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RESEARCH ARTICLE | JU NE 0 9 20 23
Effect of drying and storage conditions towards the
bioactive compounds content and antioxidant activity of
mango peel powder
N. S. Mohd Isa; N. Mohdmaidin; M. Abdul hamid; I. N. Madzuki
AIP Conference Proceedings 2703, 080002 (2023)
https://doi.org/10.1063/5.0118067
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Effect of Drying and Storage Conditions Towards the
Bioactive Compounds Content and Antioxidant Activity of
Mango Peel Powder
N.S. Mohd Isa1, b), N. Mohdmaidin1, c), M. Abdul hamid3, d), I.N. Madzuki2, a)
1Faculty of Fisheries and Food Science, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu,
Malaysia
2Faculty of Chemical Engineering Technology, Universiti Malaysia Perlis, Campus Unicity Alam, 02600 Padang
Besar, Perlis, Malaysia
3Faculty of Food Science and Nutrition, Universiti Malaysia Sabah, Jalan UMS, 88400 Kota Kinabalu, Sabah,
Malaysia
a) Corresponding author: iffahmadzuki@unimap.edu.my
b)n.suaidah@umt.edu.my
c)nurmahani@umt.edu.my
d)chot@ums.edu.my
Abstract. Mango peel is one of the wastes produced by the mango processing industry that contains bioactive compounds
such as polyphenol and carotenoids. This study was carried out to determine the effect of drying methods on the antioxidant
activity of mango peel powder and its stability during storage. Mango peel was dried by using vacuum and cabinet hot air-
drying methods followed by bioactive content and antioxidant activity determination. The change in bioactive compounds
content and antioxidant activity were also evaluated during 8 weeks of storage in dark/light and airtight/non-airtight
conditions. The results obtained show that vacuum-dried powder had higher antioxidant activity than cabinet hot air-dried
samples with higher content of total phenolic (48.27 ± 0.28 mg GAE/g), better scavenging activity of DPPH free radical
(66.69 ± 0.88%) and β-carotene oxidation inhibition activity of 83.32 ± 0.93%. However, the carotenoid content of vacuum-
dried powder was lower than the cabinet hot air-dried powder with 83.21 ± 1.13 µg/g and 98.83 ± 0.93 µg/g respectively.
The antioxidant activity of the samples was also comparable to butylated hydroxyanisole (BHA), which is the standard
antioxidant. Besides that, storage studies revealed that samples kept in the dark and airtight conditions have the highest
antioxidant activity retention compared to other storage conditions. The results obtained from this study reveals the
potential use of mango peel powder as a source of natural antioxidants for food applications.
Keywords: mango peel, food waste, antioxidants, storage quality, drying technology
INTRODUCTION
The processing of mango-based products such as juices and purees leads to wastes production, i.e., peel and kernel.
Mango peel constitutes over 15-20% of whole mango fruit, and it is discarded during processing due to its low
commercial value [1]. According to the Food and Agriculture of the United Nations (FAO), mango was ranked as the
leading tropical fruit produced worldwide [2]. It is estimated that the worldwide production of mango will increase up
to 72.8 million tonnes by 2029 [2]. The increment also resulted in solid wastes production. Therefore, various studies
have been conducted to utilize mango by-products as beneficial substances, for example, as a source of antioxidants
and dietary fibre [3–6].
The Proceeding of the 1st International Conference of Chemical Science, Engineering and Technology
AIP Conf. Proc. 2703, 080002-1–080002-10; https://doi.org/10.1063/5.0118067
Published by AIP Publishing. 978-0-7354-4480-5/$30.00
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Mango peel has a high potential as a natural source of antioxidants replacing artificial antioxidants such as
butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) [7, 8]. Previous studies showed that mango
peel extract contains many bioactive compounds such as polyphenol and carotenoids [8, 9]. Some of the phenolic
compounds found in mango peel are syringic acid, quercetin, mangiferin pentoxide and ellagic acid. Carotenoid
compounds found in mango peels are β-carotene, lutein and violaxanthin [10]. Drying is important in the processing
of mango peel to cease the enzymatic reaction that caused pectin degradation and avoid microbial spoilage [11].
However, the drying process also affects the original characteristic of mango peel, whereby it may affect the
biochemical activity and stability of bioactive compounds due to the evaporation and thermal degradation process
[12].
The storage of foods with high antioxidant content depended on several environmental factors. Storage
temperatures and the presence of light during pre-and post-harvest of fruits affect their total phenolic content and other
compounds such as anthocyanin [13]. A study on raspberries showed an increase in total phenolics and anthocyanin
content when stored with light [14]. In contrast, storage of dried Piper betle extracts without natural light at low
temperatures provides high retention of phenolic compounds with high antioxidant activity [15]. In addition, another
factor such as controlled atmospheric condition is also crucial. Li et al. [16] reported a high antioxidant activity of Sea
Buckthorn berries stored in controlled atmospheric conditions as compared to control samples, while the study
conducted on strawberries reported that the use of biobased packaging films helps in retaining phenolic compounds
during storage with high antioxidant activity [17].
Despite various studies conducted on mango peel powder, study on its stability during storage is still scarce. Thus,
results obtained from this study provide valuable information on the drying process and storage of mango peel powder
to increase its potential as a natural food additive. The focus of this study is to determine the effect of different drying
processes and storage conditions on the antioxidant activity of mango peel powder.
MATERIALS AND METHODS
Mango Peel Powder Preparation
The variety of mango used in this study was Mangifera indica L. var. Carabao that was bought from a local market
in Kota Kinabalu, Sabah, Malaysia. The cleaned mango peels were dried until it reaches the moisture content level of
8.27±0.5% which is less than 10%, the maximum content allowed for powder [18]. Half of the samples were dried by
using a cabinet hot air dryer (Thermoline, Australia) at 50±1 C according to Ajila, Leelavathi and Prasada Rao [19]
while the other half of samples were vacuum-dried (Labtech, India) according to Lee and Kim [20] with some
modifications at 50±1 C and 500 mmHg of pressure. The moisture content of the fresh and dried samples was
determined by using a moisture analyzer (Mettler Toledo, United States). The dried mango peels were then ground
into powder form by using an electric blender and was sieved by using a 150µm siever to ensure uniform particle size.
Storage of Mango Peel Powder
Storage studies were conducted according to Yang et al. [21] on mango peel powder produced with the best drying
method. The samples were tested for antioxidant activity every 14 days during 8 weeks of storage period. The samples
were kept in four different conditions such as dark/airtight, dark/non-airtight, light/airtight and light/non- airtight. For
samples stored under airtight conditions, the samples were packed in a double zip-locked bag and placed in an airtight
container while for samples stored under non-airtight conditions, the samples were packed in propylene (PP) bags and
stapled. Half of the packed samples were then stored in a dark container, wrapped with aluminium foil while the other
samples were left in an illuminated room at room temperature.
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Antioxidant Content and Activity Analysis
Total Phenolic Content (TPC)
The method used for total phenolic content analysis (TPC) is the Folin-Ciocalteu technique according to Swain
and Hillis [22] with some modifications. Mango peel powder was extracted with 80% acetone [6]. Briefly, 20 µl of
sample extract was pipetted into a test tube along with 1.58 ml of distilled water and Folin-Ciocalteu reagent. The
mixture was then left to stand for approximately 30 seconds and was then added with 300 µl of 7.5% (w/v) of sodium
carbonate solution and was shaken thoroughly. The test tube was then incubated at 40°C for 30 minutes in a dark
condition. The absorbance of the solution was measured at 765 nm against a reagent blank. Gallic acid was used as
the standard curve and the TPC for each sample was determined as gallic acid equivalents, mg GAE/g of samples.
Total Carotenoids
The total carotenoids contents of mango peel powder samples were determined according to Dere, Güneş and
Sivaci [23]. The absorbance of the acetone extracts was measured at 400-700 nm by using a spectrophotometer. The
maximum absorbance for chlorophyll a is at 662 nm while for chlorophyll b is 646 nm. The absorbance for total
carotenoids is at 470 nm and the total of these pigments was calculated according to Lichtenthaler and Wellburn [24].
Chlorophyll a, chlorophyll b and the total carotenoids were calculated by using the following equations:
Chlorophyll a (Ca) = 12.25 A663.2 – 2.79 A646.8 (1)
Chlorophyll b (Cb) = 21.50 A646.8 – 510 A663.2 (2)
Total Carotenoids = 1000 A470 – 1.82 Ca – 85.02 Cb/198 (3)
DPPH Free Radical Scavenging Activity
The analysis was conducted according to Duan et al. [25] with some modifications. Butylated hydroxyanisole
(BHA) was used as a reference. Briefly, 2.0±0.01 ml of acetone extract was added into 0.16 Mm of methanol-DPPH
solution. The mixture was then vortexed for 1 minute and was incubated in dark condition for 30 minutes at 25 °C.
The absorbance was then measured at 517 nm and the scavenging activity was determined by using the following
equation:
Scavenging activity (%) = [1-(Asample – Ablank)/Acontrol] x 100 (4)
Where Asample is the absorbance of sample extract with DPPH solution, Ablank is the absorbance of sample extract
only and Acontrol is the absorbance of DPPH solution only.
β-Carotene/Linoleic Acid Bleaching Assay
The method used is according to Ikram et al. [26]. BHA was used as a reference. The mixture of 1.0 ml of β-
carotene solution, 20 µl of linoleic acid, 200 µl of Tween 20 and 200 µl of the acetone extract was evaporated at 30 C
for 20 minutes by using a rotary evaporator. After the evaporation process, 50 ml of distilled water was added into the
mixture and vigorously agitated to form an emulsion. Approximately 2.0 ml of this emulsion was then transferred into
a test tube and was placed in a water bath at 50±1 C for 2 hours. The absorbance of the sample was measured by using
a spectrophotometer and the antioxidant activity was determined with the following equation:
Antioxidant activity (%) = (A0 – A1)/A0 x 100 (5)
Where A0 is the absorbance of the sample at time 0 while A1 is the absorbance of the sample at 2 hours.
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Statistical Analysis
The experiment was conducted with three replicates. The generated data were analysed with Excel (Microsoft
Corp.). T-test was conducted to compare two means while One-way ANOVA with Tukey’s HSD was conducted to
compare data with several means by using IBM SPSS statistical software version 23. The difference between the
means was considered significant at P < 0.05.
RESULTS AND DISCUSSION
Drying Time for Mango Peel Powder Preparation
Referring to Table 1, it was determined that the vacuum dried samples had a shorter drying time as compared to
cabinet hot air-dried samples. Cabinet hot air drying showed an extra one hour of drying time as compared to vacuum
drying. According to Ishak [27], the benefit of vacuum drying is it reduces the boiling point of water with the reduction
in atmospheric pressure. At standard atmospheric pressure of 760 mmHg, water boils at 100 °C while at a lower
atmospheric pressure of 250 mmHg, the water boils at 72.2°C [27]. Besides that, the fast heat transfer between food
particles during vacuum drying also improves water movement in food samples for the evaporation process [28].
Vacuum drying helps accelerate the drying process thus, reducing the sample’s drying time and limiting its exposure
to high temperatures. Moreover, the absence of air also helps in preventing the oxidation process. Due to these benefits,
vacuum drying is often used with heat-sensitive products as the lower exposure to high temperature resulted in fewer
damages to food products and properties such as colour, texture and flavour of the dried products can be preserved
[28, 29].
TABLE 1. Drying time for mango peel samples with different drying methods
Drying Method
Weight of Fresh Sample
(G)
Drying Time (Hour)
Vacuum Drying
50.5a ± 0.1
3.10b ± 0.19
Cabinet Hot Air Drying
50.5a ±0.1
4.25a ± 0.15
a-b Mean values with different letters are significantly different at P<0.05.
Effect of Drying on The Total Phenolic and Carotenoid Content
The total phenolic content of mango peel powder samples was 44.1±0.5 mg GAE/g and 48.2±0.3 mg GAE/g for
cabinet hot air and vacuum drying respectively (Table 2). The results obtained were lower as compared to the previous
study by Ajila, Leelavathi and Prasada Rao [19] whereby a total of 96.2 mg GAE/g of phenolic content was recorded
for the acetone extract of mango peel from India prepared by using a cross-flow drier at 50 ±2°C. However, a much
lower result was obtained in the study conducted by Suleria, Barrow and Dunshea [30] on freeze-dried mango peel
whereby 27.51 ± 0.63 mg GAE/g of total phenolic content was recorded. The variations in the results obtained between
the studies are due to the difference in the type of mango tested, the methods used for extraction and drying method
[5, 9, 31].
Comparing between different drying methods, a significantly higher total phenolic content was observed for
vacuum dried samples as compared to cabinet hot air-dried samples. The results obtained are in agreement with the
study done by Vashisth, Singh and Pegg [32] on muscadine pomace whereby hot air drying resulted in a lower TPC
as compared to vacuum drying. Moreover, similar results were also observed in the drying of Echinacea Purpurea
whereby vacuum dried samples recorded a higher TPC as compared to cabinet hot air-dried samples [33]. According
to Nicoli, Anese and Parpinel [34], the reduction in phenolic content at high temperature is due to chemical, enzymatic
and thermal degradation. The reaction between bioactive compounds with antioxidants and other components in plants
occurred at high temperatures. Moreover, the low phenolic content of cabinet hot air-dried samples was also due to
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the development of pro-oxidants which normally occurred at the beginning of the drying process and during the early
process of non-enzymatic browning [35]. These pro-oxidants increased the degradation of antioxidants compounds
by an oxidation reaction and resulted in the development of free radicals [36]. In addition, hot air drying also led to
the oxidation of phytochemicals due to the high exposure of oxygen during the process [37].
However, with vacuum drying, the oxygen exposure of the samples was minimized which helps in preserving the
phytochemicals such as phenolic compounds. Besides that, the use of low pressure in vacuum drying also improved
heat penetration that helps in retaining the internal temperature of the food, resulting in a shorter drying time of 60-90
minutes [32]. A study conducted by Kwok et al. [38] also showed that the uniform internal temperature throughout
the drying process of Saskatoon berries helps in maintaining the anthocyanin content. Therefore, vacuum drying is
better compared to cabinet hot air drying in preserving the phenolic compound of mango peel powder.
Nevertheless, a significantly higher (p<0.05) amount of total carotenoid was observed with cabinet hot air-dried
samples as compared to vacuum dried samples (Table 2). According to the study done by Dorta, Lobo and González
[12], the total carotenoid of cabinet hot air-dried mango peel is higher as compared to freeze-dried samples that also
used low atmospheric pressure during the drying process. The high carotenoid content for cabinet hot air-dried samples
is attributed to the more effective removal of water content. The removal of water from the sample improved the
extraction of the lipid-soluble carotenoid [12].
The Antioxidant Activity of Mango Peel Powder
The ability to scavenge the DPPH free radical for the vacuum-dried sample is 8.29% higher as compared to samples
prepared with cabinet hot air drying. The low pressure in vacuum drying helps in lowering the boiling point of water
thus, the drying time of the sample can be shortened [27]. This method helped in retaining the antioxidant component
of the sample and therefore, increase the free radical scavenging activity. This condition is different with samples
dried with cabinet hot air drying whereby a longer drying time was required to dry the samples that caused higher
denaturation of antioxidant components. In addition, the oxidation of antioxidant components due to the use of hot air
in the cabinet hot air dryer also resulted in the reduction of free radical scavenging activity. According to Ma et al.
[39], the free radical scavenging activity of the vacuum-dried Inonotus obliquus mushroom sample was better than
the hot air-dried sample. Similar results were also reported by Fan et al. [40] on the Ganoderma lucidum extract
samples whereby vacuum dried samples showed a 16.4% higher DPPH free radical scavenging activity as compared
to hot air-dried samples.
In addition, a significant difference in antioxidant activity was also observed between the samples and the standard
butylated hydroxyanisole (BHA) sample whereby the values were 30.77% and 22.48% lower than the standard sample
for cabinet hot air-dried and vacuum dried samples respectively. These results indicated that mango peel powder had
an average activity of free radical scavenging activity. Although the value was lower than the standard antioxidant, a
study conducted by Suleria, Barrow and Dunshea [30] reported that mango peel powder showed the highest DPPH
scavenging activity as compared to other fruit peels with the highest value of total phenolic and total flavonoid
contents. Besides that, a study conducted by Ajila et al. [31] reported a variant-dependent DPPH scavenging activity
of mango peel powders prepared by freeze-drying. From the study, the DPPH scavenging activity of Raspuri mango
peel extracts was better compared to BHA while Badami mango peel extracts showed a lower scavenging activity as
compared to BHA. Furthermore, a difference in scavenging activity was also noted between ripe and raw mango peels.
Therefore, it can be concluded that the antioxidant activity of mango peel depends on the variety of the mango used,
level of maturity and also processing parameters such as the methods used for drying and extraction.
Furthermore, the percentage of inhibition for samples prepared by vacuum drying was higher as compared to
samples prepared by cabinet hot air drying from the β-Carotene/linoleic acid bleaching assay. Overall, both of the
samples exhibited a significantly (p<0.05) lower inhibition percentage as compared to the standard BHA sample. From
the results, vacuum-dried and cabinet hot air-dried samples showed 10.25% and 11.04% lower percentages of
inhibition respectively as compared to BHA that indicated an average inhibition activity against the oxidation process.
The results obtained are in agreement with the study conducted by Ma et al. [39] whereby the ability of Inonotus
obliquus mushroom extract samples to inhibit lipid oxidation is better for vacuum-dried samples as compared to hot
air-dried samples. The higher inhibition percentage of the β-carotene bleaching process shown by the vacuum-dried
mango peel sample was attributed to the high phenolic content of the sample as compared to cabinet hot air-dried
samples [41].
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TABLE 2. The bioactive compound content and antioxidant activity of mango peel powder samples, prepared by
using different drying methods
Mango Peel Powder
BHA (standard)
Cabinet Hot Air
Drying
Vacuum Drying
Total Phenolic Content (mg GAE/g)
44.11a ± 0.51
48.27b ± 0.28
Total Carotenoids (µg/g)
98.83a ± 0.93
83.21b ± 1.13
DPPH Free Radical Scavenging Activity (%)
58.40a ± 1.11
66.69b ± 0.88
89.17c ± 1.84
β-carotene/ Linoleic Acid Bleaching Assay (%)
82.53a ± 1.62
83.32b ± 0.93
93.57c ± 2.21
a-c Mean values with different letters within the same row are significantly different at P<0.05.
Change in Total Phenolic and Carotenoids During Storage
Referring to Figure 1, a significant reduction in total phenolic and carotenoid content was observed for all samples
during 56 days (8 weeks) of storage. Samples stored in the dark/airtight condition showed a 12.09% reduction in total
phenolic content followed by samples stored in the dark/non-airtight condition with a 15.36% of reduction. For
samples stored under light/airtight and light/non-airtight conditions, the percentage of total phenolic content reduction
was 20.42% and 23.22% respectively after 56 days of storage (Figure 1a). A slight increase in total phenolic was
observed during the first 28 days of storage for samples stored under the dark condition which reduces after 28 days
while a constant reduction was observed for light condition samples throughout the storage period. For total
carotenoids, 7.25% of reduction was observed for samples under dark/airtight conditions followed by dark/non-
airtight, light/ airtight and light/non-airtight samples with 12.75%, 14.59% and 22.17% reduction respectively (Figure
1b). From the results obtained, samples stored in dark/airtight conditions showed significantly higher retention of
phenolic and carotenoid content while samples stored under light/non-airtight conditions showed significantly lower
retention as compared to other samples.
It was reported that the decrease in phenolic content during storage was variable and non-uniform due to the variety
of different phenolic compounds present in foods whereby each of these compounds exhibits different stability [42].
A study conducted on blueberries stored under dark conditions reported that the biosynthesis process for various
anthocyanin and flavonoids continued after harvest [43]. This is due to its response to the mechanical effects of the
environment that are directly related to polyphenols especially phenolic acids. The study conducted on C. asiatica
drink also showed an increase in phenolic content during the first month of storage followed by a significant reduction
during the second month [44] which is in agreement with the study conducted by Moraga et al. [45] on grapefruit
powder whereby the phenolic content was stable during the first month of storage. Besides that, an increase in
quercetin content was also observed for onion samples (Allium cepa L.) stored under a dark condition where quercetin
is also one of the flavonoid compounds that can be found in mango peel [6, 46]. The above reasons explain the increase
in total phenolics for samples stored under dark conditions during the first 28 days of storage. However, longer storage
time resulted in the reduction of the total phenolic content which is in agreement with a study conducted on wheat
flour that shows a 60% reduction in total phenolics after 6 months of storage [47] and on bayberries whereby an
increase in storage time resulted in a decrease in phenolic content [48]. Moreover, the presence of light during storage
resulted in chemical degradation that caused a reduction in phenolic content as reported previously for noni powder
samples whereby samples stored under light conditions showed lower phenolic content retention as compared to
samples under dark conditions [21].
Other than the presence of light, the type of packaging materials also played a significant role in the stability of
polyphenols during storage. The use of polypropylene bag (PP) for non-airtight samples resulted in the oxidation
process as it has a medium gas permeability [49]. On the other hand, the storage of airtight samples with a double-
sealed polyethylene bag (PE) helps in minimizing the oxidation process due to its good barrier against oxygen [50].
Phenolic compounds are prone to oxidation processes that resulted in food quality degradation. The reduction in
phenolic content can also occur due to enzymatic reaction by polyphenol oxidase. However, it is less likely to occur
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in dried products as the high temperature during drying leads to enzyme deactivation. This can be observed in a study
by Yang et al. [21] whereby the stability of phenolic content in the noni (Morinda citrifolia L.) powder is higher as
compared to its juice during storage.
Furthermore, the trend of changes in carotenoid content was in agreement with a study conducted on dried orange
peel, carrots and sweet potato whereby samples stored under dark conditions retained a higher carotenoid content as
compared to samples under light conditions [51]. Atmospheric conditions also play a role in carotenoids retention as
reported by Wright and Kader [52] on sliced persimmons and peaches whereby high retention was observed for
atmospheric-controlled storage as compared to air-exposed storage. The reduction is caused by the oxidation process
during storage that is affected by the presence of light, oxygen and storage temperature. This process can be minimized
by controlling these parameters and selecting a good packaging material. It has been reported that the use of laminated
bags helps to minimize moisture and oxygen absorption that leads to a reduction in the oxidation process of mango
tablets [53].
(a)
(b)
FIGURE 1. Change in total phenolic content (a) and total carotenoids (b) of vacuum-dried mango peel powder during 56
days of storage (8 weeks). Samples were evaluated every 14 days of storage. a-eMean values with different letters indicate a
significant difference between storage days within the same sample while A-Dmean values with different letters indicate a
significant difference between samples within the same storage day at P<0.05
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Change in Antioxidant Activity During Storage
Figure 2 shows the change in antioxidant activity during storage based on DPPH scavenging activity (Figure 2a)
and ability to inhibit the chain reaction of lipid peroxidation (β-carotene/linoleic acid assay) (Figure 2b). From the
results obtained, reduction in antioxidant activity was observed during storage with sample stored under dark/airtight
condition showed the highest antioxidant activity for both DPPH scavenging activity and β-carotene/linoleic acid
assay at the end of the storage period as compared to light/non-airtight sample with the lowest antioxidant activity.
About 10.93% reduction in free radical scavenging activity was recorded for dark/airtight samples followed by
light/airtight, dark/non-airtight and light/non-airtight samples with 12.31%, 15.6% and 18.34% of reduction after 56
days of storage respectively (Figure 2a). A similar trend was observed for β-carotene/linoleic acid assay where
dark/airtight samples showed the least reduction in percent inhibition with 12.67% reduction followed by light/airtight,
dark/non-airtight and light/non-airtight samples with 14.56%, 14.64% and 16.8% reduction. These results indicated
that dark/airtight condition is the best storage condition in maintaining the antioxidant activity of mango peel powder
as compared to the other storage conditions.
It has been reported that the free radical scavenging activity and the ability to inhibit β-carotene peroxidation for
tea samples reduces during 5 months of storage where a 35.5% of reduction in free radical scavenging activity was
recorded with an average reduction of 7.1% per month [54]. The reduction in antioxidant activity is associated with a
reduction in bioactive compounds such as phenolic compounds [55]. According to Dorta et al. [12], there is a
correlation between phenolic and carotenoid content and the antioxidant activity of mango peel powder. Therefore,
the storage condition of mango peel powder is crucial in maintaining the stability of bioactive compounds which is
directly related to its antioxidant activity. This is also an important aspect that should be taken into account to increase
its potential as a natural source of antioxidants for food applications.
(a)
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(b)
FIGURE 2. Change in antioxidant activity of mango peel powder during 56 days of storage based on DPPH scavenging
activity (a) and ability to inhibit β-carotene peroxidation in β-carotene/linoleic acid assay (b). Samples were evaluated every 14
days of storage. a-eMean values with different letters indicate a significant difference between storage days within the same
sample while A-Dmean values with different letters indicate a significant difference between samples within the same storage day
at P<0.05
CONCLUSION
In conclusion, this study provides beneficial information on the effect of drying methods on the stability of
bioactive compounds that are mainly found in mango peels such as polyphenols and carotenoids whereby vacuum-
dried methods showed better retention as compared to cabinet hot air drying. The high retention of bioactive
compounds, in turn, resulted in a higher antioxidant activity with mango peel powder showed a relatively high
antioxidant activity as compared to BHA. This indicates the high potential of mango peel powder as a natural source
of antioxidants replacing artificial antioxidants for food applications. In addition, dark/airtight condition provides
better antioxidant stability for mango peel powder. Further studies should be conducted in a variety of food
applications to further determine its suitability as a food additive replacing synthetic antioxidants.
ACKNOWLEDGMENTS
The authors are grateful for the expertise and laboratory facilities provided by the laboratory personnel and
members of the Faculty of Food Science and Nutrition, Universiti Malaysia Sabah, Malaysia.
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