Chen Chen, Zhou Junnan, Yu Haiyan, Pan Xin, Tian Huaixiang
School of Perfume and Aroma Technology, Shanghai Institute of Technology, Shanghai, 201418, People's Republic of China.
Food Microbiol. 2025 Sep;130:104768. doi: 10.1016/j.fm.2025.104768. Epub 2025 Mar 7.
3-Methylbutanal, a key volatile compound contributing to the nutty flavor of cheese, was primarily produced through the microbial catabolism of leucine. This study focused on the metabolic pathway of 3-methylbutanal at the genetic level during the ripening of Cheddar cheese. The influence of key genes (kdcA, pdhD, and codY) in Lactococcus lactis 408, a specifically selected adjunct culture, on the production of 3-methylbutanal was evaluated. Over a 14-day ripening period, a minor difference in leucine production was observed among different samples with adjunct culture, while alterations in the genes kdcA and pdhD, which were overexpressed in the strain, led to a decreased concentration of α-ketoisocaproate. Utilizing headspace solid-phase microextraction coupled with gas chromatography-flame ionization detection, a reduction was observed in 3-methylbutanal levels as ripening progressed. However, cheese fermented with the codY knockout strain displayed the highest level of 3-methylbutanal at both 0.5-day and 28-day ripening milestones. Further analysis using an Ag/AgCl electrode to assess the redox environment revealed that the higher redox potential in the codY knockout strain was instrumental in retaining elevated levels of 3-methylbutanal. These findings underscored the critical role of genetic factors in the flavor development of cheese and offered promising targets for enhancing flavor profiles in dairy products through biotechnological interventions.
3-甲基丁醛是一种对奶酪坚果风味有重要贡献的关键挥发性化合物，主要通过亮氨酸的微生物分解代谢产生。本研究聚焦于切达干酪成熟过程中3-甲基丁醛在基因水平上的代谢途径。评估了特别挑选的辅助培养物乳酸乳球菌408中的关键基因（kdcA、pdhD和codY）对3-甲基丁醛产生的影响。在14天的成熟期间，添加辅助培养物的不同样品间亮氨酸产量存在微小差异，而该菌株中过表达的基因kdcA和pdhD的变化导致α-酮异己酸浓度降低。利用顶空固相微萃取结合气相色谱-火焰离子化检测，发现随着成熟进程3-甲基丁醛水平降低。然而，用codY基因敲除菌株发酵的奶酪在成熟0.5天和28天这两个时间节点时3-甲基丁醛水平最高。使用Ag/AgCl电极进行进一步分析以评估氧化还原环境，结果表明codY基因敲除菌株中较高的氧化还原电位有助于维持较高水平的3-甲基丁醛。这些发现强调了遗传因素在奶酪风味形成中的关键作用，并为通过生物技术干预改善乳制品风味提供了有前景的靶点。
