In this study, headspace solid phase microextraction in combination with comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (HS-SPME-GC × GC-TOFMS) was used to analyze the volatile compounds in whole (WM), low-fat milk (LFM) and non-fat milk (NFM). Altogether 49 volatile compounds were detected, among which methyl ketones with odd-numbered carbon chain lengths such as 2-nonanone and 2-undecanone constituted the main flavor compounds of WM. Using partial least squares discriminant analysis (PLS-DA), a model which could well differentiate among the 3 milks was developed and it was found to have good variance and cross-validation predictive ability. Nine differential key aroma compounds were identified using variable importance in the projection (VIP) > 1, P ≤ 0.05 and their contents ≥ 1% as criteria, which may be the main factors contributing to the differences in flavor profiles among the 3 milks. The heatmap from clustering analysis indicated that NFM had poor sensory performance due to the presence of off-flavor compounds (e.g., hexadecanal), whereas WM and LFM contained more aroma compounds, having a full and rich sensory aroma profile. The HS-SPME-GC × GC-TOFMS method can provide theoretical guidance for dairy flavor improvement and dairy flavoring formulation.

As increasing attention has been paid to the flavor of dairy products, research on dairy flavors will promote the rapid development of the dairy flavor industry. In this paper, we summarize recent progress in research on dairy flavors, review the main flavor compounds of some common dairy products, analyze the mechanism of off-flavor formation, and provide some solutions to this problem based on the preparation process for dairy flavors. It is expected that this review will provide new ideas for the development of flavored dairy products and dairy flavors in the future.