Effect Of Wheat Gluten On The Quality Of Fermented Bean Curd

Soybean-based fermented bean curd is a long-established traditional food that has an important market share in condiments.Gluten is wheat gluten protein,a high-quality vegetable protein with unique viscoelastic properties and high amino acid content such as glutamic acid and proline.It is widely used in food industry.In this study,the new fermented bean curd was prepared by adding wheat gluten,in order to provide reference for enriching the flavor of the fermented bean curd,improving its texture and taste,and broaden the application range of gluten.Firstly,according to the results of single factor experiment,the yield,the water retention rate and the gel strength were used as the response values.The response surface test was carried out on the three factors of the amount of gluten,the amount of coagulant and the pressing time.The preparation process was further optimized.The results showed that the optimal process conditions were 39.45% of gluten,10% coagulant,and 1.2 h of pressing time.The water retention rate of white bean curd was 75.18%,the yield was 183.55% and the gel strength was 95.99 g.Secondly,the effects of adding gluten on the white bean curd were studied by evaluating water retention rate,yield,gel strength,sensory score,free amino acid content,texture characteristics and flavor substances.The results showed that the addition of gluten powder could increase the yield and water retention rate of white bean curd and improve the sensory score,but the gel strength decreased.The hardness and chewiness were decreased,the elasticity and adhesion were increased,and the free amino acid content did not differ significantly.Adding gluten can reduce the taste of beans and the content of soybean odor such as acetic acid,hexanal and hexanol in white bean curd was reduced by 7.58% in total.Thirdly,the fermentation temperature,fermentation time and Mucor inoculation amount were tested by single factor experiment with protease activity as the evaluation index.The effects of three factors on the protease activity in the pre-fermented were analyzed.The results showed that the fermentation temperature was 25°C,the fermentation time was 60 h,and the inoculation amount 12% of Mucor was the optimal condition for pre-fermentation.Then,the effects of adding gluten on mature fermented bean curd were studied by chemical composition,texture characteristics,free amino acid content,flavor substance,molecular weight distribution of the polypeptide and surface color difference.The results showed that the addition of gluten reduced the hardness and chewiness of fermented bean curd,and the elasticity and adhesion were increased;the free amino acid content increased by 54.31%,especially the glutamic acid content increased by 60.09%;the flavor species increased by more than ten kinds,especially there are 20 kinds of ester substances more,and the content was increased by about 15%.Adding gluten improved the surface color of mature fermented bean curd.The addition of gluten has improved the sensory,nutritional and flavor aspects of traditional fermented bean curd.Finally,the fermented bean curd and the commercial fermented bean curd were compared in terms of chemical composition content,texture characteristics,free amino acid content and flavor substances.The results showed that the hardness and chewiness of the fermented bean curd added with gluten were lower than that of the commercial fermented bean curd.The free amino acid was slightly lower than the commercial fermented bean curd and the glutamic acid content was 5 times that of the commercial fermented bean curd.The kinds of volatile compounds were two times of fermented bean curd.The alcoholic substances in commercial fermented bean curd,especially ethanol,accounted for more than 70% of volatile flavor substances and the content of esters only accounted for less than 8%,while the ester content of fermented bean curd added with gluten is more than 50%,and the alcohol content is about 35%.The addition of gluten can increase the overall flavor quality of fermented bean curd and the improvement of the umami taste of fermented bean curd was particularly remarkable.