Research On The Antifreeze Properties Of Antifreeze Protein And Its Effect On Quality Improvement Of Frozen Food Made From Wheat Flour

After quick-freezing and frozen storage of dough,some unfavorable changes such as small dough proofing volume,long proofing time,dry and hard dough,low specific volume and high hardness were observed,which caused by the loss of product moisture,yeast cell damage and the destruction of the dough structure caused by the migration of moisture and the recrystallization of ice in the dough.The addition of quality improvers is the most convenient,efficient and low-cost way to improve the quality of frozen dough.In this paper,the antifreeze properties of deep sea fish skin antifreeze protein(fs AFPs),cod blood antifreeze protein(Cb AFPs),alfalfa antifreeze protein(LAFPs)and Ligustrum lucidum leaf antifreeze protein(Ll AFPs)and their effects on the quality improvement of frozen dough were studied,and a composite quick-frozen pasta quality improver was developed.The main research contents are as follows:1.The antifreeze performances of four antifreeze proteins(AFPs)were investigated.The DSC method was used to compare the heat flow curve and thermal hysteresis activity of different solution systems,and at the same time,the state of ice crystals in the freezing and thawing process of different AFPs solution systems was observed and monitored with a biological microscope.The results show that the heat flow curve of the AFPs solution is not much different at the concentrations of 1mg/m L and 5mg/m L,and the addition of AFPs reduces the melting enthalpy of the system;at the retention temperature of-0.3?,the BSA solution has no heat hysteresis,and the THA value of the water system containing Ll AFPs,LAFPs,fs AFPs,Cb AFPs and Cb AFPs-LAFPs are 0.95?,0.85?,0.41?,0.27?,3.76?.The micrographs showed that the ice crystals formed by freezing water solution without AFPs were the largest and the shape of ice crystals is single.Adding AFPs into water solution significantly reduced the size and changed the shape of ice crystals.Among them,the size of ice crystals formed in LAFPs-water system is the smallest,and the shape of ice crystals in LAFPS-water system is the largest.It shows that the four AFPs all have thermal hysteresis activity,can modify the morphology of ice crystals and inhibit ice recrystallization,and there is a synergistic effect between different kinds of AFPs.At the same time,it shows that plant-derived AFPs are better than fish AFPs in inhibiting ice recrystallization.2.The effect of different AFPs on dough freeze protection was studied.The microstructure,texture properties and yeast activity of the dough frozen for 90 days and after freezing and thawing cycles were investigated by scanning electron microscopy,texture analyzer and thawing proofing.The results showed that compared with the control group,the texture characteristics,gluten network structure,fermentability and water loss rate of the frozen storage and freeze-thaw dough added with AFPs were significantly better than those without added dough.Among them,the freeze-thaw dough with 0.13%LAFPs can better maintain the integrity of the gluten membrane and the arrangement of starch granules,the water loss rate of the dough is only 0.70%,and the volume expansion rate of the dough proofing reached 101.8%.3.The effect of different AFPs on the quality of frozen steamed bread was studied.The frozen dough was subjected to proofing and steaming treatment,and the texture and sensory evaluation of steamed buns were carried out.The results showed that the overall hardness of the steamed buns with the frozen dough added with fs AFPs was the lowest,followed by Ll AFPs and LAFPs,and the effect of different addition amounts was relatively stable,while the frozen dough with Cb AFPs showed a large change with the addition amount;Sensory scores of 85 and above include 0.2%fs AFPs,0.3%fs AFPs,0.5%fs AFPs,0.7%fs AFPs,0.11%LAFPs,0.13%LAFPs and 0.15%Ll AFPs;fs AFPs has the highest comprehensive score for sensory evaluation,and Cb AFPs has the lowest comprehensive score,but Both were higher than the control group steamed bread.It shows that the addition of AFPs reduces the hardness and chewiness of steamed bread,and can improve the sensory quality of frozen steamed bread.4.Researched and developed a new type of dough cryoprotectant.After 90 days of frozen storage,the dough was proofed and steamed,and the texture properties and sensory evaluation of the steamed buns were carried out.According to the results of single-factor experiments,three additives,fs AFPs,LAFPs and trehalose,were selected for response surface optimization tests.The results show that the ratio of fs AFPs:LAFPs:trehalose in the compound additive is 1.7:1:1.3,and the dough prepared by adding 0.56% of the compound additive to flour has strong water retention during frozen storage,and the steamed bread made had a smooth surface,dense pores,and had the highest comprehensive score.