Controlled Conversion of Proteins into High-Molecular-Weight Peptides without Additives with High-Temperature Water and Fast Heating Rates

Reaction of bovine serum albumin (BSA) protein in high temperature (200-260 degrees C) water (HTW) with fast heating rates (ca. 135-180 K.s(-1)) without acid or base additives gives high-molecular-weight (1500-8300 Da) peptides with minimal formation of amino acids and ammonia. The decrease in the number-average molecular weight of peptides after HTW treatment of BSA could be described by a kinetic model based on random scission mechanism of the polymer chain. Reaction of BSA in HTW under identical conditions with slow heating rates (ca. 0.25 K.s(-1)) gives peptides of low molecular weight with formation of amino acids and ammonia for which the kinetics could not be described by a random scission mechanism. The activation energy determined for the conversion of BSA into high-molecular-weight peptides with fast heating rates in high-temperature water was 16.4 kJ.mol(-1). Reaction of proteins in high-temperature water with fast heating rates inhibits initial aggregation that occurs during slow heating rates and allows controlled conversion of the denatured polymer chain into high-molecular-weight peptides.