Quality of oil from damaged soybeans

Abstract

Abstract and SummaryVarious processing steps were explored in an at‐tempt to improve the quality of oil from field‐ and storage‐damaged soybeans. A crude soybean oil (5.7% free fatty acid) commercially extracted from damaged soybeans was degummed in the laboratory with different reagents: water, phosphoric acid, and acetic anhydride. Two alkali strengths, each at 0.1 and 0.5% excess, were used to refine each degummed oil. After vacuum bleaching (0.5% activated earth) and deodorization (210 C, 3 hr), these oils were un‐acceptable as salad oils. A flavor score of 6.0 or higher characterizes a satisfactory oil. Scores of water and phosphoric acid degummed oils ranged from 4.5 to 5.1, while acetic anhydride degummed oils aver‐aged 5.6. Flavor evaluations of (phosphoric acid de‐gummed) single‐ and double‐refined oils (210 C deodorization) showed that the latter were signifi‐cantly better. Flavor scores increased from 5.0 to about 6.0. To study the effects of deodorization tem‐perature, the crude commercial oil was alkali‐refined, water‐washed and bleached with 0.5% activated earth, but the degumming step was omitted. Flavor evalua‐tion of oil deodorized at 210, 230, and 260 C showed that each temperature increment raised flavor scores significantly. Further evaluations of specially proc‐essed oils (water, phosphoric acid, and acetic anhy‐dride degummed oils given single and double refinings and deodorized at 260 C) showed that deodorization temperature is the most important factor affecting the initial quality of oil from damaged beans. Flavor evaluations showed that hydrogenation and hydro‐genation‐winterization treatments produced oils of high initial quality, but with poorer keeping proper‐ties than oils from normal beans. No evidence was found implicating nonhydratable phosphatides in the oil flavor problem. Iron had a deleterious effect in oils not treated with citric acid during deodorization.