Utilization of Polyunsaturated Lipids in Red Muscled Fishes 1. Lipid Composition and Seasonal Variation in Fatty Acid Composition of Body Oil and Lipids from Different Sections of Sardine and Mackerel

적색육어류의 고도불포화지질의 이용에 관한 연구 1. 정어리${\cdot}$고등어의 부위별 지질함량 및 지방산 조성의 계절적 변화

As the first part of the studies on utilization of polyunsaturated lipids in red muscled fishes like sardine (Sardinops melanosticta) and mackerel (Scomber japonicus), lipid distribution in body sections, whole body, meat, viscera, skin, and head, lipids, polar and nonpolar, and fatty acid composition of the oils obtained from these body sections, and seasonal variations in fatty acid composition, particularly in the content of polyenoic acids, EPA and DHA, were determined, The content of total lipids was ranged $22.2\%\;to\;27.2\%$ in case of sardine without broad difference between body sections, while in case of mackerel $36.7\%\;to\;38.8\%$ unevenly in skin and head. The lipids of both fish were composed of more than $80\%$ of non-polar lipid and there was not much differences in the fatty acid composition between the lipids, polar and non-polar. The major fatty acids of the lipids were $C_{14:0},\;C_{16:0},\;C_{18:0},\;C_{16:1},\;C_{18:1},\;C_{20:1},\;C_{20:4},\;C_{20:5},\;and\;C_{22:6}$, and these acids, $C_{18:1},\;C_{16:0},\;C_{22:6},\;C_{18:0},\;C_{20:5},\;C_{14:0},\;C_{16:1}$, were in high quantity in order. Seasonal variation in fatty acid composition of sardine oil did not show any great variety between sections. There was a tendency in general that saturated and monoenoic acids began to decrease in winter and showed the minimum in April; hereafter get to increase again, while polyenoic acids showed the maximum in April. Both $C_{20:5}\;and\;C_{22:6}$ acids were high in the season of April to July. Variation in fatty acid content was in a width of $8\%$ for saturated, $5\%$ for monoenoic, and $12\%$ for polyenoic acid. $C_{20:5}\;and\;C_{22:6}$ acid were varied in $9.4\%\;and\;9.8\%$, respectively. In case of mackerel oil, seasonal variation tended same as in sardine oil except the fact that the saturated and monoenoic acid decreased to the minimum in the term of April to July in which the polyenoic acid content was also higher marking $27.3\%\;to\;36.1\%$ in average. Fatty acid variation was in a range of $6.3\%$ for saturated, $8.3\%$ for monoenoic, and $13.8\%$ for polyenoic acid but variation of $C_{20:5}\;and\;C_{22:6}$ acid was 4, $3\%$ and 3, $4\%$ respectively. When fresh sardine was stored for 10 days at $5^{\circ}C$, oxidation was rapidly initialed and consequently resulted in fast loss of $C_{20:5}\;and\;C_{22:6}$ acids. It is concluded from the results that the catch of sardine and mackerel in the season of April to June would be adequate for the preparation of polyunsaturated lipid condenced oil in regard to sectional lipid distribution and its variation in seasons.