Studies On Rheofermentometer Properties Of Frozen Sweet Doughs

The evaluation methods of yeast leavening ability in frozen sweet dough, influences of processing parameters of freezing and thawing on fermentation properties of yeast in frozen sweet dough, response surface methodology to investigate reofermentomer characteristics of yeast in frozen sweet dough, as well as the effects of physical-chemical pretreatments to yeast on fermentation characteristics of frozen sweet dough were mainly studied in this paper.Four kinds of appraisal methods of fermentative power, such as drainage method, floating method, graduated cylinder method and rheofermentometer method were compared. The results showed that graduated cylinder method for fermenting power evaluation of yeast in frozen sweet dough was best of all. And the addition amount of active dry yeast was between 0.5%-2.5%. The increasing volume of dough during 0-1.5h fermentation was used to evaluate the leavening ability of yeast in frozen sweet dough. The effects of different freezing rates and the thawing conditions on quality of frozen sweet dough were investigated. The results indicated that, the medium frezezing rate 0.8-1.0℃/min was suitable to preserve yeast activity thus maintained the good fermentation ability, improved gluten network and hence obtained frozen sweet dough with good quality. Compared to thawing temperature of 38℃, the condition of 4℃is more advantageous. Frozen sweet dough was thawed evenly, and gave the bread quality improvement, increased the bread specific volume, reduced the crumb hardness and made the crumb evener.The influences of trehalose, shortening, salt, lactic acid and dough temperature on rheofermentometer characteristics of frozen sweet dough were investigated by Chopin rheofermentometer F3. The results obtained showed that shortening and trehalose had a notable impact on Hm'and CO2 production. Salt, dough temperature and trehalose had a significant effect on Hm. Response surface methodology was used to establish the models reflecting the relations between factors and dependent variables. All models indicated that they were suitable and response surface methodology could be a useful tool to predict the effects of shortening, trehalose, salt, lactic acid, and dough temperature on frozen sweet dough rheofermentometer properties and specific volume.Pretreatments of cold, heat treatment to yeast namely 10℃for 3h, 40℃in water baths for 60min or combination of the two enhanced yeast anti-freeze performances. 10% trehalose solution binding with cold, heat treatment better enhanced the yeast freezing survival rate and increased the content of intracellular trehalose in yeast. Under the identical kind of processing condition, yeasr survial rate was in the corresponding of intracellular trehalose content basically. F3 rheofermentometer was used to study the effect of different concentrations of trehalose solution(0, 5%, 10%) on fermentation characteristics (Hm, Hm'and CO2 production). After frozen storage of 4 weeks, Hm, Hm', CO2 production, and bread specific volume of frozen sweet dough were 28, 35, 37mm, 22, 32, 38mm, 562, 549, 530, 526mL, 4.90, 5.10, 5.29mL/g respectively, and baking score were 66.8, 73.3, 77.4 respectively. The results showed that trehalose improved the rheofermentometer properties (Hm, Hm'and CO2 production) and baking qualities.