THERMAL KINETIC STUDY OF COLOR CHANGES AND 5-HYDROXYMETHYL FURFURAL FORMATION IN LITCHI JUICE
Effect of different thermal treatments on formation of 5-hydroxymethyl furfural (5-HMF) and its relation with nonenzymatic browning of litchi juice (cv. Huaizhi) were studied. The results showed that the rate of change in browning index (A420) and formation of 5-HMF followed a first-order kinetic pattern when heated under 60, 70, 80, 90 and 98°C for a prolonged period of 5h. The activation energy for the browning and the formation of 5-HMF was 51.19 and 143.64 kJ/mol, respectively. As the prolongation of heating time, the rate of 5-HMF formation increased as the temperature rose. The amount of 5-HMF formed under 98°C was approximately 40 times of that under 60°C after 5h of heating, i.e., 66.98 and 1.69 mg/kg respectively. The formation of 5-HMF, and A420, total color difference (TCD*) of litchi juice during heating exhibited a significant positive correlation. This study indicated the browning problems related to litchi juice after thermal processing was caused by the formation of 5-HMF, a Maillard Reaction intermediate product, and therefore the color of litchi juice is vulnerable to high temperature treatment and prolonged heating time.
Chen, W.W., Yu, K., Hu, Z.Y., Yu, X.L., Cui, S.S. and Qiu, T.Q. (2010). THERMAL KINETIC STUDY OF COLOR CHANGES AND 5-HYDROXYMETHYL FURFURAL FORMATION IN LITCHI JUICE . Acta Hortic. 863, 525-532
litchi juice, thermal treatment, 5-HMF, browning index