Study On The Technology Of Producing Frozen Dough Of Southern Steamed Bread

Steamed bread is a traditional flour staple food in China.Due to the differences of regional diet and culture,steamed bread is divided into northern steamed bread and southern steamed bread.In addition to the basic flour,yeast and water of northern steamed bread,southern steamed bread is also supplemented with shortening,sugar,baking powder and other auxiliary materials..Compared with the large and chewy northern steamed bread,the southern steamed bread is small,square,soft and non-sticky,with obvious sweetness.At present,the northern steamed bread has been industrialized through quick-frozen technology or frozen dough production technology,but the production and consumption of southern steamed bread basically remain in the form of "ready-to-sell".In this paper,the basic technology of producing Southern steamed bread by frozen dough technology and the technology of improving the quality of Southern steamed bread by frozen dough technology were studied,and the regularity of quality change of frozen Southern steamed bread during storage period was discussed,in order to provide theoretical basis and practical reference for industrialized production of Southern steamed bread by frozen dough technology.The main contents and conclusions of this paper are as follows:1.Basic technology of frozen dough for Southern steamed bread production.(1)The determination of freezing technical parameters: Taking the sensory evaluation,hardness and specific volume of Southern steamed bread as the evaluation indexes,the effects of freezing time and temperature on the quality of frozen dough were studied.At the same time,combined with the freezing temperature curves of frozen dough under different freezing temperatures,the freezing temperature was determined to be-30 ?and the freezing time was 50 min.(2)Determining the basic formula and fermentation technical parameters: Taking the sensory evaluation,hardness and specific volume of Southern steamed bread as the evaluation indexes,the effects of sugar content,yeast content,fermentation temperature and fermentation time on the quality of Southern steamed bread were investigated.At the same time,the mathematic model of the influence of the above parameters on the quality of Southern steamed bread produced by frozen dough was established by response surface methodology,and the basic formula and fermentation parameters of Southern steamed bread produced by frozen dough were optimized: 100% flour,8.2% sucrose,1.0% yeast;fermentation temperature 35 ?,fermentation time 41 min.Under the optimum conditions,the sensory score,hardness and specific volume of frozen dough produced Southern steamed bread reached 79.7 points,805.26 g and 2.98 mL/g.2.Study on quality improvement technology of Southern steamed bread produced by frozen dough.Based on the basic technology of frozen dough for Southern steamed bread production,the effects of quality improvers such as sodium carboxymethyl cellulose(CMC-Na),xanthan gum and sodium dihydrogen phosphate on the characteristics of frozen Southern steamed bread and the quality of Southern steamed bread were explored.And through orthogonal test,the compound quality improver for the production of Southern steamed bread from frozen dough was optimized.The purpose is to provide theoretical basis and practical reference for improving the quality of Southern steamed bread produced by frozen dough..The study found that:(1)When trehalose content is 4%,it can increase the maximum tensile resistance of dough,increase the elastic modulus and viscous modulus of dough,and improve the rheological properties of dough.Trehalose can protect yeast cells and maintain yeast activity.The Southern steamed bread produced from the frozen dough has high specific volume and good quality.(2)Sodium carboxymethyl cellulose(CMC-Na)can significantly increase the maximum tensile resistance,elastic modulus and viscous modulus of dough,but the addition of CMC-Na above 0.06% will increase the dough hardness,making the final steamed bread hardness too high,not in line with the taste of Southern steamed bread,and its quality will also decline.The quality of steamed bread with0.06% CMC-Na was the best.(3)When the dosage of sodium dihydrogen phosphate was 0.1%,the pull-up resistance,elastic modulus and viscous modulus of frozen dough were the largest.However,the addition of sodium dihydrogen phosphate has little effect on the hardness and specific volume of the final steamed bread.Sodium dihydrogen phosphate can improve the pH value of dough,protect the surface of dough,and eventually make the surface of steamed bread smoother.(4)Xanthan gum as a hydrophilic colloid can increase dough tensile resistance,dough elasticity and hardness,but the amount of xanthan gum above 0.15% will reduce dough elongation,affect dough air holding capacity,and make the final steamed bread smaller,harder and worse quality.The addition of xanthan gum ranged from 0.05% to 0.1%,which could alleviate the damage of frozen dough and improve the quality of steamed bread.(5)Orthogonal test was used to determine the optimum proportion of compound improver: 100% flour,4% trehalose,0.15% sodium dihydrogen phosphate,0.05% xanthan gum and 0.04% CMC-Na.3.Study on Quality Change of Frozen South Steamed bread dough during Frozen StorageFrozen dough with compound quality improver and frozen dough with southern steamed bread without compound quality improver were preserved under –18?frozen storage conditions.Changes of quality(tensile properties,dynamic rheological properties,secondary structure of protein and microstructure)of frozen dough from southern steamed bread during frozen storage and the trend of quality change of processed steamed bread were studied.To provide theoretical reference for the selection of frozen dough storage period for Southern steamed bread.The results show that:In the process of frozen storage,the maximum tensile resistance of dough decreases with the prolongation of frozen storage time.After 30 days of frozen storage,the sensory score of frozen Southern steamed bread without compound quality improver had dropped to 53.2 points,but 71 points still existed in the use of compound quality improver.After adding compound quality improvers,the changes of protein secondary structure during frozen storage decreased from 65% of beta folding,37% of non-return curling,63% of alpha helix and 38% of beta rotation to 51% of beta folding,13% of non-return curling,33% of alpha helix and 9% of beta rotation.The results of scanning electron microscopy(SEM)showed that ice crystals mainly damaged gluten protein and gluten network during freezing storage,but also damaged starch granules,which resulted in deterioration of dough and deterioration of steamed bread quality.With the same frozen storage time,the dough with compound quality improver has smaller porosity,less starch damage and more complete gluten structure.