Effects of season and processing on oil content and fatty acids of Baltic herring (Clupea harengus membras)

Fatty acid composition, oil content, free fatty acid content, and peroxide value of Baltic herring (Clupea harengus membras) and two processed product s (fried fillets and fish burgers) were investigated. The highest oil conte nt of the fillets was found in autumn (10%), at the time when the free fatt y acids had their minimum (1.4%). The main fatty acids were oleic (18-23%), palmitic (17%), palmitoleic (8-12%), and docosahexaeneoic (8-10%) acids. T he proportion of saturated fatty acids was a constant 23% all year around, whereas mono- and polyunsaturated acids varied from 34 to 39% and 33 to 37% , respectively. During processing the oil content doubled and the fatty aci d composition changed to the pattern of the rapeseed oil used for frying. O leic acid was a major fatty acid in the products comprising over 40% of the total fatty acids. The proportion of n-3 acids decreased during processing but the total amount of polyunsaturated acids remained fairly constant.