Characterization And Flavor Impact Of Volatile Sulfur Compounds In Chinese Liquors

Volatile sulfur compounds are a class of very important aroma substances in food due to their low aroma thresholds and unique aroma characterization,which are characteristic aroma components in many foods.However,due to the volatile chemical structure and the nature of instability,the concentration of most volatile sulfur compounds is very low.The analysis of volatile sulfur compounds and flavor function has been a very challenging work in food flavor research.Chinese liquor is one of the oldest distilled spirits in the world which has a history in China for thousands of years.The flavor components of the liquor are very complex,there are more than 400 volatile flavor components found in liquors.However,there are only a few researches on volatile sulfur compounds,and the contribution of volatile sulfur compounds to the overall aroma characterization is not clear.In this paper,we have chosen the Chinese liquor as the research object.Modern flavor chemistry methods were used to analyze the volatile sulfur compounds in liquor.We have analyzed the contribution of the sulfur compounds on flavor and the existence of the sulfur compounds in Chinese liquor.The main contents are as follows:(1)A sensitive method for sulfur compounds of Chinese liquor using headspace solid phase microextraction(HS-SPME)coupled with gas chromatography-pulsed flame photometric detection(GC-PFPD)was developed.A total of 18 sulfur compounds were identified in the liquor.Among them,three sulfur compounds,3-methylthiophene,1-hexanethiol and 1-heptanethiol were first detected in Chinese liquor.The method of quantitative limit,precision and accuracy are satisfied with the requirements of liquor analysis.After then,the quantitative analysis was carried out in different flavor type liquors.It was found that the types and contents of sulfur compounds in roasted sesame-like flavor type liquor were the most abundant,followed by the lower contents of sulfur compounds in soy sauce flavor type liquor,and the lowest in strong and light flavor type liquors.(2)The method of modern flavor chemistry was used to systematically study the flavor contribution of volatile sulfur compounds in liquor.2-Furfurylthiol was a key compound for the overall aroma of roasted sesame-like flavor type liquor.Roasted sesame-like flavor type liquor was chosen for the flavor analysis on sulfur compounds.The aroma profile of Chinese roasted sesame-like flavor type liquor was investigated by means of headspace solid phase microextraction-aroma extract dilution analysis(HS-SPME-AEDA).Sixty-three odor-active regions were detected by HS-SPME-AEDA with flavor dilution(FD)factors > 5,and 8 sulfur compounds were further identified.On the basis of quantitative results,odor active values(OAVs)of these sulfur compounds were calculated to determine the contribution degree of each sulfur compound to the overall flavor.The OAVs analysis showed: 2-furanmethanethiol,methanethiol,dimethyl trisulfide,1-heptylthiol,1-hexylthiol and ethanethiol,whose OAVs > 100,were important to the overall aroma of the liquors.2-Furfurylthiol(OAV 1182)exhibiting intense roasted,and coffee-like notes,might be the character-impact odorant for Chinese roasted sesame-like flavor type liquor.Omission experiment further confirmed 2-furfurylthiol was a key compound for the overall aroma of roasted sesame-like flavor type liquor.(3)Source analysis of volatile sulfur compounds in liquor.In this study,the sulfur compounds in the process of fermentation,distillation and storage were analyzed for the sources and changes of sulfur compounds in liquors.It was found that the sulfur compounds detected in the roasted sesame-like flavor liquor were mostly produced in the distillation process,and only eight sulfur compounds were produced in the fermentation process.All of the detected sulfur compounds were detected in the distillation process.In the storage process,the sulfur compounds showed a downward trend.