Separation and quality of fish oil from precooked and non-precooked tuna heads

Separation of crude oil from precooked and non-precooked skipjack tuna heads by a wet reduction method was carried out. Both heating temperature and time affected the separation and oil quality. Optimum conditions for separation of crude oil involved heating samples at 85 degrees C for 30 min, followed by pressing at 140 tons/m(2) using a hydraulic press. Yields of crude oil prepared from precooked and non-precooked samples were 2.8 and 4.8%, respectively. Crude oil obtained from non-precooked samples showed markedly higher quality than that from precooked samples. Crude oil from precooked samples had a higher peroxide value and much darker colour than that from non-precooked samples. However, crude oil from precooked samples had higher DHA (25.5%) than that from non-precooked samples (18.5%). (C) 2000 Elsevier Science Ltd. All rights reserved.