الفهرس 
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Abstract
Occurrence of mycotoxins in cereal foodstuff is unavoidable. The attendant challenges to crop production, yield and quality loss is about 25% annually according to FAO.
Aflatoxin B1 is the most potent hepatocarcinogen known in animals and it is classified by the International Agency of Research on Cancer (IARC) as Group I carcinogen meaning that it is a proven cancer-inducing agent. It also occurs in the environment contaminating a lot of different food and feed commodities. Aflatoxins are a group of mycotoxins produced in tropical and sub-tropical regions. Aflatoxins are hepatic and carcinogenic secondary metabolities of moulds that produce mainly from Aspergillus flavus and Aspergillus paraciticus. Aflatoxins contaminate a variety of agricultural commodities in countries with hot and humid climates.
The aim of this study was to assess the possible effect of gamma irradiation on the reduction of aflatoxin B1 in some cereal grains and the impact on nutritive values including, ash, moisture, fat, protein, carbohydrates, crude fibers, calories, fatty acids profiles and amino acid profiles.
One group pre and post intervention study was performed on 60 samples (one kilogram for each sample) divided equally among the three cereals including maize, wheat, and rice.
To achieve this aim the following was carried out:
Samples (maize, wheat, and rice) were randomly selected from the local markets and wholesale markets in Alexandria city during June, July, and August-2013. Each one kilogram sample was subdivided into equal four sub-groups. Samples were stored in plastic bags at 4ο C until analysis.
A. The first quarter quantity of each cereal sub-sample (control sample) was taken to the central lab of High Institute of Public Health for the following analysis:-
1. Determination of aflatoxin B1 by high performance liquid chromatography.
2. Proximate analysis for cereal samples include:
• Determination of moisture contents
• Determination of fat contents by Soxhlet method.
• Determination of protein contents by Kjeldahl nitrogen method.
• Determination of ash contents.
• Calculation of carbohydrate contents.
• Determination of crude fibers
• Calculation of sample calories.
3. Preparation of methyl esters by sodium methoxide method followed by determination of fatty acid profile by gas liquid chromatography.
4. Determination of amino acid profile by amino acid analyzer.
B. The second quarter sub-sample of each cereal type was irradiated using gamma irradiation source from 60CO at an absorbed dose level of 4 kGy each followed by analysis for aflatoxin B1, proximate analysis, fatty acid profile and amino acid profile, analysis was performed as described previously.
C. The third quarter sub-sample of each cereal type was irradiated using gamma irradiation from 60CO at an absorbed dose level of 6 kGy each followed by analysis for aflatoxin B1, proximate analysis, fatty acid profile and amino acid profile as described previously.
D. The fourth quarter sub-sample of each cereal type was irradiated using gamma irradiation from 60CO at an absorbed dose level of 8 kGy each followed by analysis for aflatoxin B1, proximate analysis, fatty acid profile and amino acid profile as described previously.
The results of this study was statistically analyzed; data were fed to the computer and analyzed using IBM SPSS software package version 20.0 and significant data was taken at p < 0.05 using ANOVA test.
It was found that:
1. Maize samples contain the highest level of aflatoxin B1 than wheat and rice.
2. Gamma irradiation is a suitable technique which reduces the levels of aflatoxin B1 in cereal samples without affecting the nutritive values, at 4 KGy the reduction percents of aflatoxin B1 were 15.54%, 22.25%, and 27.46% for maize, wheat, and rice, respectively whereas at 6 KGy the reduction percents of aflatoxin B1 were 32.39%, 43.84%, and 56.38% for maize, wheat, and rice, respectively and the 8 KGy radiation dose removed about 60.26% of the toxin in maize, 64.68% in rice and 69.29% in wheat samples.
3. Higher radiation doses than 8 KGy are required to remove the toxin until it reaches the legal limit (5ppb) according to FAO.
4. By increasing the radiation doses the percents of reduction of aflatoxin B1 increase (dose dependent manner) in cereal samples.
5. The percents of reduction decrease with increasing the oil contents of cereals so maize had the lowest aflatoxin B1 reduction level.
6. Gamma irradiation affect on fatty acid profiles of wheat and rice, causes reduction in mono-unsaturated fatty acid (oleic acid, C18:1) and poly-unsaturated fatty acid (linolenic acid, C18:3) which disappear completely in rice at 8 KGy, while in maize samples there was increase in the saturated fatty acid (palmitic acid, C16:0) and decrease in the mono-unsaturated fatty acid (oleic acid, C18:1) and this consistent with other studies.
7. Gamma irradiation affects slightly on amino acid profile of cereal grains in maize samples there is a reduction in phenyl alanine and threomine and increase in leucine, in wheat samples there is a decrease in tryptophan, isoleucine, phenylalanine, arginine and lysine and an increase in leucine and in rice samples there is increase in leucine and decrease in phenylalanine.