| The development of starchy foods has become an inevitable trend,and steamed bread of frozen dough is becoming more and more popular among consumers.However,quick-frozen foods’ quality may deteriorate due to increased storage time and repeated freeze-thaw cycles in every aspect of storage,transportation and sales,such as degradation and hardening of the epidermis,poor taste and cracks,etc.,which are caused by aging of the starch,destruction of the dough structure etc..In order to reduce the occurrence of these phenomenon,In this paper,the effect of y-polyglutamic acid(γ-PGA)on gelatinization,gel aging,freeze-thaw stability of wheat starch,and the effect of γ-PGA on the freezing and freeze-thaw stability of frozen dough and the quality of steamed bread,which was studied by using some methods,mainly including rapid velocity meter,differential scanning calorimeter,low field nuclear magnetic resonance instrument.X-ray diffractometer,scanning electron microscope,texture analyzer,water dissolution rate,specific volume method.The results of γ-PGA on the gelatinization and aging property of wheat starch showed that γ-PGA reduced the peak viscosity,bottom viscosity,final viscosity and gelatinization value of wheat starch paste,increased the gelatinization temperature and made the gelatinization process difficult.γ-PGA reduced the disintegration value and the regenerative value,slowed down the short-term aging caused by amylose.Wheat starch gel was stored at 4℃ for different time,γ-PGA reduced the gelation aging value.When the addition amount was 0.7%,the enthalpy value decreased 1.453 J/g after 28 days of storage.γ-PGA increased the gel-bound water content,reduced the free water content,and delayed the migration of 5.65%water molecules at 28 days.γ-PGA inhibited recrystallization of wheat starch,reduced relative crystallinity,and effectively inhibited long-term aging caused by amylopectin molecules.γ-PGA reduced the pores of the starch gel,made the microstructure more uniform and fine.The results of γ-PGA on freeze-thaw stability of wheat starch gel showed that the antifreeze activity of γ-PGA was 6.17,and the antifreeze activity was more obvious,which could fix more water molecules and reduce the content of freezeable water-γ-PGA reduced the aging value after wheat starch gel was subjected to 1,3,5,and 7 freeze-thaw cycles.When the addition amount was 0.7%,the enthalpy value reduced 0.84 J/g after 7 freeze-thaw cycles.γ-PGA slowed the conversion of bound water to free water and reduced the growth of ice crystals.γ-PGA reduced hardness by 11.96%,elasticity by 13.31%,and chewiness by 15.99%after 7 freeze-thaw cycles.γ-PGA reduced water separation rate of 6.74%,inhibited aging of starch gel and improved freeze-thaw stability.The results of γ-PGA on the freeze-thaw stability of frozen dough showed that the quality of frozen dough and steamed bread decreased with the increase of freeze-thaw cycles.γ-PGA reduced the thawing enthalpy of the frozen dough.when the γ-PGA addition amount was 0.7%,the ice crystal thawing enthalpy decreased by 2.10 J/g after 7 freeze-thaw cycles,which inhibited the increase of the freezeable water content.γ-PGA reduced moisture migration in the dough,prevented damage to starch molecules and proteins by large ice crystals,and protected the dough network structure.γ-PGA made the large cavity gradually less,the more uniform the particle distribution,the closer the structure.γ-PGA increased the specific volume of steamed bread of the frozen dough by 27.43%,and the texture properties were improved after 7 freeze-thaw cycles.γ-PGA delayed the aging of the starch and increased the freeze-thaw stability of the dough.The results of γ-PGA on the freeze-thaw stability of frozen dough showed that the frozen dough was stored at-18℃,γ-PGA reduced the thawing enthalpy of the frozen dough.when the γ-PGA addition amount was 0.7%,the thawing enthalpy decreased by 1.11 J/g after storage for 28 days.γ-PGA reduced the migration of bound water to free water by 0.262%,reduced the freezeable moisture content,and reduced the damage of ice crystals to the dough.γ-PGA made the dough hole smaller and uniform,and the particles are more complete,which the starch granules were more firmly embedded in the gluten matrix,made the dough structure more stable.γ-PGA increased the specific volume of steamed bread of the frozen dough by 18.90%,which reduced the hardness by 14.58%,the chewiness by 14.41%and increased the elasticity by 4.69%after 28 days of frozen storage.γ-PGA inhibited the aging of starch,and improved the texture and taste of steamed bread.The addition amount of γ-PGA was gradually increased,and the effect on wheat starch,starch gel,frozen dough and steamed bread was more obvious.When the addition amount was 0.7%,the effect is best.Experiments showed that γ-PGA delayed the aging of wheat starch gel,increased the freeze-thaw stability of the gel,improved the freeze-thaw and frozen stability of frozen dough,and improved the quality of steamed bread of frozen dough. |
PDF Full Text Request