毛酸浆发酵过程中非酶褐变动力学研究

Kinetic Study of Non-enzymatic Browning of Physalis pubescens L. during Fermentation

摘要:

以毛酸浆为原料，同时接入酵母菌和植物乳杆菌，在25 ℃、30 ℃和37 ℃条件下对其进行发酵，研究毛酸浆发酵过程中与非酶褐变有关的指标总多酚、还原糖、维生素C（Vc）、褐变度（BD）、5-羟甲基糠醛（5-HMF）、氨基酸态氮和色度（L*、a*、b*、?E）值的变化，分别用零级、一级和联合动力学模型分别对其进行拟合分析。结果表明，在25 ℃、30 ℃和37 ℃发酵条件下，用联合模型能更好解释5-HMF、褐变度、还原糖、Vc、总多酚、氨基酸态氮和?E的动态变化，联合模型拟合程度均优于一级模型和零级模型。同时，对发酵过程中5-HMF和BD这两项重要品质指标的回归分析表明，二者呈现良好的线性函数关系，说明5-HMF含量的变化可以预测其对应温度下的褐变程度。5-HMF积累反应活化能为36.299 kJ/mol，非酶褐变色素物质的积累反应活化能为12.287 kJ/mol，表明非酶褐变反应速率非常大，毛酸浆发酵中很容易发生非酶褐变反应。

Abstract:

Physalis pubescens L. was used as the raw material and fermentations were carried out at 25 ℃, 30 ℃, and 37 ℃ with inoculation of both yeast and Lactobacillus plantarum. The changes in the non-enzymatic browning indices, -the content of total polyphenols, reducing sugar, vitamin C (Vc), 5-hydroxymethylfurfural (5-HMF), and amino acid nitrogen, browning degree (BD), and the color difference (L*, a*, b*, ?E)-during the fermentation were studied. The zero-order, first-order, and combined kinetic models were employed to fit the data. The results indicated that for the fermentations at 25 ℃, 30 ℃, and 37 ℃, the combined kinetic model was better for describing the dynamic changes of all indices, including the content of 5-HMF, reducing sugar, Vc, total polyphenols, and amino acid nitrogen, BD, and ?E, than the other two models. Furthermore, regression analysis showed that 5-HMF content and BD-the two important quality indices-had a very good linear relationship during the fermentation, which indicated that BD could be predicated by the 5-HMF content at the corresponding temperature. Meanwhile, the activation energies of 5-HMF and non-enzymatic browning material were 36.299 kJ/mol and 12.287 kJ/mol, respectively, which showed that the reaction rate of non-enzymatic browning was very fast and could easily occur during the fermentation of Physalis pubescens L.