Effect of Different Heat Treatments on the Volatile Flavor Compounds in Yak and Jersey Milk

To explore the changes in volatile compounds of yak and Jersey cow milk at different heat treatments (63 ℃/30 min, 75 ℃/15 s, 85 ℃/15 s, 90 ℃/15 s) , electronic nose, HS-SPME-GC/MS combined with radar charts, principal component analysis and OAV, were utilized to explore the odor variation patterns of yak and Jersey cow milk at different heat treatments. Results demonstrated that electronic nose effectively discriminated between the two milk types, with Jersey milk exhibiting greater sensitivity to heat-induced flavor alterations. A total of 102 volatile compounds were identified across all samples, categorized as 10 ketones, 9 aldehydes, 32 esters, 25 alcohols, 14 acids, 3 phenols, and 9 miscellaneous compounds. Fresh yak milk was characterized by dominant alcohols and acids, whereas fresh Jersey milk was rich in ketones and acids. Heat treatments significantly modified both the concentration and composition of volatile compounds in both milk types. Key flavor compounds, determined by OAV>1, were 3-hydroxy-2-butanone, 1-octen-3-ol, and 2-nonanol in fresh yak milk, and 3-hydroxy-2-butanone, 2-nonanol, and butyric acid in fresh Jersey milk. Notably, The 75 ℃/15 s treatment augmented the variety of key flavor compounds in both yak and Jersey milk, and this processing condition was more conducive to the formation of these key flavor substances. These findings can provide valuable insights for optimizing thermal processing parameters to improve flavor quality in dairy products derived from these distinct milk sources.