiourea
to reduce the excess bromine. Then, 1 mL of 2,4-dinitrophenylhydrazine was added. The
solution was placed in a water bath at 30 ◦ C for 3 h and cooled for 30 min, then 5 mL of 85%
H2 SO4 was added. The vitamin C was cooled at a refrigeration temperature of 10 ◦ C. The
absorbance of the colored solution was measured at 521 nm, with the vitamin C content
calculated based on an ascorbic acid standard curve [22].
Polyphenol Content: The polyphenol concentration was quantified using the Folin–
Ciocalteu method. After the extract was diluted to the appropriate concentration, 0.5 mL
of the diluted extract was added to a test tube, following which 5 mL of Folin–Ciocalteu
reagent was added. The mixture was homogenized using a vortex, and then 4 mL of 7.5%
Na2 CO3 was added. The reaction mixture was kept at room temperature for 30 min before
the absorbance at 765 nm was measured on a spectrophotometer, with results reported as
milligrams of gallic acid equivalent (mg GAE)/g dry matter [23].
Beverages 2024, 10, 61 5 of 19

DPPH Radical-Scavenging Activity: The antioxidant capacity was assessed by the

DPPH assay, which measures the ability of antioxidants to stabilize the purple DPPH free
radical, detected spectrophotometrically at 517 nm [24]. One milliliter of the extract was
placed in a test tube, and this step was followed by the addition of 3 mL of methanol
and 0.5 mL of 0.6 mM 2,2-Diphenyl-1-picrylhydrazyl (DPPH) in methanol. A blank was
prepared by adding 0.5 mL of DPPH to 4 mL of methanol. The samples were incubated at
room temperature for 28–30 min. The radical-scavenging activity was determined using
the following formula:
DPPH (%) = ((Ac − A)/Ac) × 100
Total Acidity: The total acidity was determined using an automatic potentiometric
titrator (Titroline 7000, SI Analytics, Oberbayern, Germany). Ten milliliters of the sample
were pipetted into an Erlenmeyer flask, and this step was followed by the addition of
50 mL of distilled water and 3 drops of 0.1% phenolphthalein. The glass electrode was
cleaned with distilled water before it was immersed into the sample solution. The flask
was placed on a magnetic stirrer with a magnetic stir bar. The electrode was immersed in
the solution, with the researcher ensuring it did not touch the sides or bottom of the flask
and maintained a 1 cm distance from the stir bar to avoid breakage. The magnetic stirrer
was turned on for continuous stirring during the titration. The sample was titrated with
0.1 N NaOH until the endpoint was reached, and the result was recorded in g/L [25]. The
volume of 0.1 N NaOH used (mL) was recorded, and the acidity was calculated using the
following formula:

(K × V2)/V((m2 − m1) × 0.92)/V × 1000 (g/L)

V: Volume of the sample used for titration (mL)

V2: Volume of 0.1 N NaOH consumed in titration (mL)
K: The amount of acid (in grams) equivalent to 1 mL of 0.1 N NaOH. For milk and fermented
foods, the result is expressed as lactic acid, K = 0.0090K = 0.0090K = 0.0090
Reducing Sugars: Reducing-sugar levels were analyzed by the DNS method. This
involves a colorimetric assay where reducing sugars react with 3,5-dinitrosalicylic acid to
form a colored complex measurable at 540 nm. The fresh dragon fruit juice was weighed
into a 50 mL centrifuge tube, ensuring equal weights for all tubes. The samples were
centrifuged at 3070× g for 15 min and diluted to the appropriate concentration, and 1 mL
of the diluted sample was pipetted into a test tube. This step was followed by the addition
of 2 mL of DNS reagent. The test tubes were placed in a boiling water bath for 5 min and
cooled to 25–30 ◦ C, and the absorbance was measured at 540 nm [26].
Alcohol Content: The alcohol concentration in the wine samples was determined through
distillation followed by density measurement using an Anton Paar densitometer [27].
Yeast Cell Counting: Yeast viability and concentration were assessed using a hemocy-
tometer under a microscope, allowing for precise cell counts within specified grid areas.
The cell suspension was vortexed, and 10 µL of the suspension was pipetted onto the
surface of the counting chamber, which was placed under the microscope. The microscope
was adjusted with a 40× objective lens and appropriate light intensity, and the number of
cells in 5 large squares was counted [28].
Soluble Solids Content: Soluble solids were measured using a handheld refractometer,
which provides a direct reading of the Brix value in the samples [29].
pH Measurement: The pH values of the samples were determined using a benchtop
pH meter calibrated with standard buffers, ensuring accurate acidity assessment [30].
Total Sugar Content: Total sugars were quantified by hydrolyzing the samples with
dilute hydrochloric acid and then by measurement with the DNS method, providing a
colorimetric estimate of sugar concentration. The sample was treated by pipetting 1 mL
of the sample with 40 mL of 2% HCl into a 50 mL centrifuge tube, which was then heated
at 110 ◦ C for 60 min, cooled, adjusted to pH 7 with 10% NaOH, transferred to a 100 mL
volumetric flask, made up to volume with distilled water, filtered, and diluted to the
 pH Measurement: The pH values of the samples were determined using a benchtop
pH meter calibrated with standard buffers, ensuring accurate acidity assessment [30].
Total Sugar Content: Total sugars were quantified by hydrolyzing the samples with
dilute hydrochloric acid and then by measurement with the DNS method, providing a
Beverages 2024, 10, 61 colorimetric estimate of sugar concentration. The sample was treated by pipetting 1 mL of
6 of 19
the sample with 40 mL of 2% HCl into a 50 mL centrifuge tube, which was then heated at
110 °C for 60 min, cooled, adjusted to pH 7 with 10% NaOH, transferred to a 100 mL
volumetric flask, made up to volume with distilled water, filtered, and diluted to the ap-
appropriate concentration. Exactly 1 mL of the sample was pipetted into a test tube. Next,
propriate concentration. Exactly 1 mL of the sample was pipetted into a test tube. Next, 2
2 mL of DNS reagent was added and the mixture was boiled in a water bath for 5 min, then
mL of DNS reagent was added and the mixture was boiled in a water bath for 5 min, then
cooled to 25–30 ◦ C, at which point the absorbance was measured at 540 nm [31].
cooled to 25–30 °C, at
Transmittance: The which point
juice wasthe absorbance
shaken, wasmL
and a 10 measured
portion at
of 540
juicenm [31].
was centrifuged
Transmittance: The juice was shaken, and a 10 mL portion of juice was centrifuged
at 1590× g for 10 min to remove pulp and coarse cloud particles. Percent transmittance at
1590× g for 10 min to remove pulp and coarse cloud particles. Percent transmittance
was determined at 660 nm by spectrophotometer (Systronics, Gujarat, India). The percent was
determined
transmittanceat was
660 considered
nm by spectrophotometer
a measure of juice(Systronics,
clarity. TheGujarat,
formula India). The percent
was as follows:
transmittance was considered a measure of juice clarity. The formula was as follows:
%T%T = 100.10
= 100.10 −A
−A

A-is the
A-is the optical
optical absorbance
absorbance at
at wavelength
wavelength 660
660 nm
nm [32].
[32].
Anthocyanin
AnthocyaninContent:
Content:Anthocyanin
Anthocyaninlevels
levelswere
weredetermined
determinedbybydifferential
differentialpH
pHspec-
spec-
trophotometry,
trophotometry, exploiting the color change undergone by anthocyanins between pH1.0
exploiting the color change undergone by anthocyanins between pH 1.0
and
and4.5,
4.5,quantified
quantifiedatat520
520nm
nm[33].
[33].Ten
Tenmilliliters
millilitersofofthe
thesample
samplewere
werepipetted
pipettedinto
intoaa50
50mL
mL
volumetric
volumetric flask
flask with
with pH
pH1.0
1.0buffer
buffersolution
solution(0.025
(0.025MMKCl).
KCl).The
Theappropriate
appropriatedilution
dilutionfactor
factor
was determined
was determined at at 520
520 nm.
nm. The
Thediluted
dilutedtest
testsample
samplewas wasprepared
preparedusing
usingpHpH1.01.0(KCl)
(KCl)
buffer, and
buffer, and another
another was
was prepared
prepared using
using pH
pH 4.5
4.5 (CH
(CH33COONa)
COONa)buffer.
buffer. Both
Bothsolutions
solutionswere
were
measured at 520 nm and 700 nm. Anthocyanin content was calculated using
measured at 520 nm and 700 nm. Anthocyanin content was calculated using the formula: the formula:
𝐴 × 𝑀𝑊× 𝐷𝐹× 103
C = (A × MW × DF) × 103
C=( 𝜀×𝑙 )
ε×l
1.0
𝐴520 Absorbance of the sample at pH 1.0 measured at a wavelength of 520 nm;
1.0
𝐴A1.0
520 Absorbance of the sample at pH 1.0 measured at a wavelength of 520
700 700 nm;
1.0
4.5
𝐴A520
700 Absorbance of the sample at pH 1.0
4.5 measured at a wavelength of 700
520 nm;
𝐴A4.5
4.5 Absorbance of the sample at pH 4.5 measured at a wavelength of 700
700
520 nm.
520 nm;
4.5
A700Figure
Absorbance of the the
sample at pH 4.5 measured at a wavelength of 700 nm.
2 illustrates comprehensive dragon fruit wine fermentation process. This
includes the2preparation
Figure of comprehensive
illustrates the dragon fruit juice, the introduction
dragon of yeast, and
fruit wine fermentation the detailed
process. This in-
cludes the preparation of dragon fruit juice, the introduction of yeast, and the
monitoring of fermentation conditions such as temperature, pH, and sugar content over detailed mon-
itoring of fermentation conditions such as temperature, pH, and sugar content over time.
time.

Figure
Figure2.2.Dragon
Dragonfruit
fruitWine
Winefermentation
fermentationprocess.
process.

2.2.4. Optimization of Fermentation Parameters

The experimental setup for the fermentation of dragon fruit juice involves a system
that was carefully designed to ensure optimal conditions for yeast activity and efficient
fermentation. The system comprises a fermentation tank equipped with an agitation system;
sensors for monitoring pH, temperature, and oxygen levels; and a sample outlet for periodic
analysis. The tank has a capacity of 30 L, with the liquid volume maintained below 75% to
allow adequate headspace for foam and gas formation during fermentation (Figure 3).
 that was carefully designed to ensure optimal conditions for yeast activity and efficient
fermentation. The system comprises a fermentation tank equipped with an agitation sys-
tem; sensors for monitoring pH, temperature, and oxygen levels; and a sample outlet for
periodic analysis. The tank has a capacity of 30 L, with the liquid volume maintained be-
Beverages 2024, 10, 61
low 75% to allow adequate headspace for foam and gas formation during fermentation 7 of 19
(Figure 3).

Figure 3.
Figure 3. Experimental
Experimental setup
setup for
for the
the fermentation
fermentation process.
process.

Dragon fruit
Dragon fruit juice,
juice, pre-treated
pre-treated with
with pectinase
pectinaseenzyme
enzymeandand inoculated
inoculatedwith
with yeast,
yeast, was
was
pumped into the fermentation tank through an inlet pump on the upper leftside.
pumped into the fermentation tank through an inlet pump on the upper left side. All
All
chemicalsand
chemicals andenzymes
enzymeswere wereadded
added toto
thethe juice
juice at this
at this stage
stage to ensure
to ensure thorough
thorough mixingmixing
and
and interaction.
interaction. The mixture
The mixture was then
was then subjected
subjected to primary
to primary fermentation
fermentation at room
at room temper-
temperature
(approximately 25 ◦ C)25
ature (approximately for°C) for seven
seven days. days.
Key components
Key components of of the
the setup
setup include
include thethe following:
following:
(1) Fermentation
(1) Fermentation Tank:
Tank: A A temperature-controlled
temperature-controlled vessel where the
vessel where the fermentation
fermentation takes
takes
place. The tank is equipped with an agitation system to ensure continuous mixing.
place. The tank is equipped with an agitation system to ensure continuous mixing.
(2) Agitation System:
(2) Agitation Ensures the
System: Ensures the homogeneity
homogeneity of of the
the fermenting
fermenting mixture,
mixture, preventing
preventing
sedimentation of yeast cells and facilitating efficient fermentation.
sedimentation of yeast cells and facilitating efficient fermentation.
(3) System Monitor:
(3) System Monitor: Includes
Includes sensors
sensors that
that continuously
continuously monitor
monitor critical
critical parameters
parameters such
such
as pH, temperature, and oxygen levels to ensure optimal fermentation
as pH, temperature, and oxygen levels to ensure optimal fermentation conditions. conditions.
(4) Pump: Used
(4) Pump: Used to
to introduce
introducethe themixture
mixtureofof dragon
dragonfruit juice,
fruit enzyme,
juice, enzyme, andand
yeast intointo
yeast the
fermentation tank.
the fermentation tank.
(5) Airlock: Maintains anaerobic conditions by preventing the ingress of external air;
(5) Airlock: Maintains anaerobic conditions by preventing the ingress of external air; es-
essential for anaerobic fermentation.
sential for anaerobic fermentation.
(6) Sensors Probe: Measures the fermentation parameters, ensuring real-time monitoring
(6) Sensors Probe: Measures the fermentation parameters, ensuring real-time monitor-
and adjustments to maintain ideal conditions.
ing and adjustments to maintain ideal conditions.
(7) Sample Outlet: Located at the bottom of the tank, this outlet allows for the periodic collec-
(7) Sample Outlet: Located at the bottom of the tank, this outlet allows for the periodic
tion of samples for analysis to track the progress and quality of the fermentation process.
collection of samples for analysis to track the progress and quality of the fermentation
The fermentation process is divided into two stages: primary fermentation and sec-
process.
ondary fermentation. Primary fermentation occurs at room temperature for seven days,
The fermentation process is divided into two stages: primary fermentation and sec-
during which the majority of the sugars are converted into ethanol and carbon dioxide.
ondary fermentation. Primary fermentation occurs at room temperature for seven days,
After two days, the viscosity decreases and the foam dissipates, indicating active fermenta-
during
tion. Thewhich the majority
fermentation of the sugars
environment are converted
is strictly anaerobic to into ethanol
prevent and carbon
oxidative dioxide.
degradation
After two days, the viscosity decreases and the
of bioactive compounds and the production of unwanted acids.foam dissipates, indicating active fermen-
tation. The fermentation environment is strictly anaerobic to prevent
Following primary fermentation, the mixture undergoes secondary fermentation at oxidative degrada-
tion of temperatures
cooler bioactive compounds
(15–18 ◦and theten
C) for production
days. This of unwanted
stage aimsacids.to stabilize the wine and
enhance its aroma. Cooling is achieved using an air conditioning system, eliminating the
need for water baths or additional heating/cooling systems.
Throughout both fermentation stages, the system monitor ensures that the conditions
remain within optimal ranges. The sensors provide continuous feedback on the pH,
temperature, and oxygen levels, allowing for immediate adjustments if necessary. This
setup prevents oxygen from entering the tank, as oxygen can oxidize bioactive compounds
in the juice and produce unwanted acids, thereby compromising the wine quality.
This comprehensive fermentation setup is designed to maximize the efficiency and
quality of dragon fruit wine production. By optimizing the fermentation parameters and
Beverages 2024, 10, 61 8 of 19

maintaining strict anaerobic conditions, the system ensures the production of a high-quality,
flavorful wine with desirable sensory and chemical properties. This setup provides valuable
insights into the fermentation process, offering potential improvements for both commercial
wine production and research applications.

2.2.5. Analytical Methods

Each experiment was conducted in triplicate, and the results were presented as the
mean ± standard error. Data analysis was performed using Microsoft Office Excel 2019
and JMP Pro 17 Statistical Discovery™ from SAS. Analysis of variance (ANOVA) was
carried out with a 95% confidence level, utilizing the least significant difference (LSD) test
for comparing means. The modeling and optimization processes were executed using
JMP 17 Pro software with an alpha level of 5%.

3. Results
3.1. Comparative Nutritional and Phytochemical Profiles of Dragon Fruit Varieties
The data outlined in Table 1 provide a detailed comparative analysis of the biochem-
ical properties of four Hylocereus species: H. polyrhizus, H. megalanthus, H. costaricensis,
and H. undatus. These species were evaluated across a range of biochemical parameters
including vitamin C content, polyphenol levels, sugar content (both total and reducing),
antioxidant activity, dry-matter content, acidity, pH, and anthocyanin concentrations. This
comprehensive profiling offers insights into the nutritional values of the samples and has
potential for various industrial applications.

Table 1. Comparative analysis of nutritional and chemical parameters of different varieties of

dragon fruit.

Vitamin C Polyphenols Antioxidant Activity Dry-Matter Anthocyanins

Parameter Total Sugars (g/L) Reducing Sugars (g/L) Acidity (g/L) pH
(mg AA/100 g) (mg GAE/100 g) DPPH (%) Content (◦ Bx) (mg/L)

H. polyrhizus 29.74 ± 5.60 a 39.18 ± 0.56 a 84.93 ± 0.52 a 73.84 ± 0.15 a 38.23 ± 2.06 a 13.00 ± 0.40 a 2.31 ± 0.02 c 3.96 ± 0.01 b 345.66 ± 6.02 a

H. megalanthus 41.63 ± 2.38 b 7.80 ± 0.96 c 84.81 ± 0.81 a 49.79 ± 0.09 c 27.57 ± 3.21 c 12.00 ± 0.10 b 5.21 ± 0.02 b 4.85 ± 0.02 a 299.72 ± 11.01 b

H. costaricensis 14.46 ± 6.05 c 12.41 ± 1.00 bc 81.79 ± 0.62 ab 66.28 ± 0.22 b 31.19 ± 2.96 b 13.00 ± 0.60 a 4.45 ± 0.08 b 3.92 ± 0.01 b 330.15 ± 6.02 ab

H. undatus 16.04 ± 6.78 c 18.45 ± 1.82 b 66.89 ± 0.30 c 60.52 ± 0.22 b 28.55 ± 2.33 c 12.00 ± 0.50 b 7.24 ± 0.01 a 4.28 ± 0.0 ab 312.28 ± 7.01 b

Means followed by the same letter (a, b, c) are not significantly different from each other at the 0.05 level by a
post-hoc test.

Among the species studied, H. megalanthus exhibited the highest vitamin C content
at 29.91 ± 2.00 mg AA/100 g; this level is significantly greater than those found in other
species, suggesting potential health benefits. Conversely, H. polyrhizus led in polyphenol
content with 580.35 ± 0.61 mg GAE/100 g, indicating its potential as a superior antioxidant
source. H. polyrhizus also showed the highest reducing-sugar content at 80.94 ± 0.19 g/L,
enhancing its sweetness and flavor profile and making it desirable for fresh consumption
and dessert production.
The antioxidant activity, measured by the DPPH assay, was significantly higher in H.
polyrhizus at 38.23 ± 2.06%, correlating with its substantial polyphenol and anthocyanin
contents, the latter being the highest among the species at 345.66 ± 0.02 mg/L. This
enhances the fruit’s antioxidant capacity and contributes to its vibrant coloration, increasing
consumer appeal.
H. undatus had the highest acidity at 7.24 ± 0.01 g/L, influencing its sensory properties
and suitability for fermentation. The pH values for the species ranged from 3.96 to 4.28, which
are typical for fruits and beneficial for food preservation and processing. All species exhibited
a consistent range of dry-matter content, approximately 12–13%, suggesting uniformity in
their physical composition and influencing textural attributes and processing behavior.
Given the results, H. polyrhizus has been chosen for further experimental studies due to
its superior polyphenol content, high levels of antioxidants and anthocyanins, and potential
for commercial applications.
 exhibited a consistent range of dry-matter content, approximately 12–13%, suggesting
uniformity in their physical composition and influencing textural attributes and pro-
cessing behavior.
Given the results, H. polyrhizus has been chosen for further experimental studies due
Beverages 2024, 10, 61 9 of 19
to its superior polyphenol content, high levels of antioxidants and anthocyanins, and po-
tential for commercial applications.

3.2. Influence
3.2. Influence of
of Fermentation
Fermentation Time
Time
The analysis
The analysis of
of the
the fermentation
fermentation process
process of
of red
red dragon
dragon fruit
fruit (H. polyrhizus) wine
(H. polyrhizus) wine over
over
a period of 168 h revealed several significant changes in the key parameters of acidity,
a period of 168 h revealed several significant changes in the key parameters of acidity, pH,
pH, Brix, ethanol concentration, and yeast ratio, which are essential for understanding the
Brix, ethanol concentration, and yeast ratio, which are essential for understanding the fer-
fermentation dynamics and wine quality (Figure 4).
mentation dynamics and wine quality (Figure 4).

(a) (b)

(c) (d)
Figure 4.4.Main
Mainparameters impacting
parameters dragon
impacting fruitfruit
dragon winewine
fermentation. (a) pH(a)
fermentation. levels
pHover theover
levels fermen-
the
tation period; (b) ethanol content over the fermentation period; (c) Brix value, indicating sugar con-
fermentation period; (b) ethanol content over the fermentation period; (c) Brix value, indicating sugar
tent; (d) yeast-cell
content; concentration.
(d) yeast-cell concentration.

Initially, the acidity

Initially, the acidity of
of the
the juice
juice started
started at
at 3.690
3.690 g/L,
g/L, and
and this
this value
value increased
increased sharply
sharply
within the first 48 h toto 5.160
5.160 g/L
g/L due
due to
to the production of organic acids rapid microbial
activity. After 48 h, the acidity stabilized, and it slightly decreased to 4.740 g/L g/L byby 168
168 h,
h,
indicating
indicating a gradual adjustment in the microbial environment. The The pH levels started at
4.500 and initially decreased
decreased to to 3.563
3.563 within
within 24
24 h,
h, reflecting
reflecting increased
increased acidity
acidity (Figure
(Figure 4a).
4a).
This pH reduction is typical in early fermentation
fermentation stages as acids are produced. Over
acids are produced. Over time,time,
the pH adjusted, ending at a slightly higher value of 3.857, which corresponded with the
reduced acidity as fermentation stabilized. This pattern reflects the active yeast metabolic
phase, which is crucial for flavor development and preservation due to the antimicrobial
properties of acids.
The Brix value, indicating sugar content, started at 24% and consistently declined
to 7% by 144 h, stabilizing over the 168 h. This decline reflects sugar consumption by
yeast, which converts sugars into ethanol and by-products (Figure 4c). This consistent
decrease highlights the yeast’s efficiency in sugar conversion, which minimized the content
of residual sugars and achieved the desired dryness level in the final product. Ethanol
content, starting at 0%, gradually increased as yeast metabolized sugars (Figure 4b). By
168 h, the ethanol content reached 13.917%, indicating efficient sugar-to-alcohol conversion,
a desirable outcome in wine fermentation.
The yeast cell concentration, shown in Figure 4d, initially rose to a peak of 21,400,000 cells/mL
by 72 h, demonstrating rapid yeast proliferation. This peak was followed by a decline to
2,150,000 cells/mL by 168 h, likely due to sugar depletion and ethanol inhibition. This
pattern indicates a well-adjusted fermentation process wherein initial yeast growth was
 startingatat0%,
starting 0%,gradually
graduallyincreased
increasedasasyeast
yeastmetabolized
metabolizedsugars
sugars(Figure
(Figure4b).
4b).By
By168168h,h,the
the
ethanol content reached 13.917%, indicating efficient sugar-to-alcohol
ethanol content reached 13.917%, indicating efficient sugar-to-alcohol conversion, a desir- conversion, a desir-
ableoutcome
able outcomeininwine winefermentation.
fermentation.
Theyeast
The yeastcell
cellconcentration,
concentration,shown
shownininFigure
Figure4d,4d,initially
initiallyrose
rosetotoaapeak
peakofof21,400,000
21,400,000
Beverages 2024, 10, 61 10 of
cells/mLby
cells/mL by7272h,h,demonstrating
demonstratingrapid rapidyeast
yeastproliferation.
proliferation.This
Thispeak
peakwaswasfollowed
followed by19
by aa
declinetoto2,150,000
decline 2,150,000cells/mL
cells/mLbyby168
168h,h,likely
likelydue
duetotosugar
sugardepletion
depletionand andethanol
ethanolinhibition.
inhibition.
Thispattern
This patternindicates
indicatesaawell-adjusted
well-adjustedfermentation
fermentationprocess
processwherein
whereininitial
initialyeast
yeastgrowth
growth
was supported by abundant sugars and subsequently declined as the environment less
supported
was by
supported abundant
by sugars
abundant and
sugars subsequently
and declined
subsequently as the
declined environment
as the became
environment be-
be-
conducive
cameless
came to growth.
lessconducive
conducivetotogrowth.
growth.
Total
Totalsugar
sugarcontent
contentstarted
startedat 149.161
149.161g/L, dropped sharply
sharplyto 86.419
86.419g/L within the
Total sugar content started atat149.161 g/L,dropped
g/L, droppedsharply toto86.419 g/Lwithin
g/L withinthe the
first
first2424 h, and
24h,h,and continued
andcontinued to decrease
continuedtotodecrease to 6.491
decreasetoto6.491 g/L
6.491g/Lg/Lbyby the
bythe end
theend of fermentation,
endofoffermentation, indicating
fermentation,indicating
indicating
first
effective sugar
effective sugar utilization
utilization byby yeast (Figure
yeast(Figure
(Figure5).5). Reducing
5).Reducing sugars,
Reducingsugars, which
sugars,which initially
whichinitially increased
initiallyincreased
increased
effective sugar utilization by yeast
from
from 28.484
28.484 g/L
g/L to
to 35.277
35.277 g/L
g/L due
due to
to non-reducing
non-reducing sugar
sugar hydrolysis,
hydrolysis, consistently
consistently declined
declined
from 28.484 g/L to 35.277 g/L due to non-reducing sugar hydrolysis, consistently declined
thereafter, reaching
thereafter,reaching 1.769
reaching1.769 g/L,
1.769g/L, reflecting
g/L,reflecting efficient
reflectingefficient yeast
efficientyeast metabolism.
yeastmetabolism.
metabolism.
thereafter,

Figure5.
Figure
Figure 5.5.Sugar
Sugarconsumption
Sugar consumptionduring
consumption duringdragon
during dragonfruit
dragon fruitwine
fruit winefermentation.
fermentation.

3.3. Effects
3.3.Effects
3.3. EffectsofofofDragon
Dragon Fruit
DragonFruit Solution
FruitSolution Concentration
SolutionConcentration
Concentrationonon Fermentation
onFermentation Dynamics
FermentationDynamics
Dynamics
The impact
Theimpact
The impactof of varying
ofvarying dragon
varyingdragon fruit-solution
dragonfruit-solution concentrations
fruit-solutionconcentrations
concentrationson on key
onkey fermentation
keyfermentation
fermentationpa- pa-
pa-
rameters
rameters was
was measured
measured with concentrations
with concentrations ranging
ranging from 10%
from to
10% 50%
to
rameters was measured with concentrations ranging from 10% to 50% dragon fruit solu- dragon
50% dragonfruit solution
fruit solu-
to
tionwater
tion (Figure
totowater
water 6). The
(Figure
(Figure 6). analysis
6).The revealed
Theanalysis
analysis substantial
revealed
revealed impacts
substantial
substantial on several
impacts
impacts crucial
onseveral
on several fermen-
crucial
crucial fer-
fer-
tation metrics,
mentationmetrics,
mentation including
metrics,including acidity,
includingacidity,pH levels,
acidity,pH ethanol
pHlevels, production,
levels,ethanol
ethanolproduction,sugar consumption,
production,sugar
sugarconsumption, and
consumption,
degrees
anddegrees
and Brix,Brix,
degrees which
Brix, collectively
which
which determine
collectively
collectively the the
determine
determine fermentation
thefermentationprofile
fermentation andand
profile
profile the the
and final qualities
thefinal
final qual-
qual-
of dragon fruit
itiesofofdragon
ities wine.
dragonfruitfruitwine.
wine.

Beverages 2024, 10, x FOR PEER REVIEW 11 of 20

(a)
(a) (b)
(b)

(c) (d)

Figure
Figure6. 6.
Impact of dragon
Impact fruitfruit
of dragon solution concentration
solution on fermentation
concentration parameters.
on fermentation (a) Acidity
parameters. (g/L)
(a) Acidity
and pH value; (b) degrees Brix (°Bx); ◦
(c) ethanol content (%); (d) sugar content (g/L), including re-
(g/L) and pH value; (b) degrees Brix ( Bx); (c) ethanol content (%); (d) sugar content (g/L), including
ducing sugars and total sugars.
reducing sugars and total sugars.

Results indicate a significant impact of fruit-solution concentration on acidity and pH

(Figure 6a). As the concentration increased, acidity values exhibited fluctuations, peaking at
4.740 in the 50% concentration solution. Simultaneously, pH levels progressively declined
from 4.240 at 10% concentration to 3.857 at 50%. This pattern suggests that higher fruit con-
centrations create a more acidic environment, which is generally beneficial for yeast activity,
thus enhancing the fermentation process. Additionally, ethanol production demonstrated a
Beverages 2024, 10, 61 (c) (d) 11 of 19
Figure 6. Impact of dragon fruit solution concentration on fermentation parameters. (a) Acidity (g/L)
and pH value; (b) degrees Brix (°Bx); (c) ethanol content (%); (d) sugar content (g/L), including re-
ducing Results
sugars and total sugars.
indicate a significant impact of fruit-solution concentration on acidity and
pH (Figure 6a). As the concentration increased, acidity values exhibited fluctuations,
Results
peaking at indicate
4.740 in athe
significant impact of fruit-solution
50% concentration concentration pH
solution. Simultaneously, on acidity and pH
levels progressively
(Figure
declined from 4.240 at 10% concentration to 3.857 at 50%. This pattern suggests thatathigher
6a). As the concentration increased, acidity values exhibited fluctuations, peaking
4.740
fruitinconcentrations
the 50% concentration
create asolution. Simultaneously,
more acidic environment,pH levels
whichprogressively
is generally declined
beneficial for
from 4.240 at 10% concentration to 3.857 at 50%. This pattern suggests
yeast activity, thus enhancing the fermentation process. Additionally, that higher fruitproduction
ethanol con-
centrations create a more acidic environment, which is generally beneficial for yeast activity,
demonstrated a positive correlation with the increase in the concentration of the dragon
thus enhancing the fermentation process. Additionally, ethanol production demonstrated a
fruit-solution concentration, rising from 11.340% at 10% concentration to 13.917% at 50%
positive correlation with the increase in the concentration of the dragon fruit-solution con-
(Figure 6c). This trend suggests that higher concentrations not only potentially enhance
centration, rising from 11.340% at 10% concentration to 13.917% at 50% (Figure 6c). This
the flavor profile of the wine but also improve ethanol yield, likely due to the increased
trend suggests that higher concentrations not only potentially enhance the flavor profile of
availability of fermentable sugars. Correspondingly, both reducing sugars and total sugars
the wine but also improve ethanol yield, likely due to the increased availability of ferment-
showed significant declines as the concentration increased—reducing sugars decreased
able sugars. Correspondingly, both reducing sugars and total sugars showed significant de-
from 11.839 g/L at 10% to 1.769 g/L at 50%, and total sugars decreased from 11.969 g/L to
clines as the concentration increased—reducing sugars decreased from 11.839 g/L at 10% to
6.491g/L
1.769 g/L (Figure
at 50%, and6b,d).
total sugars decreased from 11.969 g/L to 6.491 g/L (Figure 6b,d).
3.4. Optimization of Yeast Strain and Concentration
3.4. Optimization of Yeast Strain and Concentration
The study evaluated the effectiveness of different yeast strains (Fermentis, Angel, and
The study evaluated the effectiveness of different yeast strains (Fermentis, Angel, and
Sai Gon) in fermenting dragon fruit wine under identical conditions (Figure 7a).
Sai Gon) in fermenting dragon fruit wine under identical conditions (Figure 7a).

(a) (b)

(c) (d)
Figure
Figure7.7.Impact
Impactofofyeast
yeaststrains
strainson
onfermentation
fermentationparameters
parametersinindragon
dragonfruit
fruitwine
wineproduction.
production.(a)
(a) Acid-
Acidity (g/L) and pH value; (b) degrees Brix
ity (g/L) and pH value; (b) degrees Brix (◦ Bx);(°Bx); (c) ethanol content (%); (d) yeast ratio
(c) ethanol (x10⁶
content (%); (d) yeast ratio (×106 CFU/mL).
CFU/mL).
Acidity levels varied significantly among the yeasts, with Sai Gon exhibiting the highest
acidity at 12.12, suggesting a stronger acid-production capability. The pH readings correlated
with these acidity levels, where Sai Gon had the lowest pH at 3.530, indicating a more acidic
environment compared to those associated with Fermentis (3.887) and Angel (4.000).
In the comparative study of yeast strains for dragon fruit wine fermentation, distinct dif-
ferences in sugar utilization were evident. Both Fermentis and Angel maintained a moderate
Brix level of 7, indicative of consistent sugar-conversion rates. In contrast, Sai Gon showed
a higher Brix of 10, alongside significantly greater levels of reducing sugars at 15.340 g/L,
compared to just 2.393 g/L and 2.945 g/L for Fermentis and Angel, respectively (Figure 7b).
Ethanol-production figures support this inference, with Fermentis and Angel achieving
13.23% and 13.46% ethanol content, outperforming Sai Gon’s 8.11% (Figure 7c). Despite
Angel’s higher yeast concentration (4,220,000 cells/mL), it did not yield the highest ethanol
output, hinting that the conversion efficiency of yeast strains may rely on specific metabolic
traits beyond simple cell count (Figure 7d).
 at 15.340 g/L, compared to just 2.393 g/L and 2.945 g/L for Fermentis and Angel, respec-
tively (Figure 7b).
Ethanol-production figures support this inference, with Fermentis and Angel achiev-
ing 13.23% and 13.46% ethanol content, outperforming Sai Gon’s 8.11% (Figure 7c). De-
Beverages 2024, 10, 61 spite Angel’s higher yeast concentration (4,220,000 cells/mL), it did not yield the highest 12 of 19
ethanol output, hinting that the conversion efficiency of yeast strains may rely on specific
metabolic traits beyond simple cell count (Figure 7d).
Figure
Figure8 8illustrates
illustratesthethe
sugar content—including
sugar content—including both both
reducing and total
reducing andsugars—across
total sugars—
three different
across yeast strains
three different (Fermentis,
yeast Angel, Sai Gon)
strains (Fermentis, Angel,used
SaiinGon)
dragon fruit
used inwine fermentation.
dragon fruit wine
The
fermentation. The data indicate that Sai Gon yeast was associated with significantlysugars
data indicate that Sai Gon yeast was associated with significantly higher total higher
compared to compared
total sugars Fermentis to and Angel, reaching
Fermentis approximately
and Angel, 20 g/L; Fermentis
reaching approximately 20 g/L;and Angel
Fermentis
both
and were
Angelassociated
both were with lower sugar
associated withlevels.
lower This
sugaranalysis
levels. indicates that the
This analysis Sai Gon
indicates yeast
that the
strain may be less efficient at converting sugars into ethanol, potentially producing
Sai Gon yeast strain may be less efficient at converting sugars into ethanol, potentially sweeter
wines with lower
producing sweeter alcohol
winescontent. The high
with lower levels
alcohol of reducing
content. The highsugars in of
levels thereducing
Sai Gon sugars
strain
further underscore its diminished fermentation efficiency compared to the
in the Sai Gon strain further underscore its diminished fermentation efficiency compared Fermentis and
Angel strains.
to the Fermentis and Angel strains.

Beverages 2024, 10, x FOR PEER REVIEW 13 of 20

peaked within
Figure8.8. the lower
Sugar-content concentration
variation range (13.08%
acrossdifferent
different to 13.74%
yeaststrains
strains at 0.5% to 1%)fermentation.
and de-
Figure Sugar-content variation across yeast inindragon
dragon fruitwine
fruit winefermentation.
clined as sugar levels increased, indicating a possible threshold beyond which sugar levels
adversely
3.5.
3.5.Factors
Factorsaffect ethanolSensory
Influencing
Influencing yield
Sensory(Figure 9c).
Evaluation
Evaluation
Managing these sugar levels is vital to preventing excessive acidity that might com-
The
Thedata
dataderived
derivedfromfrom Figure
Figure9 elucidate
9 elucidate thethe
profound
profound impact of dragon
impact of dragon fruit-solution
fruit-solu-
promise the desirable fruity characteristics of the wine. The variation in sugar content
concentration on fermentation dynamics and the resultant sensory qualities of the wine.
across different concentrations highlights this crucial balance in winemaking. While theof the
tion concentration on fermentation dynamics and the resultant sensory qualities
As the dragon
wine. As the fruit-solution
dragon concentration
fruit-solution increased, marked changes
concentration were observed ob-in
increase in sugars at higher concentrations (1.25% and increased, markedthe
1.5%) can enhance changes
sensorywere
ap-
acidity
served and pH
in wine levels.
acidity Specifically, acidity escalated sharply from 3.3 at 1% to 12.54 at 1.5%
peal of the by and pH levels.
producing Specifically,
a sweeter and moreacidity
robustescalated sharply
flavor profile, from 3.3 at 1% to
it simultaneously
concentration,
12.54 at 1.5% significantly
concentration, influencing
significantlythe influencing
tartness of thethe wine. Concurrently,
tartness of the wine.pHConcur-
levels
poses challenges for ethanol production, likely due to osmotic pressure or yeast nutrient
dropped,
imbalance. creating
rently, pHThese a more
levels conditionsacidic
dropped, creating environment,
can impair a more which
yeastacidic enhances
environment,
metabolic the perceived
activities which sharpness
enhances
and reduce the and
ethanol per-
intensity
ceived of the
sharpness
yields (Figure 9d). wine
andflavors (Figure
intensity of 9a).
the wine flavors (Figure 9a).
The sugar profile, indicated by Brix, reducing sugars, and total sugars, exhibited no-
table variations with changing dragon fruit-solution concentrations. While lower concen-
trations (0.5% to 1%) were associated with relatively stable sugar levels, conducive to op-
timal ethanol production, concentrations of 1.25% and 1.5% yielded a significant increase
in sugars (Figure 9b). This elevation in sugar content could potentially result in sweeter,
fuller-bodied wines, appealing to certain consumer preferences. However, it is crucial to
note that while these higher sugar concentrations may enhance sweetness and body, they
also risk inhibiting ethanol production. This is evident from the fact that ethanol content

(a) (b)

(c) (d)
Figure 9.
Figure 9. Impact
Impactof ofdragon
dragonfruit-solution
fruit-solutionconcentration
concentrationononkey
keyfermentation
fermentationmetrics.
metrics.(a)(a)
Acidity (g/L)
Acidity (g/L)
and pH value; (b) sugar content (g/L), including reducing sugars and total sugars; (c) ethanol
and pH value; (b) sugar content (g/L), including reducing sugars and total sugars; (c) ethanol content
(%); (d) yeast ratio (×10⁶ CFU/mL).
content (%); (d) yeast ratio (×106 CFU/mL).
3.6. Impact of Fermentation on the Biochemical and Nutritional Properties of H. polyrhizus
Table 2 delineates significant alterations in the biochemical composition of H. polyrhi-
zus following fermentation, offering insights into the metabolic impacts of this process.
Fermentation, a biotechnological application involving microbial activity, profoundly af-
Beverages 2024, 10, 61 13 of 19

The sugar profile, indicated by Brix, reducing sugars, and total sugars, exhibited
notable variations with changing dragon fruit-solution concentrations. While lower con-
centrations (0.5% to 1%) were associated with relatively stable sugar levels, conducive to
optimal ethanol production, concentrations of 1.25% and 1.5% yielded a significant increase
in sugars (Figure 9b). This elevation in sugar content could potentially result in sweeter,
fuller-bodied wines, appealing to certain consumer preferences. However, it is crucial
to note that while these higher sugar concentrations may enhance sweetness and body,
they also risk inhibiting ethanol production. This is evident from the fact that ethanol
content peaked within the lower concentration range (13.08% to 13.74% at 0.5% to 1%) and
declined as sugar levels increased, indicating a possible threshold beyond which sugar
levels adversely affect ethanol yield (Figure 9c).
Managing these sugar levels is vital to preventing excessive acidity that might compro-
mise the desirable fruity characteristics of the wine. The variation in sugar content across
different concentrations highlights this crucial balance in winemaking. While the increase in
sugars at higher concentrations (1.25% and 1.5%) can enhance the sensory appeal of the wine
by producing a sweeter and more robust flavor profile, it simultaneously poses challenges
for ethanol production, likely due to osmotic pressure or yeast nutrient imbalance. These
conditions can impair yeast metabolic activities and reduce ethanol yields (Figure 9d).

3.6. Impact of Fermentation on the Biochemical and Nutritional Properties of H. polyrhizus

Table 2 delineates significant alterations in the biochemical composition of H. polyrhizus
following fermentation, offering insights into the metabolic impacts of this process. Fer-
mentation, a biotechnological application involving microbial activity, profoundly affects
the nutritional and phytochemical profile of substrates, as is evident from the changes
observed in various parameters measured

Table 2. Biochemical composition of fruit juice made from H. polyrhizus before and after fermentation.

Fruit Juice Made from Fruit Juice Made from

Parameter H. polyrhizus H. polyrhizus
before Fermentation after Fermentation
Vitamin C (mg AA/100 g) 29.74 ± 5.60 11.36 ± 0.05
Polyphenols (mg GAE/100 g) 39.18 ± 0.56 55.042 ± 3.31
Total Sugars (g/L) 84.93 ± 0.52 13.48 ± 1.11
Reducing Sugars (g/L) 73.84 ± 0.15 9.88 ± 0.19
Antioxidant Activity DPPH (%) 38.23 ± 2.06 45.69 ± 1.63
Dry-Matter Content (Brix) 13.00 ± 0.40 11.17 ± 0.89
Acidity (g/L) 2.31 ± 0.02 5.59 ± 0.02
pH 3.96 ± 0.01 4.35 ± 0.03
Anthocyanins (mg/L) 345.66 ± 6.02 250.34 ± 5.25

There was a noticeable decrease in vitamin C content from 29.74 mg AA/100 g to

11.36 mg AA/100 g post-fermentation. This reduction could be attributed to the sensitivity
of vitamin C to oxidative processes and enzymatic activity during fermentation, which
often leads to its degradation. Such a decrease might impact the antioxidant capacity of the
fruit, although other components may compensate for this loss.
Contrastingly, the polyphenol content increased from 39.18 mg GAE/100 g to 55.04 mg
GAE/100 g. This increase suggests that fermentation facilitates the release or synthesis
of polyphenols, possibly through the breakdown of cell walls by enzymes produced by
fermentative microbes or the conversion of bound phenolic compounds into free forms.
This enhancement enhances the fruit’s health-promoting properties, given the role of
polyphenols in preventing oxidative stress.
A significant transformation was observed in the sugar profiles. Total sugars decreased
sharply from 84.93 g/L to 13.48 g/L, and reducing sugars decreased from 73.84 g/L to
9.88 g/L. This substantial reduction is typically a result of sugar utilization by yeast for
alcohol production during fermentation. The reduction in sugar content is beneficial for
Beverages 2024, 10, 61 14 of 19

reducing caloric intake and can be particularly advantageous for consumers monitoring
sugar consumption.
The DPPH antioxidant activity increased from 38.23% to 45.69%. This increase aligns
with the rise in polyphenol content, as these compounds are known for their antioxidant
properties. This finding suggests that fermentation not only preserves but also enhances
the antioxidant potential of H. polyrhizus, potentially increasing its efficacy in combating
oxidative stress in the body.
There was a slight decrease in dry-matter content from 13.00 Brix to 11.17 Brix, which
might be linked to the breakdown of structural carbohydrates and other dry-matter con-
stituents. The acidity of the sample increased from 2.31 g/L to 5.59 g/L, indicative of
organic-acid production during fermentation, which is typical, as microbes metabolize
sugars and produce acids as byproducts.
The pH value slightly increased from 3.96 to 4.35, which could have been the result of
organic-acid production and other fermentative transformations. The anthocyanin content
decreased from 345.66 mg/L to 250.34 mg/L, possibly due to the structural breakdown of
these compounds under fermentation conditions or to their conversion into other molecules.

4. Discussion
Red dragon fruits (Hylocereus spp.) are celebrated for their high levels of health-promoting
betalains, although these compounds exhibit notably low bioavailability in plasma (less than
1.0%) [34]. To address this issue, fermentation techniques utilizing autochthonous strains
have been developed to enhance the yield of betalains in fermented red dragon fruit drinks
through concentration processes [35]. Additionally, the production of fruit wines, including
red dragon fruit wine, is a burgeoning field of biotechnological advancement with substantial
commercial implications. As the demand for alternative fruit wines increases, understanding
the nuances of their production is becoming essential [36–38].
Historically, wine is globally cherished for its distinctive flavors and aromas and is
traditionally crafted from grapes [39]. However, there is growing consumer interest in
wines made from non-grape fruits such as mango, jackfruit, and, notably, red dragon
fruit, which offer unique aromas, lower alcohol content, and additional health benefits
due to their high levels of phenolics and flavonoids [40]. This shift is particularly notable
in Vietnam, the world’s second-largest producer of red dragon fruits, where rapid post-
harvest processing can mitigate sucrose degradation, thereby enhancing product stability
and shelf life while also improving the bioavailability of health-promoting compounds
through fermentation [2,41–43]. Recent studies have highlighted the potential of red dragon
fruit wine in terms of its antioxidant properties. For instance, Jiang et al. found that using
different yeast strains can significantly impact the wine’s physicochemical and oenological
properties. They reported that certain yeast strains enhanced the antioxidant activity by
up to 20% and improved color stability by 15% compared to control strains [44]. Similarly,
Xiong et al. observed that red dragon fruit wine has a high phenolic content, measuring
approximately 180 mg GAE/L, which contributes to its significant antioxidant properties,
which are associated with a 25% increase in DPPH radical-scavenging activity compared
to traditional fruit wines [45]. These findings underscore the importance of selecting
appropriate yeast strains and fermentation conditions to optimize the wine’s health benefits
and sensory attributes. Effective yeast selection and fermentation techniques can maximize
the retention of bioactive compounds in the wine, enhancing both its nutritional value
and its consumer appeal. Thus, the strategic optimization of fermentation variables is
crucial for producing high-quality red dragon fruit wine with superior health benefits and
sensory qualities, highlighting the potential for these wines in the growing market for
health-promoting beverages.
Yeast plays a crucial role in wine fermentation, converting sugars into ethanol, carbon
dioxide, and secondary metabolites such as esters, which significantly contribute to the
wine’s flavor profile [46]. The type of yeast significantly affects the quality of the wine, with
various strains of Saccharomyces cerevisiae being widely utilized due to their fermentation
Beverages 2024, 10, 61 15 of 19

efficiency [47]. These include strains reported in several studies highlighting their different
impacts on fermentation dynamics and wine characteristics [48–51]. During fermentation,
these yeasts metabolize glucose and fructose into ethanol and CO2 [52]. However, red
dragon fruit naturally lacks the requisite sugar levels to achieve the standard ethanol
concentrations found in traditional wines, necessitating adjustments to the sugar content in
the must [53,54].
The soluble solids content (SSC) serves as a rapid and accurate metric for assessing
fruit ripeness and sugar adequacy for fermentation, measures that are crucial for selecting
high-quality raw materials [55]. The inherently acidic environment of dragon fruit juice (pH
approximately 3.0–4.0) and the presence of enzymes such as invertase aid in the hydrolysis
of sucrose into fermentable sugars, facilitating yeast metabolism [56]. Our study meticu-
lously monitored the transformation of reducing sugars during fermentation, revealing a
substantial correlation between sugar consumption and ethanol production. This correla-
tion underscores the efficacy of our fermentation strategy, which was carefully designed to
maximize alcohol yield while minimizing the production of unwanted by-products.
By conducting detailed measurements of soluble solids content (SSC) and tracking
sugar transformation, the study highlighted the successful adaptation of the fermentation
process, optimizing alcohol production to ensure that sugars were efficiently converted
into ethanol [57]. This approach is crucial, as it prevents the formation of undesirable
compounds that could degrade the wine’s quality and flavor. Precision in managing sugar
levels and their conversion to ethanol is vital in winemaking, as it directly affects the final
alcohol content and overall sensory attributes of the wine. Achieving an optimal balance
in this conversion process sets a valuable benchmark for future fermentation endeavors,
particularly with non-traditional fruits like dragon fruit [58]. This method serves as a model
for similar applications in the wine industry, emphasizing the efficient use of natural sugar
resources to produce high-quality wines with the desired alcoholic strength and minimal
residual sugars.
To further validate the influence of soluble solids content (SSC) on fermentation
outcomes, we investigated the effects of diluting the dragon fruit juice. Reducing the juice
concentration lowered the sugar content and degrees Brix from the original range of 10–12
to below 10, necessitating the addition of sucrose. This added sucrose underwent hydrolysis
due to the acids and enzymes present in the juice, indicating that the observed reduction in
sugar levels primarily resulted from yeast activity. Additionally, the residual sugar content
helps categorize the resulting wine into dry, off-dry, or sweet categories and informs storage
strategies. For example, storing wine without pasteurization in cool conditions could lead
to ongoing fermentation, potentially increasing alcohol content and generating gases, as
is seen in sparkling wines such as Champagne [59–61]. This underscores the necessity
of appropriate storage methods and highlights how monitoring reducing sugars during
fermentation aligns with SSC management to ensure quality control and the achievement of
the desired wine characteristics. This study also observed a significant increase in volatile
components, particularly ethanol and esters, following fermentation. Fatty acids and
aldehydes were predominantly decomposed, with ethanol emerging as the most abundant
volatile compound in the fermented wine samples [62–64]. The fermentation process,
starting with an initial Brix of 24, produced an alcohol level of approximately 12%, aligning
with standard wine alcohol content. The study emphasized the importance of using the
manufacturer-recommended yeast concentrations for optimizing fermentation efficiency
and cost-effectiveness. While Fermentis yeast resulted in satisfactory alcohol production,
its higher cost compared to Angel yeast made it less cost-effective. The use of Saigon yeast
led to increased acid content and decreased pH, resulting in a more acidic and potentially
hazy wine and indicating that it was not economically viable or beneficial for wine clarity.
Finally, our findings illuminate the multifaceted nature of wine fermentation, espe-
cially when using unconventional fruits like red dragon fruit. This study accentuates the
necessity of meticulous substrate selection, the use of specific yeast strains, and precise
fermentation management to enhance the transformation of raw materials into superior-
Beverages 2024, 10, 61 16 of 19

quality wines. The implemented techniques not only extend the product’s shelf life but
also amplify the bioavailability of health-promoting compounds, potentially setting a new
precedent in fruit-wine production for both commercial and health-oriented markets. This
holistic approach not only seeks to refine the sensory and quality attributes of the wine, but
also demonstrates the potential associated with integrating innovative biotechnological
strategies to boost economic efficiency and sustainability in fruit-wine manufacturing. As
consumer interest in diverse, health-supportive wines intensifies, this research provides
a crucial foundation for further exploration and refinement of fermentation techniques
tailored to meet both flavor and nutritional demands. Looking forward, the prospects of
fruit wine production are promising, poised to introduce a new genre of specialty wines
that align with modern consumer preferences.
The study noted a significant decrease in vitamin C content from 29.74 mg AA/100 g
to 11.36 mg AA/100 g after fermentation, likely due to its susceptibility to oxidative and
enzymatic breakdown; this decrease could influence the antioxidant capacity of the wine,
though other components might compensate for this loss. Yeasts are crucial in the produc-
tion of polyphenols during the fermentation process. They contribute significantly to the
transformation of raw materials into final products with enhanced bioactive properties [65].
Specifically, certain yeast strains have been shown to either synthesize polyphenols directly
or facilitate their release from the plant matrix through enzymatic activity. This enzymatic
disintegration of cell walls or conversion of bound phenolics into free forms significantly
enhances the health benefits of the fermented product [66]. In our study, we observed a
significant increase in polyphenol levels from 39.18 mg GAE/100 g to 55.04 mg GAE/100 g
post-fermentation. This rise suggests that fermentation not only preserves these compounds
but may also boost their availability and efficacy. The increased polyphenol content is likely
due to the yeast’s metabolic activities, which can enhance the release or synthesis of these
beneficial compounds. By leveraging the metabolic capabilities of yeast, our fermentation
process optimizes the polyphenol content, thus enhancing the antioxidant properties of
the final product. This finding underscores the importance of selecting appropriate yeast
strains to maximize the health benefits and sensory attributes of red dragon fruit wine.
Despite the promising findings of this study, several limitations should be noted. One
significant limitation is the inherently low bioavailability of betalains in plasma, which
remains less than 1.0%. This low bioavailability can affect the overall health benefits of the
wine. Future research should explore methods to enhance betalain bioavailability, poten-
tially through advanced fermentation techniques or novel delivery systems. Additionally,
while our study optimized fermentation conditions for red dragon fruit wine, the scope
was limited to specific parameters. Future studies should investigate a broader range of
variables, including different yeast strains, fermentation temperatures, and durations, to
further refine the process. Another area for future research is the long-term stability of
the bioactive compounds in the wine and their effects on health over extended storage
periods. By addressing these limitations, future research can provide a more comprehensive
understanding of the fermentation process and its impact on the nutritional and sensory
qualities of red dragon fruit wine.

5. Conclusions
This study on dragon fruit wine fermentation has demonstrated the pivotal roles of yeast
strain selection and fermentation parameters in influencing wine quality. Saccharomyces cerevisiae
RV002 was identified as the most effective yeast strain due to its robust fermentation
capabilities and tolerance to high alcohol and acidic conditions. Optimal wine quality was
achieved with a 50% dilution ratio, which led to enhanced clarity and sensory attributes,
whereas dilution ratios exceeding 90% significantly reduced ethanol content below the
standards stipulated by QCVN 6-3:2010/BYT. An optimal yeast concentration of 1 g/L was
established; concentrations above this threshold adversely impacted the wine’s appearance
and flavor, and lower concentrations failed to adequately suppress microbial contamination,
resulting in off-flavors and diminished alcohol yields. These findings underscore the
Beverages 2024, 10, 61 17 of 19

importance of maintaining meticulous control over fermentation variables to optimize

wine quality and highlight the potential of using agricultural by-products to mitigate
post-harvest losses and diversify product offerings in agriculture. This research provides
a foundational framework for scaling up dragon fruit wine production and encourages
further exploration into value-added processing of other fruits.
The study has limitations, including the fact that it was conducted under controlled
lab conditions that may not reflect commercial-scale complexities. Future research should
scale up fermentation, evaluate industrial feasibility, and explore the use of temperature
variations, nutrient supplementation, and extended aging periods to enhance wine quality.
Broader sensory evaluations could offer valuable insights into consumer preferences.

Author Contributions: Conceptualization, P.V.T., T.B.N., L.Q.H., L.H.U. and N.N.K.N.; methodology,
N.T.K.T., P.H.T.K., D.T.M., T.B.N., L.H.U. and N.N.K.N.; formal analysis, N.T.K.T., P.H.T.K., D.T.M. and
T.B.N.; investigation, T.N.M.; resources, P.V.T. and L.Q.H.; data curation, T.N.M., D.T.M. and N.Q.T.;
writing—original draft preparation, T.N.M. and N.Q.T.; writing—review and editing, T.N.M. and
N.Q.T.; visualization, P.V.T.; supervision, N.Q.T. All authors have read and agreed to the published
version of the manuscript.
Funding: The APC was funded by Nguyen Quang Trung and Truong Ngoc Minh.
Data Availability Statement: Data are contained within the article.
Acknowledgments: The research support was provided by the Faculty of Food Science and Tech-
nology at Ho Chi Minh City University of Industry and Trade, along with Caty Foods Joint Stock
Company, which supplied the necessary facilities for this study.
Conflicts of Interest: Author L.Q.H. is employee at Caty Foods Joint Stock Company; Author T.N.M.
is employee at Vicomi Tam an Investment and Commercial Company Limited; Author N.Q.T. is
employee at Hera USA Corporation; Other authors declare no conflict of interest.

References
1. Golino, D.A. Trade in grapevine plant materials: Local, national and worldwide perspectives. Am. J. Enol. Vitic. 2000, 51, 216–221.
2. Jiang, X.; Lu, Y.; Liu, S.Q. Effects of pectinase treatment on the physicochemical and oenological properties of red dragon fruit
wine fermented with Torulaspora delbrueckii. LWT 2020, 132, 109929. [CrossRef]
3. Thang, N.; Thai, P.M.; Dat, V.H.; Van Ngoc, V.T. Agricultural exports from Vietnam to China. Agric. In Trade between China and
the Greater Mekong Subregion Countries: A Value Chain Analysis; Menon, J., Roth, V., Eds.; ISEAS Publishing: Singapore, 2022;
pp. 256–267.
4. Chakraborty, K.; Saha, J.; Raychaudhuri, U.; Chakraborty, R. Tropical fruit wines: A mini review. Nat. Prod. 2014, 10, 219–228.
5. Yu, Z.H.; Gao, L.; Liu, Y.; Tian, Y.; Zhao, L.; Sun, X.; Wang, L.; Liu, M.; Yu, L. Winemaking characteristics of red-fleshed dragon
fruit from three locations in Guizhou Province, China. Food Sci. Nutr. 2021, 9, 2508–2516. [CrossRef]
6. Tenore, G.C.; Novellino, E.; Basile, A. Nutraceutical potential and antioxidant benefits of red pitaya (Hylocereus polyrhizus) extracts.
J. Funct. Foods 2012, 4, 129–136. [CrossRef]
7. German, J.B.; Walzem, R.L. The health benefits of wine. Annu. Rev. Nutr. 2000, 20, 561–593. [CrossRef] [PubMed]
8. Sudiarta, I.W.; Saputra, I.W.R.; Singapurwa, N.M.A.S.; Candra, I.P.; Semariyani, A.A.M. Ethanol and methanol levels of red
dragon fruit wine (Hylocereus costaricensis) with the treatment of sugar and fermentation time. J. Phys. Conf. Ser. 2021, 1869, 012032.
[CrossRef]
9. Foong, J.H.; Hon, W.M.; Ho, C.W. Bioactive compounds determination in fermented liquid dragon fruit (Hylocereus polyrhizus).
Borneo Sci. 2012, 31, 37–56.
10. Wang, X.; Liu, X.; Long, J.; Shen, K.; Qiu, S.; Wang, Y.; Huang, Y. Isolation, screening, and application of aroma-producing yeast
for red dragon fruit wine. Food Biosci. 2024, 59, 103878. [CrossRef]
11. Huan, P.T.; Hien, N.M.; Anh, N.H.T. Optimization of alcoholic fermentation of dragon fruit juice using response surface
methodology. Food Res. 2020, 4, 1529–1536. [CrossRef]
12. Guigou, M.; Lareo, C.; Pérez, L.V.; Lluberas, M.E.; Vázquez, D.; Ferrari, M.D. Bioethanol production from sweet sorghum:
Evaluation of post-harvest treatments on sugar extraction and fermentation. Biomass Bioenergy 2011, 35, 3058–3062. [CrossRef]
13. Hocking, M.B.; Hocking, M.B. Fermentation processes. Mod. Chem. Technol. Emiss. Control 1985, 338–377.
14. Silcox, H.E.; Lee, S.B. Fermentation. Ind. Eng. Chem. 1948, 40, 1602–1608. [CrossRef]
15. Thommes, K.; Strezov, V. Fermentation of biomass. Biomass Process. Technol. 2014, 257, 52.
16. Minh, N.P.; Nhan, N.P.T.; Tha, D.T.; Thuy, L.K.; Khai, L.Q.; Tu, L.N. Different Aspects Affecting to Production of Dragon Fruit
(Hylocereus undatus) Nectar. J. Pharm. Sci. Res. 2019, 11, 1040–1043.
Beverages 2024, 10, 61 18 of 19

17. Ha, H.P.; Trang, V.T.; Nghia, N.C.; Son, V.H. Development of Freeze-dried red dragon fruit yoghurt containing probiotics. Red
2021, 31, 14–18.
18. Luu, T.T.H.; Le, T.L.; Huynh, N.; Quintela-Alonso, P. Dragon fruit: A review of health benefits and nutrients and its sustainable
development under climate changes in Vietnam. Czech J. Food Sci. 2021, 39, 71–94. [CrossRef]
19. Le, P.T. Research processing process of fermented juice from red dragon fruit (Hylocereus polyrhizus): Research processing process
of fermented juice from red dragon fruit (Hylocereus polyrhizus). JSTGU 2021, 1, 20–30.
20. Mai, H.T.Q.; Pham, V.T.; Do, V.L.; Phuc, T.B.; Truc, T.T.; Ngan, T.T.K. Production process of a carbonated drink from red flesh
dragon fruit (Hylocereus polyrhizus). Mater. Sci. Forum 2022, 1048, 514–523. [CrossRef]
21. Vietnam National Technical Regulation TCVN 7523:2014; Specifications and Test Methods for Dragon Fruit. Vietnam National
Technical Regulation: Hanoi, Vietnam, 2014.
22. Mussa, S.B.; Sharaa, I.E. Analysis of vitamin C (ascorbic acid) contents packed fruit juice by UV-spectrophotometry and redox
titration methods. IOSR J. Appl. Phys. 2014, 6, 46–52. [CrossRef]
23. Sánchez-Rangel, J.C.; Benavides, J.; Heredia, J.B.; Cisneros-Zevallos, L.; Jacobo-Velázquez, D.A. The Folin–Ciocalteu assay
revisited: Improvement of its specificity for total phenolic content determination. Anal. Methods 2013, 5, 5990–5999. [CrossRef]
24. Minh, T.N.; Xuan, T.D.; Van, T.M.; Andriana, Y.; Viet, T.D.; Khanh, T.D.; Tran, H.D. Phytochemical analysis and potential biological
activities of essential oil from rice leaf. Molecules 2019, 24, 546. [CrossRef] [PubMed]
25. Rathod, B.B.; Murthy, S.; Bandyopadhyay, S. Is this solution pink enough? A smartphone tutor to resolve the eternal question in
phenolphthalein-based titration. J. Chem. Educ. 2019, 96, 486–494. [CrossRef]
26. Teixeira, R.S.S.; da Silva, A.S.A.; Ferreira-Leitão, V.S.; da Silva Bon, E.P. Amino acids interference on the quantification of reducing
sugars by the 3,5-dinitrosalicylic acid assay mislead carbohydrase activity measurements. Carbohydr. Res. 2012, 363, 33–37.
[CrossRef] [PubMed]
27. Majstorovic, D.M.; Zivkovic, E.M.; Kijevčanin, M.L. Density, viscosity, and refractive index data for a ternary system of wine
congeners (ethyl butyrate + diethyl succinate + isobutanol) in the temperature range from 288.15 to 323.15 K and at atmospheric
pressure. J. Chem. Eng. Data 2017, 62, 275–291. [CrossRef]
28. Martyniak, B.; Bolton, J.; Kuksin, D.; Shahin, S.M.; Chan, L.L.Y. A novel concentration and viability detection method for
Brettanomyces using the Cellometer image cytometry. J. Ind. Microbiol. Biotechnol. 2017, 44, 119–128. [CrossRef] [PubMed]
29. Urraca, R.; Sanz-Garcia, A.; Tardaguila, J.; Diago, M.P. Estimation of total soluble solids in grape berries using a hand-held NIR
spectrometer under field conditions. J. Sci. Food Agric. 2016, 96, 3007–3016. [CrossRef] [PubMed]
30. Hu, Y.B.; Chen, L.C.; Mou, L. Quality control of potentiometric pH measurements with a combination of NBS and Tris buffers at
salinities from 20 to 40 and pH from 7.2 to 8.6. J. Oceanogr. 2022, 78, 467–473. [CrossRef]
31. Başkan, K.S.; Tütem, E.; Akyüz, E.; Özen, S.; Apak, R. Spectrophotometric total reducing sugars assay based on cupric reduction.
Talanta 2016, 147, 162–168. [CrossRef]
32. Pettinati, J.D.; Swift, C.E.; Cohen, E.H. Moisture and fat analysis of meat and meat products: A review and comparison of
methods. J. Assoc. Off. Anal. Chem. 1973, 56, 544–561. [CrossRef]
33. Hurtado, N.H.; Morales, A.L.; González-Miret, M.L.; Escudero-Gilete, M.L.; Heredia, F.J. Colour, pH stability and antioxidant
activity of anthocyanin rutinosides isolated from tamarillo fruit (Solanum betaceum Cav.). Food Chem. 2009, 117, 88–93. [CrossRef]
34. Choo, K.Y.; Kho, C.; Ong, Y.Y.; Thoo, Y.Y.; Lim, L.H.; Tan, C.P.; Ho, C.W. Fermentation of red dragon fruit (Hylocereus polyrhizus)
for betalains concentration. Int. Food Res. J. 2018, 25, 2539–2546.
35. Lourith, N.; Kanlayavattanakul, M. Antioxidant and stability of dragon fruit peel colour. Agro. Food Ind. Hi Tech 2013, 24, 56–58.
36. Vidal, J.C.; Bonel, L.; Ezquerra, A.; Hernández, S.; Bertolín, J.R.; Cubel, C.; Castillo, J.R. Electrochemical affinity biosensors for
detection of mycotoxins: A review. Biosens. Bioelectron. 2013, 49, 146–158. [CrossRef] [PubMed]
37. Villamor, R.R.; Evans, M.A.; Ross, C.F. Effects of ethanol, tannin, and fructose concentrations on sensory properties of model red
wines. Am. J. Enol. Vitic. 2013, 64, 342–348. [CrossRef]
38. Alarcón-Flores, M.I.; Romero-González, R.; Vidal, J.L.M.; Frenich, A.G. Multiclass determination of phytochemicals in vegetables and
fruits by ultra high performance liquid chromatography coupled to tandem mass spectrometry. Food Chem. 2013, 141, 1120–1129.
[CrossRef]
39. Millon, M. Wine: A Global History; Reaktion Books; The University of Chicago Press: Chicago, IL, USA, 2013.
40. Hu, L.; Liu, R.; Wang, X.; Zhang, X. The sensory quality improvement of citrus wine through co-fermentations with selected
non-Saccharomyces yeast strains and Saccharomyces cerevisiae. Microorganisms 2020, 8, 323. [CrossRef]
41. Wakchaure, G.C.; Kumar, S.; Meena, K.K.; Rane, J.; Pathak, H. Dragon fruit cultivation in India: Scope, constraints and policy
issues. Tech. Bull. 2021, 27, 47.
42. Tran, D.H.; Yen, C.R.; Chen, Y.K.H.; Le, T.K.O. Dragon Fruit Production and Consumption in Vietnam; Agricultural Experimental
Institute, Fengshan Tropical Horticulture Experimental Branch, National Pingtung University of Science and Technology,
Department of Agricultural Production: Kaohsiung, Taiwan, 2015; pp. 15–22.
43. Longhi, S.J.; Martín, M.C.; Fontana, A.; de Ambrosini, V.I.M. Different approaches to supplement polysaccharide-degrading
enzymes in vinification: Effects on color extraction, phenolic composition, antioxidant activity and sensory profiles of Malbec
wines. Food Res. Int. 2022, 157, 111447. [CrossRef]
44. Berovič, M.; Mavri, J.; Wondra, M.; Košmerl, T.; Bavčar, D. Influence of temperature and carbon dioxide on fermentation of
cabernet sauvignon must. Food Technol. Biotechnol. 2003, 41, 353–359.
Beverages 2024, 10, 61 19 of 19

45. Jiang, X.; Lu, Y.; Liu, S.Q. Effects of Different Yeasts on Physicochemical and Oenological Properties of Red Dragon Fruit
Wine Fermented with Saccharomyces cerevisiae, Torulaspora delbrueckii and Lachancea thermotolerans. Microorganisms 2020, 8, 315.
[CrossRef]
46. Niyomvong, N.; Sritawan, R.; Keabpimai, J.; Trakunjae, C.; Boondaeng, A. Comparison of the Chemical Properties of Vinegar
Obtained via One-Step Fermentation and Sequential Fermentation from Dragon Fruit and Pineapple. Beverages 2022, 8, 74.
[CrossRef]
47. Torija, M.J.; Rozes, N.; Poblet, M.; Guillamón, J.M.; Mas, A. Effects of fermentation temperature on the strain population of
Saccharomyces cerevisiae. Int. J. Food Microbiol. 2003, 80, 47–53. [CrossRef]
48. Belda, I.; Navascués, E.; Marquina, D.; Santos, A.; Calderon, F.; Benito, S. Dynamic analysis of physiological properties of
Torulaspora delbrueckii in wine fermentations and its incidence on wine quality. Appl. Microbiol. Biotechnol. 2015, 99, 1911–1922.
[CrossRef] [PubMed]
49. Perrone, B.; Giacosa, S.; Rolle, L.; Cocolin, L.; Rantsiou, K. Investigation of the dominance behavior of Saccharomyces cerevisiae
strains during wine fermentation. Int. J. Food Microbiol. 2013, 165, 156–162. [CrossRef]
50. Querol, A.; Barrio, E.; Ramón, D. Population dynamics of natural Saccharomyces strains during wine fermentation. Int. J. Food
Microbiol. 1994, 21, 315–323. [CrossRef]
51. Mouret, J.R.; Cadière, A.; Aguera, E.; Rollero, S.; Ortiz-Julien, A.; Sablayrolles, J.M.; Dequin, S. Dynamics and quantitative analysis
of the synthesis of fermentative aromas by an evolved wine strain of Saccharomyces cerevisiae. Yeast 2015, 32, 257–269. [PubMed]
52. Gueddari-Aourir, A.; García-Alaminos, A.; García-Yuste, S.; Alonso-Moreno, C.; Canales-Vázquez, J.; Zafrilla, J.E. The carbon
footprint balance of a real-case wine fermentation CO2 capture and utilization strategy. Renew. Sustain. Energy Rev. 2022,
157, 112058. [CrossRef]
53. Ali, A.; Sharma, N.; Vishwakarma, P.K.; Chavda, D. Exploring Dragon Fruit in India: From Taxonomy to Nutritional Benefits and
Sustainable Cultivation Practices. Appl. Fruit Sci. 2024, 1, 1–15.
54. Jalgaonkar, K.; Mahawar, M.K.; Bibwe, B.; Kannaujia, P. Postharvest profile, processing and waste utilization of dragon fruit
(Hylocereus spp.): A review. Food Rev. Int. 2022, 38, 733–759. [CrossRef]
55. Muzaifa, M.; Rohaya, S.; Nilda, C.; Harahap, K.R. Kombucha fermentation from cascara with addition of red dragon fruit
(Hylocereus polyrhizus): Analysis of alcohol content and total soluble solid. In Proceedings of the International Conference on
Tropical Agrifood, Feed and Fuel (ICTAFF 2021), Balikpapan, Indonesia 7 September 2021; Atlantis Press: Amsterdam, The
Netherlands, 2022; pp. 125–129.
56. Wong, Y.M.; Siow, L.F. Effects of heat, pH, antioxidant, agitation and light on betacyanin stability using red-fleshed dragon fruit
(Hylocereus polyrhizus) juice and concentrate as models. J. Food Sci. Technol. 2015, 52, 3086–3092. [CrossRef] [PubMed]
57. Panjaitan, R.G.P. Anti-diabetic activity of the red dragon fruit peel (Hylocereus polyrhizus) in ethanol extract against diabetic rats.
Pharmacogn. J. 2021, 13, 1079–1085. [CrossRef]
58. Cauilan, P.L. Hepatoprotective potential of Hylocereus polyrhizus (dragon fruit) on carbon tetrachloride induced hepatic damages
in albino wistar rats. Int. J. Sci. Basic Appl. Res. 2019, 46, 49–61.
59. Hutkins, R.W. Wine fermentation. In Wine Fermentation; Blackwell Publishing: Ames, IA, USA, 2006; pp. 349–396.
60. Amerine, M.A.; Singleton, V.L. Wine: An Introduction; University of California Press: Berkeley, CA, USA, 1976.
61. Lea, A.G.; Drilleau, J.F. Cidermaking. In Fermented Beverage Production; Springer: Boston, MA, USA, 2003; pp. 59–87.
62. Ma, Y.; Li, T.; Xu, X.; Ji, Y.; Jiang, X.; Shi, X.; Wang, B. Investigation of volatile compounds, microbial succession, and their relation
during spontaneous fermentation of Petit Manseng. Front. Microbiol. 2021, 12, 717387. [CrossRef] [PubMed]
63. Shi, X.; Liu, Y.; Ma, Q.; Wang, J.; Luo, J.; Suo, R.; Sun, J. Effects of low temperature on the dynamics of volatile compounds and
their correlation with the microbial succession during the fermentation of Longyan wine. LWT 2022, 154, 112661. [CrossRef]
64. Zhao, C.; Su, W.; Mu, Y.; Jiang, L.; Mu, Y. Correlations between microbiota with physicochemical properties and volatile flavor
components in black glutinous rice wine fermentation. Food Res. Int. 2020, 138, 109800. [CrossRef]
65. Ndlovu, T. Mannoprotein Production and Wine Haze Reduction by Wine Yeast Strains. Doctoral Dissertation, Stellenbosch
University, Stellenbosch, South Africa, 2012.
66. Tadioto, V.; Giehl, A.; Cadamuro, R.D.; Guterres, I.Z.; dos Santos, A.A.; Bressan, S.K.; Werlang, L.; Stambuk, B.U.; Fongaro, G.;
Silva, I.T.; et al. Bioactive Compounds from and against Yeasts in the One Health Context: A Comprehensive Review. Fermentation
2023, 9, 363. [CrossRef]

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual
author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to
people or property resulting from any ideas, methods, instructions or products referred to in the content.