Thermal denaturation and aggregation of oat proteins – Formal reaction kinetics and thermodynamics

Plant-based beverage quality is influenced by processing conditions, including enzymatic and thermal treatments that modify protein structure and functionality. In this study, heat-induced denaturation kinetics of oat proteins were quantified in supernatants prepared from two oat materials (oat groat flour and oat flake flour) obtained via a pilot-scale decanter centrifuge, under α-amylase–treated and untreated conditions. Throughout this work, denaturation is used in an operational sense, denoting the loss of native extractable protein arising from the combined effects of unfolding and subsequent aggregation. Following thermal treatments at 100 to 115 °C for up to 1024 s, denatured proteins were removed, and the remaining native protein fraction was quantified by RP-HPLC. Oat globulin was primarily detected and used for kinetic evaluation. By Bayesian nonlinear regression of concentration ratio versus holding time, denaturation was shown to follow non-first-order kinetics across all conditions, with treatment-averaged reaction orders of 2.14 for oat groat supernatant and 1.72 for oat flake supernatant. By Arrhenius analysis, activation energies were estimated to range from 480 to 575 kJ/mol across trials, and significant increases following α-amylase treatment were observed within each material (an increase of 95 kJ/mol for oat groat supernatant and 71 kJ/mol for oat flake supernatant), indicating that the energetic barrier and temperature sensitivity of globulin denaturation were substantially elevated. This behavior was considered consistent with stabilization of native proteins by sugars released during enzymatic starch hydrolysis. By Eyring analysis, activation enthalpies of 477 to 573 kJ/mol and activation entropies of 961 to 1217 J/(mol·K) were obtained, corresponding to Gibbs free energies of activation of 102 to 125 kJ/mol over 100 to 115 °C. These findings provide novel insights for optimizing the quality of oat-based beverages.