| Yellow rice wine is a kind of fermented raw wine brewed from grain.Malt and wheat germ contain a lot of carbohydrates,amino acids and antioxidant substances,which are rich in nutrition and easy to obtain.Both of them are highquality raw materials for brewing yellow rice wine.Wheat germ,as a by-product of flour processing,couldn’t be effectively utilized,but a large number of wheat germ are produced every year in China.Therefore,this paper used malt and wheat germ as main raw materials to produce malt-wheat germ wine by fermentation and studied the brewing technology and antioxidant activity,so as to improve the utilization rate of wheat germ and realize high-value utilization of agricultural products.The specific research contents and results of this paper are as follows:(1)Optimization of saccharification process of malt-wheat germ wine: The saccharification technology was optimized by single factor experiment combined with Box-Behnken response surface experiment with three factors and three levels.Variance analysis showed that the influence order of the selected factors on the saccharification effect of wine was wheat germ addition amount> saccharification temperature > saccharification time.The optimum saccharification conditions were saccharification temperature 66.2 ℃,saccharification time 10.6 h,and wheat germ addition 23.5 %.Under the optimum conditions,the average sugar content of the mash was 33.1 ± 0.4 °Bx,and the reducing sugar content could reach241.015 ± 0.659 g/L.(2)Optimization of fermentation process of malt-wheat germ wine: Three saccharifying leavens were selected,and the best saccharifying leaven was koji.The single factor experiment combined with L9(34)orthogonal design was used to optimize the fermentation process.Variance analysis showed that the order of the influence of the selected factors on the alcohol content was fermentation temperature > koji inoculation amount > fermentation time.The optimum fermentation conditions were fermentation temperature 30 ℃,fermentation time3 d and koji inoculation amount 2.5 ‰.Under these conditions,the alcohol content could reach 13.4 ± 0.2 %Vol,the total phenol content could reach 2.917± 0.011 g/L,the total flavonoids content could reach 663.785 ± 10.399 mg/L,the reducing sugar content was 7.962 ± 0.543 g/L,and the total acid content was 6.733± 0.115 g/L.(3)Optimization of clarification process of malt-wheat germ wine: Nine clarifiers were selected,and the best clarifier was acid protease.The saccharification process was optimized by single factor experiment combined with Box-Behnken response surface methodology with four factors and three levels.Variance analysis showed that the order of the factors influencing the light transmittance of wine was: acid protease addition amount> clarification temperature > citric acid addition amount> clarification time.The best clarification conditions were clarification temperature 55.6 ℃,clarification time11.6 h,citric acid addition amount 12.0 % and acid protease addition amount 1.15g/L.Under these conditions,the average light transmittance of fermented wine was 93.8 ± 0.3 %.(4)Study on antioxidant activity of malt-wheat germ wine: The antioxidant substances of malt-wheat germ wine,commercial yellow rice wine,commercial beer and distilled wine were determined.The results showed that the total phenol content and total flavonoids content of malt-wheat germ wine were much higher than those of other three kinds of wine.Meanwhile,the free radical scavenging capacity and total reducing capacity of malt-wheat germ wine were compared with those of commercial beer,yellow rice wine,Vc and distilled wine.The results showed that malt-wheat germ wine had good antioxidant capacity.(5)Analysis of nutritional components of malt-wheat germ wine: The samples of malt-wheat germ wine were tested.The results showed that malt-wheat germ wine was rich in amino acids,and the content of essential amino acids required by human body was extremely high.Meanwhile,malt-wheat germ wine was rich in protein,calcium and zinc. |
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