Aldehydes in oxidized oils and fried foods and their associations with animal growth performance

Abstract

Thermally oxidized oils from cooking and industrial processing contain diverse lipid oxidation products (LOPs), in which aldehydes are an important group of reactive secondary LOPs because of their unique sensory and toxicological properties. Besides being the major contributors to the flavor of fried foods, aldehydes, especially unsaturated alkenals and hydroxyalkenals, can react with proteins and DNA and disrupt the redox balance, resulting in the initiation of the toxic events in humans on consuming fried foods and in other animals exposed to thermally oxidized oils. Therefore, examining the formation and distribution of aldehydes in cooking oils and fried foods as well as their associations with animal performance are imperative for understanding the chemical composition and biological activities of thermally oxidized oils and fried foods. In this project, chemometric comparisons of camellia oil, a high-oleic acid oil, with other plant-derived cooking oils were conducted to determine their triacylglycerol composition and heating-induced chemical changes, including aldehyde formation and distribution, through both liquid chromatography-mass spectrometry (LC-MS) analysis and the analysis of common quality indicators. The transfer of aldehydes from frying oils to fried food as well as their potential interactions with the food matrix was examined by chemometric comparisons of heated soybean oil, frying soybean oil, and the extracted oils from French fries. The potential influences of aldehydes on animal performance were examined by analyzing the correlations between the aldehyde levels in thermally oxidized soybean oils and the growth and feed intake of the pigs and broilers fed these oxidized oils. The results of these analyses are summarized as follows. (1) Camellia oil can be distinguished from other cooking oils based on its triacylglycerol profile. Under the thermal stress, the formation of aldehydes in virgin camellia and olive oils was affected by both fatty acid composition and antioxidant contents. (2) Distribution and abundances of individual aldehydes in the extracted oils of French fries differed greatly from that of heated oils and frying oils, potentially due to the interactions between aldehydes and food matrix. C9-11 aldehydes had higher transfer rates to fried food than C7-8 aldehydes. (3) Individual C9-C11 unsaturated aldehydes could be more reliable prediction markers of growth performance compared to common quality indicators when feeding heavily-oxidized soybean oil to non-ruminants. Overall, this new knowledge on the formation and distribution of aldehydes in frying oils and fried foods as well as the aldehyde markers for predicting animal response could assist future research efforts on reducing the formation of reactive aldehydes in frying oils and fried food, and alleviating the adverse effects associated with the consumption of fried food and oxidized oils in humans and other animals.