The Influence Of Modification On The Foaming Properity Of Soy Protein And It’s Application In The Cake

First,the foaming property of soy protein isolatedwere measured.Thougn soy protein itself has certain foamability, it does not satisfy the current production demand of foaming agents. In this paper, the effect of the foaming property of soybean protein isolated was improved by using the alkali protease to hydrolysis protein. And several influencing factors were discussed in this paper, such as reaction time, temperature, substrate concentration, enzyme dosage, and pH value. The results showed that the successive order of factors affecting the foaming capacity was temperature, substrate concentration or enzyme concentration,time;the successive order of factors affecting the foaming stability was temperature,time,pH,enzyme,the influence of temperature is the largest.Then by the orthogonal design method the optimal conditions of alkali protease hydrolysis soybean protein isolated to improve foaming property was: time 40 min, temperature 50 ℃,substrate concentration 8%, enzyme dosage 0.04%(w/v),p H 8; while the optimal hydrolysis conditions to improve the foaming stability was: time 30 min,temperature 40 ℃,substrate concentration 12%, enzyme dosage 0.04%(w/v),pH 9. The foaming capacity and foaming stability of modified soybean protein isolated was improved in this study. The foaming capacity and the stability was increased by 61.11%and 20.38% respectively than the raw material of soybean protein.Second,Based on foamability optimization, the physical and chemical properties of modified protein were detected,the aim is to provide reliable theory basis for the application and impact of enzyme-modified protein in cake processing.Choose raw soy protein isolated,modified protein under 30 and 50℃ as sample,the foaming capacity is 111.65%,167.50% and 217.50% respectively,their molecular weight distribution, secondary structure and of amino acid composition were tested.Use maldi- tof analysis sample molecular weight distribution, the results showed that with the increase of foaming ability, response value of small molecular weight proteins is increase.Through the infrared detection, we are find that there was no significant alteration in the secondary structure of raw material and 30 ℃ modified protein, the main chain of 50 ℃ modified protein compared with raw material protein and 30 ℃ modified protein, a slight increase in the proportion of the β-folding structure, β-corner appears to reduce the proportion of the structure, α-spiral, random coil structure change is not significant.The result of automatic amino acid analysis shows that except threonine and histidine, the change of other amino acids are not significant.Raw material protein, 30 ℃ modified protein and 50 ℃ modified protein preparation into 10% of protein solution, with 10%, 20%, 30%, 40% of the rate of substitution were added to the cake, discuss the influences of added protein on cake quality.In the test, each of the protein sample content reaches 20% in the cake, moisture have a litter degree of increase compared with blank, the product with 50 ℃ modified protein moisture content is the highest.The results showed that specific volume of raw protein increases as dosage increase;the specific volume of 30℃ modified protein decreased as dosage increase;the specific volume of 50℃ modified protein firstly increased and then decreased as dosage increase.It is generally believed that specific volume of cake reached 4.8 is the best, thus the raw material protein content in 20 ~ 40% is most appropriate, 30 ℃ and 50 ℃ modified products dosage in 10 ~ 20% is most appropriate.The results of cake quality and structure properties by Texture Profile Analysis(TPA) show that the raw protein have no obvious regularity, 30 ℃ modified product has better Texture properties when dosage is 20 ~ 30%, 50 ℃ modified products dosage is 10 ~ 30% has better quality and structure evaluation.Finally, the cake quality from the perspective of specific volume, core structure, taste, appearance were analyzed by the sensory evaluation, results show that the dosage and variety of protein has a significant influence on quality of cake.Raw material of protein and 50 ℃ modified sample addition amount of 10%, the quality of cake is the best;30 ℃ modified sample addition amount of 10% or 20%, the quality of cake is the best;the cake with 30 ℃ modified protein is the best quality in all the samples.