Effect of different technological methods on the quality of soybean oil and meal

ABSTRACT

Soaking of soybean seeds in 2% NaOH solution up to 24 hours inactivated the trypsin inhibitor activity [TIA] by 90%. The alkaline treatment was more effective than soaking in pure water for the same period. Also, TIA was effectively destroyed by heating in boiling water up to 30min. Refractive index, acid value, iodine value and peroxide value of soybean oil were not affected by water soaking treatment. Soaking the soybeans in alkaline solution increased peroxide value and decreased acid value. Heating in boiling water [30min.] caused an increase in the acid value, peroxide value, unsaponifiable matter and total saturated fatty acids, while decreasing a total unsaturated fatty acids of soybean oil. Palmitic acid, which represents the major saturated fatty acids showed remarkable decrease in seeds soaked in alkaline solution for 24hrs. Boiling the beans for 10min. caused an increase in palmitic acid and a decrease in the major unsaturated fatty acid [Linoleic acid]. Also, odd number fatty acid [C[17.0]] was detected upon boiling for 30min. or soaking in alkaline solution for 24hours. Fractionation of the hydrocarbon and sterol components revealed n-tricosane and beta-sitosterol to be respectively the major components. Percentages of such a forementioned compounds were drastically changed due to different treatments. Boiling treatments caused some hydrocarbon and sterol compounds to disappear such as C[20], C[21], C[28] and delta 7-avenasterol