Food Chemistry 411 (2023) 135488

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Food Chemistry
journal homepage: www.elsevier.com/locate/foodchem

Multi-dimensional pungency and sensory profiles of powder and oil of

seven chili peppers based on descriptive analysis and Scoville heat units
Yiwen Zhu a, Xiang Li b, Shui Jiang a, *, Yin Zhang c, Lihua Zhang b, *, Yuan Liu a
a
Department of Food Science & Technology, School of Agriculture & Biology, Shanghai Jiao Tong University, Shanghai 200240, China
b
Shanghai Laiyifen Co., LTD, Shanghai 201605, China
c
Key Laboratory of Meat Processing of Sichuan, Chengdu University, Chengdu 610106, China

A R T I C L E I N F O A B S T R A C T

Keywords: The pungency and flavor experience of peppers determines their economic benefits and consumption; thus, a
Heat systematic sensory evaluation of peppers is essential to monitor their production. Here the Scoville heat units
Spiciness (SHUs) of powders and oils of seven commercial peppers in China (i.e., Indian, Erjintiao, Shizhuhong, Zidantou,
Odor
Xinyidai, Mantianxing and Denglong) were derived based on concentrations of capsaicin and dihydrocapsaicin.
Taste
Mouthfeel
Then, the pungency and sensory profiles of pepper products were investigated by 11 trained panelists. The
potential indicators for predicting perceived pungency in peppers were found based on correlation analysis. The
Indian pepper stood out for its highest SHU (85909), bright redness, peppery, and bitterness, but lacked herb/
woody flavor. But other species had more varied flavor profiles and gentler mouth-feelings. SHU and capsaicin
were more recommended in predicting the perceived pungency in pepper powder and pepper oil. This study
offers a framework for evaluating the sensory characteristics of pepper products.

1. Introduction In addition to pungency, people consume chili peppers to pursue

their unique flavor experience. Although volatile components have been
The pungency in the cuisine is revered by customers worldwide and identified in processed peppers (Zhang et al., 2021), it fails to reveal the
is even becoming a fundamental component in food flavor (Green, consumers’ flavor experience (i.e., the interaction of taste, aroma,
1996). Chili peppers, a fruit of the Solanaceae family (Capsicum genus), texture, appearance, and sound) when tasting chili products. Given this,
are primarily responsible for appealing pungency (Mariano et al., 2022). a comprehensive sensory profile of chili peppers that are commonly
Specifically, capsaicinoids in chili peppers activate vanilloid receptors farmed and consumed is required.
and thus result in the pungent sensation. These receptors are located at The precise determination of pungency is critical for consumer and
the free nerve terminals of the human trigeminal nervous system. industrial use of chili peppers. However, due to the long-lasting and
Four pungent qualities (burning, tingling, numbing, overall), two fatigue-inducing nature of pungency, means to complement or partially
temporal qualities (lag time, overall duration), and three spatial quali­ replace sensory evaluation to determine pungency is needed. Scoville
ties (longitudinal location, lateral location, localized/diffuse) were first heat unit (SHU) has been proposed to represent the heat level or pun­
developed to characterize oral pungency (Cliff & Heymann, 1993). In gency of peppers, which is obtained by converting the concentrations of
detail, pungent sensations produced by capsaicin were burning, warmth, capsaicin and dihydrocapsaicin in samples (Scoville, 1912). However,
tingling, biting, and itching (Lawless & Stevens, 1988). Capsaicin- whether SHU fits with the actual sensory results is still needed to be
sensitive sites included the tip and side of the tongue, lips and poste­ verified. Furthermore, the correlation between perceived pungency and
rior palate. The pungency of capsaicin started slower, lasted longer at chemically measured concentrations was limited to a single capsaicin
the peak, and decayed slowly, but it varied in different peppers (Green, (Krajewska & Powers, 2006). Therefore, it needs to be further explored
1996; Prescott & Stevenson, 1995b). These findings reflect the multi- in various food matrices.
dimensional perception of single pungency-representative substances. Considering that ground powder and oil are common forms of con­
Due to the complexity in the practical application of chili peppers, sumption and trade in chili peppers (Korkmaz, Atasoy, & Hayaloglu,
further pungency exploration on actual chili pepper products is needed. 2020), the purpose of the study was to: (1) Determine the content of

* Corresponding authors.
E-mail addresses: jiangshui@sjtu.edu.cn (S. Jiang), zhanglihua@laiyifen.com (L. Zhang).

https://doi.org/10.1016/j.foodchem.2023.135488
Received 22 June 2022; Received in revised form 26 December 2022; Accepted 12 January 2023
Available online 13 January 2023
0308-8146/© 2023 Elsevier Ltd. All rights reserved.
Y. Zhu et al. Food Chemistry 411 (2023) 135488

capsaicinoids in seven pepper powders and oil and calculate the SHUs; ( )/
V V
(2) Establish multi-dimensional perception and sensory profile of chili W= C1 × + C2 × 0.9 (1)
powders and oil; (3) Evaluate the relationship between the SHU and 1000m 1000m
perceived pungency in both groups.
Where W is the total amount of capsaicin-like substances in the spec­
imen in grams per kilogram (g/kg); C1 and C2 is the amount of capsaicin
2. Materials and methods
and dihydrocapsaicin, respectively in micrograms per millilitre (μg/
mL); V is the volume of the sample fixation in millilitres (mL). m is the
2.1. Chemicals and pepper samples
value of the mass of the test material in grams (g). And 0.9 is the coef­
ficient of converting capsaicin and dihydrocapsaicin to total capsaicin-
Powder and oil products from seven commercial varieties of chili
like substances.
peppers (Capsicum frutescens L) including Indian, Shizhuhong (SZH),
Additionally, the Scoville Heat Units (SHU) of samples were calcu­
Mantianxing (MTX), Xinyidai (XYD), Zidantou (ZDT), Erjintiao (EJT),
lated from capsaicinoids concentrations using conversion factors
and Denglong (DL, red bell), gathered from various provinces were
developed by Todd Jr, Bensinger, and Biftu (2006).
provided by Laiyifen Co., Ltd. (Shanghai, China). Whole peppers were
dried at 103 ◦ C for 25 min (3 % moisture level) and then crushed into 25- SHU = W × 0.9 × (16.1 × 103 ) + W × 0.1 × (9.3 × 103 ) (2)
mesh with a blender (HR2784, Philips, the Neverlands) to produce
pepper powders. Pepper oil, a mixture of oil and powder, was made by where W is the total amount of capsaicin-like substances in the specimen
extracting powder with rapeseed oil at 180 ◦ C in a 1:5 (w/w) ratio for 24 in grams per kilogram (g/kg); 0.9 is the conversion factor of total cap­
h. The powder and oil products were freshly processed one month before saicinoids; 0.1 is the conversion factor for the content of the remaining
the experiment. The powder samples were stored at room temperature capsaicinoids. And 16.1 × 103 is the coefficient of conversion of the
(26 ◦ C), whereas the oils were kept at refrigerator (4 ◦ C). sample’s capsaicin and dihydrocapsaicin content to the SHU, whereas
The reference standards of capsaicin (≥95 % purity) were procured 9.3 × 103 is the coefficient of conversion of the remaining capsaicinoids’
from Aladdin (Shanghai, China), dihydrocapsaicin (≥95 % purity) were content to the SHU.
procured from Macklin (Shanghai, China) and stored at 4 ◦ C. Capsicum
oleoresin was purchased from Chenguang Biotech Group Co., Ltd. High- 2.3. Sensory evaluation for pepper powder and oil by a trained panel
performance liquid chromatography (HPLC)-grade acetonitrile, acetic
acid, methanol, and ethanol were obtained from Sigma-Aldrich 2.3.1. Panelists selection and training
(Shanghai, China). The panel consisted of 11 panelists (4 males and 7 females) with a
mean age of 25.6 ± 2.0 years (mean ± SD) were recruited from
2.2. HPLC analysis of capsaicinoids in pepper powder and oil Shanghai Jiao Tong University. Before this study, they had long-term
experience (exceeding 80 h) in quantitative descriptive analysis (QDA)
2.2.1. Standard solutions preparation and could discriminate pungency intensity. All panelists were confirmed
Solutions of capsaicin and dihydrocapsaicin (0, 0.5, 5.0, 12.5, 25.0, to show no pungency addiction or exclusion feelings and to have typical
50.0, 100.0 ppm) were prepared from a 1000.0 ppm stock solution of taste sensitivity satisfying ISO 8586 (2012) requirements.
pure capsaicin or dihydrocapsaicin by dissolving 10.5 g of each sub­ The panel attended ten 2-h training sessions. In the first two training
stance in 10 mL of methanol. Quantification of capsaicin and dihy­ sessions, seven varieties of pepper were introduced to the panel to
drocapsaicin was conducted by comparison to the retention times and strengthen their impression. The panel was then asked to score the
peak areas of external capsaicin and dihydrocapsaicin standards. pungency of three stimuli (0.25, 0.5, and 3.0 g/L capsicum oleoresin) on
a 100-point scale under red light in the next two sessions. The three
2.2.2. Extraction and analysis of capsaicinoids in pepper powder and oil ascending concentrations were assigned values of 33.0, 50.0, and 74.0
The pepper powder was dried for 3 h at 50 ◦ C in a continuous tem­ (Table S1 of Supplementary). It was ensured that the evaluators’ pun­
perature blast oven, then sieved using a 20-mesh standard sieve. Pepper gency ratings were within plus or minus 20 % of the group results.
powder (3.0 g) or oil (6.0 g) was weighed, and 20 mL of methanol were In other sessions, pepper powders and oils were provided to famil­
added to a 50 mL beaker. After sealing the breakers by plastic wraps iarize the panel with the sensory criteria and to feel the sensory expe­
with tiny holes, the mixtures were ultrasound-assisted (SK5200HP ul­ rience in two matrices. The panel was encouraged to describe the odor,
trasound system, Kudos, China) extracted for 30 min (80 ◦ C), then taste, flavor, and texture of pepper powders and oils. Then, some items
centrifuged at 4500 g and 4 ◦ C for 10 min. This precipitating process was such as hedonistic, quantitative, and similar terms were deleted under
repeated twice, and the supernatant was gathered for further analysis. the guidance of the panel leader. After several sessions of deliberation,
The supernatant phase was diluted to 50 mL using methanol. All the the panel settled on a list of descriptors and their definitions (Table 2).
diluted supernatants were filtered through 0.22 μm water filters (Navi­ Some reference samples were provided for confusing attributes during
gator, Lab instrument Co., Ltd., China). Three replicates of each sample another two sessions. Then the panel was trained to distinguish the low,
were performed. moderate, and high intensity ranges of each attribute.
Capsaicin and dihydrocapsaicin were quantitated on a high-
performance liquid chromatography with a diode array detector 2.3.2. Sensory criteria
(HPLC–DAD; Agilent 1260, Shanghai, China). The separation was per­ Each sample of powder (0.5 g) or oil (2.5 g) was supplied in a 27-mL
formed by a 250 × 4.6 mm, 5 μm, Shim-pack GIS column (Shimadzu, plastic cup with a lid for sniffing. The same amount of sample was served
Japan) at 35 ◦ C. The mobile phase was methanol/water (70:30, v/v) at with a 1 cm3 white steamed bread cube as a carrier in an 85 mL plastic
an isocratic flow rate of 1 mL/min. The sample injection volume was 20 plate for tasting (Labahua Co., Ltd, China). A three-digit number was
μL, and the LC run time was set to 15 min. The detection was achieved at assigned to each serving sample. All the samples were prepared 3–4 h
280 nm. Identification and quantification were performed with capsa­ before sensory tests and served at 25 ± 1 ◦ C.
icin and dihydrocapsaicin as external standards. Panelists were asked to chew the cubes with pepper powder or oil for
at least 20 s, and then expectorate. Palate cleaners included red carrot
2.2.3. Total capsaicin content and Scoville heat unit calculation and cucumber slices, white bread, water (room temperature), and full-
Around 90 % of capsaicinoids present in ordinary chili peppers are fat milk (Oldenburger, Germany). In each session, a maximum of four
capsaicin and dihydrocapsaicin (Zhang et al., 2021). To compute the samples were served with interstimulus intervals of 5 min to reduce
total capsaicinoids, the following equation (1) was used: sensory fatigue. The sensory criteria were applicative in both QMA and

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Y. Zhu et al. Food Chemistry 411 (2023) 135488

Table 1
Capsaicin, dihydrocapsaicin, and total capsaicin contents, and Scoville heat units (SHU) of seven varieties of chili pepper powder and oil as determined by HPLC.
Variety# Powder Oil Extraction rate (%)

Capsaicin Dihydrocapsaicin Total SHU Capsaicin Dihydrocapsaicin Total SHU Capsaicin Dihydrocapsaicin
(g/kg) (g/kg) capsaicinoid (g/ (g/kg) (g/kg) capsaicinoid (g/
kg) kg)

Indian 3.76 ± 1.26 ± 0.01 g 5.571 ± 0.14 g 85,909 0.24 ± < 0.11 ± < 0.01 g 0.39 ± < 0.01e 6044 6.41 ± 8.92 ± 0.14
0.11f 0.01 g 0.22
MTX 2.24 ± 1.23 ± 0.01f 3.849 ± 0.04f 59,348 0.34 ± < 0.21 ± < 0.01f 0.61 ± < 0.01 g 9447 15.39 ± 16.87 ± 0.26
0.03e 0.01f 0.27
e e e f
SZH 1.61 ± 0.53 ± 0.01 2.383 ± 0.07 36,753 0.27 ± < 0.10 ± < 0.01 0.41 ± < 0.01 6323 16.65 ± 18.94 ± 0.37
0.05d 0.01e 0.63
d d d d
ZDT 1.06 ± 0.46 ± 0.01 1.692 ± 0.03 26,089 0.13 ± < 0.07 ± < 0.01 0.21 ± < 0.01 3303 12.04 ± 14.14 ± 0.48
0.02c 0.01d 0.37
XYD 0.48 ± 0.30 ± 0.01c 0.864 ± 0.02c 13,325 0.08 ± < 0.06 ± < 0.01c 0.15 ± < 0.01c 2381 16.98 ± 19.30 ± 0.58
0.01b 0.01c 0.25
EJT 0.29 ± 0.17 ± 0.00b 0.503 ± 0.01b 7749 0.05 ± < 0.04 ± < 0.01b 0.09 ± < 0.01b 1456 17.06 ± 21.79 ± 0.94
0.01a 0.01b 0.69
a a a a
DL 0.16 ± < 0.09 ± < 0.01 0.277 ± 0.01 4279 0.02 ± < 0.02 ± < 0.01 0.04 ± < 0.01 661 11.17 ± 23.40 ± 0.34
0.01a 0.01a 1.08

Values are expressed as mean ± standard deviation of triplicate analysis. The same letter shows no significant difference between hybrids in the content of the total
capsaicin content according to Tukey’s HSD post hoc test (at p < 0.05).
#
MTX: Mantianxing; SZH: Shizhuhong; ZDT: Zidantou; XYD: Xinyidai; EJT: Erjingtiao; DL: Denglong.

Table 2
Qualitative multi-dimensional analysis of powder and oil of seven peppers.
Kind Variety# First location Strongest location Mode Dynamic characteristics

Property Latency time (s) Duration (min)

Powder Indian Tongue (80 %) Tongue (80 %) Surface Explosive 0–3 3–5
SZH Tongue (90 %) Tongue (80 %) Surface Explosive 0–3 3–5
MTX Tongue (70 %) Tongue (70 %) Surface Explosive 0–3 3–5
XYD Tongue (90 %) Tongue (70 %) Point Explosive 3–5 2–3
ZDT Tongue (80 %) Tongue (60 %) Point Explosive 0–3 1–2
EJT Tongue (70 %) Tongue (60 %) Point Delayed 0–3 2–3
DL Tongue (80 %) Tongue (70 %) Point Delayed 3–5 1–2

Oil MTX Tongue (73 %) Tongue (73 %) Surface Explosive 0–3 3–5
SZH Tongue (80 %) Tongue (60 %) Surface Explosive 3–5 3–5
Indian Tongue (64 %) Tongue (46 %), palate (36 %) Surface Delayed 3–5 3–5
ZDT Tongue (55 %), palate (27 %) Tongue (64 %), throat (27 %) Point Delayed 3–5 2–3
XYD Tongue (55 %), throat (36 %) Tongue (45 %), throat (36 %) Surface Delayed 3–5 2–3
EJT Tongue (80 %) Tongue (60 %), palate (30 %) Point Delayed 0–3 2–3
DL Tongue (90 %) Tongue (70 %), palate (20 %) Point Delayed 0–3 0–1
#
: MTX: Mantianxing; SZH: Shizhuhong; ZDT: Zidantou; XYD: Xinyidai; EJT: Erjingtiao; DL: Denglong.

QDA tests. samples into their mouths for taste, texture, and aftertaste evaluation.
The attributes were scored on a 100-point unstructured scale anchored
2.3.3. Qualitative multi-dimensional analysis (QMA) of pungency with none to extremely strong. Tests were performed in individual
perception of pepper powder and oil sensory booths. All the samples were assessed in random order over 12
At least 10 panelists attended each session of QMA. The introduction sessions separated by 24-h to prevent desensitization. The powder
was given, and time and location-related parameters of pungency were samples were analyzed first in six sessions, followed by the oil samples in
recorded in a questionnaire in Supplementary. QMA featured a stimu­ the remaining six sessions.
lation site, dynamic features (latency time, property, duration), and
pattern (Guzmán & Bosland, 2017). Pungency was characterized by the 2.4. Statistical analysis
degree and duration of burning in the orality (Schneider, Seuß-Baum, &
Schlich, 2014). The stimulation site includes the first and strongest lo­ Each test was performed in triplicate. The sensory data were repre­
cations to feel the pungency (the palate, tongue, lips, throat, and nose). sented as the mean value ± standard error (SE), while the rest were
The dynamic characteristics (latency time, property, and duration) of represented as the mean value ± standard deviation (SD). The total
pungency comprised delayed or explosive pungent sensation and its capsaicinoids and SHU were calculated using Eqs. (1) and (2), respec­
latency time and duration. Point stimulation based on pinching sensa­ tively. The mean values of the different parameters, one-way ANOVA
tion and surface stimulation based on burning sensation were among the and Tukey HSD test were employed with the software XLSTAT, in which
stimulation modes available. p < 0.05 was used to determine the significant difference between
samples. The contrast of numbness, astringent and burning in mouthfeel
2.3.4. Quantitative descriptive analysis (QDA) of pepper powder and oil and after-effect were analyzed by t-test (p < 0.05). Pearson correlation
The panel (n = 11) was required to score the intensities of the sen­ analysis by SPSS (Version 23.0, IBM Inc., New York, USA) was per­
sory attributes (Table 2). Firstly, the panel was requested to remove the formed to determine the correlative effects.
plastic cup lid and sniff the samples. Then they were asked to put the

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Y. Zhu et al. Food Chemistry 411 (2023) 135488

3. Results and discussion slurping and swallowing procedure, whereas here the excretory pro­
cedure was used. The swallowing action allows the stimulus to reach and
3.1. The total capsaicinoids and SHU in pepper powder and oil remain more in the throat area, leading to a stronger perception. This
distinction is also related to the type of stimulation. Most of research
The contents of capsaicin, dihydrocapsaicin and total capsaicinoid in employed capsaicin in aqueous and oil-based solutions rather than
chili pepper powders and oils were shown in Table 1. The total cap­ actual pepper samples as we did. When the panelist placed the sample in
saicinoid contents ranged from 5.571 ± 0.139 g/kg in Indian pepper the mouth, the pepper sample dropped in by gravity and came into
powder to 0.277 ± 0.005 g/kg in DLJ pepper powder (p < 0.05), cor­ direct contact with the tongue resulting in the strongest stimulation.
responding to SHU values of 85,909 and 4279, respectively. The MTX Interestingly, this study found a trend in the location, mode, and
powder had lower total capsaicin content (3.849 ± 0.039 g/kg) than dynamic characteristics for the perception of peppers. According to the
Indian ones (p < 0.05). Our findings on total capsaicinoids and SHUs perceived pungency ranking results in Table 2, the more pungency had a
match prior studies on mature, dry chili peppers (Sweat, Broatch, Bor­ surface stimulation mode, implying that the pungency extended across
ror, Hagan, & Cahill, 2016; Topuz, Dincer, Ozdemir, Feng, & Kushad, the orality. Additionally, peppers with a higher pungency intensity
2011). exhibited an explosive sensation, a shorter latency period (0–3 s), and a
The indices exhibiting pungency in the oil group tended to be lower longer duration (3–5 min), such as pepper powders and oil of MTX.
than those in the powder group. For example, the oil of MTX had the Some descriptors such as the sharp heat (sense of a pinprick) and the
highest total capsaicin content (0.613 ± 0.004 g/kg), and the next was flat heat (sense of a brush coating), have been proposed for the specific
SZH (0.410 ± 0.003 g/kg) and Indian (0.392 ± 0.004 g/kg). While the application in fresh peppers (Guzmán & Bosland, 2017). However, this
total capsaicin contents in the powders of MTX, SZH and Indian peppers study modified the sensation mode to include “point” and “surface”
were 3.849 ± 0.039, 2.383 ± 0.070, and 5.571 ± 0.139 g/kg. The su­ stimulations to fit the powder and oil samples. The panel defined the
pernatant oil was chosen to portray the pungency level of oil in this surface mode as scorching, heatwave-like, and even searing sensations
study, while a large proportion of capsaicin-like material remained in throughout the mouth. In contrast, the point mode was hot or burning in
the precipitate. This procedure generally resulted in lower total capsa­ specific areas of the mouth, most notably in the tissue contacted by
icin levels in the oil samples. The heat treatment during the preparation pepper seeds. And when the level of pungency increased, a more “sur­
of pepper oils might lead to the degradation of capsaicin and dihy­ face” mode developed.
drocapsaicin (Mba, Dumont, & Ngadi, 2017). In addition, the lipid Two temporal qualities (lag time, overall duration) and three spatial
peroxide free radicals are produced in large amounts after rapid heating qualities (longitudinal location, lateral location, localized/diffuse) have
of the oil, which also leads to the possible degradation of capsaicin by been discovered in capsaicin (Cliff & Heymann, 1993). This research
the free radical attack (Mba et al., 2017; Zhang, Chen, Chen, Yang, & extended this complicated matrix of pungency sensory perception to
Kan, 2021). pepper powders and oils, which allowed for greater variation in the
The dihydrocapsaicin dissolved more in oil than capsaicin when pungency level and dynamic properties. Therefore, these elements of
comparing the extraction rate of these two compounds (Table 1). In the pungency perception in peppers might be an indicator to scale the level
oil matrix, the degradation rate of dihydrocapsaicin increased more of pungency, which provided explicit instructions for training the panel.
slowly than that of capsaicin. It was probably because the former had a
higher molecular saturation and thermostability (Zhang et al., 2021). 3.3. Sensory profile of pepper powder and oil
Despite that, the contents of capsaicin and dihydrocapsaicin were still
highly correlated in both pepper powders (correlation coefficient (r) = 3.3.1. Sensory wheel development
0.914) and oils (r = 0.947). These findings corroborated those of Lozada A total of 32 and 31 attributes were developed in pepper powders
et al., who discovered that r-values between capsaicin and dihy­ and oils through term selection and grouping. They were separately
drocapsaicin concentrations were significant (p < 0.001). They ranged depicted in a three-tiered wheel (Fig. 1). Sensory attributes were clas­
between 0.88 and 0.90 across dried chile peppers (Lozada, Coon, sified into the following categories: appearance, odor, taste, flavor,
Guzmán, & Bosland, 2021). In general, the pungency indices in this mouthfeel, and aftertaste-effect, as seen in the inner circle. The middle
paper were in the same order of magnitude as other reports, but variety was assigned to distinct sub-groups to which attributes belong. Finally,
and geographical origin still led to inconsistencies between chili oil and all the qualities were listed on the exterior. Definitions and references
powder groups. for sensory attributes were also provided in Table 3.
Sensory attributes of pepper powders and oils varied according to the
3.2. Qualitative multi-dimensional pungency profile of peppers different processing procedures such as baking and oil extraction. For
example, the dry wood, musty, grassy odors, and earthy flavor were
The perceived stimulation locations and dynamic characteristics discovered in the pepper powder, while the rapeseed oil odor and greasy
(latency time, property, and duration) of pungency in pepper powders mouthfeel were found in the oil group. The reason might be that the
and oils were summarized in Table 2. Based on the first and strongest heated oil extraction kept the oil flavor and masked some odors of
stimulation locations chosen by more than half of the panelists, the pepper powder. The wheels demonstrated the sensory characteristics of
powder stimulated the tongue, while the oil stimulated the throat and powders and oil, which had significance for evaluating pepper products
palate. Given that chemical analogues of capsaicin and their concen­ in the food industry.
trations differ among species will result in diverse pungent perceptions.
Specifically, capsaicin and dihydrocapsaicin can stimulate the mouth, 3.3.2. Quantitative descriptive analysis (QDA)
palate, throat, and back of the tongue (Krajewska & Powers, 2006). The attributes that differed significantly (p < 0.05) in the powders
These locations were also reported in our study. For dynamic charac­ and oils of seven chili peppers were depicted in Fig. 2, respectively. Four
teristics, these two chemicals in aqueous solutions were observed to attributes were used to define the appearance, including red, yellow,
cause the first stimulation in the throat (Schneider, Seuss-Baum, & particle size, and uniformity. Color is an essential factor in determining
Schlich, 2014). And capsaicin responded more strongly to stimulation in the commercial quality of peppers. Differences in color among pepper
the throat than in the front or rear of the tongue (Rentmeister-Bryant & varieties at the same stage of maturity are mainly attributed to different
Green, 1997). However, the tongue was the first and strongest location flavonoid and carotenoid accumulation patterns (Liu et al., 2020). In
for pepper powders and oils in our study, though throat and palate were this paper, Indian peppers exhibited the reddest but the least yellow
also mentioned by some panelists. The plausible explanation for the appearance, but DL peppers were the exact opposite. Indian pepper
inconsistency is that the location found in the literature is based on the powders had the highest contents of capsaicin (3.759 ± 0.114 g/kg) and

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Y. Zhu et al. Food Chemistry 411 (2023) 135488

Fig. 1. Sensory wheel of chili pepper powder (a) and oil (b).

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Y. Zhu et al. Food Chemistry 411 (2023) 135488

Table 3
Consensus vocabulary for pepper powder and oil developed by 11 trained Chinese panelists during sensory profiling.
Attribute Definition Reference Anchors Powder Oil

Appearance
Red Red color of pepper White to red √ √
Yellow Yellow color of pepper White to √ √
yellow
Particle size Size of shape of pepper particles Small to large √ √
Uniform shape of pepper particles Irregular to √
regular

Odor
Pepper The overall aroma of chili peppers Nil to extreme √ √
Peppery Salt Aroma of pepper fried with salt 0.05 g of Pepper salt powder (McCormick, Nil to extreme √ √
Shanghai) into 27 mL tasting cup with lid)
Choking Impact and tingling aroma Nil to extreme √ √
Dry wood Woody aroma from cutting wood Solid wood laminate flooring blocks Nil to extreme √
Herb Aroma associated with cumin, which is characterized as dry, spicy, 0.05 g of cumin (Cangyao, Guangxi) to a 27 mL Nil to extreme √ √
woody and floral tasting glass with lid
Pickled Aroma produced when vegetables are pickled in salt, which is linked Nil to extreme √ √
vegetable with pickle jars
Choking oil Aroma of vegetable oil when heated to high temperature Nil to extreme √ √
Musty Aroma emitted when the spice is wet and moldy Nil to extreme √
Smoky Aroma associated with dry dust when wood is burned Nil to extreme √ √
Grassy Sharp, slightly pungent aroma associated with plants or vegetables Nil to extreme √
(such as spinach, fresh grass, etc.)
Rapeseed oil Aroma of rapeseed oil 0.05 g of rapeseed oil (Xiancan, Chengdu) to a 27 Nil to extreme √
mL tasting glass with lid

Taste
Salty Elicited by sodium chloride Nil to extreme √ √
Bitter Elicited by caffeine Nil to extreme √ √
Sour Elicited by citric acid Nil to extreme √ √

Flavor
Herb Flavor associated with cumin, which is characterized as dry, spicy, 0.05 g of cumin (Cangyao, Guangxi) to a 27 mL Nil to extreme √ √
woody and slightly floral tasting glass with lid
Smoky Flavor associated with dry dust when wood is burned Nil to extreme √ √
Spice Flavor produced by mixing with various spices Nil to extreme √ √
Earthy Flavor from soil and vegetation with moisture Nil to extreme √
Rapseed oil Flavor of rapeseed oil 0.05 g of rapeseed oil (Xiancan, Chengdu) to a 27 Nil to extreme √
mL tasting glass with lid

Mouthfeel
Overall Integration of the irritation, numbness, and burning sensation Nil to extreme √ √
pungency produced by the chili pepper after stimulating the mouth
Greasy Sensation oil left in the mouth Nil to extreme √
Numbness Sensation of numbness, reduced or lost taste on the tongue and the Nil to extreme √ √
surface and/or edges of the mouth
Astringent Wrinkled or astringent sensation on the surface and/or edges of the Nil to extreme √ √
tongue and mouth, associated with tannins or alum
Burning Hot, dry sensation that occurs when the tongue and mucous Nil to extreme √ √
membranes, etc.
Grainy Sensation produced by chili pepper particles stimulating the mouth Nil to extreme √ √
Tingling Stinging and painful sensation on the surface and/or edges of the Nil to extreme √ √
tongue and mouth

After-effect
Rapeseed oil Residual rapeseed oil odor and flavor in mouth after swallowing 0.05 g of rapeseed oil (Xiancan, Chengdu) to a 27 Nil to extreme √
mL tasting glass with lid
Bitter Residual bitterness in mouth after swallowing Nil to extreme √ √
Numbness Sensation of numbness, reduced or lost taste on the tongue and the Nil to extreme √ √
surface and/or edges of the mouth
Astringent Wrinkled or astringent sensation on the surface and/or edges of the Nil to extreme √ √
tongue and mouth, associated with tannins or alum
Burning Hot, dry sensation that occurs when the tongue and mucous Nil to extreme √ √
membranes, etc.
Grainy Sensation produced by chili pepper particles stimulating the mouth Nil to extreme √ √

dihydrocapsaicin (1.255 ± 0.012 g/kg) among all samples based on the redder the pepper variety will be, and vice versa, the more yellow it
HPLC analysis. Both were lowest in DL pepper powders (0.162 ± 0.003 will be.
g/kg capsaicin, 0.088 ± 0.002 g/kg dihydrocapsaicin). And the capsa­ ZDT peppers had the most uniform and smallest particle size, while
icin shows a red color (Gómez-García Mdel & Ochoa-Alejo, 2013). diversity was found in EJT. In the powder group, homogeneity was
Therefore, it can be deduced that the more capsaicin in a pepper variety, negatively correlated with particle size (r = − 0.557, p < 0.01). In

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Y. Zhu et al. Food Chemistry 411 (2023) 135488

Fig. 2. Significant sensory attributes of powders and oils of seven chili peppers. (a) appearance, (b) powder taste, odor and flavor, (c) mouthfeel, (d) after-effect of
powders. (e) Appearance, taste, odor and flavor, (f) mouthfeel of powders. Attributes are different with levels of significance: ** p < 0.01. are significantly different
via Tukey’s HSD at p < 0.05. Note: MTX: Mantianxing; SZH: Shizhuhong; ZDT: Zidantou; XYD: Xinyidai; EJT: Erjingtiao; DL: Denglong.

addition to inaccurate crushing, this may be related to the size of the slightly lower than those for mouthfeel sensations. This could be owing
seeds and the hardness of the peel. Physical qualities varying with to capsaicin’s masking impact on flavor (Kostyra, Baryłko-Pikielna, &
different varieties of peppers can result in different shrinkage rates Dąbrowska, 2010). According to the published article, oral capsaicin can
during drying and the formation of complex porous or fibrous structures conceal gustatory and olfactory perceptions but cannot impair flavor
(Fries, 2021). Combined with the findings in wheat: harder wheats have identification to some extent (Lawless, Rozin, & Shenker, 1985). The
more uniform grains after breakage than softer wheats, while softer sweetness was too weak to be detected in pepper or oil, yet the sourness
wheats have a higher proportion of grains after breakage (Campbell, was detected. This is consistent with an existing finding that sweetness
Fang, & Muhamad, 2007). Thus, it might be concluded that the smaller was all reduced by capsaicin, but did not affect sourness (Prescott &
the pepper with similar sized seeds and the softer the peel, the more Stevenson, 1995a).
uniform and finer the particles after crushing. According to the previous study, sixteen aroma compounds in fried
The perceived scores for taste, odor, and flavor attributes were mountain peppers were categorized into four groups based on their

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Y. Zhu et al. Food Chemistry 411 (2023) 135488

olfactory characteristics: oily, citrus, herbal–like, and others (mush­ solutions (0.080–0.31 ppm) (Lawless, Hartono, & Hernandez, 2000;
room, caraway and camphoreous) (Ni, Wang, Zhan, Tian, & Li, 2021). In Schneider et al., 2014, 2015). Allyl isothiocyanate, a trigeminal sensory
line with this study, we found oily, herbal–like, and wood-like odors in stimulant similar to capsaicin, has a lower pungency strength in oil-
dried peppers. In particular, DL peppers tended to be woodier, and had based carriers than in water-based carriers (Eib, Schneider, Hensel, &
higher scores for earthy and dry wood odors than other peppers. But Seuß-Baum, 2021).
their pepper and peppery salt odors were the weakest. Indian peppers Pungency sensation is a type of chemesthesis that includes tingling
had the strongest pepper aroma and bitter taste. Despite the general and numbing sensations, as well as pain, warmth, and touch (Zhao,
opinion that capsaicinoids are flavorless, dihydrocapsaicins have a Zhang, Zhong, Shi, Wang, & Wang, 2022). It was purposed that the
peppery odor and a slightly sour taste (Krajewska & Powers, 2006). As a sensory output of peppers was general pungency, which included
result, peppers containing more capsaicinoids and dihydrocapsaicins burning, numbness, astringency, tingling, and grainy sensations. In both
would express a fabulous pepper and peppery salt aroma. Hexanal the pepper powders and oil groups, the overall pungency was substan­
(grassy, bell pepper), octanal (sweet, sickly/musty, grassy, rancid), 1- tially associated to mouthfeel sensations such as numbing, burning,
octen-3-one (mushroom), 1-octen-3-ol (fatty, sickly/musty, mush­ tingling, astringent, and grainy (p < 0.01). The r-values of the first three
room) were identified as odor active compounds in DL peppers by gas sensations, in particular, was greater than 0.60 (Table S2). We found a
chromatography/sniffing port analysis (Van Ruth, Roozen, Cozijnsen, & more positive relationship between burning sensation and overall pun­
Posthumus, 1995). Then the accumulation of these components resulted gency in both powder (r = 0.903, p < 0.01) and oil (r = 0.880, p < 0.01)
in woody, herbal-like odors in peppers. Yang et al. (2020) found that groups, implying that the burning sensation mostly determines pepper
capsaicin inhibited the in-nose aroma release of 3-methylbutanal, pungency.
1-octen-3-ol, and linalool in an ice-cube model. This may explain why Overall pungency is correlated with dihydrocapsaicin, capsaicin, and
the more pungent peppers (for example, Indian peppers) tended to have SHU content, with r-values higher than 0.650 in pepper powders
an unsaturated or unbalanced flavor profile in this study. (Table 4). On the other hand, this relationship existed in pepper oils with
Since pepper powder is treated with hot air during processing, it is a smaller r-value (<0.605). Thus, SHU was particularly rational in
inevitable to produce Maillard reactions and obtain unique flavors and assessing the burning and tingling sensations in pepper powders, but the
colors. According to Song et al. (2021), the primary components in chili capsaicin in pepper oils. In certain studies, linear associations between
powder during the Maillard reaction were olefins, alcohols, esters, al­ sensory pungency and concentrations of isolated natural capsaicinoids
dehydes, and ketones, and flavor attributes varied between samples. The have been detected within a narrow range. For example, the total pun­
differences between sweet pepper Capsicum genotypes are determined gency of the capsaicin mixture was highly correlated with the sum of the
by phenolic derivatives, greater alkanes, sesquiterpenes, and lipid- pungencies of the individual capsaicin (Krajewska & Powers, 2006).
derived volatiles (Eggink, Maliepaard, Tikunov, Haanstra, Bovy, & Even the coulometric electronic tongues have been developed as an
Visser, 2012). Besides that, carotenoids contribute to the aroma and alternative to estimate the pungency of some chilis to avoid unpleasant
flavor of food. Octanal and hexanal both exhibit green aroma, 1-octen-3- feelings and difficulties in evaluating chili peppers (Dejmkova, Moro­
ol has an attractive mushroom aroma (Song et al., 2021). Wood is a zova, & Scampicchio, 2018; Morozova, Rodríguez-Buenfil, López-
characteristic of ketoisophorone (Korkmaz et al., 2020). Also, these Domínguez, Ramírez-Sucre, Ballabio, & Scampicchio, 2019; Oney
volatile chemicals may contribute to the pepper’s musty or earthy odors Montalvo, Morozova, Ferrentino, Ramirez Sucre, Rodríguez Buenfil, &
and flavors in peppers. Certain characteristics (sweetness, malty taste, Scampicchio, 2021). However, research is somehow limited to con­
and juiciness) of sweet peppers with different genotypes can be pre­ ventional chemicals or simple matrices. In a more complex dietary
dicted using volatile and/or non-volatile chemicals. However, flavor matrix, the sensory responses can be affected by other factors besides the
characteristics such as grassy, perfumed, musty, carrot, petrified, and capsaicin concentration. Our investigation found that perceived pun­
mung bean could not be predicted significantly (Eggink et al., 2012). gency was not entirely dependent on total capsaicinoid concentration or
Therefore, additional research on the components that contribute to the SHU. Although most studies have found that capsaicin and dihy­
unique wood-like aroma profile found in many pepper species is needed, drocapsaicin account for approximately 90 % of pungency, undetectable
as this will aid in the scientific breeding of peppers. but still present derivatives may promote the pungency perception.
The rankings of the powders and oils of seven peppers based on Therefore, this correlation needs to be optimized by measuring a more
perceived overall pungency were: Indian > MTX > SZH > ZDT > XYD > comprehensive range of capsaicin derivatives in different matrices.
EJT > DL (powder); MTX > SZH > Indian > ZDT > XYD > EJT > DL
(oil). The SHUs revealed a consistent ordering of perceived pungency,
which indicated a positive correlation between perceived pungency and
SHU.

3.4. The relationship between pungency perception, capsaicinoid content Table 4

and SHU Correlation coefficients between Scoville Heat Unit (SHU), content of capsaicin
and dihydrocapsaicin by chemical analysis and overall pungency, numbness,
There was no significant difference in partial mouthfeel sensations stringent, burning, grainy, tingling by quantitative descriptive analysis and in
(numbness, astringency, and burning) during chewing and after spitting powder and oil of seven chili peppers (p < 0.01).
out pepper powder. However, there was a significant difference in Group Chemical index Sensory attribute
numbness (p = 0.007) and burning (p = 0.050) in oils (Fig. 2(d)). Overall Numbness Burning Tingling
Numbness is linked to pungency in the oil group, with a lower r-value pungency
(0.686, Table S2). Compared to oils, the relationships between overall Powder SHU 0.670 0.619 0.693 0.689
pungency and numbness, burning, and tingling in powder had greater r- Capsaicin 0.657 0.613 0.681 0.680
values. Because of its powerful residual nature, the oil protects the Dihydrocapsaicin 0.673 0.606 0.694 0.682
tongue from the immediate pungency (Schneider, Seuß-Baum, &
Schlich, 2015). Still, it also extends the pungency across the mouth, Oil SHU 0.592 0.466 0.593 0.586
intensifying the experience in the palate and throat. In general, higher Capsaicin 0.605 0.469 0.605 0.601
fat levels are associated with lesser pungency, as evidenced in various Dihydrocapsaicin 0.540 0.440 0.543 0.530

carriers or matrices (Schneider et al., 2014). Capsaicin in oil solutions Values close to 0 and 1 correspond to low and high correlation. The values are
has a better estimated threshold (0.826–11.75 ppm) than in aqueous different with levels of significance: p < 0.01.

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Y. Zhu et al. Food Chemistry 411 (2023) 135488

4. Conclusion Quality and Preference, 87, Article 104039. https://doi.org/10.1016/j.

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