草莓汁贮藏期维生素C的降解动力学研究

Degradation Kinetics of Vitamin C in Strawberry Juice during Storage

摘要:

本文研究了不同贮藏条件对草莓汁中维生素C降解的影响，分别采用玻璃瓶和PET瓶为包装材料对草莓汁在不同贮藏温度（4 ℃、20 ℃和37 ℃）下维生素C的降解规律进行分析，并分别建立动力学模型。结果表明：草莓汁中的维生素C对热不稳定，随贮藏温度的升高，降解速率增大，半衰期减小；同一贮藏温度下，PET瓶的降解速率大于玻璃瓶；玻璃瓶和PET瓶中草莓汁维生素C的降解均符合一级动力学模型，其反应活化能分别为32.04 kJ/mol和28.26 kJ/mol。两种包装材料预测模型的验证值与实测值的相关系数R2>0.99，表明了模型的有效性，可用于预测任意温度下贮藏的维生素C含量及草莓汁货架期。同时对草莓汁中维生素C活化热力学函数（ΔG≠，ΔH≠，ΔS≠，K≠）的值进行了计算分析，为阐释维生素C降解机制提供了依据。

Abstract:

The effects of different storage conditions on the degradation of vitamin C in strawberry juice was investigated, the contents of vitamin C in strawberry juice which was stored in glass or PET bottles at 4 ℃, 20 ℃ and 37 ℃ were analyzed during the whole storage period. Corresponding kinetic models were also established. The results showed that the degradation rate of vitamin C in strawberry juice increased with the increase of storage temperature and the half-life period declined accordingly. At the same storage temperature, the degradation rate of vitamin C in PET bottles was higher than that in glass bottles. The degradation kinetics of vitamin C in strawberry juice from glass and PET bottles followed by first-order kinetic model, with the reaction activation energies of 32.04 kJ/mol and 28.26 kJ/mol, respectively. The correlation coefficient between the verified values of prediction models and the measured values was R2 > 0.99, indicating the validity of the model. It means the equation could be used for estimating the first-order losses of vitamin C in the stored strawberry juice, at any specific temperature and degradation ratio. The thermodynamic functions of activation (ΔG≠, ΔH≠, ΔS≠, and K≠) were determined and can provide valuable information for degradation mechanism of vitamin C.