Current Practice and Future Trends of Aroma and Flavor Research in Chinese Baijiu

Chinese baijiu (liquor) is one of the oldest distillates in the world and can be classified into 11 categories according to their aroma characteristics. Volatile compounds are extremely important to the flavor profile of baijiu. However, not all of these compounds are important to the aroma and flavor. The aroma and flavor compounds in baijiu was first studied using gas chromatography–olfactometry (GC–O) in 2004 by Qian and Fan. Since then, more than 300 aroma compounds of 10 different aroma type baijius were detected by GC–O coupled with gas chromatography–mass spectrometer (GC–MS), and key aromas of 5 aroma type baijius were confirmed using GC–O, OAV, recombinate, and omission tests. Esters were very important aroma compounds; these include ethyl hexanoate, ethyl butanoate, and ethyl acetate. Ethyl hexanoate was the key aroma compound in strong aroma and flavor type baijiu. Fatty acids were important aromas for Chinese baijiu. Some compounds are particularly important for certains types of baijiu. β-Damascenone is a positive aroma compound for light aroma type of baijiu, whereas geosmin contributes a negative characteristic aroma for light aroma and flavor type baijiu. However, geosmin was a key aroma contributor for laobaiganxiang-aroma type baijiu. (E)-2-Enals are very important aroma compounds for chixiang-aroma type baijiu. Sulfur-containing compounds were very important aroma compounds. Many of the volatile compounds also affect the bitter taste and astringent mouthfeel. The knowledge obtained in the past decade about aromas and flavors of baijius has provided a direction for baijiu quality improvement and new technology implementation in industry.