الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 196 |  |  |
| | | from | 196 | | |
Abstract
The study of food contamination with mycotoxins is one of the most important topics in recent time because of its dangerous effects on human health as it can cause a lot of diseases in both humans and animals. Also contamination of foodstuffs by mycotoxin causes huge economic losses. The mycotoxins that usually contaminate cereal grains are aflatoxins, ochratoxins, deoxynivalenol, zearalenone and fumonisins.. These toxins may be not completely destroyed during food-processing operations and can contaminate finished processed foods.
Economically and hygienically, it is important to minimize the mycotoxins occurrence in food by designing appropriate strategies for each type of food.
The present thesis was aimed to study each of the following topics:
1. Isolation and identification of fungi associated with wheat grains and some of its traditional products in Upper Egypt (Wheat flour, Kishk, Burghol, Shamsy bread and Biscuits) collected from local markets of Assiut Governorate.
2. Study the ability of some isolated fungi to produce mycotoxins.
3. Survey the natural occurrence of mycotoxins in the studied products.
4. Study the fate of three types of mycotoxins (Aflatoxins, Ochratoxin A and Sterigmatocystin) during preparation of some traditional wheat products (Balila, Kishk and Shamsy bread).
5. Introducing some modifications to the manufacturing steps of some of the aforementioned products to help get rid of toxins that may be contaminated with it.
The obtained results could be summarized as follows:
1. Isolation of fungi from tested samples:
• Nine fungal species belonging to six genera were identified from wheat grain samples as follows: Aspergillus (4 species), Alternaria alternata, Cladosporium cladospoioides, Epiococcum nigrum, Penicillium chrysogenum and Rhizopus nigricans with total count of 238 CFUs/ 10 g.
• Five species belonging to three genera were identified from wheat flour samples as follows: Aspergillus flavus, Aspergillus niger, Aspergillus versicolor, Penicillium ducluxi and Rhizopus nigricans with total count 711 CFUs/ 10 g.
• Nine species belonging to five genera were isolated and identified from kishk samples as follows: Aspergillus (5 species), Alternaria alternata, Curvularia spicifera, Epiococcum nigrum and Penicillium ducluxi with total count 391 CFUs/ 10 g.
• Four species of Aspergillus in addition to Cladosporium cladospoioides, Penicillium chrysiogenum and Rhizopus nigricans were isolated and identified from Burghol samples with total count 622 CFUs/ 10 g.
• Seven species belonging to five genera were identified from Shamsy bread samples as follows: Aspergillus flavus, A. niger, A. versicolor, Alternaria alternata, Curvularia specifera, Penicillium ducluxi and Scopulariopsis brevicaulis with total count 55 CFUs/ 10 g.
• Three Aspergillus species (A. fumigatus, A. niger and A. versicolor) in addition to Penicillium ducluxi were identified from Biscuits samples with total count 266 CFUs/ 10 g.
2. Ability of the isolated fungi to produce mycotoxins
All the examined isolates of Aspergillus flavus, Alternaria alternata, Penicillium ducluxi and Penicillium chrysiogenum were proved to be non-producers of mycotoxins while one strain of each of Aspergillus niger and Aspergillus versicolor was able to produce ochratoxin A and sterigmatocystin, respectively.
3. Natural occurrence of mycotoxins in the studied samples
• Forty percent of wheat grain samples were contaminated by mycotoxins (Aflatoxin and sterigmatocystin).
• Twenty percent of wheat flour samples were contaminated by low concentration (less than 300 µg/Kg) of zearalinon
• One sample of Kishk out of five samples was contaminated by moderate concentration (300 - 500 µg/Kg) of aflatoxin B1.
• For wheat burghol, 40% of the examined samples contained moderate concentrations (300 - 500 µg/Kg) of aflatoxin B1.
• Each of Shamsy bread and Biscuits samples were free from any mycotoxin.
4. Fate of mycotoxins during preparation of Balila
• Aflatoxins content in samples was completely disappeared by washing the grains twice, soaking in sodium carbonate solution (0.1 M, pH 11) and boiling the grains in the same solution for at least 45 min. These treatments decreased aflatoxins content from 63.0503 to 2.1777 µg/ Kg.
• OchratoxinA was removed from balila by washing wheat grains three timeswith water, followe by soaking in water or sodium carbonate solution (0.1 M, pH 11) for 6 h and boiling for any suitable period.
• Sterigmatocystin could be eliminated during manufacture of balila after washing twice with tap water.
5. Fate of mycotoxins during preparation of Kishk
• Aflatoxin content was decreased from 13.8701 to 0.0215 µg/ Kg after washing wheat grain followed by sundrying for three days.
• Washing grains and sundrying it for two days was enough to eliminate all amount of Sterigmatocystin during manufacture of Kishk.
6. Fate of mycotoxins during preparation of Shamsy (sunny) bread
• Raw wheat flour used for preparation of Shamsy bread was free from Ochratoxin A & Sterigmatocystin and their aflatoxins content detected by HPLC was only 0.0096 µg/ Kg.
• First stage of fermentation was enough eliminating aflatoxins and ochratoxn A from artificially contaminated dough. Meanwhile, sterigmatocystin was disappeared after the second fermentation stage.