Study On The Effect Of Flavourzyme On The Quality Of Bread

Enzymes are often used in baking field,and have great potential to replace chemical additives because of their high safety and effectiveness.Proteases are commonly used in baking field,but they often have a damaging effect on bread volume due to the hydrolysis of gluten.Flavourzyme is a mixture of exopeptidase and endopeptidase,which is different from other proteases because its main exopeptidase activity acts more on the end of polypeptide.However,there are few studies on the effect of Flavourzyme on bread quality including flavor characteristics,and its mechanism.Therefore,this paper studied the influence of different Flavourzyme contents on toast quality,and preliminarily explored its influencing mechanism,aiming to provide theoretical basis for the application of Flavourzyme to replace chemical additives in bread making.The main results are as follows:The appropriate amount of Flavourzyme addition(0.01%-0.04%)could obviously improve the specific volume,texture and internal texture structure of bread.Flavourzyme could also improve the taste of bread crumb and enhance the flavor of bread crumb and crust.The effects of different Flavourzyme contents(0%,0.01%,0.04%,0.08%,0.12%and 0.16%,flour basis)on bread quality were studied and the addition of 0.04%Flavourzyme had the best effect on improving bread quality,the specific volume of fresh bread increased from 3.86m L/g to 4.42 m L/g,the height/width ratio increased from 0.94 to 1.05,the hardness decreased from 212.32 g to 130.67 g,and the chewiness decreased from 155.87 g to 94.69 g.At the same time,the smallest average cell area(0.27 mm~2),the largest cell density(70.20 cells/cm~2)and porosity(19.12%)made it obtain the most delicate and uniform internal texture structure.The addition of Flavourzyme deepened the color of bread,delayed the hardening of bread during storage.Flavourzyme addition enhanced the umami and saltiness,reduced the bitterness of the bread crumb,and also enhanced the alcoholic,cheesy flavor of the bread crumb and enhanced the caramel,burnt and fatty flavor of the crust.However,high concentration(0.08%-0.16%)of Flavourzyme reduced the elasticity and cohesiveness of bread crumb,made the internal texture structure more irregular and rougher,which had a negative impact on the quality of bread.The addition of Flavourzyme weakened the strength of the dough,but enhanced the extensibility,and the proper contents(0.01%-0.08%)improved the fermentation characteristics of the dough.The effect of Flavourzyme on dough characteristics was studied.The addition of Flavourzyme reduced the water absorption,dough development time,stability and the area of extensograph curve of dough,and increased the dough extensibility from 213mm(control)to 255 mm(0.16%).Appropriate concentration(0.01%-0.08%)of Flavourzyme improved the fermentation characteristics of dough.When the Flavourzyme content is 0.04%,the maximum height of dough expansion increased from 74.2 mm to 79.4 mm,the maximum height of gas release curve increased from 88.4 mm to 105.2 mm,and the yeast activity and gas production were also enhanced.And the maximum height of dough expansion and the maximum height of the gas release curve had good correlations with the specific volume and hardness of the bread.The addition of Flavourzyme also reduced the elastic modulus(G’)and viscous modulus(G’’)of dough,and weakened the viscoelasticity of dough.The microstructure results showed that the low concentration of Flavourzyme(0.01%-0.04%)had no obvious damage to the dough,while the high concentration(0.16%)made the internal pores of fermented dough became large and irregular,which inhibited dough expansion.Gluten protein was hydrolyzed and depolymerized by the addition of Flavourzyme,proper concentration of Flavourzyme(0.01%-0.04%)had no obvious effect on gluten network.The addition of Flavourzyme resulted in the hydrolysis of glutenin polymers,especially high molecular weight glutenin subunits(HMW-GS),resulting in more production of low molecular weight proteins.Flavourzyme also reduced the content of glutenin macropolymers(GMP),increased the content of free sulfhydryl groups,resulting in the rupture of disulfide bonds and depolymerization of gluten.Low concentration of Flavourzyme(0.01%-0.04%)had no significant effect on the secondary structure of gluten(p>0.05),while high concentration(0.12%-0.16%)showed a significant decrease in the content ofα-helices(p<0.05)and significant increases in the contents ofβ-sheets and random coils(p<0.05).The results of laser scanning confocal microscopy(CLSM)analyses showed that the gluten network was not obviously affected by the addition of 0.01%-0.04%Flavouryzme,but the gluten network was destroyed and became loose and sparse with 0.16%Flavourzyme.The addition of Flavourzyme increased the contents of free amino acids and small molecular peptides,and enriched the volatile flavor substances in bread,and the flavor substances were closely related to the flavor attributes of bread.Compared with the control,the total content of volatile compounds in bread crumb and crust with the highest Flavourzyme content(0.16%)increased by 13.73%and 29.61%respectively,and the content of Maillard reaction products in bread crust also increased obviously.Hierarchical cluster analysis showed that flavor compounds in the bread were significantly different between low-addition and high-addition groups.Network analyses showed that nine compounds(2-methyl-1-propanol,3-methyl-1-butanol,3-(methylthio)-1-propanol,(E)-5-decen-1-ol,phenethyl alcohol,hexanal,2-methyl-propionic acid,phenethyl acetate and indole)were closely related to the flavor attributes of bread crumb,and seven flavor compounds(3-methyl-1-butanol,(E)-5-decen-1-ol,phenethyl alcohol,benzaldehyde,(E,E)-2,4-decadienal,acetoin,indole)were closely related to the flavor attributes of the crust.