Effect of thermal processing and reducing agents on trypsin inhibitor activity and functional properties of soybean and chickpea protein concentrates

Legumes are among the most important sources of protein worldwide, but their consumption is limited by the presence of antinutritional factors such as trypsin inhibitors (TIs). The most common strategy to inactivate TIs is by thermal treatments (TT) and other methods such as the use of reducing agents seems promising, because of their selectivity. The objective of this work was to evaluate the effect of TT and reducing agents (metabisulfite -MB- or L-cysteine -LCys-) over TIs activity from chickpea (CP) and soybean (SB) and to determine the influence of these treatments over protein functionality. The results showed that the most effective method for SBTI inactivation was the combined use of TT and MB, reducing trypsin inhibitor activity (TIA) up to 99.4%. This treatment changed the secondary structure of SB proteins, reduced water solubility index (WSI) 44.4% and increased water absorption index (WAI) more than 4 fold. For CP, LCys was the most effective to reduce TIA (up to 89.1%) with no influence over WSI and WAI. The different effect of TT and reducing agents in SB and CP makes evident the differences in the TI structure for both legumes.