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Journal of Renewable Natural Resources Bhutan
ISSN: 1608-4330
Effects of Chitosan and Aloe Vera Coating Treatments on Antioxidant
Activity and Colour
Changes of Kiwi Slices
Nazanin Sepheri1*, Amirhoosein Elhamirad1, Mohammad Armin2, Akram Sharifi1, Hanie
Yarabi
1
Department of Food Science & Technology, Sabzevar Branch, Islamic Azad University,
Sabzevar, Iran
2
Departmen of Agronomy and Plant Breeding, Islamic Azad University, Sabzevar, Iran
ABSTRACT
In order to investigate the changes in phenolic compounds and antioxidant properties of kiwi
slices covered during storage, an experiment was conducted at Islamic Azad University of
Sabzevar with three replications. Treatments were: control (no cover), 100% aloe vera, 20%
aloe vera + 80% chitosan, 40% aloe vera + 60% chitosan and 100% chitosan. Changes in
phenolic compounds, antioxidant properties and the colours of the samples were studied at 7, 14
and 21 days after exposure to 6° . The results showed that at the end of storage the highest
phenolic compounds and antioxidant properties were observed in the 60% chitosan +
40%aloevera, and the lowest were observed in control samples. During the storage period
antioxidant properties varied in different coatings. Increasing coverage caused an increase in
antioxidant properties. Although the 100 percentage of chitosan into coverage were unable to
produce desired antioxidants properties. In the colorimetric parameters L* and b* were higher,
and parameter a* was lower, than the control samples.
Key words: Aloe vera, Chitosan, Edible coating, Kiwi, Phenolic compounds
Introduction
Kiwi fruit is in actinide class, Ericales order, Actinidiaceae that grows in moderate climates. This
fruit has a substantial amount of fibre, vitamin C, vitamin E and minerals, especially potassium,
copper and manganese, high antioxidant capacity (fourth of all fruits), and has great medicinal
and nutritional value . Italy is the largest producer of fruits in the world (330,000 tons per year.).
Most of this fruit (96%) is known as Hayward (Cassano et al. 2006). Among the producing
countries, Iran comes eighth.
The use of edible films and coatings have been considered for better protection and increase the
shelf life of foods, and try to reduce the layers of packaging and replacement of packaging
preservation of food and degradation. Edible coating prevents the passing of moisture and gases,
and improves food preservation conditions, and is a strategy for improving the quality and shelf
life of food products. In addition, these materials are very good carriers for bioactive substances
including antimicrobial agents, antioxidants, minerals and vitamins (Bonilla et al. 2012). In a
study, Xu et al. (2001) examined the survival of kiwi fruit with edible films at room temperature,
and reported that the optimal combination of edible films from soy protein, Estearic acid and
Polulan are good for the storage of kiwi, and testing indicates it a three-fold increased shelf life
occurs in fruits that have an edible film.
The combination of N-acetyl chitin is called chitosan and its derivates in many foods,
pharmaceutical, cosmetics, biotechnology and agriculture have been used. Hassani et al. (2012),
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in a study of the shelf life of kiwi fruit coated with whey protein concentrate and rice bran oil,
reported that coated fruit compared with the control group had less weight loss. In the
colorimetric, covered kiwi higher level of (L*) factors and factors in (a *), (b*) and (ab*) was
lower than control samples in this test sensory tests of the coated fruits had more points. Chien et
al. (2007), in experiments on mango with 0, 0/5, 1, 2% chitosan concentrations, observed that a
1% chitosan concentration was better able to maintain vitamin C. Hernández-Muñoz et al. (2006)
found that coating strawberries with 1.5% chitosan had a significant effect on preventing
moisture loss and the dehydration of the strawberries.
Jiang et al. (2005) found that weight loss in mushrooms and peppers and cucumbers reduced
with increasing in chitosan. Dong et al. (2004) found chitosan coatings to improve the quality
and shelf life of lychee without skin.
Bourtoom (2008) reported that aloevera gel is a new edible coating. This is a polysaccharide
coating and has features such as a protective layer on the product, reducing the loss of fruit juice,
and reducing the flow rate of the gases of the skin. Chauhan et al. (2011) showed that the
aloevera gel coating reduced perspiration and the enzyme polyphenol oxidase and peroxidase in
apple slices, while there is a piece of apple polyphenol oxidase and peroxidase enzyme activity is
not covered in most modes. Mohebbi et al. (2012) examined the physico-chemical properties of
mushrooms coated with aloe vera, gum, tragacanth, and a combination of the two coatings, and
observed that the coated samples compared to the control had lower weight loss and discoloration.
They conclude that mixed coating was the best covered. Krupa et al. (2011) found the maximum
amount of phenolic compounds in kiwi fruits after seven days, and especially after 14 days.
Martínez-Romero et al. (2006) studied cherry fruit treatment of edible aloe vera and found that
bare fruit during the storage period showed symptoms including high respiration rate, weight
loss, changes in fruit colour, fruit firmness, stem browning and increase in microbial population,
but the fruits that were treated with aloe vera gel did not show these signs.
Today, the demand for high quality products and a high shelf life is rising. These products
continue to breathe after harvest and the stability of breathing becomes spoiled. Owing to the
importance of kiwi in nutrition and consumers’ trend in the use of products such as fresh fruit,
and a lack of sufficient information on the possibility of aloevera coating quality and its impact
on kiwi properties, this study was designed to investigate the antioxidant properties of kiwi slices
coated with chitosan and aloevera during storage.
Material and methods
Sample preparation
Hayward kiwi fruit species was purchased from a local market in the city of Mashhad. The
shape, colour and size of kiwi fruits was uniformed and to remove foreign matter, pesticide
residues on the skin and part of the villi the fruits were washed well with distilled water. After
peeling the samples were transformed to coating dishes.
The experimental treatments included five treatments: control (without coating) coating with
100% aloe vera, coating with 20% aloe vera + 80% chitosan, coating with 60% chitosan + 40%
aloe vera gel and coating with 100% chitosan was done with three replications.
Method of producing the coating
Chitosan powder prepared at 80, 60 and 100% ratios was mixed with aloe vera gel at proportions
of 40, 20, 0%, and this mixture was heated at 30oC. After cooling, kiwi slices were immersed in
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gel and moved to an incubator at 6℃. Samples were analyzed after 7, 14, and 21 days during
storage.
Method of measuring antioxidant (DPPH)
2.5 ml of the prepared extract of kiwi was poured into test tubes, then mixed with 4.5 ml of
DPPH solution which was prepared by adding 100% methanol and stirred for 30 seconds. Then it
was kept in a dark room at ambient temperature for 30 minutes until the reactions were carried
out and samples were converted to a purple colour. Then, the absorbance was read at 567 nm by
spectrophotometer. Control samples were prepared as previous samples (Kalt et al. 2005). Then
the absorption was measured according to the formula.
(
)
Antioxidant activity% =
× 100
A blank: absorption in control samples (Methanol, water, DPPH)
A sample: absorption of samples containing methanol extract (extract, DPPH)
Measuring the total amount of phenolic compounds
In this method, the phenolic compounds react with Folin-siocalto reagent, and this reaction leads
to the formation of a blue-green colour with a maximum absorbance at 765nm. A good
correlation has been observed between the total amount of phenolic compounds and the
antioxidant activity of these samples.
Colour measurement
The coated samples were prepared on days 7, 14, and 21 for photos to be taken, and a *,L*,b*
parameters were studied with ImageJ software. Measurement of the colour of the image
processing techniques was made by ImageJ. Each uniformed sample was laid on a smooth and
uniform surface. For imaging, the camera distance to the sample was 20 cm. After processing the
image, the pixel value of each sample of colour was shown by a*,L*,b* colour index.
SAS (Ver 9.1) software was used for variance analysis and mean comparison of the data
collected by a Fisher protected LSD (FLSD) test. The tables and figures were drawn using Office
Word and Excel.
Results and Discussion
Absorption of free radicals
Analysis of variance showed that these compounds have been affected by the coverage (p‹0.01).
Comparison of treatment means showed that the maximum absorption of free radicals in a
coating of 60% chitosan + 40%aloe vera and the lowest level in the control sample was
observed. Significant differences were not observed between the coverage of 60% chitosan +
40% aloe vera and 100% in absorbance of free radicals.
The absorption changes rate of free radicals showed differences at different days of storage. On
all sampling days (days 7, 14, 21) the highest free-radical absorbance was observed with a 60%
chitosan + 40% coating, which indicated this type of coverage to have the ability to maintain the
favourable properties of kiwi fruit. During different days of sampling the absorption change rates
of free radicals were different between samples: the rate on the seventh day was increased with
100% chitosan coverage but with this coverage day 21 free radical absorption was reduced by
15% compared to the seventh day. Similar changes to the 100% chitosan coverage were
observed in 80% chitosan + 20% aloe vera. But the 60% chitosan + 40%aloe vera coverage from
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the beginning to the end of the sampling rates steadily increased free radical absorbance (Fig1).
The interaction effects of phenolic compounds, flavonoids and ascorbic acid may decrease
antioxidant capacity changes over time. Antioxidant activity in fruits of different varieties,
irrespective of the type of coverage, is high at the beginning of storage. This increase is due to
resistance to chemical and enzymatic oxidation of polyphenols and antioxidants, thereby
preventing loss of antioxidants during storage as well. Shen et al. (2013) found that the decrease
in antioxidant activity is associated with decreases in the amount of phenolic compounds and
ascorbic acid. Reduced antioxidant capacity changes over time in samples of the results reported
by other researchers. Fattahi Moghadam and Kiaeshkevarian (2013) reported that the antioxidant
capacity of the different varieties of citrus fruits can reduce during storage time.
1
2
3
4
5
6
7
8
9
10
Figure1. The effect of time on antioxidant compounds during storage time
Phenolic compounds
Phenolic compounds were affected by the type of coverage. Changing rates of phenolic
compounds during storage time were shown in table 1. The highest amount of phenolic
compounds was observed in the control sample at day 14, and by increasing storage duration
phenolic content was reduced in the control sample. Phenolic compounds of kiwi slices were
increased by coating, with the highest amount of changes observed in 60% chitosan + 40%aloe
vera. That rose 116.66% compares with the first day. After 60% chitosan + 40% aloe vera
coverage the highest amount of total phenols was observed in 100% chitosan coverage with a
93.68% change. At the end of storage day 21 significant differences were not found between the
100% chitosan, 80% chitosan + 20% aloe vera, 100% chitosan coverage. Although at these times
after 60% chitosan + 40% aloe vera coverage the highest amount of phenolic compounds was
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observed in 80% chitosan + 20% aloe vera coverage (table 1) when chitosan is blended with aloe
vera make insoluble hydrocolloid coating that causes increased barriers against oxygen and water
that polyphenol oxidase(PPO) and peroxidase (POD) enzymes cannot hydrolyse phenolic
compounds. This effect is greater with 100% compared with 100% chitosan. It can be concluded
that the greater percentage of mixing with chitosan can maintain a greater percentage of phenolic
compounds. According to the research results, there is a close relationship between the levels of
phenolic compounds and antioxidants, and this relationship was shown in this research to be
between 60% chitosan + 40% aloe vera coverage which could maintain phenolic and antioxidant
compounds. Gil et al. (2006) found that the highest correlation is between phenolic and
antioxidant compounds. Pen and Jiang (2003), in experiments on chestnuts with concentrations
of 0.5, 1 and 2% chitosan found the reduction of phenolic compounds to be under the influence
of three enzymes, POD, PPO, L-phenylalanine (PAL). They found that the concentration of
chitosan coating prevents changes in phenolic compounds. The accumulation of phenolic
compounds on coated and uncoated samples is due to the high activity of the phenylalanine
ammonia-lyase (Oms-Oliu et al. 2008).
Treatment
Day 0
Day 7
Day 14
control
23.16
32.92
39.53
100% aloevera
25.83
30.16
36.31
80%chitosan+20%aloevera
40.83
44.55
52.23
60%chitosan+40%aloevera
38.58
37.75
60.70
100%chitosan
26.9
28.51
43.34
FLSD (α=0.05)
2.35
3.15
5.14
Table1. The effect of time on phenolic compounds during storage
Day 27
30.65
37.79
59.53
83.59
52.1
4.35
Measurement of (a*) factor
Analysis of variance has shown that factor was affected by coating (p‹0.01). The result showed
that all coatings have been soaring, but the highest changes of factor were in 80% chitosan +
20%aloe vera and 100% coverage, and the lowest changes were in 60% chitosan + 40% aloe
vera coverage (Fig 2). The reason for this phenomenon is that when chitosan is blended with aloe
vera inhabiting the enzymatic activity. Xu et al. (2001) found that a coating of chitosan and aloe
vera increased (a*) factor, which is consistent with our results. Khoshnoudinia et al. (2012)
reported that the use of an edible gelatine coating along with antioxidants, especially ascorbic
acid, maintains a desirable green colour of pistachio in kiwi fruits. This might be the effect of
edible coatings on reducing the oxidation process of grains and nuts.
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y = 0.7335x - 14.902
R² = 0.9984
2
y = 0.3613x - 10.201
R² = 0.9432
Nazanin Sepheri et al
y = 0.4386x - 9.6203
R² = 0.9994
y = 0.4031x - 7.813
R² = 0.9993
y = 0.2679x - 7.311
R² = 0.9865
0
0
5
10
15
20
25
-2
-4
*
a
-6
control
100% aloevera
80%chitosan+20%aloevera
60%chitosan+40%aloevera
100%chitosan
-8
-10
-12
Storage Time (Day)
Figure2. The effect of time on (a*) during storage time
Measurement of (b*) factor
The results showed that all coatings have been soaring, but the highest changes were observed in
60%chitosan + 20% aloe vera coverage (Fig 3). Hassani et al. (2012) found that coating have not
been effective in reducing b* factor, which is consistent with our results. This may be due to the
inhibition of the coverage of chlorophyll (II) breakdown or reduction in the synthesis of
anthocyanin and carotenoids. Coating quince samples during storage show an increase in b*
factor (Akbarian et al. 2014).
y = -1.2222x + 41.156
R² = 0.9548
y = -0.675x + 35.629
R² = 0.7911
y = 0.2044x + 41.243
R² = 0.512
y = 0.5563x + 31.962
R² = 0.8109
y = 0.0461x + 36.644
R² = 0.073
50
45
40
35
30
* 25
b
20
15
control
100% aloevera
80%chitosan+20%aloevera
60%chitosan+40%aloevera
100%chitosan
10
5
0
5
7
9
11
13
15
17
19
21
23
Storage Time (Day)
Figure 3. The effect of time on b* during storage time
Measurement of (L*) factor
The results showed that all samples have been affected by coatings (p‹0.01). The results showed
that all L* factors of samples were reduced during storage. The lowest changes of L* factor were
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in 60% chitosan + 40%aloe vera coverage and the highest changes were observed in 100%
coverage. Significant differences were not observed between 100% chitosan and 80% chitosan +
20%aloe vera coverage (Fig 4). This is because hydrolysis of phenolic compounds cannot be
prevented by aloe Vera, thus causing darkening of the samples during storage. Higher amount of
aloe vera increases the turbidity of samples (Khoshgozaran-Abras et al. 2012). Khoshnoudinia et
al. (2012) found that L* factor in the purple coverage of pistachio shows a significant difference
between control and covered samples, so that the formulation containing ascorbic acid showed a
higher level of L* factor and the pistachio shell was lighter in colour. This colour reduction in
the gelatine coating containing antioxidant propyl gallate was found.
y = -1.2786x + 65.352
R² = 0.9919
y = -0.5987x + 56.913
R² = 0.3467
y = -0.4875x + 67.187
R² = 0.9999
y = -0.1036x + 59.629
R² = 0.096
y = -0.4346x + 66.104
R² = 0.9092
70
60
50
40
*
L
control
30
100% aloevera
80%chitosan+20%aloevera
20
60%chitosan+40%aloevera
100%chitosan
10
0
5
7
9
11
13
15
17
19
21
23
Storage Time (Day)
Figure 4. The effect of time on L* during storage time
Conclusion
The results showed that the 60% chitosan + 40% coating delays maturation and fruit ripening,
and reduces oxygen levels, and results in lower phenolic and antioxidant compounds during
storage. This is due to when chitosan and aloe vera mixed together, can be a further barrier to
oxygen and the oxidation of phenolic compounds and antioxidant activity during storage.
According to the results of this research we can conclude that 60% chitosan + 40% aloe vera
maintains phenolic and antioxidant compounds and has the best effect on the antioxidant
properties of the samples.
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