Studies On Fermentation Process And Baking Properties Of Bread Dough Made Of Fermented Glutinous Rice

Fermented glutinous rice is a Chinese traditional snack.In this study,5 kinds of Chinese Qu traditional starter(AQ,SZ,GX,AH,HB)were used to ferment glutinous rice to be used in bread making.The fermentation characteristics of the fermented glutinous rice were determined using culture dependent methods.The fermented glutinous rice was used in bread making,with the resulting bread screened and selected for unique volatile flavor compounds using GC/MS.The selected bread was investigated on the effects of fermented glutinous rice on dough and bread baking properties.Additionally,the effects of glucose oxidase(GOX),transglutaminase(TG)and xylanase(XYL)on gluten network,baking and staling properties of bread with fermented glutinous rice were studied.The main results of this study were as followed:By comparison of basic chemical characteristics of five kinds of different fermented glutinous rice as well as the baking properties of bread which made of fermented glutinous rice,combined with the GC/MS results,bread-GXFRB,made with fermented glutinous rice(fermented with GX for 48 h)had the richest flavor,including ethyl caprate and ethyl caprylate(brandy flavor),phenethyl alcohol(rose scent)as well as butyl butyryllactate(buttery),with the least relative damage to bread quality,and hence was selected for further studies.The fermentation characteristics of the fermented glutinous rice(GX)showed that the number of molds was stable after 24 h of fermentation and decreased later.The yeasts grew into the stationary phase after 40 h of fermentation.The main metabolites found were organic acids,reducing sugars and ethanol all stabilized after 48 h of fermentation.The effects of fermented glutinous rice(GX)on dough(fermented for 0 h,24 h,48 h,72 h)and bread quality were researched.Wheat dough(WD)and bread(WB)were used as control samples.The dough rheology properties analysis showed that the thermomechanical characteristics,dynamic rheological properties and fermentation rheological properties were significantly affected by fermented glutinous rice addition.With increase in the fermentation time,the water absorption ability of dough decreased from 57.1% to 50.0% and the gluten protein weakened.Also,the viscoelasticity of dough decreased as well as the gas production and gas holding capacity.The content of free sulfhydryl and ?-amino nitrogen in the dough significantly increased 60% and 30% respectively with the extension of the fermentation time(by comparison of 0hFRD and 72 h FRD).Hence,might have led to the damage of the gluten structure and the decrease of cohesiveness,elasticity as well as baking quality of the final bread observed.Besides the mouth feel,48 hFRB shows the higher score in all the tests,so it is selected to be modified.Glucose oxidase(GOX)(10.7 mg/kg),transglutaminase(TG)(1168 mg/kg)and xylanase(XYL)(0.03 mg/kg)amounts were optimized in bread with fermented glutinous rice using the response surface optimization method to improve the baking quality.Under optimum conditions,the overall satisfaction of the bread was highest at 0.620.Wheat dough(WD),dough with fermented glutinous rice(FRD)and bread dough with both fermented glutinous rice and optimized enzymes(MFRD)were analyzed.The free thiol and ?-amino nitrogen content,molecular weight distribution of gluten protein(SDS-PAGE)and the microstructure(observed by laser scanning confocal microscope)were reported on.It was found that the complex enzyme could re-crosslink the gluten protein,and the gluten network structure could be repaired so that the baking quality of the bread with optimized enzymes(MFRB)was greatly improved.The texture properties and sensory scores of MFRB were all close to or even better than wheat bread(WB).During the storage of bread,the increase in hardness of MFRB was significantly similar to WB,which was significantly lower(p<0.05)than FRB.In addition,the water loss of MFRB was less than FRB.However,there was no significant difference in aging enthalpy changes of the three kinds of bread.Furthermore,although very weak,bread with fermented glutinous rice showed antibacterial capacity.Therefore,due to its unique flavor,improved and better baking quality with a slower aging rate coupled with a certain degree of antibacterial capacity,MFRB bread had the highest consumer acceptance score.