Response surface optimization of Pueraria thomsonii Benth. beer fermentation process and flavor characteristics analysis

【Objective】To optimize the fermentation process of Pueraria thomsonii Benth. beer and analyze its flavor characteristics，with the aim of developing a unique-flavored and highly market-accepted Pueraria thomsonii Benth. beer，and providing theoretical basis for the comprehensive utilization of Pueraria thomsonii Benth. and the development of new types of beer.【Method】Pueraria thomsonii Benth. was used as raw material. The Box-Behnken response surface method was used to optimize 3 process parameters，namely，Pueraria thomsonii Benth. addition，hops addition and yeast addition，through a sensory evaluation system. Further，the physical and chemical indexes，flavor substances and active ingredients of Pueraria thomsonii Benth. beer were detected and identified.【Result】The sensory evaluation（Y）of Pueraria thomsonii Benth. beer was taken as the response value，and Pueraria thomsonii addition（A），hops addition（B）and yeast addition（C）were taken as dependent variables. The regression equation obtained by fitting was Y=87.75-2.48A-1.1B+0.47C+0.76AB+0.68AC+0.44BC-4.75A²-3.09B²-1.71C²，and the effects of Pueraria thomsonii Benth. addition and hop addition on sensory evaluation were extremely significant（P<0.01）. The effect of yeast addition on sensory evaluation was significant（P<0.05，the same below），and the interaction between Pueraria thomsonii Benth. addition and hops addition and yeast addition was significant. The optimal process parameters for Pueraria thomsonii Benth. beer were 47% Pueraria thomsonii Benth. addition，0.75 g/L hops addition，0.94 g/L yeast addition，and the sensory score of dense Pueraria thomsonii Benth. beer was 89.69 points，with clear body，rich foam，mellow and refreshing taste. The original wort obtained by this process had a concentration of 10.00 °P and an alcohol content of 4.12%vol. The contents of isoflavone active ingredient，puerarin，daidzin and daidzein，were 73.96，21.34 and 31.61 mg/L respectively. The odor substances were mainly phenylethyl alcohol，isoamyl alcohol and other alcohols and aromatics，as well as nitrogen oxides，sulfur compounds，alkanes. The bitter taste was the most prominent，followed by saltiness and umami，bitter aftertaste and astringent aftertaste were also abundant，and the sour and sweet tastes were slightly inferior.【Conclusion】The Pueraria thomsonii Benth. beer produced by optimizing the fermentation process through single-factor and response surface experiments has a rich flavor，a slightly bitter and astringent overall taste，and a mellow texture. It has a high content of isoflavone active ingredients，providing a new idea for the current diversified research and development of edible and medicinal beer products.