초록
The study was carried out to investigate interrelationships among the acid, peroxide, iodine, thiobarbituric acid values, and changes of fatty acid compositions of some vegetable oils added to soybean milk. A storage temperature of $100^{\circ}C$ was used for the oxidation of the oils, and to determine of variation of the chemical properties and changes of the fatty acid composition, all the samples were carried out in every 8 hours for 40 hours. The changes in fatty acid compositions of the vegetable oils were measured by high performance liquid chromatography. The results obtained were as follow; 1. The acid values of the fresh soybean, corn, and palm oils added to the soybean milk were 0.05, 0.12, and 0.06, whereas those of the oils stored for 40 hours were 0.08, 0.18, and 0.09, respectively. 2. The peroxide values of the fresh soybean, corn, and palm oils added to the soybean milk were 0.3, 1.0, and 0.3, whereas those of the oils stored for 40 hours were 1.1, 1.1, and 0.9, respectively. 3. The iodine values of the fresh soybean, corn, and palm oils added to the soybean milk were 132.7, 124.1, and 57.0, whereas those of the oils stored for 40 hours were 127.3 108.3, and 52.0, respectively. 4. The thiobarbituric acid values of fresh soybean, corn, and palm oils added to the soybean milk were 0.18, 0.05, and 0.02, whereas those of the oils stored for 40 hours were 0.25, 0.19, and 0.07, respectively. 5. The percent content of the major fatty acids of the soybean, corn, and palm oils freshly added to the soybean milk were 2.3%,2.5%,and 25.2%for palmitic acid, 3.2%,3.2%,and 4.8%for stearic acid, 39.7%, 40.7%, and 59.3% for oleic acid, 49.9%, 53.0%, and 10.5% for linoleic acid, and 4.7%, 0.4%, and 0.7% for linolenic acid, respectively. Those of the oils stored for 40 hours were 2.9%, 4,5%, and 36.7% for palmitic acid, 8.5%, 6.8%, and 7.0% for stearic acid, 37.8%, 38.8%, and 49.2% for oleic acid, 46.2%, 49.5%, and 5.8% for linoleic acid, and 4.2%, 0.1%, and 0.1% for linolenic acid, respectively. The fatty acid compositions changed significantly: the amounts of the unsaturated fatty acid decreased considerably. The rsults of the present study demonstrated greater stability of the palm oil as compared with the stability of soybean oil and corn oil added to the soybean milk.