Nutritional Value of Fried Potatoes and Onions in Sesame, Canola and Frying Oils

Fats and oils play important sensory and functional roles in food products. They are responsible for enhancing and releasing flavor components that react with other components to enhance the texture and mouthfeel of fried foods. Fat is a natural factor in making the food delicious. When frying food, hot oil penetrates into it, replaces its water content and makes it significantly more pleasant. This absorbed fat makes the crust crispy and affects the taste. In this study, the effect of deep frying process in sesame, canola and frying oils on nutrients and bioactive compounds of onions and potatoes and evaluation of their antioxidant activity were investigated.

Slices of potato and onion were fried in sesame oil, canola and special frying oils for 8 minutes and 4 minutes, respectively. Deep frying was carried out in three separate steps (for new samples but in that oils) with an interval of three hours between each step. Slices of fried potatoes and onions were evaluated by measuring total polyphenol factors, fatty acid composition and antioxidant activity.

During frying, elaidic acid is produced in canola oil (1.14-1.53% in the first and third stages of frying, respectively), but no significant difference was observed between the first stage and the third one. Due to the oxidation of linoleic acid in all fried onion and potato samples the content of linoleic acid decreased palmitic acid content was increased. The height amount of total poly phenols in fried potato slices were found in potatoes fried in sesame oil followed by potatoes fried in canola and finally in frying oils. The same observations were made for onion slices fried.The amount of polyphenols in fried samples showed a significant difference as compared to pre-frying (P <0.05). The highest oxidation resistance as indicated by Rancimat test was observed in potato slices fried with sesame oil, followed by special frying and finally canola oils. The same observation was made for onion slices.

It might be concluded that sesame oil probably due to its fatty acid composition and oxidational contents might be regarded as a better media for deep frying applications as completion to canola and frying oils.