Presenting author: Ru Shen

Co-authors: Yunxian Liu, Dennis Pinto, Nick Martsch, Anthony Cam, William Helferich, and Nicki J. Engeseth

Department of Food Science and Human Nutrition

Introduction: Deep-fat frying promotes desirable flavors, colors and textures in foods; yet, it can also result in the development of undesirable compounds especially using repeatedly reutilized oil which is named thermally Abused Frying Oil (TAFO). Consumption of foods with TAFO may have adverse health outcomes due to the accumulation of undesirable compounds. A factor affecting formation of these undesirable compounds is composition of foods for frying. Therefore, the goal of the current research was to investigate the influence of food source on the formation of potential health-damaging undesirable compounds in deep-fat frying. Method: Frying experiments were performed repeated frying cycles of three most consumed fried foods in the US: chicken, fish, and potato in soybean oil intermittently (100 cycles, 180 ± 5°C). Unheated oil and oil simultaneously heated without food served as controls. Oil and foods were sampled at select time points and frozen for further analysis of composition, physical properties (color and viscosity), chemical properties (peroxide value, p-anisidine value, free fatty acids, and polar compounds). Undesirable compounds, including epoxy fatty acids and aldehydes, in foods and TAFO were characterized using GC and HPLC. Results: Repeated exposure of frying oil to high temperature resulted in significant deterioration of the oil and the food. This deterioration was highly dependent upon the type of food fried. Oils subjected to heating but no food introduction maintained quality, with less deterioration and less viscosity. TAFO with fish had the most dramatic increase in free fatty acids, total polar compounds (TPC), and peroxide value; chicken TAFO was similar to fish and potato TAFO had the lowest deterioration. Differences in undesirable component formation in the fried foods (that ultimately may lead to adverse health outcomes) will also be highlighted. After 100 cycles of repeated frying, the TPC content in TAFO ranged from 10.529 to 24.290%, whereas in control heated oil it was 3.853%. Significance: This study clarifies the impact of food source and repeated frying cycles on undesirable compound formation during deep-fat frying, which enables the industry to control the quality of fried foods and potentially reduce the health risks associated with these highly desired foods.