J. Agric. zyxwvuts Food Chem. zyxwvut 1990, zyxwvuts 38. 809-812 809 Changes zyxwvut in Flesh Lipids and Fill Oils of Albacore (Thunnus alalunga) during Canning and Storage Santiago P. Aubourg, Carmen G. Sotelo, and Jose M. Gallardo* Instituto de Investigaciones Marinas del CSIC, Muelle de Bouzas s/n, 36208 Vigo, Spain Three different parts of the muscle of cooked albacore were canned in soybean oil and stored at room temperature for 11 months. Cans were opened at different times; flesh lipids and fill oils were ana- lyzed for free fatty acid (FFA), sterol (ST), and phospholipid (PL) contents, as well as fatty acid composition. The thermal treatment during the sterilization step produced a decrease in the flesh lipid content and increases in FFA, ST, and PL. Due to canning storage, the lipid content increased significantly after 7-11 months and the FFA and PL amounts decreased. With respect to fatty acid composition, an interaction between the two types of lipids exists. In the flesh lipids a steep increase in fatty acids abundant in fill oil was noticed (18:2,18:3), and at the same time the characteristic fatty acids of the flesh lipids in fill oil (22:6, 205, and others) showed an increase. Canned fish and other marine species are products of economic importance in many countries. Among the most common species, sardine, herring, albacore, and other tuna fishes, mackerel, anchovy, mussel, etc., can be men- tioned (Cheftel and Cheftel, 1976). It is well-known that the quality of canned products has a very close relationship with their lipid content and composition. Canned fishery products are especially sus- ceptible to flavor and other changes due to the high lev- els of polyunsaturated fatty acids (Ackman, 1979; Maeda et al., 1985). Many studies relative to the precooking effect in the quality of the canned product (Slabyj and True, 1978; Joshi and Saralaya, 1982) have been carried out as well as those focusing on the fatty acid and lipid class com- positions of canned species (Melva et al., 1982; Hale and Brown, 1983). Changes in quality of canned fish have been investigated as a function of packaging method (Oliveira et al., 1986) and storage temperature (Pirazzoli et al., 1980). Fatty acid composition of fill oil and flesh muscle and hydrocarbon composition in canned sardines on the Span- ish market have been studied by Val1 et al. (1983) and Coll e t al. (1983), respectively. Nevertheless, there is not enough information about the changes produced from the earlier steps of processing until the end of the canned storage of both fill oil and fish flesh lipids. In the present work, three different parts of albacore zyxwvuts (Thunnus alalunga) muscle were separated and canned separately. Lipids of the edible muscle as well as lipids from the fill oil were investigated and compared so as to determine their changes and interactions during can- ning and storage. Albacore was chosen because of its great commercial significance to the canning industry in north- west Spain. MATERIALS AND METHODS Raw Material and Processing. The albacore tuna (2%. alalunga) used was caught by a tuna fishing vessel on the Atlan- tic Ocean (43" N and 27" W) during June 1985. The fish were kept in boxes and transported on ice for 10 days. After arrival to our laboratory, the fish were frozen at -40 "C and stored at -18 "C for 6 months. Six individual fish were selected. The fish were cooked in our pilot plant according to the following procedure: Whole evis- cerated and beheaded fish were cooked (at 102-103 "C) with steam until a final backbone temperature of 65 "C (90 min); the fish were then cooled at room temperature (14 "C) for about 5 h. After the fish were cleaned, sampling began. The six indi- vidual fish were kept in three groups of two; within each group, three different parts of the muscle, known in the commercial literature as back muscle, belly flap muscle, and ventral mus- cle, were separated. As a result, three batches of each muscle part were obtained for statistical purposes. Once each batch was homogenized, lipids from these cooked samples were isolated according to the Bligh and Dyer method (1959). At the same time, portions of 90 g of each homogenized batch were placed in OL-120 cans (105.1 X 64.7 X 28.8 mm) and soy- bean oil (30 mL) and salt (2 g) added. The cans were vacuum- sealed and sterilized in a retort at 115 "C for 60 min. The cans were stored at room temperature until required for analysis. From the catch of the fish until the end of processing, the procedure employed in this work simulated the method used in commercial canneries. Preparation of the Lipid Samples. The cans were opened and analyzed at different times of storage (5 days and 3 and 11 months for the back muscle; 7 months for the belly flap mus- cle; 3, 7, and 11 months for the ventral muscle). After the cans were opened, the liquid part was drained off carefully and lipids were extracted from the fish flesh follow- ing the Bligh and Dyer method (1959). The fill oils of the cans were dried with anhydrous Na,SO, and analyzed the same way as the flesh lipid extracts. Spectrophotometric Methods. The free fatty acid (FFA) content was determined by the Lowry and Tinsley method (1976), based on a complex formation with (AcO),Cu-pyridine. Sterols (ST) were determined by the method of Huang et al. (1961), based on the Liebermann and Buchardt reaction. Phospholipids (PL)were determined according to the method of Raheja et al. (1973), based on a complex formation with ammo- nium molybdate. Transesterification of Lipid Extracts and Determina- tion of Fatty Acids. Lipid extracts were transesterified with use of the BF,-MeOH complex according to Morrison and Smith (1964). Fatty acid methyl esters (FAME) were analyzed on a Varian Vista 6000 gas chromatograph equipped with a 30-m flexible capillary column with SP-2330 (Supelco) as stationary phase. The operating conditions were isothermal separation at 190 "C, with an injector temperature of 220 "C and detector at 230 "C. Carrier gas used was nitrogen flowing with a linear velocity of 0 1990 American Chemical Society