Exploring the Key Indicators for Off-Flavor in Industrial Osmanthus Absolute through Sensomics and Chemometric Approaches

The occurrence of off-flavor in osmanthus absolutes has emerged as a significant concern that could hinder its broad market acceptance and associated economic development. In this study, key off-flavor molecules in industrial osmanthus absolute were identified through sensomics and chemometric approaches. A group of 10 off-flavor (OF) samples, eliciting smoky/phenolic, sweaty/sour, and spicy odors, were compared with 10 pleasant aroma (PA) samples through various analyses, including overall aroma assessment, comprehensive chemical profiling, aroma extract dilution analysis (AEDA), and orthogonal partial least-squares-discriminant analysis (OPLS-DA). High-throughput gas chromatography-tandem mass spectrometry proved to be a powerful tool for efficiently and accurately identifying trace compounds in complex matrices. 50 odor-active compounds were identified, and further filtering resulted in 25 markers with variable importance in projection scores (VIP) greater than 1. All these markers, except citronellol, exhibited higher odor activity values (OAVs) of ≥1 in OF samples. Subsequent spiking and omission experiments confirmed that 4-ethylphenol, 4-ethylguaiacol, o-cresol, and 2,6-dimethoxyphenol significantly contributed to the smoky/phenolic attribute. Moreover, 3-methylbutyric acid, hexanoic acid, citronellic acid, butyric acid, and 2-methylbutyric acid had significantly negative effects on the sweaty/sour odor. Additionally, a combination of ethyl cinnamate and p-anisaldehyde may have contributed to the spicy off-flavor through a synergistic effect.