| Zhenjiang aromatic vinegar(ZAV)is one of the four-famous vinegars in China and has a unique and pleasant aroma.Aging is one of the key processes in vinegar brewing,which has an important impact on the flavor quality of the product.However,the lack of research on the aroma changes and the environmental impact of the volatile flavor compounds in ZAV during aging has seriously affected people's scientific understanding and the effective regulation of aged ZAV,which has also restricted the modernization of ZAV aging technology.In this study,the changes of aroma characteristics during aging of ZAV were studied,the key aroma compounds were identified,and the effects of temperature and oxygen on aroma compounds were also discussed.The main research contents and results were shown as follows:(1)The aroma profile of ZAV at different aging times were studied through sensory quantitative description analysis.The analysis showed that the aroma intensities of acidic/pungent,burnt,caramel-like,buttery,and overall complex had significant differences in ZAV of different aging times.The fresh vinegar had a strong intensity of burnt and bran aroma,while the aged ZAV have typical aroma characteristics of caramel-like and buttery and its stimulation is weak.(2)The methods of SPE,HS-SPME combined with GC-MS were used to quantitative the volatile flavor compounds in ZAV at different aging times.A total of 67 volatile compounds were selected and quantitated.Among them,sotolon was firstly reported in traditional Chinese vinegars.During vinegar aging,the total concentrations of alcohols,esters and pyrazines changed obviously.Correlation analysis found that 9 kinds of aroma compounds showed significant positive correlation with aging time while 12 kinds of aroma components showed negative correlation.Based on the changes of aroma compounds concentrations,the samples of ZAV of different aging times were clearly distinguished through the multivariate statistical analysis and the compounds that had a greater impact on it were 3-hydroxy-2-butanone,2,3-butanedione,2,3-butanediol,tetramethylpyrazine,furfural,ethyl lactate,2-phenylethanol,3-methyl-1-butanol and ethyl acetate.(3)The key aroma compounds of ZAV were systematically analyzed by sensomics approach.GC-O-MS analysis found that with the extension of aging time,the aroma intensity of most alcohol and ester compounds with odors of alcohol,fruit and flower weakened,while the aroma intensity of pyrazines and furans enhanced significantly,which further enriched the complex sensory aroma of vinegar.Methyl butyrate,3-methylbutyl acetate,2,3-butanediol and 2-phenylethanol had higher aroma intensity in fresh vinegar,while 2,3-butanedione,2,4,5-trimethyloxazole,tetramethylpyrazine,sotolon had higher aroma intensity in aged vinegar.The analysis of OAVs indicated that the important aroma components,whose OAVs>100,in fresh vinegar were acetic acid,2-methylpropanal,3-methylbutanoic acid,sotolon,3-methylbutanal,dimethyl trisulfide and 2,3-butanedione,acetic acid,2,3-butanedione,2-methyl-1-propanal,sotolon,3-methylbutanoic acid,dimethyl trisulfide,3-hydroxy-2-butanone,2,4,5-trimethyloxazole and methional,were important contribution to the overall aroma of aged ZAV.Finally,through the aroma recombination and omission experiments,it was confirmed that acetic acid,2-methyl-1-propanal,3-methylbutanoic acid,sotolon,3-methylbutanal and 2,3-butanedione were the key aroma compounds of fresh ZAV.The key aroma compounds of aged ZAV were 2,3-butanedione,acetic acid,2-methyl-1-propanal,sotolon,2,4,5-trimethyloxazole,3-methylbutanoic acid and tetramethylpyrazine.(4)The effects of temperature and oxygen on the content of volatile compounds during the vinegar aging process were investigated.It was found that the contents of most aroma compounds increased significantly with increasing temperature or the number of times of oxygenation.Among them,temperature and oxygen had significant effect on the formation of esters,aldehydes,ketones and pyrazines.High temperature and oxygen can obviously promote the formation of key aroma compounds such as 2-methyl-1-propanal,tetramethylpyrazine and sotolon.In addition,combined with the multivariate statistical analysis,5-(hydroxymethyl)furan-2-carbaldehyde,furfural,ethyl lactate,2,3-butanedione,and 3-hydroxy-2-butanone were potential markers caused by temperature changes,and the effect of oxygen on the concentrations of 2,3-butanedione,3-methylbutanal,furfural,benzaldehyde,3-methylbutanoic acid,2-methyl-1-propanal,3-hydroxy-2-butanone,2-methylpropanoic acid,methionol,3-methyl-1-butanol and ethyl acetate were obvious.(5)The formation path of 2,3-butanedione,a characteristic aroma compound of aged vinegar,was preliminarily clarified.It was clear that 3-hydroxy-2-butanone,2,3-butanediol,glyoxal and pyruvaldehyde are the possible precursors for the formation of 2,3-butanedione,of which 3-hydroxy-2-butanone is the main precursors,temperature and oxygen have an important influence on its formation. |
PDF Full Text Request