蛋白酶和脂肪酶对稀奶油-乳清体系发酵特性及风味的影响

通过测定发酵过程中发酵动力学参数变化，利用顶空-固相微萃取和气相色谱-质谱法测定发酵60?h体系中挥发性风味物质，并进行主成分分析和感官评定，研究单独添加及复配添加蛋白酶和脂肪酶对稀奶油-乳清体系发酵特性及风味的影响。结果表明：风味物质以挥发性羧酸类、酮类和酯类为主。蛋白酶促进pH值下降、乳酸菌增殖和产酸，明显促进酮类生成，可增强体系的风味，提高风味品质；脂肪酶可引起滴定酸度大幅度上升，抑制乳酸菌增殖和产酸，但明显促进羧酸类生成，并产生酯类，可明显改变风味，赋予体系丰富的风味；复配添加后，结合2?种酶的特点，酯类产量上升，增香效果更明显，可显著改变风味，具有缓和大量挥发性羧酸带来的刺激性酸味作用。

Effect of Protease and Lipase on Fermentation Characteristics and Flavor of Cream and Whey Mixture

The effect of protease and lipase added individually and in combination on fermentation characteristics and flavor of cream and whey mixture was investigated by determining the changes in viable cell number of lactic acid bacteria, titratable acidity, pH value and volatile flavor components. After 60 h fermentation, the volatile flavor components were extracted by using headspace solid-phase microextraction (HS-SPME) and analyzed by gas chromatography-mass spectrometry (GC-MS) combined with principal component analysis and sensory evaluation was also performed. The results showed that carboxylic acids, ketones and esters were the main volatile flavor components isolated by GC-MS. Protease promoted the growth of lactic acid bacteria, acid production and the formation of ketones and improved the flavor quality. Lipase significantly increased titratable acidity, suppressed the growth of lactic acid bacteria acid production, pronouncedly promoted the generation of carboxylic acids, resulted in the formation of esters, evidently improved and enriched the flavor of the fermented system. Protease and lipase added in combination increased the production of esters, significantly enhanced the aroma, remarkably improved the flavor and attenuated the sour taste of carboxylic acids, had the biggest influence as revealed through principal component analysis. Protease and lipase could improve the quality of flavor, and their combination mitigated sour taste by the sensory evaluation.