本文研究了不同脂肪含量（7%、14%和21%）和蛋白质含量（2.3%和4.6%）对稀奶油-乳清发酵液的影响，研究新型风味发酵体系组成和发酵特性之间的关系。测定在发酵过程中活菌数、酸度和pH的变化，利用顶空-固相微萃取（HS-SPME）和气相色谱-质谱联用（GC-MS）分析发酵60 h后发酵液中挥发性风味物质，并对其进行感官评定。结果发现：蛋白质含量较低时，脂肪含量增加对乳酸菌增殖和pH值无影响，蛋白质含量较高时，脂肪含量增加抑制乳酸菌增殖和pH值下降；脂肪含量增加促进产香和挥发性风味物质增加，抑制菌种产酸。蛋白质含量增加促进乳酸菌增殖和挥发性风味物质明显增加，使pH值下降减缓；脂肪含量较低时，蛋白质含量增加促进产酸，脂肪含量较高时，抑制产酸。发酵60 h后，体系中主要挥发性风味物质有乙酸、丁酸、2,3-丁二酮和3-羟基-2-丁酮。通过感官评定，14%脂肪和4.6%蛋白质的发酵液具有最佳的组织状态以及最强的特征性酸奶风味。

The effects of different fat content (7%, 14%, and 21%) and protein content (2.3% and 4.6%) on cream-whey fermentation liquid and the relationship between the composition of new flavor fermentation systems and fermentation characteristics were studied. Changes in the number of viable bacterial cells, titratable acidity, and pH value during the fermentation process were measured. The volatile flavor components were extracted using headspace solid-phase microextraction (HS-SPME), analyzed by gas chromatography-mass spectrometry (GC-MS) after fermentation for 60 h, and evaluated by sensory tests. The results showed that the increase in fat content had no influence on the proliferation of lactic acid bacteria or on the pH value at low protein levels, but suppressed the proliferation of lactic acid bacteria and prevented the decline in pH at high protein levels. In addition, increased fat content promoted the production of flavor and volatile compounds and inhibited the production of acids by the bacteria. Increased protein content promoted the proliferation of lactic acid bacteria, significantly increased the content of volatile flavor components, and slowed the decline in pH values. Moreover, increased protein content promoted the production of acids at low fat levels, but inhibited the production of acids at high fat levels. After 60 h of fermentation, the main volatile compounds in the system were acetic acid, butyric acid, 2,3-butanedione, and 3-hydroxy-2-butanone. The sensory evaluation showed that the mixed fermentation liquid with 14.0 % fat and 4.6 % protein had the best structural state and the strongest yoghurt flavor.

广州市产学研协同创新重大专项产学研协同创新联盟专题（201604046011）