The quality of soybeans and oil extracted from seeds stored at different moisture contents was evaluated by static headspace gas chromatography, near‐infrared spectrometry, fluorescence measurements, and silicic acid chromatography. Headspace gas chromatographic analysis of both ground beans and crude oils provided a sensitive measure of oxidative deterioration based on hexanal and total volatiles. Near‐infrared analyses at 2260 nm showed a correlation coefficient of 0.864 with titratable free fatty acids. Fluorescence measurements on chloroform‐methanol extracts were much less sensitive and showed an increase only in the most damaged samples. Silicic acid chromatography of crude oils showed a significant decrease of polar lipids and increase of less polar lipids with storage at high moisture levels, in agreement with the decrease in phosphorus observed. Among the methods tested, headspace gas chromatography is most sensitive to evaluate oxidative deterioration, and near‐infrared analysis is most suitable and rapid to evaluate hydrolytic deterioration in stored soybeans. This methodology can be used to evaluate factors affecting the food quality of soybeans for domestic and foreign markets.

No abstract

Soybean protein isolated by acidification of an aqueous extract of hexane-defatted soybean meal contains 2 to 4% of a phospholipide-like material. These lipides cannot be removed by isoelectric precipitation, washing with water, dialysis, or ammonium sulfate precipitation. However, they are extractable with aqueous alcohols. The concentration of alcohol used to wash the protein has a pronounced effect on the amount of material removed and on the nitrogen content of the extracted protein. Optimum concentrations of alcohol are: methyl, 95 to 97% (v./v.); ethyl, 84 to 88% (v./v.); and isopropyl, 78 to 88% (v./v.). The effects of extraction time, temperature, pH, and solvent to protein ratio were also studied. The washed protein has improved color and flavor and produces extremely stable, low density foams and whips similar to egg white and commercially available soy products. Food utilization of soybeans in the United States is still expanding, and the potential is much greater than its present use.Extensive reviews (Z, 25, 30) on the use of soybean protein products in foods have been published. They indicate that color and flavor of soybean protein are important considerations.

Damage to soybeans due to pre-harvest stress, storage, and export shipment has been related to an increase in the nonhydratable phospholipid content of crude oil. Phospholipids in crude soybean oil extracted from such distressed soybeans have been analyzed by gradient high-performance liquid chromatography. Crude oil was fractionated by solid phase extraction using sequential elution for recovery of phosphatides. High-performance liquid chromatography of the concentrated phospholipids was accomplished on a Lichrosorb Si-60 10 ~ column, 250 x 4.6 mm with ultraviolet detection at 206 ran. A 20-min solvent gradient of 2-propanol/hexane/water (42:56:2, 51:38:11) gave retention profiles of phospholipid distribution (major subclasses) that changed with impact of stress applied to plant or seed. Soybeans stored at high moisture levels (16% and 20% moisture) for up to 28 days yielded oils having phosphorus contents which decreased in direct relationship to days of storage. Retention profiles were unusable for fractions isolated from oils with phosphorus content below 100 ppm. Data show that during progressive damage, the content of phosphatidylcholine and phosphatidylinositol decreased while the phosphatidic acid content increased.