Changes of bacterial microbiota and volatile flavor compounds in ewe milk during dielectric barrier discharge cold plasma processing

Abstract

Dielectric barrier discharge cold plasma (DBD-CP) processing can be considered as a potential alternative to conventional pasteurization in ewe milk, which has previously been shown. However, residual microorganisms in ewe milk during DBD-CP processing have not yet been evaluated. This study investigated the microbiota present in ewe milk that was cold plasma-treated. Pasteurized ewe milk was used as a positive control. The bacterial community analysis demonstrated that 8 phyla and 16 genera were identified as dominant microbiota, and Proteobacteria and Pseudomonas were the predominant phyla and genera in cold plasma-treated milk samples. In addition, 23, 22, and 16 volatile flavor compounds (VFCs) were detected in raw milk, pasteurized milk, and cold plasma-treated milk samples, respectively. Fourteen different VFCs were produced according to the variable importance in the projection (VIP ≥ 1.0). The application of DBD-CP might lead to the absence of mutton odor produced by some carboxylic acids, further improving the characteristic flavor of ewe milk by facilitating lipid oxidation. Six bacterial genera, including Porphyromonas, Streptococcus, Fusobacterium, Prevotella, Treponema_2 and Leptotrichia, were highly negatively correlated (|ρ| > 0.5 and P < 0.05) with the flavor substances, according to Spearman correlation coefficient analysis. Overall, the systematic method employed in this study could identify core microbiota present and important VFCs in cold plasma-treated milk ewe milk. The study also provided a better understanding of the potential relationship between bacterial profiles and flavor compounds, which might be useful for further enhancing the quality of ewe milk products.