Origin of the nonhydratable soybean phosphatides: Whole beans or extraction?

Abstract

Whole soybeans and flakes, tempered to normal (10%) and elevated (14%) moisture levels, were stored and then extracted under a variety of conditions in both the presence or absence of phospholipase activity. Crude oils were degummed, and the resulting nonhydratable phosphatide (NHP) content was determined. Extractions performed on flakes at ambient temperature or at the boiling point of hexane showed that at normal (10%) moisture levels the temperature of extraction had little effect on the magnitude of NHP formation; whereas at 14% moisture, considerably higher levels of NHP were observed at the higher extraction temperature. Studies performed with 10- and 14%-moisture whole beans stored at 40°C for extended periods, with or without inactivation of enzymes, showed that at normal 10% moisture levels little deterioration occurs after one week of storage; however, after four weeks considerable NHP is formed. At 14% moisture, NHP formation was rapid during the first week of storage, and complete destruction of the phospholipid occurred after four weeks’ storage at 40°C. The results of these experiments indicate that the adverse effects of storage conditions, excessive moisture levels and elevated temperatures cannot be overcome by inactivation of phospholipase D prior to solvent extraction of the flakes.