Influence of food type, oil type and frying frequency on the formation of trans-fatty acids during repetitive deep-frying

Frying oil quality is immensely affected by frying frequency, type of food and oil used for frying. The main aim of this study was to investigate the impact of food type (fish, chicken, potato and peas), oil type (soyabean and mustard oil) and frying frequency on the trans-fatty acid (TFA) formation in both deep-fried oils and the foods fried in these oils. Increase in frying-time leads to an increased TFA content with trans18:1 in higher concentration (0.87-2.41%) followed by trans18:3 (0.38-1.70%) and trans18:2 (0.22-1.37%) with trans18:2 formed at a higher rate comparatively. Highest TFA was accumulated in soyabean-oil used for frying fat rich food followed by protein, carbohydrate (CHO) and vegetable-based foods as compared to mustard oil-based foods. Total TFA in soyabean-oil used for frying fish after 25th hour was 5.48% and the TFA content retained in fried fish after 50 frying cycles was 3.98%. TFA content increased 2.56, 2.98, 3.29-folds and 2.38, 2.70 and 3.15-fold for one, two and three frying per half hour while frying fish-fillets in soyabean and mustard oil respectively. Oxidative stability and TFA formation were found to have a direct correlation and soyabean oil used for frying fat rich group shows higher degradation compared to mustard oil in terms of acid value, peroxide value, TBARS value and panisidine value. Thus, proximate composition of a food and fatty acid composition of an oil plays a key role in the formation of TFA during deep frying.

Automated summary

Frying oil quality is influenced by frying frequency, type of food, and oil used. The study investigates the impact of food type, oil type, and frying frequency on the formation of trans-fatty acids (TFA) in oils and fried foods. Increased frying time leads to higher concentrations of trans18:1, trans18:3, and trans18:2 TFA. Soybean oil used for frying fat-rich food accumulates the highest TFA content, followed by protein, carbohydrate, and vegetable-based foods compared to mustard oil-based foods. Oil degradation is higher in soybean oil compared to mustard oil. The composition of the food and fatty acid composition of the oil play a significant role in TFA formation during deep frying.