Release of Free Fatty Acids From Lipids During Ensilation of Herring Mince: The Possible Role of Ethoxyquin

Studies were conducted on the release of free fatty acids (FFA) from lipids during ensilation of herring mince at room temperature. The silages were produced by the addition of 3.5% formic acid and the effects of heat treatment and also the presence or absence of an antioxidant (ethoxyquin) were examined. The lipid classes extracted from silages at different ensiling stages were determined by Chromarod/Iatroscan‐TLC/FID. Free fatty acids were rapidly released from lipids at the beginning of ensilation in all three silages examined. The maximum level of FFA released in silages without heat treatment was reached after only 6 days of ensilation and levels of about 6% of true FFA in total lipids were maintained until the end of the ensilation process. The heat treatment of 55C for 10 min effectively inhibited the release of FFA from lipids and the amounts of FFA released were significantly lower than in those lots without heat treatment. The presence of ethoxyquin in silage did not show a significant effect in controlling the production of Iatroscan‐detectable FFA from lipids when compared with the silage made without ethoxyquin. A large amount of oxidized lipid, corresponding to a decrease in triacylglycerol, was detected by TLC‐FID in the lot of silage made without the addition of ethoxyquin; however, the addition of antioxidant in two other silages effectively protected the lipids from oxidation during the ensilation period. The experimental results confirmed that lipases play an important role in lipid autolysis. By examining the changes in phospholipids, it was possible to show that the majority of the FFA released originated from phospholipids and only a small fraction came from neutral lipids. The maximum production of FFA in herring silage should depend, to a large extent, on the amount of phospholipids present in the raw materials.