Changes in volatile flavor compounds and metabolites during processing of Ginger milk curd from buffalo milk by GC-IMS and LC-MS

Ginger Milk Curd (GMC), a traditional Chinese cheese of Guangdong, remains not fully elucidated regarding the changes of volatile organic compounds (VOCs) across its different processing stages. This study employed electronic nose (E-Nose), electronic tongue (E-Tongue), gas chromatography-ion mobility spectrometry (GC-IMS) and ultra-high performance liquid chromatography-Q-Exactive HF-X mass spectrometer (UHPLC-Q-Exactive HF/MS) to investigate the alterations in VOCs and low molecular weight metabolites throughout the processing of GMC. The results revealed significant alterations in VOCs, resulting in flavor transitioning from the original flavor to fruity, sweet, green, and citrus flavor. The E-Nose and E-Tongue effectively differentiate the aroma and flavor characteristics of samples at four key processing stages. Among them, GMC contains higher levels of alcohols, aldehydes, ketones, and sulfides compared to samples from other stages, and it shows significant differences in umami, saltiness, and astringency taste characteristics. 71 volatile compounds were identified via GC-IMS, with 13 key volatile compounds, including 1-octen-3-one, 1,8-cineole, dimethylsulfide, and methyl 2-methylbutanoate, contributing to the flavor variations in GMC. Meanwhile, protein degradation, lipid oxidation, and the Maillard reaction were identified as key factors significantly impacting the levels of metabolites and VOCs. The enhancement of flavor characteristics in GMC was attributed to the rise in taste-active peptides, aromatic amino acids, and free fatty acids during processing.