The influence of soybean genotypes and HTC processing method on trypsin inhibitor activity of soymilk

Abstract

Kunitz inhibitor (KTI) and Bowman-Birk trypsin inhibitor (BBI) are inhibitors of digestive enzymes in raw soybeans. Due to their antinutritive properties in the active state, their inactivation by heat treatment is commonly used. Soymilk is a turbid and stable colloidal solution, obtained by thermal treatment of soybean. In this study soymilk was made on a pilot-plant scale from six soybean cultivars using hydrothermal cooking (HTC) as the production method. This procedure is significantly different from the traditional one. The aim of this investigation was to evaluate the impact of the HTC processing for soymilk production and different soybean genotypes on trypsin inhibitor content and activity. Obtained soymilk contained BBI in trace amounts, in the BBI-polymeric forms. The BBI monomeric forms were not detected. The soymilk of the investigated soybean genotypes had very similar KTI levels (2.34-2.99%). Results have suggested that the soybean genotype does not have substantial effects on the levels of KTI, as well as on the value of residual trypsin inhibitor activity (rTIA). The total content of TI and rTIA showed a strong dependence (r=0.91; p lt 0.05). HTC-soymilk rTIA was lt 20% (7.15-19.89%). These results have indicated that HTC processed soymilk is applicable for human consumption.

U sirovoj soji Kunitz-ov (KTI) i Bowman-Birk-ov inhibitor tripsina (BBI) su inhibitori digestivnih enzima. Da bi se poboljšao nutritivni kvalitet hrane od soje, tripsin inhibitori (TI) se inaktiviraju uglavnom termickom obradom. Sojino mleko je mutni i koloidni rastvor, dobijen nakon termičkog tretmana sojinog zrna. U ovoj studiji sojino mleko je napravljeno od šest sorti soje u pilot postrojenju metodom koja uključuje hidrotermičko kuvanje (engl. hydrothermal cooking - HTC). Ovaj postupak se znatno razlikuje od tradicionalnog. Cilj ovog rada je bio da se proceni uticaj HTC postupka za proizvodnju sojinog mleka i različitih genotipova sojinog zrna na sadržaj i aktivnost tripsin inhibitora. Dobij eno sojino mleko je sadržalo BBI u tragovima, u formi BBI-polimera. BBI-monomerne forme nisu detektovane. Sojina mleka od ispitivanih genotipova soje imaju veoma slične sadržaj e KTI (2,34-2,99%). Rezultati su pokazali da genotip sojinog zrna nema značajne efekte na sadžaj KTI, kao i na vrednost rezidualne tripsin inhibitorske aktivnosti (rTIA). Ukupan sadržaj TI i vrednost rTIA je u snažnoj korelaciji (r= 0,91; p lt 0,05). HTC sojina mleka imala su vrednosti za rTIA lt 20% (7,15-19,89%). Ovi rezultati su pokazali da sojina mleka dobijena nakon HTC obrade mogu biti namenjena za ishranu ljudi.