| Proteins of soy belonging to the plant origin proteins, compared with the animal origin proteins,whether in terms of nutritional value or in terms of economic costs have a significantadvantage.Today,in order to ease the undersupply of plant protein,many countries around the worldresearch and development actively. protein of soybean as a new resource and get widespreadattention,while soybean protein isolate has a high nutritional value and many good functionalitiesand is widely used in food industry. In order to enhance the application of soy protein isolate,thathow to improve their functional properties became research frontier and hot topics. In recent years,both at home and abroad for study on improvement of functional properties of soybean proteinisolate by enzyme gradually increased, especially the modification of microbial proteases, butresearch of modification of soybean protein isolate by Bacillus natto protease modification wasrelatively fewer.In this experiment, modification of soy protein isolate by protease from Bacillus nattoscreening by previous, and determinate functional properties parts of soybean protein isolate, thenexamining and analyzing its changes. Modified soy protein isolate added to pork sausage toexplore the impact on the quality of pork sausage.There were total3study in this research:1. Obtain of Bacillus natto protease through activation and liquid fermentation of Bacillusnatto. Method used to detect enzyme activity index was diazonium tetrazole casein. Concentratedthrough different levels of the three concentrations of Bacillus natto protease enzyme solution,respectively,1.613,1.072,0.597the U/mL. Enzyme activity and activity stability was mainlyinfluenced by the environmental pH and temperature,and research single factor in these two areas.Found that protease had maximum enzyme activity at pH=8, and enzyme had a relatively betterstability performance at pH=7.0~11.0; protease had maximum catalytic activity at50℃,andbelow or equal to50℃protease thermal stability changes smoothly, concentrated above90%, andthermal stability sharply decline when temperature was higher than50℃.2. Protease produced by Bacillus natto modified soy protein isolate, and investigatedfunctionality changes of SPI, as well as impact on their stability. Thermal insulation after2.5h at30,40,50℃, the modified SPI nitrogen solubility index (NSI) respectively were86.1%,90.2%,94.5%,and soy protein isolate solubility have been enhanced by enzyme modified; The G’ was mainly affected by the reaction temperature and the enzyme concentration, Gel was preferablyobtained at40℃, and enzyme concentration was1.072U/mL; SPI hydrolysis degrees wasincreasing with temperature,when it above12%, G ’ values began to decline and the gel structurewas fragile; emulsion activity (EAI) had upward trend when reaction temperature at30, and40℃,respectively reached at69.3and67.1,and EAI increased with time before1.5h and thendecreased after1.5h；emulsion stability (ES) increased with time extended at30℃,butn it firstincreased and then decreased at40℃and50℃,respectively reached maximum value58.3, and57.8at2h and1.5h; oil absorption of modified SPI under different conditions respectively reacheda maximum at4h,2h and1h,and then had a downward trend; sulfhydryl content of modified SPIhad an increase of17%,30%and58%respectively at30,40,50℃;the impact of temperature onthe content of the SPI disulfide (-SS-) is not obvious.3. Enzymatic Modification SPI and SPI added to the sausage as an ingredient. The resultsshowed that using the modified SPI produced sausage, its indicators of the texture (hardness,elasticity, cohesive,chewiness, etc.), sensory indicators (organizational status, flavor, etc.) andyield are better, and it had better storage stability. |
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