Unraveling the aroma profiling of Baijiu: Sensory characteristics of aroma compounds, analytical approaches, key odor-active compounds in different Baijiu, and their synthesis mechanisms

More than 2700 trace compounds were reported in Chinese Baijiu. Among these compounds, odor-active compounds (OACs) can directly exhibit sensory characteristics, which play a crucial role in determining the overall aroma characteristics of Baijiu. The OACs in Baijiu have been extensively studied through sensory evaluation, instrumental analysis, aroma extract dilution analysis (AEDA), odor activity value (OAV), aroma recombination, and omission experiments. The principal pathways for the synthesis of OACs through microbial metabolism. The primary objective of this review is to provide a detailed exploration of the techniques employed in the extraction and evaluation of OACs, the compounds that contribute to the distinctive aroma, the metabolic mechanisms behind the key odor-active compounds (KOACs) in Baijiu, and the KOACs found in various types of Baijiu. Each extraction method has its distinct advantages. Combining multiple methods proves to be an effective approach to analyzing OACs in Baijiu. The integration of GC-O/MS with AEDA, OAV, aroma recombination, and omission tests not only enables both quantitative and qualitative detection but also facilitates the identification of KOACs. The metabolic pathways of most OACs are well understood, but there are also some compounds, such as sulfur compounds, whose formation mechanisms require further exploration. There are variations in KOACs among different types of Baijiu, the KOACs responsible for certain characteristic aromas, such as 'sauce' and 'medicinal' aromas, warrant further investigation.