Effects of ethanol defatting on nutritional components, lipid oxidation, flavor characteristics and antioxidant capacity of snakehead peptides

This study systematically quantified the effects of defatting degree on the quality of snakehead peptides, focusing on the interrelationships among lipid oxidation, off-flavor formation, and antioxidant capacity. Compared with non-defatted peptides (NFD), twice-defatted peptides (FD2) significantly reduced crude fat content by 74.6% (from 8.86 to 2.25 g/100g, p < 0.05), and decreased lipid oxidation indicators including TBARS by 60.2% (from 5.90 to 2.35 mg MDA/kg, p < 0.05), POV by 48.6% (from 0.241 to 0.124 meq/kg, p < 0.05), and free fatty acid content by 66.9% (from 66.39 to 21.96 μmol/g, p < 0.05). Among the 70 volatile compounds identified by GC-MS, 8 key compounds were significantly associated with off-flavor substances, namely octanal, nonanal, 1-octen-3-ol, decanal, (E)-2-nonenal, 1-octanol, (2E,4Z)-deca-2,4-dienal, and (2E,4E)-deca-2,4-dienal. They all showed varying degrees of decline after defatting, with the most potent off-flavor contributor (2E,4E)-deca-2,4-dienal decreasing by 90.7% (from 6.46 to 0.60 μg/kg, p < 0.05). Furthermore, FD2 treatment increased the proportion of peptides with molecular weights of 0.5-3.0 kDa, enhanced ABTS cation radical scavenging activity by 4.2% (from 83.4% to 87.6%, p < 0.05) and DPPH radical scavenging activity by 2.7% (from 50.9% to 53.6%, p < 0.05), while slightly decreased the ferrous ion chelating ability. This study demonstrates that two-cycle ethanol defatting is a promising and scalable processing technology for mitigating off-flavors and improving the overall quality of snakehead peptides for food industry.