Changes in free amino acid content,physicochemical indicators and yeast count during the fermentation process of Niulanshan Erguotou fermented grains
In this study,the dynamic changes of free amino acids contents in fermented grains at different fermentation stages were analyzed by ultra performance liquid chromatography(UPLC)using the fermented grains during the brewing process of Niulanshan Erguotou Baijiu as experimental materials.The dynamic changes of yeast count,ethanol content,total acid and pH value in fermented grains were analyzed.The results showed that during the fermentation process of fermented grains,the number of yeast showed a trend of first increasing and then decreasing,with a maximum of 77.7×106 CFU/ml.The ethanol content showed an overall upward trend,with a maximum of 6.61 ml/100 g.The total acid content increased from 0.54 g/g to 5.27 g/g.The pH continuously decreased from 4.77 to 3.28.During the fermentation process of fermented grains,a total of 15 free amino acids were detected,and the total content showed a trend of first increasing and then decreasing,reaching a maximum of 232.93 mg/g on the 17th day of fermentation.At the end of fermentation,the three most abundant free amino acids were alanine(34.40 mg/g),proline(33.09 mg/g),and argi-nine(19.74 mg/g).
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