TRYPSIN-INHIBITOR LEVELS IN SOY-BASED INFANT FORMULAS AND COMMERCIAL SOY PROTEIN ISOLATES AND CONCENTRATES

Trypsin inhibitor levels in raw soybeans, soy protein isolates and concentrates and ready-to-feed, concentrate and powder forms of soy-based infant formulas were measured by two modifications of the standard enzymatic method for trypsin inhibitor determination. Levels were usually higher following sodium hydroxide extraction compared to glycine-buffered extraction. Soy protein concentrates had inhibitor levels intermediate to those in the raw soy and soy protein isolates tested. Infant formulas also varied with ready-to-feed forms generally having higher, and concentrates and powders lower levels of activity. Residual trypsin inhibitor contents of the infant formulas tested ranged from 3 to 28% of the highest levels measured in raw soy samples.