الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
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Abstract
The world losses of food grains due to storage fungi are about 25of the harvested crops before consumption (FAO). During storage these fungi might produce chemical substances (mycotoxins) that cause toxic symptoms when man or animals ingest contaminated food. Aflatoxin is one of the most frequent contaminating mycotoxins in food stuffs. Aflatoxins are toxic mold metabolites produced by some toxigenic strains of Aspergillus flavus and A. Parasiticus that occur in many foods and feeds. Aflatoxins are among the most toxic substances known, being acutely toxic to the liver, and with chronic exposure, potent carcinogens of the liver. Symptoms of acute aflatoxicosis are fever, vomiting, coma and convulsions. The aim of this study was to study the effect of growth of aflatoxin and ochratoxin producing fungi separately and combined on the chemical properties of wheat ; to evaluate the effect of growth of these fungi species separately and combined on the rheological properties of the dough and to determine the effect of bread processing on the stability of aflatoxins. To achieve this aim, the following was carried out: 1. The moisture of wheat was raised to 16 and then each cultivar of wheat (Sakha 8 and Gemaiza 5) was divided into four groups; the first was the control, the second was inoculated with 8.68 x 109 spore/kg Aspergillus flavus, the third was inoculated with 8.68 x 109 spore/kg Aspergillus ochraceus, fourth sample was inoculated with 8.68 x 109 spore/kg mixture of both types of fungi. All the samples were incubated at 27 ?C for 7 days. 2. The effect of different treatments with mold species on the protein, oil, free fatty acids (as oleic acid), ash and iron contents in the two studied wheat cultivars (Sakha 8 and Gemaiza 5) was determined. 3. The effect of growth of these fungi species separately and combined on the rheological properties of the dough of the two wheat cultivars of the different treatments was evaluated by studying the farinograph characteristics, studying the extensograph characteristics, studying the amylograph characteristics and finally studying the falling number of 82 flour and 100 flour. 4. Aflatoxins (B1, G1 and G2) content was determined in different fractions (whole grain, bran, short and flour) of the two studied wheat cultivars. 5. The effect of milling and bread baking processes on aflatoxins levels was also studied. This study revealed the following results: 1. Effect of mold growth on the chemical composition of wheat: 1. Protein and free fatty acids percentages increased significantly at p < 0.05 in the samples inoculated with Aspergillus species than the control samples in each of Sakha 8 and Gemaiza 5 wheat cultivars. 2. Ash content of Sakha 8 and Gemaiza 5 wheat cultivars decreased significantly after treatment with Aspergillus spp. 3. Iron content of Sakha 8 and Gemaiza 5 wheat cultivars showed a non significant decrease after treatment with Aspergillus spp. The lowest concentration was in combined treatment. Iron content was higher in Sakha 8. 2. Aflatoxin production in different wheat cultivars: 1. The total aflatoxins concentration in the whole grain, bran, short and flour of Sakha 8 cultivar were significantly higher than those of Gemaiza 5 cultivar at p < 0.05. 2. There was a significant difference at p < 0.01 between the two treatments (single and combined) of the different wheat fractions concerning AFG1 and the total aflatoxins contents. 3. In most of the cases of wheat treatment, the highest total aflatoxin concentration was found in bran fraction, followed by whole grain, short, then flour. 3. Effect of bread making steps on aflatoxin concentration in wheat: 1. The total aflatoxins contents in Sakha 8 and Gemaiza 5 either treated singly or treated in a combined way after milling were lower than those before milling. The concentration of each of AFB1, AFG1 and AFG2 separately was also reduced after milling.