School of Chemical and Environmental Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou City, Jiangsu 215123, PR China; Laboratory of Food Process Engineering, Wageningen University, Bornse Weilanden 9, 6708 WG Wageningen, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
School of Chemical and Environmental Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou City, Jiangsu 215123, PR China; Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen City, Fujian 361005, PR China.
Food Chem. 2017 Jun 15;225:107-113. doi: 10.1016/j.foodchem.2017.01.010. Epub 2017 Jan 5.
In this study, β-galactosidase was utilized as a model enzyme to investigate the mechanism of enzyme inactivation during bread baking. Thermal inactivation of β-galactosidase was investigated in a wheat flour/water system at varying temperature-moisture content combinations, and in bread during baking at 175 or 205°C. In the wheat flour/water system, the thermostability of β-galactosidase increased with decreased moisture content, and a kinetic model was accurately fitted to the corresponding inactivation data (R=0.99). Interestingly, the residual enzyme activity in the bread crust (about 30%) was hundredfold higher than that in the crumb (about 0.3%) after baking, despite the higher temperature in the crust throughout baking. This result suggested that the reduced moisture content in the crust increased the thermostability of the enzyme. Subsequently, the kinetic model reasonably predicted the enzyme inactivation in the crumb using the same parameters derived from the wheat flour/water system. However, the model predicted a lower residual enzyme activity in the crust compared with the experimental result, which indicated that the structure of the crust may influence the enzyme inactivation mechanism during baking. The results reported can provide a quantitative understanding of the thermal inactivation kinetics of enzyme during baking, which is essential to better retain enzymatic activity in bakery products supplemented with heat-sensitive enzymes.
在这项研究中，β-半乳糖苷酶被用作模型酶，以研究面包烘焙过程中酶失活的机制。在不同温度-水分含量组合的小麦粉/水中系统以及在 175 或 205°C 下烘焙的面包中研究了β-半乳糖苷酶的热失活动力学。在小麦粉/水系统中，β-半乳糖苷酶的热稳定性随水分含量的降低而增加，并且可以准确拟合相应的失活动力学数据（R=0.99）。有趣的是，尽管在整个烘焙过程中面包皮的温度更高，但烘焙后面包皮中的残留酶活性（约 30%）比面包心（约 0.3%）高 100 倍。这一结果表明，面包皮中水分含量的降低提高了酶的热稳定性。随后，使用从小麦粉/水系统中得出的相同参数，该动力学模型合理地预测了面包心的酶失活动力学。然而，与实验结果相比，该模型预测面包皮中的残留酶活性较低，这表明面包皮的结构可能会影响烘焙过程中酶失活的机制。所报道的结果可以提供对烘焙过程中酶热失活动力学的定量理解，这对于更好地保留添加了热敏酶的烘焙产品中的酶活性至关重要。
