A chemometric study on the identification of 5-methylfurfural and 2-acetylfuran as particular volatile compounds of oxidized fish oil based on SHS-GC-IMS

Abstract

Fish oil develops particular off-odors, mainly fishy odor, from the oxidation of its characteristic fatty acids, docosahexaenoic (DHA) and eicosapentaenoic (EPA). Anchovy oil (AO) was taken as representative of fish oils. This was compared to three vegetable oils with different fatty acid compositions, i.e. camellia, sunflower and linseed oil, and differential volatile compounds were identified by static-headspace gas-chromatography ion-mobility-spectrometry (SHS-GC-IMS) and orthogonal partial-least-squares discriminant analysis (OPLS-DA) during oxidation at 60 °C. Three groups of differential volatile compounds detected at higher concentrations in the AO were screened out and two compounds, identified as 5-methylfurfural and 2-acetylfuran, were characteristic to the AO and not found in the vegetable oils. They were formed from both EPA and DHA, only present in the AO, and their formation mechanisms were proposed. The contents of 5-methylfurfural and 2-acetylfuran increased linearly with the oxidation time and consequently they could be used as oxidative markers of fish oils.