Journal of Agriculture and Food Research 15 (2024) 100916

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Journal of Agriculture and Food Research

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Study on the preparation and use of edible coating of fish scale chitosan and
glycerol blended banana pseudostem starch for the preservation of apples,
mangoes, and strawberries
Betelhem Abera a, b, Ramesh Duraisamy a, *, Tewodros Birhanu a
a
Department of Chemistry (Industrial Chemistry Division), College of Natural & Computational Sciences, Arba Minch University, Arbaminch, Ethiopia
b
Department of Chemistry, Adigrat University, Adigrat, Ethiopia

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

Keywords: Agro-industries and the fish processing sector generate large amounts of waste, which may be converted into
Agro-wastes useful ingredients for preserving fruit. Studies show that starch-based edible film still needs some improvement
Banana pseudostem starch because it’s brittle and weaker, which might be improved by adding chitosan. The study aimed to investigate the
Composite film
optimal composition of edible film-forming material prepared from banana pseudostem starch and fish-scale
Fish scale chitosan
Fruit preservation
chitosan to preserve the selected fruits. In the current study, chitosan and starch were extracted from the
waste of Nile tilapia fish scale and Dwarf cavendish banana pseudostem as found to be 29.66 ± 0.46 % and 4.26 ±
0.21 %, respectively. Central composite response surface experimental design combined banana pseudostem
starch, chitosan, and glycerol to prepare the edible films. Using the Design-expert program, the ideal film-
forming composition with an overall acceptability of 0.968 was identified based on the physico-mechanical
characteristics of the created composite edible films. It comprised 15 mL of 1 % banana pseudostem starch,
3.2 mL of 0.5 % chitosan, and 0.6 mL of 30 % glycerol. The persistence of the microbial load on coated and
uncoated fruits throughout the storage was also assessed in the study. The microbial and fungal growth was
significantly lower (>37 %) in optimal edible film-coated fruits than in the control fruits. After 28 days of storage
of fruits at room temperature, the microbial count (in CFU/mL) on the edible coated surfaces of apples, mangoes,
and strawberries was found to be 2.04 ± 0.32x103, 2.71 ± 0.29x103, and 2.5 ± 0.51x104, respectively. Also
noticed the fungus counts of 1.86 ± 0.48x03 (in apples), 1.09 ± 0.11x104 (in mangoes), and 1.56 ± 0.04x104 (in
strawberries) in the studied coated fruits after 28 days of storage. Furthermore, the film-coated fruits had a
significantly lower weight loss than uncoated fruits. Thus, the studied banana pseudostem starch-chitosan-
glycerol composite edible coating potentially preserves by inhibiting the development of natural microbes
when storing apples, mangoes, and strawberries, and it is adequate to extend their shelf life.

1. Introduction achieve better barrier and mechanical properties [3]. Adequate con­
servation of fruits extends the shelf life in the post-harvest [4]. Modified
Fruits and vegetables provide an abundant and inexpensive energy starch-based biodegradable coatings have been used successfully in
source, nutrients, vitamins, and minerals. Their nutritional value is high preserving fruits, as stated in earlier studies (as shown in Table 1).
when fresh, but they have a short shelf-life [1]. Different microorgan­ According to the literature (shown in Table 1), some properties of
isms can spoil them rapidly, greatly influenced by their composition, starch-based edible films developed from different sources still need
production technology, applied packaging material, etc. Researchers are improvement. However, native starch-based films are brittle and weak,
developing and using edible films made from natural materials, like agro which can be improved by chemical, physical, and enzymatical modi­
products and animal waste, to preserve fruits (Table 1) [2]. Edible films fication. A standard method to enhance starch-based films’ physical and
contain one or more organic constituents (polysaccharides, lipids, and mechanical properties is adding plasticizers like glycerol and sorbitol
proteins), a solubilizing media, and plasticizers. These are combined to [5–19]. In most cases, the practical application of coatings reduces the

* Corresponding author.
E-mail addresses: betelehemabera2017@gmail.com (B. Abera), drrameshmcas@gmail.com, ramesh.duraisamy@edu.et (R. Duraisamy), teddybir@gmail.com,
tewodros.birhanu@amu.edu.et (T. Birhanu).

https://doi.org/10.1016/j.jafr.2023.100916
Received 14 October 2023; Received in revised form 1 December 2023; Accepted 6 December 2023
Available online 11 December 2023
2666-1543/© 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-
nc-nd/4.0/).
B. Abera et al. Journal of Agriculture and Food Research 15 (2024) 100916

Table 1 Table 1 (continued )

The starch-based natural edible coatings (polymer and additive composites) Composites (type of Studied film The main results of Reference
applied to fruits and their advantages with results of improved properties. edible coating properties/fruits to improved properties
Composites (type of Studied film The main results of Reference composition) preserve
edible coating properties/fruits to improved properties properties and colour
composition) preserve characteristics, and
Rice starch (2 % w/ Studied the film Tensile strength and [7] great sensory
v), Stearic acid properties through elongation-at-break acceptance.
(0.3 % w/v) XRD and FTIR of film improved 3 % cassava starch, Studied the Edible coating with [16]
Carrageenan (2 % when Carrageenan 4 % Arrowroot Physicochemical sorbitol plasticizer of
w/v), Glycerol was increased. starch, and 5 % Properties of films arrowroot starch (4
(30 % w/v), Canna starch %) provides the best
Tween 20 (0.2 % physicochemical
w/v) properties.
Pea starch (4 % w/ Apple, Tomato All the coatings [11] Cassava starch (2 Mango Extending the shelf [17]
v), Potato starch Cucumber better retained KS %); chitosan (2 life of the Mango.
(4 % w/v), Guar concentration on the %); cassava
gum (1 % w/v), fruit surface during starch/chitosan
glycerol (ratio refrigerated storage (2 %)
(polymer: to provide effective Sweet corn starch, Studied the The mechanical, [18]
glycerol 2:1), antifungal activity. 10–40 % and Poly mechanical, thermal, thermal, and barrier
Potassium (N-Vinyl-2- and barrier properties of the
sorbate (KS) (1 % Pyrrolidone) properties Starch films were
w/v) improved through
Cassava starch (1.0, Strawberry Cassava starch [12] PVP incorporation
2.0 and 3.0 % w/ coatings, with or inside the starch
v), Potassium without potassium matrix.
sorbate (0, 0.05 sorbate, did not cause 5 g of tef starch, 0.4 Studied the Starch-based edible [19]
and 0.1 % w/v) changes in g of agar, and 0.3 mechanical biofilm with 23.18
strawberries’ % glycerol properties MPa of tensile
mechanical strength, 1.42 % of
properties, colour, or elongation at break,
sensory acceptance. 88.67 MPa of elastic
Coatings showed modulus, 10.65 N of
good integrity for 2 % puncture force, and
and 3 % starch, 12.65 mm of
reducing the puncture
strawberries’ deformation
respiration rate.
Starch (2 % w/v), Strawberry Starch coatings were [13]
Carrageenan (0.3 less effective at weight loss and ripening rate; a series of physical and biochemical
% w/v), Chitosan reducing loss of changes occur that vary depending on the type of fruit [5].
(1.0 % w/v), firmness than Plasticizers make films more flexible, but they also make them
Sorbitol (2 % w/ chitosan and
v), Glycerol (0.75 carrageenan films,
weaker; to solve this problem, chitosan can be added to improve the
% w/v) Tween 80 which better reduced physicochemical properties of starch-based films. In other words, adding
(0.01–0.1 % w/ the fruit weight loss. chitosan to a starch-based film with glycerol or sorbitol can make the
v), Calcium The minimum film more flexible and more robust at the same time. This is because
chloride firmness loss was
chitosan can form intermolecular bonds with starch, which helps
obtained with
carrageenan and improve the film’s structure and physical properties, increase gloss
calcium chloride values, transparency, and antibacterial activity, and reduce the coating
coatings. mixture’s wettability [6,7].
Starches with Strawberry Both sorbitol and [14] The banana is a tropical herbaceous plant whose stem comprises
medium amylose glycerol contributed
content (MAS) to reducing weight
concentric layers of leaf sheaths. After harvesting, the pseudostem is
(corn and potato loss and maintaining typically cut down and left to decompose in the soil to become waste.
starch); Starches the texture and Therefore, using banana stems will significantly benefit the environment
with high surface colour of and generate additional benefits for farmers [8]. Starch and other
amylose content fruits. Coatings with
polysaccharides from banana pseudostem are promising materials for
(HAS) (corn sorbitol exhibited
starch, better water vapor film-forming compounds. Furthermore, the banana stems are readily
genetically barrier capacity than available, nutritious, low-cost, biodegradable, biocompatible, and
modified and those containing edible with better functional properties [9].
acorn starch glycerol. Sorbitol at 2 Chitosan, obtained from fishery waste, has unique properties: clean,
product (HAP) (2 % w/v was the most
% w/v) Glycerol effective plasticizer
rigid, flexible, suitable oxygen barriers, biocompatibility, biodegrad­
and sorbitol (0, option. ability, non-toxicity, physiological inertness, and excellent film-forming
1.0 %, and 2 % capacity [7,10]. Also, chitosan is a positively charged polymer that can
w/v) interact with negatively charged polymers, such as starch. This inter­
Cassava starch (1.0 Fresh-cut mango Cassava starch [15]
action can be used to create composite edible films that are stronger and
% w/v) and (Pre-treated with 0.5 coatings and citric
Glycerol (1.0 % % w/v citric acid and acid dipping more durable than films made from either starch or chitosan alone.
w/v) 0.05 % w/v peracetic promoted decreased Despite the potential benefits of this approach, there have been no prior
acid) respiration rate, studies on using blended edible films made from banana pseudostem
better preservation of starch and chitosan to preserve fruits and vegetables. Thus, this study
mechanical
aimed to investigate the optimal composition of the
starch-chitosan-glycerol composite edible coating solution for

2
B. Abera et al. Journal of Agriculture and Food Research 15 (2024) 100916

preserving apples, mangoes, and strawberries. to the literature [21,26].

2. Materials and methods 2.4.2. Determination of swelling power, solubility, and water absorption
capacity
2.1. Materials The starch (1 %, w/w) and chitosan (0.5 % w/w) were prepared
using water and glacial acetic acid, respectively. The solutions were kept
Banana pseudostems (Musa acuminate spp.) were collected from (at 70 ◦ C) separately in a flask and shaken every 5 min for 30 min. The
banana cultivars in Arba Minch, Ethiopia. Nile tilapia (Oreochromis slurry was centrifuged for 10 min at 5000 r.p.m (for swelling power &
niloticus) fish scales were collected from Ethio-fishery, Arba Minch, solubility, calculated using Eqns. (3) and (4), respectively) and 15 min at
Ethiopia. Researchers selected the fruits depending on storage time, 1000 rpm (for water absorption capacity, WAC; it was calculated using
availability, and harvesting stage. Apple (Malus domestica) was collected Eqn. (5)) according to the literature [27].
from cultivators in Chencha during the better harvesting time of apples.
Swelling power = (Sedimental paste weight, g / Dry sample weight, g) (3)
Mango (Mangifera indica) was collected from cultivators in Kulfo, and
the selection was based on peel color and development of the shoulder. Solubility = (Dried residue weight, g / Dry sample weight, g)100 (4)
Fresh strawberry (Fragaria x ananassa) was ordered from the suppliers in
Arba Minch market, Arba Minch, Ethiopia. Glycerol (98 %, w/v) and WAC (%) = (Weight of Water hold, g / Weight of sample at initial, g) 100
glacial acetic acid were obtained from the Arba Minch University, (5)
Ethiopia Chemistry laboratory.
2.4.3. Structural analysis using FTIR
2.2. Banana pseudostem starch preparation FTIR spectrum of the banana pseudostem starch, chitosan, and the
optimized film was recorded using an FTIR spectrometer (Spectrum 65,
The starch content in different varieties of banana pseudostem, PerkinElmer) by employing the KBr pellet method; frequency 4000 -
namely, Dwarf Cavendish, Giant Cavendish, and Poyo (1 kg from each 400 cm− 1 range was used for each spectrum [2,20].
variety), was analyzed separately. The pseudostem was cut into longi­
tudinal pieces and crushed with water (1:2 w/v ratio). After grinding, 2.5. Edible film preparation
the starch slurries were kept for sedimentation for 12 h. Starch was
allowed to settle in the container, the upper liquid portion was removed, The starch solution was prepared (by dissolving the 5 g of starch in
and the starch was separated. About 1 % sodium sulfate solution was 100 mL of distilled water) and heating it for 20 min on a hot plate
added to the crude starch for 5 min and washed with distilled water. The (85 ◦ C). Chitosan solution was prepared by mixing 2 g of chitosan with 2
prepared crude starch was kept for evaporation and dried. The yield of % glacial acetic acid (100 mL). The dispersion was carried at 50 ◦ C with
the obtained starch was calculated [20] as given in Eqn. (1): The banana stirring until the solution was completely homogenous. After that, the
stem with a high percentage of starch and abundance in the study area solution was filtered to remove any residue. The practical range level
was used for film formation from the three varieties. and optimization of starch, chitosan, and glycerol were prepared by
keeping their concentration ratios as described in Table 2. The starch-
Yield = (Mass of dried starch, g / Total mass of pseudostem, g) x 100 (1)
chitosan-glycerol solutions were homogenized using a stirrer for 45
min and dried (at 40 ◦ C) for 24 h in a Petri dish. The casted edible film
2.3. Chitosan preparation was peeled off, kept in plastic bags at ambient temperature, and
remained in desiccators before further examination [28].
The collected fish scales (700 g) were washed with pure water, dried
at 60 ◦ C, and deproteinized using 4 % NaOH (1:1, w/v) through heating 2.5.1. Experimental design
(1 h) to dissolve proteins and sugars. Then, the deproteinized samples Minitab software version 18.1 (Minitab Inc., PA, USA) was used to
with distilled water until the pH became neutral were dried for 24 h at design the experiments. Three independent variables, including banana
50 ◦ C and heated for 24 h (at 30 ◦ C) by demineralized using 1 % HCl pseudostem starch (15–25 mL), chitosan (3–10 mL), and glycerol (0–3
solution (1:5 w/v). The resulting product was washed with distilled mL), were selected as experimental parameters. A three-factor design
water until the pH became neutral (obtained 160 g of chitin). It was was employed in the current study, and 20 experiments were formed.
dissolved in 50 % NaOH (1:4) for deacetylation and heated (at 70 ◦ C) for The central composite design (CCD) response surface methodology
2 h. Washed the resulting product with distilled water, dried it at 120 ◦ C (RSM) was used to optimize the experimental parameters. Based on the
(up to 24 h), and took chitosan as the final mass. The obtained chitosan response results in Table 2, proportions of one of the better-optimized
was calculated using Eqn. (2) [21,22]. film-forming solutions (characterized through physico-mechanical
Yield of chitosan=(Amountof chitosan obtained,g / Amount of chitin,g) x100 properties) were selected.
(2)
2.6. Physicochemical characterization of the composite film

2.4. Physicochemical characterization of starch and chitosan 2.6.1. Determination of solubility

The solubility test was carried out in boiling water. Cut each film into
The moisture and ash contents of banana pseudostem starch and 1.5*1.5 cm pieces, which were weighted. About 50 mL of distilled water
chitosan were determined using the AOAC standard method [23]. The was brought to a boil by heating at 100 ◦ C and pre-weighted films
pH of starch and chitosan samples was determined using a pre-calibrated immersed for 4 min. Samples were recovered subsequently, dried in a
pH meter [24,25]. hot air oven (at 70 ◦ C) for 24 h, and re-weighted. The average solubility
percentage (as shown in Eqn. (6)) was calculated based on earlier [29]:
2.4.1. Degree of deacetylation of chitosan
The degree of deacetylation was assessed through the acid-base Solubility(%) = [(X − Y)/ X]100 (6)
titration method. In brief, the prepared chitosan (0.1 g) was in 30 mL
HCl (100 mmol/L) at room temperature, and the red chitosan solution Where: X - initial film piece mass, and Y - final film piece mass.
was titrated (used methyl orange as an indicator) with 100 mM NaOH
until it turned orange. The degree of deacetylation is computed according

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B. Abera et al. Journal of Agriculture and Food Research 15 (2024) 100916

Table 2
The RSM-CCD design matrix of the three variables and physicochemical properties with the actual and predicted values.
Runs Variables Physicochemical properties

Banana starch Chitosan Glycerol Act. Sol (%) Pr. Sol A. WAC (%) Pr.WAC Act.TS Pr. TS Act. EB (%) Pr. EB
(ml) (ml) (ml) (%) (%) (MPa) (MPa) (%)

1 22.97 8.58 0.60 42.53 ± 42.45 21.66 ± 21.63 19.18 ± 19.1 4.45 ± 4.44
0.24l 0.22a 0.02g 0.01k
2 20 6.5 3 48.09 ± 48.14 19.42 ± 19.42 19.17 ± 19.15 6.06 ± 6.05
0.13a 0.10i 0.03g 0.10b
3 20 10 1.5 44.69 ± 44.74 19.69 ± 19.67 17.29 ± 17.28 4.55 ± 4.53
0.10f 0.30f 0.03i 0.21j
4 15 6.5 1.5 43.53 ± 43.45 19.13 ± 19.09 19.94 ± 19.94 5.29 ± 5.26
0.09h 0.29g 0.01c 0.02g
5 20 6.5 1.5 43.42 ± 43.51 19.50 ± 19.50 18.11 ± 18.11 5.05 ± 5.55
0.20k 0.08g 0.10i 0.02e
6 17.02 4.41 2.39 44.85 ± 44.90 20.39 ± 20.40 20.35 ± 20.35 6.84 ± 6.85
0.31e 0.10c 0.10b 0.02c
7 22.97 4.41 0.60 41.12 ± 41.12 19.21 ± 19.19 21.03 ± 21.03 3.65 ± 3.64
0.04n 0.07j 0.45a 0.01n
8 20 6.5 0 39.26 ± 39.24 20.52 ± 20.52 19.93 ± 19.94 4.10 ± 4.09
0.09o 0.10b 0.03d 0.03m
9 17.02 8.58 0.60 41.50 ± 41.55 20.39 ± 20.42 18.09 ± 18.09 3.59 ± 3.6
0.08m 0.20c 0.11j 0.04o
10 20 3 1.5 41.17 ± 41.15 19.93 ± 19.95 19.52 ± 19.53 5.7 ± 0.02d 5.7
0.09n 0.30e 0.02e
11 20 6.5 1.5 43.52 ± 43.51 19.51 ± 19.5 18.11 ± 18.11 5.64 ± 5.55
0.03j 0.67g 0.04i 0.03f
12 22.97 8.58 2.39 46.66 ± 46.6 19.42 ± 19.42 17.62 ± 17.64 5.77 ± 5.77
0.20c 0.05i 0.20k 0.20d
13 17.02 8.58 2.39 47.89 ± 47.86 17.64 ± 17.64 19.54 ± 19.53 4.64 ± 4.65
0.23b 0.12k 0.30e 0.39i
14 17.02 4.41 0.60 38.41 ± 38.43 19.51 ± 19.49 19.81 ± 19.78 5.84 ± 5.84
0.03p 0.32g 0.09d 0.21c
15 25 6.5 1.5 44.54 ± 44.64 20.3 ± 20.34 19.40 ± 19.39 4.35 ± 4.36
0.10g 0.03d 0.25f 0.01l
16 20 6.5 1.5 43.56 ± 43.51 19.50 ± 19.5 18.11 ± 18.11 5.63 ± 5.55
0.04i 0.03g 0.09i 0.10f
17 20 6.5 1.5 43.51 ± 43.51 19.54 ± 19.5 18.11 ± 18.11 5.64 ± 5.55
0.08j 0.05g 0.10i 0.01f
18 22.97 4.41 2.39 45.52 ± 45.44 20.71 ± 20.66 18.65 ± 18.64 4.95 ± 4.93
0.03d 0.13a 0.12h 0.03h
19 20 6.5 1.5 43.55 ± 43.51 19.53 ± 19.5 18.13 ± 18.11 5.67 ± 5.55
0.10i 0.19g 0.23i 0.02e
20 20 6.5 1.5 43.54 ± 43.51 19.48 ± 19.5 18.15 ± 18.11 5.68 ± 5.55
0.02i 0.03h 0.27i 0.34e

A: actual value; Pr.: predicted value; Sol, solubility; WAC, water absorption capacity; TS, tensile strength; EB, elongation at break; Means that they do not share the
same superscript letter that represent significantly differ (*p < 0.05).

2.6.2. Water absorption capacity 2.7. Application of the coatings on fruits and evaluation of their effect on
The casted films (1 x 1 cm) were weighed after drying (for 24 h at quality parameters
50 ◦ C), then cooling. Moisture absorption capacity was obtained by
soaking the sample in water for 30 min. Then, the sample was dried Fifty fruit samples for each coated and uncoated/control group of
(using a cloth), and the sample weight was recorded. Used the final apple, mango, and strawberries were washed under tap water, dis­
weight (Wf, after soaking) and initial weight (Wi, before soaking), infected with sodium hypochlorite (0.2 g/L) solution for 5 min, and
calculated the water absorption capacity (WAC) [29] by employing Eqn. dried at 30 ◦ C [31]. The fruits were dipped in a film-forming solution for
(7): 5 min. According to the literature [31,32], samples of apples and mango
were stored for 28 days, and strawberries were held for 21 days. Un­
WAC (%) = [(Wf – Wi ) / (Wi )]100 (7)
coated fruits were used as a control, and samples of both coated and
uncoated fruits were preserved at 4 ◦ C. The physicochemical parameters
2.6.3. Elongation at break and tensile strength
were evaluated for apples and mangoes every seven days, while the
ASTM D 882 tested the films’ tensile properties using a universal
strawberries were assessed every five days [32].
testing machine (M 500 - 100 AT, China). A texture analyzer was used to
measure the elongation at break and tensile strength at 30 % relative
2.7.1. Determination of pH and weight loss
humidity at 21.4 ◦ C. The films were cut into strips with 10 cm length and
The pH value of coated and uncoated fruits was determined at every
1.3 cm width like a dumbbell shape. Fixed the initial gauge separation
time interval described above. For this purpose, the fruit juice was
(at 10 cm) and crosshead speed (50 cm/min). Tensile strength and
extracted, and pH was measured using the pH meter. Coated and un­
elongation at break were calculated [30] as:
coated fruit samples were weighed regularly and determined weight loss
Tensile strength = (Fmax / A) x 100 (8) [31] as follows:
Weight loss (%)= (Wo – Wi )/ Wo x 100 (10)
Elongation at break (%)= (Length increment / Original length) x 100 (9)
Where: Wo - Sample weight at initial; Wi - Sample weight at each
Where: Fmax - maximum force (N), and A - film cross-section area.

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B. Abera et al. Journal of Agriculture and Food Research 15 (2024) 100916

interval. Table 4
Yield (%) and physicochemical properties of fish scale chitosan.
2.7.2. Microbiological analysis Parameters Current value (Mean Literature Reference
This study determined the total number of mesophilic bacteria in a ± SD) value
sample using the pour plate method with plate count agar. The samples Yield 29.66 ± 0.46 7.72, 24, 10 [22,42]
were incubated at 24 ± 1 ◦ C for three days. The spread plate method was Moisture (%) 3.59 ± 0.14 5, 3 [22,46]
used with potato dextrose agar to measure the number of fungi in a Ash (%) 1.94 ± 0.11 1, 2.28 [42]
sample. The samples were incubated at 30 ± 1 ◦ C for five days. For this pH 7.18 ± 0.07 7, 10, 16 [26,41]
Degree of deacetylation 83.88 ± 0.20 78.2, 82.45 [26]
purpose, the fruits were cut and homogenized, and the juice was pre­ (%)
pared with sterile water; the serial dilutions of juice were prepared.
Total microbial counts were calculated at each time interval and The FTIR spectra of the Dwarf cavindish pseudostem starch, fish scale chitosan,
and the composite film were shown in Fig. 1a, b, and 1c, respectively.
expressed as colony-forming units per milliliter (CFU/mL) [24].
CFU / mL = (Colonies number ∗ Dilution Factor / Culture plate volume)100 composite edible film, while the ANOVA results for determining model
(11) fit were shown in Table 5. The effect of banana pseudostem starch (A),
chitosan (B), and glycerol (C) in optimizing the physicomechanical
2.7.3. Observation of visual quality properties of edible films is shown by fitting the response data to linear,
The naked eye examines the visual appearance of the coated and 2FI (two-factorial interaction) and quadratic models. Adjusted R2 and
uncoated fruits [33]. predicted R2 values were lower for linear and two factorial interactions
(2FI), and the cubic model was aliased. A model quadratic was shown
2.8. Statistical analysis the highest adjusted R2 and predicted R2 values. The quadratic model is
statistically significant with *p < 0.05. The results obtained in this study
Each measurement was taken three times, and the results were were found to be fitted to the following second-order polynomial
averaged and expressed in mean ± standard deviation. Minitab software equation [32,33].
v.18.1 (Minitab Inc., PA, USA) was used to design the experiments and ∑
n ∑
n n− 1 ∑
∑ n
analyze the raw materials. A t-test was used to assess the means of the Y = a0 + ai xi + aii xi2 + aij xi xj
studied variables. The regression, statistical, and graphical analyses of i=1 I=1 i=1 j=i+1

edible films were carried out using the Design-Expert version 13 soft­
Where Y - predicted response, n - some factors, a - constant coefficient,
ware (Statease Inc., Minneapolis, USA). The F-test verified the statistical
ai, aii, and aij refer to the linear, quadratic, and interaction coefficients,
significance of the models at *p < 0.05 and examined the regression
respectively. The xi and xj are coded values of factors.
coefficients [34,35].
The software developed the regression equation from the quadratic
Adjusted R2 values of models were used to determine model ade­
model regarding coded factors (effective parameters). After the exclu­
quacy, and the regression coefficient (R2) was also used to assess the
sion of non-significant terms, the model is presented as follows:
quality of the fit of the polynomial model equation. 3D graphs were
Solubility = 43.52 + 0.5972A + 1.79B + 4.45C–1.26AB – 1.51AC –
created by keeping two factors constant and altering the other two
0.1129BC + 0.5358 A2 – 0.5691 B2 + 0.1758C2
factors to study the interacting effects of those studied components [36].
Water absorption capacity = 19.51 + 0.6221A–0.1409B – 0.5483C
+ 1.07AB + 0.3976AC – 2.59BC + 0.2121 A2 + 0.3073 B2 + 0.4672C2
3. Results
Tensile strength = 18.12–0.2754A – 1.13B- 0.3919C–0.1234AB –
2.09AC + 0.6085BC + 1.55 A2 + 0.2860 B2 + 1.43C2
Table 3 shows the maximum amount of starch obtained in the Dwarf
Elongation at break = 5.55–0.4505A – 0.5855B + 0.9773C + 2.14AB
variety and the minimum in the Giant variety of bananas. The present
+ 0.2006AC + 0.0247BC – 0.7347 A2 – 0.4297 B2 – 0.4747C2 s.
study has low moisture and ash values (Table 3). The pH of the studied
Adequate precision measures (shown in Fig. 2) the relation between
banana pseudostem starch tends to be neutral (6.81 ± 0.05). Swelling
actual and predicted values. The best model was found through the
power, solubility, and water absorption capacity were 6.16 ± 0.21, 5.52
higher values of R2. The R2 (regression coefficient) also represented the
± 0.18 %, and 74.2 ± 0.42, respectively.
model’s fit.
Table 4 reports the chitosan yield in the present study was 29.66 ±
A 3D surface plot of the interaction between three factors (starch,
0.46 %. In the present study, the DDA of chitosan from Nile tilapia
chitosan, and glycerol) on the solubility of edible films was reported in
(Oreochromis niloticus) was found to be 83.88 ± 0.31 %, treated with 50
Fig. 3. Film solubility increased as glycerol concentration increased
% NaOH at 70 ◦ C. The DDA of commercial chitosan usually ranged from
(Fig. 3b and c); changing the value of glycerol (0–3 mL) altered com­
66 to 95 % [24]. In the present work, chitosan was 82.23 ± 0.41 %
posite films’ solubility from 38.41 to 48.09 %, respectively.
dissolved in a diluted glacial acetic acid solution, and the water ab­
Fig. 3a and b depicted that as the starch concentration increased, the
sorption capacity of chitosan was 75.46 ± 0.83 %.
film solubility significantly increased. Increasing the amount of chitosan
Table 2 revealed the response of banana pseudostem starch-chitosan
increases the edible film’s solubility in water (Fig. 3a and c) while
keeping fixed glycerol and starch. At constant glycerol and chitosan, the
Table 3 amount of starch caused water uptake to grow considerably (Fig. 4a and
Starch yield (%) of different banana varieties and physicochemical properties of
b). Fig. 4b and c also show that the increment of water absorption was
the Dwarf cavendish banana stem starch.
observed on a more significant amount of glycerol, leading to more
Parameter Varieties Amount (g/100g) (mean ± SD) water up-taking (hydrophilic) capacity. When the amount of chitosan
Yield (%) Dwarf cavendish 4.26 ± 0.21a increased (Fig. 4a and c), the water uptake also increased.
Giant cavendish 3.54 ± 0.10c The starch concentration significantly increased the composite films’
Poyo 3.64 ± 0.09b
TS (Fig. 5a and b). At a fixed amount of chitosan and starch, tensile
Moisture (%) 8.61 ± 0.04
Ash (%) 9.21 ± 0.10
strength decreased with increasing glycerol concentration (Fig. 5b and
pH 6.81 ± 0.05 c). Fig. 6b and c reveal that at constant chitosan and starch, films with
increasing glycerol tend to have high elongation values.
Means that do not share the same superscript are significantly different (*p <
Chitosan presence (Fig. 6a and c) reduced elongation at break
0.05).

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Table 5
Sequential model sum of squares and model summary statistics of tested responses.
Source SS DF MS F value Sequential p-value Lack of fit p-value CV R2 Adj R2 Pri. R2 Press Remarks

Solubility
Mean 43.54
Linear 5.26 11 0.4778 184.7 <0.0001 <0.0001 0.9556 0.9473 0.9178 9.79
2FI 1.33 8 0.1658 64.09 0.0004 0.0001 0.9887 0.9835 0.9783 2.58
Quadratic 0.0459 5 0.0092 2237.61 <0.0001 0.0952 0.17 0.9995 0.9991 0.9968 0.3777 Suggested
Cubic 0.0000 0 – 0.0952 0.9999 0.9996 Aliased
Residual 0.0129 5 0.0026
Water absorption capacity
Mean 19.75
Linear 8.66 11 0.7874 1640.36 0.1407 <0.0001 0.2823 0.1478 − 0.3243 15.99
2FI 0.5652 8 0.0707 147.19 <0.0001 <0.0001 0.9530 0.9313 0.8778 1.48
Quadratic 0.0082 5 0.0016 1238.51 <0.0001 0.1026 0.16 0.9991 0.9983 0.9944 0.0680 Suggested
Cubic 0.0000 0 0.1026 0.9998 0.9992 Aliased
Residual 0.0021 5
Tensile strength
Mean 18.91
Linear 12.11 11 1.10 3933.42 0.0514 <0.0001 0.3756 0.2585 − 0.0147 19.69
2FI 7.33 8 0.9163 3272.35 0.0798 <0.0001 0.6222 0.4478 0.1057 17.35
Quadratic 0.002 5 0.0004 6419.17 <0.0001 0.3609 0.1 0.9998 0.9997 0.9990 0.0185 Suggested
Cubic 0.0000 0 0.3609 0.9999 0.9997 Aliased
Residual 0.0014 5
Total 7172.68 20
Elongation at break
Mean 5.15
Linear 6.11 11 0.5554 9.14 0.0058 0.0121 0.5324 0.4447 0.1934 11.06
2FI 1.46 8 0.1828 3.01 0.0006 0.1202 0.8712 0.8118 0.7052 4.04
Quadratic 0.0019 5 0.0004 48.73 0.0004 1 3.39 0.9777 0.9576 0.9671 0.4517 Suggested
Cubic 0.0000 0 1 0.9778 0.9158 Aliased
Residual 0.3039 5 0.0608

Note: SS, sum of squares; DF, degree of freedom; MS, mean square; CV, coefficient of variance; R2, coefficient of determination; Adj R2, Adjusted coefficient of
determination; Pri.R2, predicted coefficient of determination; 2FI, two factorial interaction.

Fig. 1. FTIR spectra of banana pseudostem starch (a), chitosan (b), and composite edible film (c).

significantly because of the increased crystallinity of the starch. After pH of coated and uncoated strawberries differs significantly (*p < 0.05).
determining the responses (solubility, water absorption capacity, tensile The acidity of uncoated mango and strawberry was significantly
strength, and elongation values), the best of the three optimum coating increased compared to the coated and *p < 0.05, indicating that coating
components were selected based on desirability analysis via numerical slows down changes in the pH of the fruit.
optimization (Table 6). There was a substantial difference between APC and fungus counts
The optimized results select the preferred one based on the product on coated and uncoated fruits, and *p < 0.05. After three weeks of
quantity and quality (Fig. 7). The application of the best-optimized film storing, the total fungus population in coated apple and mango was
on fruit preservation was determined by weight loss, pH, microbial detected (Table 8). The fungus cell loads were observed during the 1st
growth, and visual quality. The percent weight loss of all uncoated fruits week of storage in all the uncoated samples. The fungus was detected
was found to be increased (shown in Table 7) significantly during the only after five days of storage in uncoated strawberries. However, the
study period (*p < 0.05). There was also a notable change in the weight fungus was noticed 15 days after storing in the case of coated
loss of coated and uncoated fruits through storage (*p < 0.05). The strawberries.
highest weight loss (in %) was found in uncoated strawberries (33.67 As shown in Fig. 8, none of the coated fruits showed signs of dete­
%), and the lowest percentage was registered in samples with coated rioration; however, the strawberry did wrinkle after one week of
apples (2.29 %). application of the solution. The color and texture of the coated fruits
The pH of coated and uncoated apple and mango (Table 6) did not were shiny and attractive.
significantly differ (p-value: 0.1 and 0.26, respectively). In contrast, the

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Fig. 2. Comparision between pridicted and experimental values for the response variables.

Fig. 3. Response surface method (RSM) 3D plot for the ineraction between banana pseudostern starch, chitosan, glycerol on the solubility of composite films.

4. Discussion 4.2. Physicochemical properties of Dwarf Cavendish pseudostem starch

4.1. Percentage yield of starch from different banana varieties in Arba The mineral availability varies in different parts of the banana
Minch pseudostem. The literature reported that the tender core of the banana
pseudostem concentrated the higher minerals [38]. Accordingly, in the
The most commonly found banana varieties in Arba Minch are Dwarf present study, banana pseudostem tender core was used. The results of
cavendish, Giant cavendish, and Poyo, which are categorized under desert the currently studied study were similar to the previously reported
bananas (Musa acuminata). Most farmers produce Dwarf and Giant [37]. literature [39,40], which was studied in cassava starch and sweet potato
The availability of starch in banana pseudostem varies by the type, flour. The results of water absorption capacity might be due to
growing location, growth stage, plant functional state, seasons, and gelatinization.
moisture availability of the stems. According to the starch content and
availability (Table 2), the Dwarf cavendish variety was chosen in this
study.

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B. Abera et al. Journal of Agriculture and Food Research 15 (2024) 100916

Fig. 4. Response surface method (RSM) 3D surface plot for the interaction between banana pseudostem starch, chitosan, glycerol on water absorption capacity of
composite edible films.

Fig. 5. Response surface method (RSM) 3D plot for the interaction between banana pseudostem starch, chitosan, glycerol on the tensile strength of edible com­
posite films.

Fig. 6. Response surface method (RSM) 3D plot for the interaction between banana pseudostem starch, chitosan, glycerol on elongation at break of edible com­
posite films.

4.3. Percentage yield of fish scale chitosan concentration. However, the results increased when the deacetylation
period increased. This study reported a higher chitosan yield; this might
The chitosan yield in the present study was higher than the previous be undertaken during the deacetalization process at low temperatures
reports [26,41], which extracted the chitosan from fish scales and (70 ◦ C) and the optimum concentration of NaOH.
decreased the chitosan yield with increased temperature and NaOH

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B. Abera et al. Journal of Agriculture and Food Research 15 (2024) 100916

Table 6
Summary of the constraints and the optimum conditions for the banana pseudostem starch-chitosan composite edible film.
S. Banana starch Chitosan Glycerol Solubility Water absorption capacity Tensile strength Elongation at break Desirability
No (mL) (mL) (mL) (%) (%) (MPa) (%) (%)

1 15 3.207 0.592 36.465 19.777 20.986 6.822 0.995

(selected)
2 21.09 3 0.567 39.019 18.726 21.030 4.305 0.968
3 15 4.929 0.5 38.035 19.767 20.141 5.684 0.883

Fig. 7. Ramp desirability plot optimization of banana pseudostem, chitosan, and glyccerol for the composite film formualtion

Table 7
Weight loss (%) and pH of apple, mango, and strawberry before and after coating.
Fruit Treatment Day 7/5 Day14/10 Day 21/15 Day 28/21

Wt loss pH Wt loss pH Wt loss pH Wt loss pH

dA aA cA aA bA aA aA
Apple Uncoated 0.90 ± 0.03 3.52 ± 0.04 2.01 ± 0.22 3.55 ± 0.13 3.2 ± 0.32 3.55 ± 0.03 4.6 ± 0.12 3.55 ± 0.21aA
Coated 0.54 ± 0.21dB 3.52 ± 0.31bA 1.18 ± 0.72cB 3.52 ± 0.02abA 1.58 ± 0.31bB 3.52 ± 0.21aA 2.29 ± 0.18aB 3.51 ± 0.29aA
Mango Uncoated 1.1 ± 0.20dA 5.95 ± 0.18cA 2.02 ± 0.01cA 5.94 ± 0.06cA 2.87 ± 0.11bA 5.84 ± 0.07bA 4.33 ± 0.27aA 5.80 ± 0.30aA
Coated 0.19 ± 0.10dB 5.90 ± 0.24aA 1.71 ± 0.28cB 5.98 ± 0.16aA 2.46 ± 0.20bB 5.95 ± 0.01Aa 3.43 ± 0.05aB 5.83 ± 0.02aA
Straw Uncoated 6.17 ± 011dA 3.57 ± 0.41bB 12.41 ± 0.01cA 3.54 ± 0.51aB 24.1 ± 0.17bA 3.57 ± 0.17aB 33.67 ± 0.28A 3.57 ± 0.05aB
Berry Coated 0.93 ± 0.30dB 3.67 ± 0.04bA 5.28 ± 0.20cB 3.73 ± 0.32bA 9.48 ± 0.29bB 3.79 ± 0.27aA 16.33 ± 0.14aB 3.81 ± 0.15aA

Note: Evaluation was carried out on each coated and uncoated apple and mango every 7 days and for strawberry every 5 days, which means onseries on each category
(coated and coated) that do not share the same superscripts (a - d) are significantly different (p < 0.001) coated anduncoated fruits (within a day) of the same column
that do not share the same superscripts (A, B) are significantly different (p < 0.001).

4.4. Physicochemical properties of chitosan to increased chitosan solubility values, suggesting complete deacetyla­
tion [41].
The results of the moisture and ash contents, reported in Table 4, The disintegration of chitosan molecules brought on by heat is the
agreed with the earlier study by Mohanasrinivasan et al., 2014 [42]. cause of the water absorption capacity. This results in an increase in
They said the ash availability in shrimp shell waste chitosan. Chitosan surface area and more sites available at the end. Also, chitosan is more
ash content was found to decrease with the demineralization of fish hydrophilic-that is, it can bind more water due to the increase in –NH2
scales. The present study’s resulting lower ash level indicates that effi­ groups. Additionally, chitosan becomes more porous due to decreased
cient demineralization steps were undertaken upon removing minerals. crystallinity, improving water molecule permeation efficiency [44].
The polysaccharides’ free amino acid mainly evidenced the degree of
deacetylation (DDA). The high percentage of DDA in the present study
4.5. FTIR spectral analysis of banana pseudostem starch, chitosan, and
revealed that the produced chitosan showed a better quality and purity.
the composite film
Chitosan has free amino groups and cannot dissolve in water at a
neutral pH. However, it can dissolve at room temperature in many acids
In the spectrum for banana pseudostem starch (Dwarf cavindish), as
like glacial acetic acid, citric acid, and diluted HCl [43]. The deacety­
presented in Fig. 1a, the broadband at 3405 cm− 1 shows –OH stretching.
lation process’s operating temperature can influence the chitosan solu­
At 2927 cm− 1, the band associated with the stretching of C–H bonds,
bility in glacial acetic acid. Lower temperatures in the current study led
while the band at 1623 cm− 1 confirmed the C– –O and C– –C stretching

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Table 8
Total population of APC and fungus counts in coated and uncoated apple, mango, and strawberry in CFU/mL.
Fruits Treatment at day 1 at 7th day at 14th day at 21st day at 28th day
2eB 2dB 3cB 3bB
Apple Coated APC 0.5 ± 0.32x10 0.99 ± 0.21x10 1.24 ± 0.33x10 1.61 ± 0.42x10 2.04 ± 0.32x103a
Fungus ND ND 0.39 ± 0.25x103cB 1.01 ± 0.37x103bA 1.86 ± 0.48x103aB
Uncoated APC 1.07 ± 0.32x104aA 1.79 ± 0.36x104bA 2.28 ± 0.05x 1 05cA 2.69 ± 0.71x105dA TNTC
Fungus ND 0.56 ± 0.54x105d 0.79 ± 0.27x105cA 1.01 ± 0.37x105bA 1.41 ± 0.42x105aA
Mango Coated APC 0.78 ± 0.11x103eB 1.21 ± 0.18x103dA 1.79 ± 0.37x103cB 2.18 ± 0.58x103b 2.71 ± 0.29x103a
Fungus ND ND 0.55 ± 0.21x104aB 0.82 ± 0.36x104bB 1.09 ± 0.11x104cB
Uncoated APC 1.25 ± 0.35x104cA 1.76 ± 0.37x105bA 2.4 ± 0.12x105aA TNTC TNTC
Fungus ND 0.61 ± 0.04x104a 0.85 ± 0.33x105bA 1.04 ± 0.26x105cA 3.71 ± 0.47x105dA
Strawberry Coated APC 1 ± 0.35x103eB 1.49 ± 0.32x103dB 1.71 ± 0.56x103cB 2.13 ± 0.31x103b 2.5 ± 0.51x104a
Fungus ND ND 0.39 ± 0.77x103aB 0.79 ± 0.40x 03bB 1.56 ± 0.04x104bB
Uncoated APC 1.5 ± 0.50x104aA 2.3 ± 0.41x104bA 2.72 ± 0.22x105aA TNTC TNTC
Fungus ND 0.77 ± 0.34x105a 1.26 ± 0.43x104bA 1.79 ± 0.11x105cA 2.49 ± 0.10x105dA

Note: Evaluation was carried out on each coated and uncoated apple and mango every 7 days, which means on series on each category(coated and uncoated of
microbes) that do not share the same superscripts (a-d) are significantly different (p < 0.001); coated and uncoatedfruits on the same kind of microbes (within a day) in
columns that do not share the same superscripts (A, B) are significantly different (p < 0.001); ND, not detected; TNTC, too numerous to count.

Fig. 8. Visual appearance of uncoated and starch-chitosan-glycerol composite coated Apples, Mangoes, and Strawberries during the storage.

frequencies [45]. are physically blended or chemically interacting. The distinct peak (at
The infrared absorption bands at 1458 and 1316 cm− 1 correspond to 3405 cm− 1) of –OH in starch and –NH of chitosan (at 3426 cm− 1) shifted
the symmetric bending of H–C–H and CH2OH bonds. The vibration due to a higher wavenumber, which appeared at 3431 cm− 1.
to C–O and C–C bonding absorbs between 986 and 1160 cm− 1. The When chitosan and starch are mixed, the peak in the infrared spec­
absorption band at 926 cm− 1 corresponds to C–H bending deformation, trum that corresponds to the stretching of the methylene (CH2) group
and the band at 864 cm− 1 corresponds to asymmetric deformation of the shifts from 2927 cm− 1 to 2930 cm− 1. It indicates that hydrogen bonds
C–O–C group. The vibration frequency of methylene is between 767 and are forming between the chitosan and starch molecules. The type and
710 cm− 1, and the vibration frequencies of the carbon skeleton (C–C–C number of hydrogen bonds that form depend on the mixture’s amount of
and C–C–O) bonds are between 572 and 530 cm− 1, respectively. starch, chitosan, and glycerol. These hydrogen bonds affect the structure
The presently studied chitosan spectrum (Fig. 1b) agreed well with and properties of the polymer matrix [49].
the previous reports [46,47]. The broad band at 3426 cm− 1 is recognized The amino peak of chitosan changed from 1626 cm− 1 to 1638 cm− 1
as the stretching vibrations of –NH and –OH groups. The bands at 2927 with the addition of starch. In addition to chitosan and glycerol, the
cm− 1 and 2852 cm− 1 are allied with the C–H stretching vibrations of the starch carbonyl peak was shifted from 1623 cm− 1 to 1638 cm− 1; the
–CH2- group. The band (at 1626 cm− 1) is due to the amide’s C– –O and chitosan peak (1417 cm− 1) moved to 1451 cm− 1. C–O and C–C bonding
C––N stretching vibrations. vibration of banana pseudostem starch at 1160 cm− 1 shifted into 1167
A small peak near 1470 cm− 1 and 1417 cm− 1 indicates the C–H and cm− 1 when the chitosan and glycerol were mixed. FTIR results suggested
N–H bending vibrations (deformed NH2). The frequency at 1028 cm− 1 interaction between the starch –OH group and the chitosan –NH2 group,
may be due to C–N bending vibrations, and 565 cm− 1 is due to a C–C enhancing the compatibility between starch and chitosan [47].
single bond [48].
When starch and chitosan are mixed, the characteristic peaks in the
infrared spectrum (Fig. 1c) shift, indicating whether the two substances

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4.6. Evaluation of the response variables using surface plot model: 4.7. Model validation
physicochemical properties of the composite film
Derringer’s desirability function method was used in this present
The results of the quadratic model indicate that at least one of the study to optimize the multiple responses simultaneously. This function
regression model’s terms correlates significantly with the responses. It is finds a mixture of factor levels that concurrently meet the design’s re­
also used to select the suitable ingredient concentration and evaluate the quests for every response [49]. The best of the three optimum coating
sensitivity of the responses to the factors. The higher the F value, the components were selected based on desirability analysis via numerical
more successful the mathematical model is at predicting response vari­ optimization (Table 6). Validated the numerical optimization by
ables. The experimental values have high precision and reliability due to experimenting with the predicted parameter, and the response obtained
the low CV values and the lack of fit in the responses (Table 5). The was good, near the expected.
highest R2 values indicated a good agreement between the predicted and
experimental values. It means empirical data prediction is entirely
satisfactory. The RSM was used to study the interaction of factors that 4.8. Application of the coatings on fruits and their effect on some quality
affect response variables. Response surface plots are a function of two parameters
factors simultaneously, with one factor held constant, which helps
determine the interaction effects between the studied parameters (fac­ 4.8.1. Weight loss of the fruits
tors). There was a strong interaction between every two variables The result of weight loss of fruits up to four to five percent does not
(shown in the 3D response surface plots), which the coefficients of considerably impact the fruit’s freshness. The freshness of coated apples
interaction factors may easily understand. and mango was preserved until the last storage date. In contrast, the
freshness of uncoated strawberries was kept until the first five days of
4.6.1. Solubility storage, and coated strawberries retained their freshness until the 15th
The solubility of edible films in water is crucial since it can donate to day of storage. Strawberries are prone to losing moisture quickly
the water resistivity of the films, especially in humid environments. because they don’t have a peel or waxy coating. It can make the berries
Glycerol and chitosan concentrations substantially impacted the solu­ soft and shriveled, with dark spots on the skin [53].
bility of the starch–chitosan composite edible film. This is due to the Compared to the uncoated, coated fruits slightly reduce weight loss,
existence of hydrophobic components that help maintain film structure possibly due to the chitosan influence on the composite coatings. Since
[50]. Higher concentrations of chitosan cause significant interactions chitosan forms semipermeable films, it might be modified by the interior
between the two polymers, reducing the solubility. These findings back atmosphere (by altering the water penetrability, O2, and CO2). This re­
up prior research that found that the composite film’s solubility duces transpiration loss, delays the ripening of fruits, and sustains the
decreased as starch and chitosan concentrations increased. The solubi­ quality of harvested fruits; therefore, using edible coatings is an excel­
lity (in water) of the composite fabricated film might be modified to lent tool for weight reduction [54].
achieve the particular application’s requirements by altering the chito­
san concentration in the film formulation. 4.8.2. The pH of coated and uncoated fruits
The acidity reduction in the present study corresponds with the pH
4.6.2. Water absorption capacity increase. As storage time increases, bacteria and fungi consume sugars,
The absorption capacity can express the amount of water absorbed amino acids, and phenolic compounds as a source of energy. Bacteria
by the film-forming ingredients. Adding starch to a composite film leads and other microorganisms can produce organic acids or glucose when
to gelatinization, which induces a molecular reorganization in starch food spoils. These compounds increase the hydroxide ions (OH− ) con­
during film formation, increasing water absorption capacity [51]. The centration, making the food more alkaline. This increase in pH is one of
increment of chitosan amount on film formation promotes higher water the main reasons food deteriorates [54].
absorbency due to the strong hydrophilic amine group of chitosan.
Therefore, high chitosan content was avoided to reduce adverse effects 4.8.3. Microbial quantification of coated and uncoated fruits
on film strength [50]. The decrement in microbial growth on coated fruits is due to chito­
san because it is an antimicrobial substance with positively charged
4.6.3. Tensile strength and elongation at break molecules interacting with microbes’ negatively charged cell mem­
The tensile strength of the composite film is because of the addition branes. This interaction disrupts the cell membrane and kills the
of starch to the solution, which offers more affinity for more hydrogen microbe [32,55]. Thus, the studied banana pseudostem
bonds formed on the edible films (Fig. 5a and b), and increasing the starch-chitosan-glycerol composite edible film can potentially resist the
glycerol concentrations increases the hydrophilicity of the film. It con­ fruit-causing microbes, and this studied composite coating may preserve
tributes to the lowering of pressures between adjacent macromolecules. the fruits in prolonged storage.
Additionally, it decreases interactions between polymer chains, thereby The present study results compared with the earlier literature values
decreasing film strength. On the other hand, chitosan inclusion (Table 9) reveal that the results obtained in the presently studied coating
enhanced the composite films’ tensile strength due to the establishment material (banana pseudostem starch-chitosan-glycerol) have a promi­
of intermolecular hydrogen bonds between the chitosan NH2 group and nent alternative for preserving apples, mangoes, and strawberries.
banana starch –OH group [52].
Elongation at break values determines the ability of films to lengthen 5. Limitation of the study
before breaking. It describes the flexible nature of the film. A film’s
plasticity is usually essential to keep its integrity. Glycerol decreases The study is limited to work on banana stem starch, chitosan, and
interactions between polymer chains, thereby decreasing film strength. glycerol composite edible film used to preserve apples, mangoes, and
Chitosan presence (Fig. 6a and c) reduced elongation at break signifi­ strawberries. The study couldn’t perform more tests about the perfor­
cantly because of the increased crystallinity of the starch. The elongation mance of other fruit and vegetable by-products and wastes in enhancing
values of the edible blend membrane increase due to the influences of the shelf life of fruits and vegetables. Studied starch-based edible films
starch. However, when the amount of starch is too much, the plasticity may exhibit solubility in water, which could compromise their integrity
decreases, and the elongation values are lowered, leading to the fragile and functionality in high-humidity environments or during contact with
nature of the starch membrane [52]. moisture-rich fruits. Optimization uses a central composite mixture
design; the result may vary with other experimental design models.

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B. Abera et al. Journal of Agriculture and Food Research 15 (2024) 100916

Table 9 Table 9 (continued )

Result of comparison between the present study results with the results of the Composites (type of Studied film Results of studied Reference
earlier studies of starch-based natural edible coatings (polymer and additive edible coating properties/fruits to Properties
composites) applied to fruits. composition) preserve
Composites (type of Studied film Results of studied Reference starch,
edible coating properties/fruits to Properties genetically
composition) preserve modified and
Optimal Apple, Mango, and Resulted Current acorn starch
composite Strawberry physicochemical study product (HAP) (2
composition in properties: solubility: % w/v) Glycerol
the current 36.47 %, water and sorbitol (0, 1,
study: absorption capacity: &2%
15 mL of 1 % 19.78 %, tensile 3 % cassava starch, Studied the Edible coating with [16]
banana strength: 20.99MPa, 4 % Arrowroot Physicochemical sorbitol plasticizer of
pseudostem elongation-at-break: starch, and 5 % Properties of films arrowroot starch 4 %
starch (w/v), 3.2 6.82 %. Studied Canna starch provides the best
mL of 0.5 % coated fruits showed physicochemical
chitosan (w/v), lower weight loss with properties: thickness
and 0.6 mL of 30 longer duration of of 0,09 mm; 1,63 N
% glycerol (w/v) preservation, about tensile strength;
greater than 28 days of elongation 84.38 mm;
apples and Mangoes, water content of 11.19
and 21 days of %; solubility of 31.40
strawberries with the %; the transfer of
allowable level of water vapor 0,16 g/h
fungus and APCs and 3.20 mek/kg.
Rice starch (2 % w/ Studied the film The studied film had [7] Cassava starch (2 Mango Cassava starch/ [17]
v), Stearic acid properties through good physical, %); chitosan (2 chitosan coating
(0.3 % w/v), XRD and FTIR mechanical, and %); cassava reported a high score
Carrageenan (2 % barrier properties. starch/chitosan of appearance, lower
w/v), Glycerol Tensile strength and (2 %) weight loss, and
(30 % w/v), elongation-at-break of maintained fruit color.
Tween 20 (0.2 % film improved when Also, extending the
w/v) Carrageenan was fruit shelf life.
increased. Sweet corn starch, Studied the Starch with PVP [18]
Pea starch (4 % w/ Apple, Tomato The fruit is stored at [11] 10–40 %, and mechanical, 30–40 % showed
v), Potato starch Cucumber 4 ◦ C, and the coatings PVP: Poly(N- thermal, and barrier higher tensile
(4 % w/v), Guar provide effective Vinyl-2- properties strength: 9.0 ± 1.5c
gum (1 % w/v), antifungal activity Pyrrolidone) N/m2, elongation-at-
glycerol (ratio even after 25 days of break: 3.0 ± 0.1 %,
(polymer: storage. 1.4 ± 0.1 cm3/m2day,
glycerol 2:1), swelling power: 3800
Potassium ± 100 %, solubility:
sorbate (1 % w/v) 48 ± 01 %
Cassava starch (1.0, Strawberry Cassava starch [12] 5 g of tef starch, 0.4 Studied the Starch-based edible [19]
2.0 and 3.0 % w/ coatings with g of agar, and 0.3 mechanical biofilm with 23.18
v), Potassium potassium sorbate % glycerol properties MPa of tensile
sorbate significantly improved strength, 1.42 % of
(0, 0.05 and 0.1 the resistance to water elongation at break,
% w/v) vapor. Coatings 88.67 MPa of elastic
showed good integrity modulus, 10.65 N of
for 2 % and 3 % starch, puncture force, and
reducing the 12.65 mm of puncture
strawberries’ deformation
respiration rate.
Coatings with cassava
starch (3 %) and 3 % 6. Conclusion
cassava starch +0.05
% potassium sorbate The post-harvesting life of an apple, mango, and strawberries has
were selected for the
been successfully improved by employing banana pseudostem starch-
shelf life study of
strawberries. chitosan composite edible films. Used the central composite design
Starch (2 % w/v), Strawberry The minimum [13] (CCD) to study the physicochemical properties of composite films
Carrageenan (0.3 microbial growth rate formed from altered banana pseudostem starch, chitosan, and glycerol
% w/v), Chitosan for strawberries concentrations. The physicochemical properties of edible films were
(1.0 % w/v), coated with chitosan
Sorbitol (2 % w/ and calcium chloride
improved and significantly varied depending on banana starch, chito­
v), Glycerol (0.75 was obtained. san, and glycerol concentration.
% w/v) Tween 80 According to the finest fit and response surfaces, the optimized film-
(0.01–0.1 % w/ forming material composition conditions were 15 mL banana starch, 3.2
v), Calcium
mL chitosan, and 0.6 mL glycerol, with an overall desirability of 0.995.
chloride
Corn and potato Strawberry Both sorbitol and [14] The coated sample showed a significant difference (*p < 0.05) in weight
starch; Starches glycerol reduced eight loss and microbial growth compared to uncoated samples. Generally, the
with high losses and maintained banana pseudostem starch-chitosan composite edible coating solution
amylose content the texture and surface was better for the apple, which has a great appearance, lower weight
(HAS), Corn color of fruits.
loss, and constant pH compared to mango and strawberry. Mango also
retained its freshness compared with the coated strawberries, which

12
B. Abera et al. Journal of Agriculture and Food Research 15 (2024) 100916

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