الفهرس 
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Abstract
Deep fat frying is an important method of food preparation. Chemical reactions occur during frying and give rise to formation of complex products and oxidized fatty acids which are absorbed by the food. Consequently there is need to characterize the nutritional consequences of their ingestion. This study was performed with the aim of: 1) Studying the effect of household frying practice on the frying oil. 2) Study the effects of chronic consumption of the repeatedly heated oils on experimental animals. This study was planed as follow: The first part of this study aimed to assess the effect of heating on oils by measurement of the TBARS content in fresh, heated and repeatedly heated studied oils (sunflower, cottonseed and mixed oils). The second part of this study aimed to test the effect of chronic consumption of the repeatedly heated oils. This was conducted on seventy adult male albino rats divided into 7 groups; negative control group fed oil free diet, 3 positive control groups fed fresh oils, and 3 experimental groups fed repeatedly heated oils for three months. The test diets were prepared by mixing the test oil with the primary ration (15% W/W). The effects were assessed by; weight studies (determination of the weight gain and relative liver and kidneys weight), biochemical studies (determination of serum TBARS, glutathione peroxidase, tochopherol, AST, ALT, albumin, creatinine and urea) and pathological study of liver, kidneys, colon, testes and heart. Results revealed: ” 1) the deteriorative effect of heat increases by increasing the duration of oil use. 2) the repetition of heating was much more destructive than the continuous use of the oil. 3) Sunflower oil can tolerate heating better than cottonseed and mixed oil. ” Chronic consumption of the repeatedly heated oils leads to significant increase in the serum level of TBARS with concomitant decrease in antioxidants (glutathione peroxidase and tochopherol) and significant increase in serum AST, ALT, creatinine and urea with decreased albumin. This study has concluded that: ” Frying is better avoided. Repeated use of the oil for frying must be avoided even with short periods of use. Sunflower oil can tolerate heating better than cottonseed and mixed oil. ” Chronic consumption of the repeatedly heated oils leads to significant decrease in weight gain, increase in the serum level of peroxidative products and decrease of the antioxidants. It also alter the liver and kidney functions. It also leads to significant pathological changes in liver, , kidneys, colon and testes.