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SHELF LIFE EXTENSION OF BANANA BY GAMMA RADIATION AS A
SUBSTITUTE OF CHEMICAL FUMIGATION
W. Zaman , Dipak Kumar Paul, M. Khorshed Alam1 and M.Masihul Alam.
Department of applied Nutrition and Food Technology, Islamic University, Kushtia, Bangladesh.1IFRB, Bangladesh Atomic Energy Research Establishment, Savar, Dhaka.
ABSTRACT
Effect of Gamma radiation on the shelf life extension of Bananas was investigated. The
Bananas were treated with radiation of three doses 0.30kGy; 0.40kGy and 0.50kGy
followed the storage at room temperature. The physical conditions of the treated and
untreated Bananas were analyzed every 2 days intervals for their organoleptic properties
till spoilage at room temperature in comparison to control. The chemical analyses of the
treated and untreated Bananas were carried out quantitatively at intervals of 2-4 days at
room temperature through out the storage period. A taste-testing panel of 16 panelists
found out the acceptability of the fruit. The score given by the panelists for different
attributes of the fruits were statistically analyzed to find out the acceptability of the fruit.
The fruits treated with the three radiation doses contain 72.7%-75.7% Moisture, 2-22gm
Carbohydrates, less than 1- 20gm Soluble sugar, 0.84-1.2gm Fibre, 0.5-0.7gm Pectin,
1.1-1.3gm Protein, 0.10-0.3gmFat, 0.8-1.4gm Ash, 10-26mg Ascorbic acid and 0.003-0.
001mg Beta-carotene per 100gm respectively and were found acceptable till 21-26 days
at room temperature whereas in the case of control the fruits stored at room temperature
spoiled within 3-6 days. Thus radiation can be the safe way for the shelf life extension of
Bananas instead of chemical fumigation which is very much health hazardous.
INTRODUCTION
Banana has been an important cultivated fruits from time immemorial and by far the most
important tropical fruits (Farooqi et al., 1987) [1]. This is one of the superiors and largest
cultivated fruits of Bangladesh (Ahmed et al., 1998) [2]. The edible Banana is indigenous
to the warm moist parts of Asia. It is not only the staple food of millions of people, but is
also the most important commercial fruit of the tropical areas of the world(Gottreich et
al., 1969) [3]. In Bangladesh, Banana is a popular and economical fruit, which constitutes
42% of fruits(Mitra,1969) [4]. The important of this fruits is due to its high calories and
nutritive value and of its versatile use to the consumers. It contains appreciable amount of
vitamin B and certain amount of vitamin A & C and also minerals, such as K, P, Ca, Fe,
Na etc (Southgate, 1969) [5]. Various products like banana chips, banana figs, flour,
powder, jam confectionery, dehydrated slice etc. can be prepared from
banana(Ronald,1984) [6]. Banana is a perishable food items and cannot be preserved for
longer time after harvesting. In relation to food, we have two major problems in
Bangladesh. One is the food deficit and other is the post-harvest loss. The farmers could
be encouraged for more production if spoilage could be prevented by proper preservation,
which could result in increased and balanced consumption. Moreover, substantial amount
of foreign exchange could be earned by exporting the fresh and processed products
(Vendrell et al.,1971) [7].From the prevailing condition it seems that the lack of suitable
preservation methods is a major factor contributing to the primary limitation to
production and consumption of increased amount of the fruit.
In developing countries, the processing and preservation of food have taken the form of
commercial food industries where sophisticated techniques and equipment are being
employed. But at present, there is dearth skilled manpower, machineries and capital to
establish modern processing industries in Bangladesh (Spalding et al.,1988) [8]. In view of
the above-mentioned limitations and the prevailing socio-economic conditions, we have
to start from low cost labor-intensive technologies for food preservation in a small scale
at the first instance and then gradually shift towards large-scale industrialization. Thus
developing a processed product in Bangladesh should not involve major changes in
habits(Quinn, 1967) [9].
Post harvest fruits losses due to insect infection are a serious, costly and worldwide
problem. Ethylene Dibromide (EDB), one of the most effective and widely used fumigant
for fruits and vegetables, has been highly controversial in recent years. The
Environmental Protection Agency (EPA) subsequently banned the EDB in the USA in
September 1984 as a fumigant for fruits and vegetables and soil (Maxie,1971) [10].
Ethylene Dibromide (EDB), which has been used as an effective fumigant for fruit for
over 40 years in the USA. EDB became a controversy in the mid-1970’s when a National
Cancer Institute (NCI, USA) study showed the chemical to be cancer-causing agent in
experimental animals (Stover, 1970) [11].
When an effective fumigant is banned, it creates the problem of finding an alternative or
substitute that can do the same job or better. Ionizing radiation in the form of Gamma-
radiation or high-energy electrons has been studied for over 30 years around the world as
a food preservation technique. It is potentially feasible substitute for chemical fumigation
of fruits and vegetables. The advantages of irradiation over chemical fumigation for
decontamination and disinfestations are briefly explained in view of the fact that
irradiation could become the most effective substitute for chemical fumigants. The use of
low dose radiation for insect disinfestations is emerging as a possible substitute for
chemical fumigation because of recent events and controversies over chemicals and
pesticides in foods (Siddapa,1951) [12].
For delay ripening fruits by irradiation, a very comprehensive review was prepared by
Loaharanu (Ayyad et al., 1990) [13]. As of August 1985, 30 countries including
Bangladesh around the world have cleared more than 40 irradiated food item for human
consumption on either an unconditional or provisional basis for various purposes
(Koszler,1959) [14]. The US FDA has recently (March, 1986) announced the approval in
principle of irradiated fruits up to 1.0 kGy for delay ripening and disinfestations
(Grecz,1983) [15].
This study will minimize post harvest losses of the fruit. Thus growers will be
economically benefited and encouraged to grow more foods. The successful value added
food production will encourage the food processors to build up processing plant and their
ensured shelf life will increase the export of value added food products. Thus the surplus
Bananas will be utilized and saved from spoilage. The radiated pulp and pulp-based
products may play an important role to our national economy through formation of new
employment opportunity of our rural manpower. With this view in mind the following
objective will be tried to achieve for solution of the project.
METHODS AND MATERIALS
Collection of Banana and sample preparation: For this study mature green Bananas
(Musa sapientum) of medium sizes were collected from different local markets of Savar,
Dhaka, Bangladesh. Following collection, the Bananas were cleaned and washed with
tape water. The prepared bananas were poured into plastic bag and sealed tightly. The
sealed plastic bags were labeled by indicating the name of the product and the doses
those will have to apply.
Radiation: Bananas were treated with different doses of Gamma radiation and stored at
room temperature. The sealed plastic bags were labeled by indicating the name of the
product applied doses (Control 0.0 kGy, 0.3kGy, 0.4kGy and 0.5kGy). Radiation was
given in the filled bag by using Co-60 source of radiation. The final products were stored
in dry place at room temperature and observed shelf life of the bananas.
Techniques used: Shelf life was estimated by the data obtained in response of
organoleptic test and chemical analysis. Quality attributes were evaluated just after
radiation and at 26 days storage. Organoleptic test and Chemical composition were done
at an interval of 2-4 days respectively throughout the storage period. Samples of each lot
were chemically analyzed to find their proximate value. The moisture content was
determined by weight loss of the sample on drying at 105ºC for 6 h (AOAC,1984) [16].Ash
content was determined through Straight Combustion Method by Triebold and Aurand
(Triebold et al.,1969) [17] .Crude fiber content was determined by the method of ICMR
(ICMR, 1971)[18].Lipid was determined by AOAC official method 922.06(AOAC, 1995)[19].Using Nx6.25 calculated protein content from total nitrogen after determination of the
total nitrogen by micro Kjeldahl Method (AOAC, 1995) [19].Carbohydrate content was
determined by subtracting the sum of the total value /100g for moisture, ash, protein, fat
and crude fiber from 100 according to Anonymous (Anonymous,1971) [20].Ascorbic acid
(Vitamin-C) content was estimated by 2,4-dinitro-phenylhydrazine method (Roe et
al.,1969) [21]. β-carotene was estimated by method of Holden (Holden,1981) [22]. Total
titrable acidity, pectin content reducing sugar, calcium, phosphorous and iron content
were determined by standard methods (Ranganna, 1980) [23].
Sensory evaluation: Sensory evaluations of all formulated Bananas were done by taste-
testing panel. This taste-testing panel was carried out by 16 panelists. They were asked to
evaluate color, flavor and overall acceptability a scoring rate on a 9-point hedonic scale.
Where, 9 = Excellent, 8 = very good, 6 = acceptable and 4 = poor. The preference
differences were evaluated by statistical analysis of the data for variance.
RESULTS
The analyzed chemical compositions immediate after harvesting and
after radiation are represented in Table 1.
Table 1: Comparison of observed Chemical composition of Banana just after
harvesting (before radiation) and after radiation per 100gm.
Constituents of Banana After harvesting After radiation
Moisture content 72.8% 72.7-75.7%
Ash content(gm) 0.8 0.8-1.38
pH 4.2 4.2-5.2
Vitamin-C(mg) 24 mg 10-24 mg
Reducing sugar(gm) 2.6 2.6-18.0
Carbohydrates(gm) 21.0 2-18
Crude fat(gm) 0.25 0.1-0.25
Protein(gm) 1.3 1.1-1.3
Fibre(gm) 0.82 0.80-1.6
Pectin(gm) 0.50 0.5-0.70
The moisture content of all the stored Banana was found within the
range of 72.7-75.7%. It was observed that there were no remarkable
changes in the moisture content through the storage period. Ash
content of the samples varies from 0.8-1.4gm per 100gm. Throughout
the storage period, there were no remarkable changes in ash content
of different samples. The value of PH varies 4.2 to 5.3 of the sample for
different storage time. Slight variation of PH was observed throughout
storage period. The variation of PH was due to variation of acidity
occurred during storage period at room temperature. The ascorbic acid
of different treated Banana was determined at every 2-4 days interval.
The loss of ascorbic acid is dependent on temperature and storage
time. In general the losses in vitamin-C content rarely exceed 20 to
30%. The irradiation of bananas at doses below 1 kGy may cause only
minor and insignificant chemical changes and very little loss of
vitamin-C content occurs and it is not nutritionally significant shown in
Table-2 and Figure 1.
Table: 2 Effect of Gamma radiation on Ascorbic acid content (mg/100gm) of the
Banana stored at room temperature
Storage period
(days)
Control (Cn)
0.0kGy
Radiation
0.3kGy
Radiation
0.4kGy
Radiation
0.5kGy
0 24 20 18 17
2 22 18 17 16
4 20 17 17 16
6 18 17 16 16
8 nd 16 16 15
12 nd 15 14 13
16 nd 14 13 12
20 nd 13 12 11
24 nd 13 12 11
26 nd 13 12 10
* nd = not done as spoiled
Figure-1: Effect of Gamma radiation on the Ascorbic acid content (mg/100gm) n of the
Banana stored at room temperature
The carbohydrate contents decreased due to inversion of sugar in presence of acid during
storage. During the storage period the carbohydrate content of the control was gradually
decreased. On the other hand the radiated samples were showed slowly decrease with
increasing storage period because of radiation represented in Table-3 and Figure-2.
Table: 3 Effect of Gamma radiation on total carbohydrate content (gm/100gm) of
the Banana stored at room temperature
Storage period
(days)
Control (Cn)
0.0kGy
Radiation
0.3kGy
Radiation
0.4kGy
Radiation
0.5kGy
0 24 20 18 17
2 22 18 17 16
4 20 17 17 16
6 18 17 16 16
8 nd 16 16 15
12 nd 15 14 13
16 nd 14 13 12
20 nd 13 12 11
24 nd 13 12 11
26 nd 13 12 10
* nd = not done as spoiled
Figure-2: Effect of Gamma radiation on total carbohydrate content (gm/100gm) of the
Banana stored at room temperature
The reducing sugar contents increased due to inversion of sugar during
storage period. But in radiated it is opposite figure, sugar percentage
increases slowly after radiation. During the storage period the reducing
sugar content of the control was gradually increased. On the other
hand the radiated samples were showed slowly increase of reducing
sugar after radiation represented in Table-4 and Figure-3.
Table: 4 Effect of Gamma radiation on reducing sugar content (gm/100gm) of the
Banana stored at room temperature
Storage period
(days)
Control (Cn)
0.0kGy
Radiation
0.3kGy
Radiation
0.4kGy
Radiation
0.5kGy
0 2.6 2.5 2.4 2.3
2 6.8 2.9 2.8 2.3
4 11.7 3.6 3.2 3.0
6 14.4 7.4 6.9 5.3
8 nd 8.2 7.5 6.3
12 nd 10.7 9.2 8.0
16 nd 13.4 11.7 10.3
20 nd 14.9 13.6 11.3
24 nd 16.2 15.9 13.8
26 nd 18.0 16.4 14.7
* nd = not done as spoiled
Figure-3: Effect of Gamma radiation on reducing content (gm/100gm) of the Banana
stored at room temperature.
The crude fibre content of the Banana were determined every 2-4 days
interval of storage period of the sample. The fibre after radiation was
about 0.84-1.2gm per 100gm during storage. It was observed that
there were no remarkable changes in crude fibre throughout the
storage .The crude fat content of the pulp was comparatively too
minimum. It was determined every 2-4 days interval of storage period
of the samples. The fat varies 0.1 to 0.3gm per 100gm during storage.
It was observed that there were no remarkable changes in crude fibre
during the storage period.
Throughout the storage period the slight variation of protein content
was observed at room temperature. The protein content varies 1.1-1.3
gm per 100gm during storage. It was observed that there were no
remarkable changes in protein content throughout the storage period.
Throughout the storage period the slight variation of pectin content
was observed at room temperature. The pectin content varies 0.5-0.7
gm per 100gm during storage. It was observed that there were no
remarkable changes in pectin content throughout the storage period [26].
Throughout the storage period the slight variation of beta-carotene
content was observed at room temperature. The content beta-carotene
varies 0.003-0.001gm per 100gm during storage. It was observed that
there were no remarkable changes in beta-carotene content
throughout the storage period.
Throughout the storage period the slight variation of calcium content
was observed at room temperature. The Calcium content varies 8.0-
12.0mg/100gm during storage. It was observed that there were no
remarkable changes in Calcium content throughout the storage period.
Throughout the storage period the slight variation of Phosphorus
content was observed at room temperature. The phosphorus content
varies 18-22mg/100gm during storage. It was observed that there
were no remarkable changes in Phosphorus content throughout the
storage period. Throughout the storage period the slight variation of
Iron content was observed at room temperature. The Iron content
varies 0.6-0.8 during storage. It was observed that there were no
remarkable changes in Iron content throughout the storage period.
The sample of different doses was observed continuously to see the shelf life
extension of the Banana stored at room temperature and the results are
given in Table 5 and Figure 4.
Table 5: Effect of Gamma radiation on the shelf life extension of the Banana stored at
room temperature
% Of the Sample of ripening
Storage
period
(days)
Control (Cn)
0.0kGy
Radiation
0.3kGy
Radiation
0.4kGy
Radiation
0.5kGy
0 0 0 0 0
2 24 0 0 0
4 87 5 0 0
6 100 8 3 1
8 nd 10 7 4
10 nd 12 8 5
12 nd 16 11 8
14 nd 20 14 12
16 nd 25 18 15
18 nd 32 24 21
20 nd 40 30 27
22 nd 65 54 39
24 nd 73 62 57
24 nd 85 76 69
26 nd 100 92 85
27 nd 100 100 95
28 nd 100 100 100
nd = not done as spoiled
Figure-4: Effect of Gamma radiation on the shelf life extension of the Banana stored at
room temperature
The irradiated bananas were subjected to sensory evaluation just after
radiation and 26 days of storage at room temperature. A panel of 16
judges evaluated the flavor, color and overall acceptability of the
stored Banana. The mean scores for color, flavor and overall
acceptability of different treated Banana are presented in Table 6. The
scores given by the panelists were analyzed for each quality attributes. A statistical
analysis of the score response by the taste-testing panelists on the Banana revealed that
color, flavor and overall acceptability were not significantly different due to the
treatment. Control Bananas stored at room temperature were spoiled within 6 days
whereas the shelf life of the irradiated Bananas could extend up to 26 days of storage at
room temperature. It was found that the Banana with 0.3kGy Gamma radiation were
higher acceptable by the taste-testing panelists. A two-way analysis of variance
indicated that all the sensory attributes of different radiated Bananas
were not significantly (P<0.05) different and thus the sensory
attributes of the Banana showed equally acceptable (Gross, 1976) [24
Table 6: Rating scores for overall acceptability of the Banana after 26days storage.
No of taster Sample
Control 1kGy 3kGy 5kGy
1 7 6 7 7
2 6 5 8 7
3 5 6 7 8
4 6 6 6 7
5 5 7 7 6
6 6 6 6 8
7 6 5 7 6
8 7 7 8 7
9 8 6 8 8
10 5 5 7 7
11 6 7 7 6
12 6 6 8 6
13 6 4 8 6
14 7 6 7 7
15 6 5 9 6
16 7 8 8 7
Total 99 95 118 109
Mean 6.187 5.937 7.375 6.812
Hedonic scale: Excellent=9; Very good=8; Good=7; Acceptable=6; Poor=5.
DISCUSSION
The objectives of the present study are to extend the shelf life of Bananas using Gamma
radiation at room temperature. During storage negligible changes were observed in
moisture, ash and fiber content. Slightly change occurred in case of acidity, pH, and
Protein content. No remarkable decrease of ascorbic acid was observed. In case reducing
sugar gradual increase was observed after radiation with storage period whereas in
control sudden increase of reducing sugar was observed with storage period.
The feasibility of applying ionizing radiation technique depends on a fruit’s tolerance to a
minimum dose. At the joint FAO/IAEA panel meeting on irradiation to solve Quarantine
problems in the International Fruit Trade, December, 1970, several researchers presented
result of their studies on irradiated fruits such as Banana, Apples, Mango etc. which
showed that all of these fruits could tolerate Gamma-radiation treatment to 1.0 kGy
without any phytotoxicity (Marriott,1980).[25] More recent studies on the use of Gamma-
radiation as a substitute of chemical fumigation showed that the fruits could tolerate 0.5
kGy treatment without any external or internal chemical or sensory quality
changes(Marriott,1980; Salda et al.,1976; Kenyhercz et al.,1978 [25,26,27]. Fruits could
actually tolerate up to 0.75 kGy without any quality changes especially refrigerated at 70C
(Kesevan et al., 1966) [28].
In this study acceptability of the stored pulp was tested by a panel of 16 judges. It was
found that the Banana with 0.3kGy Gamma radiation were higher acceptable by the taste-
testing panelists. With the result of the research it will be helpful to identify the Physical,
Chemical and nutrients content of Banana, to study the shelf-life of irradiated Bananas, to
identify the nutritional condition during preservation of irradiated Bananas, to compare
the nutritional quality and quantity of irradiated and chemically fumigants Bananas, to
reduce the losses of post-harvested Bananas, to extend commercial uses of Bananas.
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