Effect Of Laccase And Ferulic Acid On The Microstructure And Frozen Stability Of Wheat Dough

Wheat flour is an important raw material for the processing of flour products.Some parts of wheat flours in China have poor quality and weak gluten tenacity due to its growth environment,storage conditions and processing technology.The flour improvers can be useful in wheat dough processing and frozen dough applications.Nowadays,composite additives have gradually become the trend of food additive industry due to their excellent synergistic effects,but the mechanism of additives on processing quality of wheat flour and dough is still unknown.Based on the oxidative properties of laccase and its potential to improve the quality of co-formed products together with ferulic acid in wheat flour,Therefore,in the present study,laccase（LAC）and ferulic acid（FA）were used as the potential flour improvers.The synergistic effects of LAC and FA on the rheological properties and microstructure of wheat dough were investigated.During the frozen storage,the mechanism of LAC and FA on the quality of wheat dough were analyzed.The main research contents and results are as follows:（1）Effect of laccase on the processing quality of wheat doughThe effect of LAC on the rheological properties and microstructure of the dough were investigated by farinographic,rheological analysis and scanning electron microscopy.The addition of LAC increased the stability time and decreased the softening degree of the dough（p<0.05）.As the LAC increased,the storage modulus of dough increased and the loss tangent decreased,which indicated that the gluten strength in the dough increased.Other changes of the indicators such as water absorption and formation time of dough were not obvious.LAC treatment resulted in dough hardening:the resistance to extension(R_max)and the ratio of R/E of dough increased,and the dough extensibility（E_x）decreased significantly when the addition of LAC came to 4-20 nkat/g flour.When dosage of 20 nkat laccase/g flour was used,the resistance to extension increased by 52%.Scanning electron microscopy showed the addition of LAC contributed to the formation of a continuous network of dough,in which the gluten proteins were bonded to each other,maintained the strength and elasticity of the dough.（2）Synergistic effects of laccase and ferulic acid on the processing quality of wheat doughThe effects of LAC and FA on the processing quality of wheat dough were investigated by farinographic characteristics,dough rheological properties and microstructure.The addition of FA significantly shortened the dough stability time,increased the softening degree of the dough,which increased from 156.6 FU to 204.9 FU（p<0.05）,resulted in weakening gluten in the dough formation.In combined with FA,the effect of LAC was predominant,the mechanical processing properties of dough were obviously improved.The dough with FA and 20 nkat/g LAC had the largest storage modulus G’and the loss modulus G’’.In improving the tensile strength of the dough,LAC exhibited synergistic effect with FA,compensated for the lack of dough extensibility,and enhanced the continuity and stability of the dough network structure.（3）Effects of laccase and ferulic acid on the frozen quality of wheat doughThe effects of LAC and FA on the quality of wheat dough during frozen storage were investigated.During the frozen storage,the tangent loss of the dough gradually increased（FA>Control>FA+LAC>LAC）.LAC and FA could play a role together in regulating the quality of the dough and delayed the deterioration of the dough quality.The dough extensibility gradually increased with only FA during frozen storage,while the LAC synergized with FA contributed to stabilize the dough extension.LAC synergized with FA in the compensation for the decrease in dough extensibility caused by LAC during dough development.The results showed that LAC and FA improved the quality of dough and frozen dough structure.（4）The mechanism of laccase and ferulic acid on the frozen qualiity of wheat doughThe synergistic effects of LAC and FA on the properties and microstructure of wheat gluten during frozen storage were analyzed by rheological experiment,Kieffer test and scanning electron microscopy.The migration of water and the recrystallization of ice crystals during the frozen storage weakened the gluten network structure.The addition of LAC and FA improved the R_max and rheological properties of gluten,strengthened the gluten network structure,which delayed the deterioration in the dough quality.