Dr. G. JEYASEKARANNIMISH MOL STEPHEN, B.F.Sc.2020-07-312020-07-312005http://krishikosh.egranth.ac.in/handle/1/5810150196The fatty acid profile of six commercially important fish viz. seerfish (Scomberomorus commersonii), pomfret (Pampus argenteus), tuna (Katsuwonus pelamis), shrimp (Penaeus semisulcatus), sardine (Sardinella fimbriata) and mackerel (Rastrelliger kanagurta) landed in Thoothukudi fish landing centers were studied. Health beneficial n-3 polyunsaturated fatty acids (PUFA) such as DHA (C22:6) and EPA (C20:5) were high in mackerel, seerfish and tuna with values ranging from 5.96-11.86% and 2.40–4.92%, respectively and were chosen for further study to find out the effect of heat processing treatments on the omega-3 PUFA. The fish were subjected to cooking at 1000C for 10, 20 and 30 min., frying at 1800C for 5, 7.5 and 10 min., canning at 1100C for 90 min., 1150C for 70 min. and 1210C for 40 min., and microwave oven heating at 2450 MHz for 10, 15 and 20 sec. Besides testing for omega-3 fatty acids, they were also analyzed for proximate composition, sensory, bacteriological, physical and biochemical quality. Cooking for 30 min., frying for 7.5 min., canning at 1100C 90 min. and oven heated for 15 sec. yielded good sensory quality products. In cooked, canned and oven heated fish, 2-4 logs reduction in aerobic bacterial load was observed. Aerobic and anaerobic bacteria were not detected in the fried fish. Anaerobes were detected only in the canned fish. The pH remained more or less unchanged in all the heat processed fish. Water activity of different heat processed fish varied from 0.98-1.00. The TBA values increased from 0.10 to 1.98 g malonaldehyde/g fat with the duration of heating or increase in temperature. The cholesterol increased to the maximum level of 99mg/100g in canned fish. However in fried fish, cholesterol increased initially and later drastically decreased on further frying. In cooked fish, the loss of C20:5 and C22:6 were high (86 and 93%) in mackerel and low (31 and 33%) in seerfish. In fried fish, the destruction of C20:5 ranged from 67-76% and C22:6 from 67-92% with tuna having minimum loss. Canning of fish at 115 and 1210C had led to 100% destruction of C22:6 and 65-94% of C20:5. The loss of C20:5 and C22:6 was high in oven heated mackerel (81 and 82%) and low in tuna (10 and 13%). Results showed that omega –3 fatty acids of mackerel were the most affected by different heat processing methods such as cooking, frying, canning and oven heating. Cooking process was found better for seerfish with minimum destruction as the n-3/n-6 ratio was found above 1.0. Oven heating process was more suitable for tuna as there was very little loss of omega-3 fatty acids. The n-3/n-6 ratio was found suitable to find out the effect on cooked fish fatty acids. P:S ratio could not reflect the actual content of omega-3 fatty acids.ennullThesis