| In order to explore the changes of flavor compounds in different fermentation stages of highland Barley liquor fermented grains,in this paper,two kinds of samples of highland Barley liquor fermented grains with the two aroma types of Qingxiang and sauce flavor were used,respectively,headspace solid-phase microextraction and gas chromatography mass spectrometry(GC-MS)were applied to the enrichment extraction and analytical characterization of the flavor substances,and their physicochemical indexes were determined at the same time,and the results were as follows:(1)Headspace solid phase microextraction(HS-SPME)and gas chromatography-mass spectrometry(GC-MS)were used to explore the optimal pretreatment process for fermented grains.The three factors,namely,the amount of water added to the fermented grains,the extraction time,and the ultrasonic treatment in an ice water bath,were determined to have a significant impact on the types of flavoring substances in the fermented grains.The amount of water added to 25 g of fermented grains was determined to be 70 m L,the extraction time was 20 minutes,and the ultrasonic treatment in an ice water bath was 35 minutes,Under these conditions,48 kinds of flavor substances in fermented grains were detected,which was the best,including 21 esters,13 alcohols,6 aldehydes,1 ketone,6 acids,and 1 aromatic substance.(2)Headspace solid phase microextraction and gas chromatography-mass spectrometry(GC-MS)combined with internal standard method were used to optimize the extraction methods of flavor substances in fermented grains.Extraction temperature and extraction time had significant effects on flavor substance contents,while the analytical time was not.The optimal extraction conditions were determined as extraction temperature 55℃ and extraction time50 min.The resolution time is 2min.Among them,alcohol content of44.78%,aromatic content of 30.58%,ester content of 17.16%,aldehyde content of 4.13%,acid content of 3.17%,ketone content of 0.15% were detected.(3)The moisture,acidity,reducing sugar and crude starch of fermented grains in different fermentation stages were determined by constant temperature drying,neutralization titration and glucose standard solution reverse titration.The results showed that the moisture content of fermented grains increased first and then decreased;It tends to be stable at the end of fermentation.The variation trend of crude starch content was that the whole fermentation period was decreased.The acidity content showed an increasing trend before 28 d,first decreased after 28 d,and then increased to the end of fermentation after 35d;The content of reducing sugar in fermented grains decreased sharply 7 days before fermentation,increased slowly 14 days after fermentation,began to decrease again 28 days after fermentation,and continued to rise 35 days after fermentation,The reducing sugar content of fermented grains continued to decrease at the early stage of fermentation,increased slowly at 21-28 d,and increased slowly at 35 d to the end of fermentation.(4)Ethyl acetate,ethyl caprylic acid,ethyl phenyl acetate,benzaldehyde and other flavor substances existed in the whole fermentation stage of fermented grains.The flavor substances such as ethyl caproate and leaf aldehyde appeared gradually with the increase of fermentation days,while the flavor substances such as p-tert-amylphenol of glacial acetic acid existed in the early stage of fermentation,but gradually disappeared in the late stage of fermentation.A total of 96 kinds of flavor substances were detected in the whole fermentation stage of Qingxiangxing Baijiu fermented grains,among which 39 kinds of esters,17 kinds of alcohols,15 kinds of acids,9 kinds of aldehydes,and ethyl acetate were found in the whole fermentation stage.A total of 96 kinds of flavor substances were detected in fermented grains of Jiangxiangxing Baijiu among which 42 kinds of esters,15 kinds of alcohols,13 kinds of acids and 9 kinds of aldehydes were the most abundant. |
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