Allergenicity, trypsin inhibitor activity and nutritive quality of enzymatically modified soy proteins

Two ultrafiltered soy flour protein fractions were evaluated; the first was obtained by hydrolysis (0.5-3 kDa, F0.5-3), and the second was an enzymatically methionine-enriched fraction (1-10 kDa, F1-10E). Amino acid profiles, protein quality, allergenicity (against soy-sensitive infant sera) and trypsin inhibitor activity were determined. Fraction F1-10E fulfilled amino acid requirements for infants, whereas the F0.5-3 fraction was methionine deficient. Both fractions were similar in net protein utilization, and F1-10E digestibility was comparable with casein and higher (P < 0.05) than F0.5-3 or soy isolate. Allergenicity of SF was reduced to 21.5% with the hydrolysis in F1-10E and it was not detected in F0.5-3. Residual trypsin inhibitor activity with respect to soy flour was 8.1%, 3.3% and 1% for hydrolysate, F1-10E and F0.5-3, respectively. Both fractions presented high nutritive quality and reduced or null allergenicity. The trypsin inhibitor activity decreased along processing and could be a useful indicator for production of hypoallergenic proteins.