Development of an Improved Method to Determine Saturated Aliphatic Aldehydes in Docosahexaenoic Acid‐Rich Oil: A Supplement to p‐Anisidine Value

Abstract

p‐Anisidine value (AV) is an important and commonly used index to determine the second oxidation statue of edible oils, but it sometimes cannot reflect the concentrations of all the secondary products, such as saturated aldehydes. An improved method for the determination of saturated aliphatic aldehydes (SAA) in docosahexaenoic acid (DHA)‐rich oils is developed in this study. This method reduces the aldehyde 2,4‐dinitrophenylhydrazone adducts (DNPhydrazones) using 2‐picoline borane, which can eliminate the analytical error caused by the isomerism of DNPhydrazone derivatives. The changes of SAA content during the oxidation of DHA‐rich oil is subsequently monitored. Acetaldehyde (168.8 µmol kg−1) and propionaldehyde (78.5 µmol kg−1) are the two main SAAs in fresh oil, and their concentrations increase to 824.8–811.9 µmol kg−1, respectively, after oxidation for 50 h at 80 °C. Furthermore, a Michael addition reaction is found to significantly reduce the AV of oxidized oils, from 172.5 to 11.7. Moreover, the concentration of SAAs shows no significant difference and could clearly identify the low‐quality oil. These results demonstrate that SAA content might be a potential index to identify oxidized oils, which could provide a good supplementary value to the traditional AV index. Practical Applications: The method that has been developed in this study makes it possible to quantify saturated aliphatic aldehydes as markers of oxidation of oils, especially when the panisidine value (AV) cannot correctly assess the levels of secondary products. It could serve as a supplement to the AV index and could be applied to oils, fats, and food products. This work provides quantitative data regarding the amounts of saturated aliphatic aldehydes that can be present in DHA‐rich oils during the oxidation process.An improved method for determinig saturated aliphatic aldehydes (SAA) in docosahexaenoic acid (DHA)‐rich oils is developed. The changes of SAA content during the oxidation of DHA‐rich oil is monitored. Furthermore, a Michael addition reaction is found to significantly reduce the AV of oxidized oils, from 172.5 to 11.7. The concentration of SAAs does not display significant differences and can clearly identify the low‐quality oil. These results demonstrate that the SAA content might be a potential index to identify oxidized oils, which could serve as a good supplement to the AV index.