4th International Science, Social Science, Engineering and Energy Conference
11th-14th December, 2012, Golden Beach Cha-Am Hotel, Petchburi, Thailand
I-SEEC 2012
www.iseec2012.com
The production of edible film mixed with pomelo peel extract
S. Aichayawanicha,e1, C. Ngaouwthong a,e2
a
Design and Production Technology of Agricultural industrial Machinery Department, Faculty of Industrial Technology and
Management, King Mongkut’s University of Technology North Banakok, 129 Muang, Prachinburi, 25230, Thailand
e1
sawanit_aichayawanich@hotmail.com, e2chackapann@hotmail.com
Abstract
Nowadays, the edible film plays an important role in the food industry for wrapping vegetables and fruits.
Typically, the film can be produced from starch and it did not inhibit disease, especially, infection from
Staphylococcus aureus (S. aureus) which cause diarrhea. Therefore, this study aimed to produce the
edible film mixed with pomelo peel extract for increasing S. aureus inhibit activity. In The first step, the
effect of extraction solutions; including ethanol, ethyl acetate, dichloromethane and hexane on S. aureus
inhibit activity were evaluated. Then, the production conditions of edible film mixed with pomelo peel
extract; including drying temperature (40, 50, 60oC) and percentage of pomelo peel extract (0.05, 0.10,
0.15% w/w) in the film were studied. The experimental results showed that the amount of pomelo peel
extract that extract by dichloromethane is highest. Moreover, the extract that extract by dichloromethane
also had highest S. aureus inhibit activity. After film production, the results of film properties testing
appeared that the tensile strength and S. aureus inhibit activity of the film mixed with 0.15% w/w pomelo
peel extract and dried at 60oC were higher than those of the films that were produced using another
condition.
Keywords: Pomelo peel; Staphylococcus aureus; Edible film
1. Introduction
Pomelo (Citrus maxima Merr.) is one of the most famous fruits in Thailand [1]. It is primarily eaten
fresh and used as a component in main dishes and desserts. Before processing, the thick peels of pomelo
are peeled. This peel has 0.3-0.9% essential oils that consist of geraniol, linolool, citral, and
methylantranilate [2]. Thai normally used this essential oil for medical purposes. In agricultural industry,
pomelo peel extract from pomelo can be used to inhibit some pathogents such as Colletotrichum
gloeosporioides [3].
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Staphylococcus aureas (S. aureas) is one of the leading causes of gastro enteritis resulting from the
consumption of contaminated foods. It is an important pathogen due to a combination of toxin-mediated
virulence, invasiveness and antibiotic resistance [4]. It can be found normally in warm-blooded animal
nose, on warm-blooded animal hair and skin, especially human nose, hair and skin. Therefore, S. aureas
has an opportunity to infect in fresh and processed foods that were provided by human.
Nowadays, edible films play an important role in the quality, safety, transportation, storage, and
display of a wide range of fresh and processed foods. However, edible film normally can not inhibit
disease. A lot of antimicrobial edible films have been developed. Therefore, this research aimed to study
antimicrobial activity of pomelo peel extract and produce the edible film mixed with pomelo peel extract
for increasing S. aureus inhibit activity.
2. Material and methods
2.1. Material
Pomelo (Tong Dee) was collected at the mature stage from fruit orchards around Prachinburi
province in Thailand.
2.2. Material preparation
Pomelo was first washed thoroughly to remove impurities. After washing, the pomelo was peeled.
The green pomelo peels (flavedo) were cut into small pieces and dried overnight in a tray dryer at 40 oC.
The dried peels were collected in desiccator.
2.3. Extraction procedures
To prepare pomelo peel extract, 250 g of dried pomelo peels was extracted overnight with 750 ml of
95 % ethanol, dichlorometane, hexane and ethyl acetate. The extract was filtered through a filter paper (
110 mm, Cat. No. 1001 110, Schleicher and Schuell GmbH, Dassel, Germany). The filtrate was
concentrated in a rotary evaporator (Resona Technics Labo Rota 300, Gossau, Switzerland) at 40 oC for 30
min. The pomelo peel extract was kept at 4oC before its use.
2.4. Film preparation
Pomelo peel extract was mixed with cassava starch and glycerin at concentrations of 0.05, 0.10,
0.15% w/w. The mixture was homogenized and poured on an acrylic plate with dimensions of 10×10 cm
to cast a film. Hot air drying of the film was performed by three temperatures, which are 40, 50, 60oC,
until moisture content of the film equal to 60% (wet basis).
2.5. Microbial growth condition
S. aureas (ATCC 25923) was obtained from the Department of Medical Sciences, Ministry of Public
Health, Thailand. The microbial was maintained in TSA at 5 oC. Stock culture of S. aureas was grown in
TSB at 37oC for 18 hr at 160 rpm. The maximum level of the microorganism was 10 10 CFU/ml. The
concentration was subsequently adjusted to 108 CFU/ml using buffer peptone water.
2.6. Determination of Clear Zone of Inhibition
To determine antimicrobial activity of pomelo peel extract and film. A suspension of the tested
microorganism was spreaded on the MHA plate. Then, 6 mm in diameter of the film or 6 mm in diameter
of filter paper which was soaked into 15 µl of the extract was placed on the inoculated plates. After
keeping at 4oC for 2 hrs, the plate was incubated at 37oC for 24 hrs. After that, the diameter of clear zone
of inhibition was evaluated in millimeters. The filter paper that was not soaked into the extract was used
as a control sample.
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2.7 .Determination of tensile strength of the film
The tensile strength of the film was determined by using texture analyzer. 1×8 cm of the film was
prepared before testing.
2.8. Statistical Analysis
The experiment was performed in duplicate. The variance was determined by ANOVA and the
difference of mean values was determined by T’s test at a statistically significant level of 0.05
3. Results and discussions
The antimicrobial activity of pomelo peel extract from pomelo peel against S. aureas was proposed to
determine the diameter of clear zone of inhibition around the filter paper. Fig. 1 shows the filter paper that
was soaked dichlorometane pomelo peel extract. The result showed that clear zone of inhibition can be
generated around the filter paper that was soaked dichlorometane pomelo peel extract. This experiment
indicated that dichlorometane pomelo peel extract can be used to inhibit S. aureus. Similar result was
obtained in 95% ethanol, hexane and ethyl acetate pomelo peel extract but the figure not shown.
Clear zones
Fig. 1 Clear zones of inhibition of the filter paper that was soaked dichlorometane pomelo peel extract
To investigate the effect of organic solvents on antimicrobial activity of pomelo peel extract. Four
organic solvents including 95% ethanol, dichlorometane, hexane and ethyl acetate, were used to extract
the extract from pomelo peel. Later, the diameters of clear zone of inhibition of the pomelo peel extract
were determined. The values are shown in Table 1.
Table 1. Diameter of clear zones of inhibition of the filter paper that were soaked 95% ethanol, dichlorometane, hexane and ethyl
acetate pomelo peel extract
Solvent
95% ethanol
Dichlorometane
Hexane
Ethyl acetate
Diameter of clear zones of inhibition (mm)
7.88b ± 0.02
8.83a ± 0.05
7.88b ± 0.03
7.54c ± 0.01
As Table 1., the result showed that the diameters of clear zones of inhibition were in the range of 7.54
to 8.83 mm. The values were significantly different among the organic solvents. It may cause from
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different components in pomelo peel extracts that were extracted from different solvent. Pomelo peel
extract that extract by using dichlorometane is the best inhibitor. However, all pomelo peel extract can be
used to protect S. aureus grown. This result corresponding to result of Naradisorn and Ruenkum [3] who
studied antimicrobial activity of pomelo peel extracts of pomelo peel against Colletotrichum
gloeosporioides. They found that pomelo peel extract from pomelo peel can inhibit this microbial that
cause a anthracnose disease.
Pomelo peel extract that extract by using dichlorometane was selected to prepare antimicrobial film
and film was dried at 40oC. The effect of percentage of pomelo peel extract that was mixed with the film
was investigated. Clear zone of Inhibition and tensile strength of the films was determined. The values
were showed in Table 2. The results showed that tensile strength of the film did not significant different
between the examples. However, S. aureus inhibit activity of the film increased with increasing of
percentage of pomelo peel extract. S. aureus inhibit activity of pomelo peel extract will active when its
amount in the film was higher than 0.05 % (w/w).
Table 2. Effect of percentage of pomelo peel extract on tensile strength and clear zone of inhibition of films
Percentage of pomelo peel extract
(% w/w)
Tensile strength
(g)
Diameter of clear zones of inhibition
(mm)
0.05
52.13NS ± 0.08
0.00c ± 0.00
NS
0.10
52.14
± 0.06
0.30b ± 0.04
0.15
52.12NS ± 0.02
1.00a ± 0.10
Tensile strength and S. aureus inhibit activity of the film mixed with 0.15% w/w pomelo peel extract
and dried at different temperature were presented in Table 3. The results reveal that the values of the film
dried at 60oC were higher than those of the films that were dried another temperature. Due to lowest
drying time, the film dried at highest temperature had high quality.
Table 3. Effect of drying temperature on tensile strength and clear zone of inhibition of films
Drying temperature
(oC)
Diameter of clear zones of inhibition
(mm)
40
Tensile strength
(g)
52.12c ± 0.02
50
57.90b ± 0.11
1.20b ± 0.08
60
59.69a ± 0.01
1.75a ± 0.02
1.00c ± 0.10
4. Conclusions
From the experimental results, it was indicated that pomelo peel extract can be used to inhibit S. aureus
that is a food pathogen. Dichlorometane is the best organic solvent to extract the extract. After film
production, the results of film properties testing appeared that the tensile strength and S. aureus inhibit
activity of the film mixed with 0.15% w/w pomelo peel extract and dried at 60oC were higher than those
of the films that were produced using another condition.
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Acknowledgements
This work was financially supported by Faculty of Industrial Technology and Management, King
Mongkut’s University of Technology North Bangkok Foundation.
References
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[2] Soffer T, Mannheim CH. Optimization of Enzymatic Peeling of Oranges and Pomelo. LWT 1994; 27:245-248.
[3] Naradisorn M, Ruenkum A. Preliminary study on antimicrobial activity of crude extracts of pomelo albedo against
Colletotrichum gloeosporioides. J. Food Ag-ind 2009; Special issue:S138-S142.
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