Study Of The Characteristic Of Potato Starch-whey Isolate Protein Mixed Systems And Their Effect On The Quality Of Bread

Starch and protein are the main sources of nutrition and energy in human diet.During the process of food processing and storage,protein can interact with starch,which has a great influence on the physicochemical properties and quality of the food.The hybrid system formed between starch and protein can improve the physicochemical properties of starch and protein,and to some extent,it can show better physical and chemical properties than itself,which is widely used in food,medicine,biomaterials and other fields.This paper investigates the physicochemical and digestive properties of potato starch(PS)and whey isolate protein(WPI),and applies them to bread to study the effects of potato starch-lactalbumin mixtures on dough characteristics and bread quality.Details and results of this research are as follows:(1)Preparation of potato starch-lactalbumin blend systems and analysis of their properties.Potato starch-lactalbumin blends with different compounding ratios(10:0,9.5:0.5,9.0:1.0,8.5:1.5,8.0:2.0)were constructed and analysed for processing characteristics,structural characteristics and digestive properties.The analysis of the processing characteristics showed that the hybrid system presents a typical weak gel structure,and the addition of WPI inhibited the gelatinization of PS,which leads to the increase of gelatinization temperature and the decrease of gelatinization enthalpy.When the ratio of the hybrid system was 8.5:1.5,the thermal stability of hybrid system is the best.The structural characterization showed that the addition of WPI did not produce new characteristic peaks in the system,and there was no covalent interaction between them.The addition of WPI increased the strength of hydrogen bonds in the mixed system,and enhanced the short-range ordered structure of starch molecules.When the ratio of the mixed system was 8.5:1.5,the starch in the mixed system has the highest degree of order and the strongest hydrogen bond effect.In vitro digestibility analysis showed that adding soy protein isolate decreased the digestibility of the mixed system.(2)Effect of potato starch-lactalbumin mixtures on wheat dough characteristics.The PS-WPI was used to replace wheat flour at different substitution rates(0,5%,10%,15%,20%)and kneaded into dough.The effect of PS-WPI mixed system on the properties of wheat flour dough was studied.The analysis of flour quality and gelatinization characteristics showed that the addition of PS-WPI decreased the flour quality characteristics of wheat flour.With the increase of PS-WPI replacement rate,the peak viscosity,final viscosity,disintegration value and retrogradation value of the mixed dough decreased,but the gelatinization temperature increased significantly.The analysis of texture and rheology showed that PS-WPI had elastic fluid characteristics,and the addition of PS-WPI reduced the texture characteristics of the mixed dough.The analysis of water distribution shows that the water in PS-WPI mainly exists in the form of weakly bound water.The addition of PS-WPI increases the peak area of bound water and reduced the fluidity of water molecules in the dough.Microstructure analysis showed that the addition of PS-WPI destroys the gluten network structure of the dough,and the damage is more obvious when the substitution rate is greater than 15%.(3)Effect of potato starch-lactalbumin mixtures on the quality of bread.PS-WPI mixture was added to bread at different substitution rates(0,5%,10%,15%,20%),and the effect of PS-WPI mixtures on bread quality was studied.The results show that the addition of PS-WPI can improve the sense and specific volume of bread.The addition of PS-WPI can improve the water retention of bread and delay its aging.The addition of PS-WPI reduces the hardness and chewiness of bread,and increases the elasticity,cohesion and resilience of bread.PS-WPI can significantly reduce the digestive characteristics of bread in the range of 5%to 20%addition.(4)Optimization of PS-WPI bread technology and quality analysis.Taking sensory and specific volume as evaluation indexes,the formula of PS-WPI bread was optimised by single factor and orthogonal experiment,and the water retention,texture and digestibility of the bread under the optimized formula were analyzed.The results show that specific volume was positively correlated with the sensory evaluation of the bread,and specific volume can be used as an auxiliary means of sensory evaluation.Using sensory score and specific volume as evaluation indexes,the optimal process formula for PS-WPI bread was based on wheat flour quality,with the PS-WPI replacing 15%,yeast powder adding 1.2%,12%sugar and water adding 56%.The PS-WPI bread produced under this formula is soft and chewy,with good texture characteristics and higher SDS and RS content than wheat bread.