Optimization of brewing process and quality analysis of Stachys affinis craft beer

Stachys affinis craft beer was brewed using malt and S. affinis as the primary ingredients. The effects of S. affinis addition time, S. affinis addition and original wort concentration on sensory score and alcohol content of S. affinis craft beer were investigated by single factor experiment. On this basis, using the sensory score as response value, the optimal brewing process of S. affinis craft beer was optimized by response surface test, and its physicochemical properties and antioxidant activity were studied. The results showed that the optimal fermentation conditions of S. affinis craft beer were original wort concentration 11 °P and S. affinis pulp addition 2.5% at 43 min after the boiling. Under these conditions, the S. affinis craft beer exhibited a clear body, mellow taste, fine foam, and sensory score 90.6 points, diacetyl content 0.043 mg/L, chroma 12.85 EBC, total acid content 1.92 mg/100 ml, bitterness value 15.26 IBU, and alcohol content 4.87%vol. Its physiochemical indexes met the requirements of relevant national standards. The S. affinis craft beer had certain antioxidant activity, and the scavenging rates of 2,2'-diazo-bis (3-ethyl-benzothiazole-6-sulfonic acid) diamiammonium salts (ABTS) and 1, 1-diphenyl-2-phenylhydrazyl (DPPH) free radicals were 94.28% and 85.51%, respectively.