Effect of high temperature treatment on amino acid residues in soy protein isolate

High temperature treatment (100~150 °C) is frequently used for preparation of long-term storage foods such as retort pouched and canned foods. Consumption of the long-term storage foods has increased in the world. However, little is known for chemical changes on amino acid residues in protein by high temperature treatment. Aim of this study was to detect chemical changes on amino acid residues in a soy protein isolate (SPI) by heating in an autoclaveThe heat treatment significantly decreased amino acid contents of SPI, while it did not change the nitrogen content. These facts indicate that some parts of amino acid residues in SPI are degraded and changed to other nitrogen compounds by the heat treatment. LC-MS/MS analysis of HCl hydrolysate revealed that some new amino compounds were generated by the heat treatment. The heat treatment also affected SEC elution profiles of the enzymatic digests of the SPI. These facts indicate that new indigestible peptides were generated by the heat treatment. Identification of the high temperature-induced nitrogen compounds and indigestible peptides is currently in progress