Analysis of Nutrition and Flavor Characteristics of mTGase-Treated Skimmed Buffalo Milk Yogurt Based on Untargeted Metabolomics

Buffalo milk has garnered significant attention due to its high nutritional value. However, its high-fat content limits its application in modern healthy diets. A novel skimmed buffalo milk yogurt was prepared using microbial transglutaminase (mTGase) cross-linking technology combined with lactic acid bacteria fermentation. The results showed that there was no significant difference (P>0.05) in the contents of protein, fat, and other nutritional components between the mTGase-treated skimmed buffalo milk yogurt and the control group. Electronic nose and electronic tongue analyses indicated that in the mTGase-treated yogurt, the contents of aromatic compounds and alkanes and aliphatic compounds increased by 10.31% and 10.38%, respectively, while sulfur-containing compounds decreased by 9.63%. Bitterness and bitter aftertaste increased by 6.72% and 10.92%, respectively, whereas sweetness decreased by 15.84%. Analysis of free fatty acids (FFA) revealed that mTGase treatment increased the content of unsaturated FFAs, which may enhance cardiovascular health-related functional activity. Additionally, the increase in long-chain FFAs contributed to a smoother texture. Analysis of free amino acid composition showed significant changes in the amino acid profile of the yogurt. The content of cysteine (Cys), which is beneficial to health, increased from (2.894±0.026) mg/mL in the control group to (3.150±0.054) mg/mL in the mTGase-treated group. However, the content of isoleucine (Ile) significantly increased to (1.508±0.063) mg/mL, imparting a certain bitterness to the yogurt. Untargeted metabolomics results showed that mTGase treatment primarily altered amino acid metabolic pathways, leading to the upregulation of some bitter free amino acids, thereby increasing the bitterness of the yogurt. Nevertheless, mTGase cross-linking also promoted the formation of more dipeptides and tripeptides, enhancing the potential cardiovascular health-related functional activity of the yogurt. Furthermore, the changes in the odor and taste of the yogurt after mTGase treatment might be related to alterations in amino acids, lipids, and carbohydrates. This study aimed to provide a theoretical basis for the development of skimmed buffalo milk yogurt and to reveal the potential application value of mTGase in improving the flavor and nutritional functionality of yogurt.