4-Hydroxy-2-Alkenals: A Potential Toxicological Concern of Vegetable Oils?

Abstract

4-hydroxy-2-alkenals, namely 4-hydroxy-2-nonenal (HNE) and 4-hydroxy-2-hexenal (HHE) are secondary lipid oxidation products of n-6 and n-3 polyunsaturated fatty acids, respectively. An overview of the current knowledge about HNE and HHE in vegetable oils, including factors influencing their formation, health effects, analytical approaches, as well as mitigation strategies and future challenges are discussed. During the last years, an increased attention is being paid to these mutagenic, cytotoxic and genotoxic compounds. Due to their high reactivity and implication in numerous undesirable reactions, they can be linked with several diseases and medical conditions. Vegetable oils were identified as one of the major sources of these compounds, becoming a potential toxicological concern for public health. Up to now, the fatty acids composition, time, temperature and type of frying, as well as different processing conditions were evaluated in order to find a relationship with the presence of these hazardous compounds in vegetable oils. With respect to mitigation strategies to reduce the occurrence of HNE and HHE in vegetable oils, atmospheres with low oxygen content during frying, carbon dioxide blanketing as well as addition of phenolic compounds to the vegetable oils were studied. In the near future, it is important to exploit other conditions to explain the different amounts reported for the same type of vegetable oil from different origins, as well as to evaluate realistic conditions of frying, especially the presence of food, frying equipment and temperatures, among others.