大豆油の低温貯蔵による変化
1969 年 18 巻 10 号 p. 750-754
詳細
1969 年 18 巻 10 号 p. 750-754
It became an important problem to controldeterioration of fats in frozen and freeze dried foods not only to prolong their shelf lives but also to maintain their flavors. In such a study, it seems necessary to find an appropriate method or methods for detection of the onset of deterioration. Thus, a study was made to find possibility to use the conventional methods of analysis employed for fats for detection of an early stage of rancidiy of vegetable oils stored at low temperatures.
Soybean oil without addition of antioxidants was stored at 25°, -5°, and -25°C and the following analyses were performed at intervals ; acid, peroxide and carbonyl values, induction periods by Warburg apparatus and the fatty acid composition of the oil by gas-liquid chromatography.
The acid, peroxide and carbonyl values of the sample stored at 25°C were found to remain somewhat unchanged up to 60 days of storage; and P.V. increased thereafter and the other values increased after 120 days. Considerable variations in these values were observed with the sample stored at -5°C, and a white floculant precipitate was found to be formed after 2 months of storage. The carbonyl value of the samples stored at -25°C remained unchanged up to 180 days but its peroxide value decreased steadily until 60 days of storage and increased thereafter. No effect of temperature was observed on the apparent induction periods, but the induction periods of the samples stored for 14 days increased and those of the samples stored for 60 days decreased. Gas-liquid chromatographic analysis of the fatty acid composition showed no significant variations among the samples. The white precipitate formed most abunduntly in the sample stored at -5°C was found as triglycerides comprising a larger proportion of saturated fatty acids than that of soybean oil.
These results suggest that the methods subjected to the present study are not appropriate for detection of an early stage of deterioration of the oil stored at low temperatures, and further studies are necessary.
