Inhibition of Maillard reaction in production of low-molecular-weight chitosan by enzymatic hydrolysis

Abstract

A low-molecular-weight chitosan (LMWC) sample was prepared by enzymatic hydrolysis, and used for investigation of special Maillard reaction products (MRPs) and factors affecting LMWC bioactivities. After undergoing MR, LMWC turned to brown color (termed BLMWC), showed reduction of several indices of rice growth promotion. This alteration of bioactivities was attributable to MRPs in BLMWC. A special MRP, 5-hydroxy-2-pyridine methanol isomer (5-H-2PMIS), was identified by HPLC and LC-MS. Analysis of key factors affecting MR, using this MRP as monitoring target compound and OD₄₂₀ value, suggested that MR process can be minimized by storing LMWC under vacuum in a dry, low-temperature, neutral-pH environment. Na₂SO₃ was effective for inhibition of MR, at optimal concentration 0.5 %. Chemical and FTIR analyses showed that Na₂SO₃-treated sample conformed to the Chinese National Standard of chitosan (GB 29941-2013). Control of MR is essential for application of LMWC in food, pharmaceutical, and other industries.

Keywords: Enzymatic hydrolysis; Inhibitors; Low-molecular-weight chitosan; Maillard reaction.