Unraveling the Impacts of Preprocessing on the Metabolite Profile of Bitter Almond Using UPLC-MS/MS and GC-MS Analysis.

As a traditional Chinese medicine, bitter almonds contain amygdalin, which can be hydrolyzed by β-glucosidase to release highly toxic hydrogen cyanide. There are safety hazards in clinical use, and high-temperature pretreatment is required for use. This study is based on the differences in β-GC activity of bitter almonds treated with different pretreatment methods. SPME-GC-MS and UPLC-MS/MS combined techniques were used to analyze the metabolic profile differences before and after processing from both volatile and nonvolatile dimensions. A total of 30 compounds were identified through volatile component analysis, among which terpenoids such as d-limonene and linalool were significantly upregulated during steaming, while benzyl alcohol was significantly downregulated. A total of 199 metabolites were identified through nonvolatile component analysis, and 80 significantly different metabolites were screened. Among them, the number of downregulated substances in steaming (45) far exceeded that in boiling (19) and frying (23), showing a clear trend of substance degradation. Of particular importance is the significant degradation of the cyanide alkaloid prunasin during the processing, resulting in the formation of volatile products such as benzaldehyde and hydrogen cyanide, which confirms the detoxification mechanism of processing at the molecular level. KEGG pathway enrichment analysis revealed that differential metabolites mainly involve 56 pathways such as α linolenic acid metabolism and purine metabolism, constructing a complex metabolic network during the processing.