Effect of frying period and repeat on composition fatty acids formation in some frying oils

Key words: Canola oil, shortening, potato, composition fatty acids, trans fatty acids.In this study, changes of fatty acid composition, oil absorbtion ratios and water contents of both potatoes and their friying oils were determined depending on friying time and repeating.For this purpose, freezing and semi-processed potatoes were fried rapeseed oil and shortening oil for 8 hours. Samples were taken from potatoes and oils at the end of each hour then changes of fatty acid compositions, ratio of oil absorbtion and water contents of potatoes were analyzed individually.Results for fried rapeseed oil and shortening oil during 8 hours and fried potatoes in these oils wereare follow oil amounts of potatoes which were fried in rapeseed oil and shortening oil, increased by 25,67% and 24,7% (on the basis of dry matter), respectively. Water content of potatoes fried in rapeseed oil and shortening were decreased by %49,32 and %48,56, respectively. ?SFA in rapeseed oil increased by %21 and ?SFA at potatoes fried in this oil increased by 17,71%. ?SFA in shortening increased 3,66% as for that fried potatoes in this oil increased by 3,08%. ?MUFA in rapeseed oil decreased by 9% as for that fried potatoes in this oil decreased by 9,57%. ?MUFA content was decreased by 1,89% in shortening, while decreased by 1,605% in fried potatoes. ?PUFA at rapeseed oil decreased by 10,68% as for that fried potatoes in this oil ?PUFA ratio decreased by 9,045%. ?PUFA in shortening decreased by 1,98% as for that fries potatoes in this oil ?PUFA ratio decreased by 1,675%. Trans fatty acids were detected in control samples of potatoes (0,125%) and only in potatoe samples fried in shortening for 32 times (%0,25).