Thermal degradation kinetics analysis of monacolin K in Monascus-fermented products

The objectives of this study were to investigate the thermal degradation kinetics of monacolin K in Monascus-fermented product (MP) solution. The results indicated that monacolin K content in MP solution remained fairly constant in the range of pH 3–9. However, heat treatment significantly decreased the content of monacolin K in MP solution, for example, from 75.8% under 100 °C, 60 min to 54.3% under 100 °C, 90 min at pH 9. Moreover, if the heating temperature was increased to 121 °C for 90 min at pH 9, the content of monacolin K rapidly decreased to 14.1%. The thermal degradation of monacolin K followed a first-order reaction kinetic. The temperature dependence of rate constants followed Arrhenius relationship, with an activation energy value of 126.64 kJ/mol (90–121 °C, r2 = 0.99). Our results suggest that monacolin K is easily degraded when the MP solution is heated to a high temperature (such as 121 °C). However, more than 50% of monacolin K could be remained when the MP solution is heated under the pasteurization temperature used for food processing.