Kinetic studies on rice bran protein hydrolysis in subcritical water

The aim of this work was to determine the kinetic parameters of rice bran protein hydrolysis under a subcritical water (SW) atmosphere in a batch reactor. The three principal parameters that were evaluated were the temperature (423–523 K), reaction time (0–60 min) and initial protein concentration (1.67 g/L and 4.16 g/L). From the obtained results, a simplified mechanism of protein aggregation and decomposition was proposed. The protein aggregation followed zero order reaction kinetics for the first 5 min and then disaggregation and decomposition took place following second order and zero order reaction kinetics, respectively, to produce polypeptides and amino acids, respectively. The obtained reaction rate constants varied with the temperature, initial protein concentration and different reaction pathways. From this investigation, a suitable condition for the SW-mediated recovery of protein or amino acids from protein-rich sources, such as rice bran, was derived.

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► A simplified mechanism of protein aggregation and decomposition during SW hydrolysis is proposed.
► Rate constants of each reaction step changed with temperature, initial protein concentration and reaction pathways.
► SW hydrolysis can be an effective way to recover amino acids produced during the protein extraction.