Study On The Preparation And Quality Of The Spreadable Soy-Cheese

Although Cheese has a very important position in the western diet,Chinese people have low acceptance to this kind of food due to its unique flavor.While soybean food is very popular among Chinese people from urban to rural,the development of the spreadable soy-cheese has great practical significance in China.The current soy-cheese product has several problems such as poor flavor and rough texture,which seriously affects the market development of the product.This study developed a kind of high quality spreadable soy-cheese,and investigated the impact of different processing methods on its quality,including grinding method,protein coagulating method,ingredient composition,emulsifying method and enzyme modification.This study provides a theoretical basis for production of the spreadable soy-cheese.Firstly,the effects of grinding method on the quality of the spreadable soy-cheese were studied.Compared with ordinary grinding method?SM1?,the use of oxygen-free grinding method?SM2?of soymilk has a lower content of volatile flavor,especially bean flavor.Under the same process condition,the soymilk of SM1 and SM2 was processed into the spreadable soy-cheese.The type and content of bean flavor components in the spreadable soy-cheese by SM2 were less than SM1,and had a pleasant soy fragrance.Secondly,the effects of protein coagulating method on the quality of the spreadable soy-cheese were studied.Six protein coagulating methods including MgCl₂,CaSO₄,GDL,lactobacillus,lactobacillus fermentation+MgCl₂,and lactobacillus fermentation+GDL were compared.The spreadable soy-cheese prepared by lactobacillus fermentation showed the softest texture and the best spreadability.Growth of lactobacillus significantly reduced the content of hexanal in soymilk,however,after pressing and removing whey in the cheese,the content of volatile components such as hexanal in protein curd increased,that is because the volatile components are easier to combine with proteins.Then,the effects of ingredients on the quality of the spreadable soy-cheese were studied.When product pH are same,using compounding emulsifying salt?sodium citrate:sodium tripolyphosphate:sodium hexametaphosphate=1:2:2?could significantly improve the fineness and stability of the product than using NaOH.The addition of oil improved the hardness and spreadability of the product,but the oxidation of unsaturated fatty acids in oil resulted in the increase of hexanal content in soy-cheese and unpleasant bean flavor.The effects of emulsifying conditions on the quality of the spreadable soy-cheese were studied.Under 80°C,the hardness and spread work of the product continuously reduced with the increased of stirring temperature,but no obvious difference observed more than 80°C.Continued to raise the temperature led to the increase of particle size,decrease of protein emulsifying ability and increase of lipid precipitation rate.The hardness,spread work and particle size of the product were reduced with the increase of stirring speed and time.However,the lipid precipitation rate increased and the product stability decreased when the speed exceeded 1800 r/min and the time exceeded 30 min.Thus,the emulsifying process condition was determined as 80°C,1800 r/min stirring 30 min.On the other hand,although emulsification at 80°C was advantageous to the formation of a fine and uniform organization state,the oxidation of fatty acid was promoted at the same time and increase the hexanal content.Sedimentation experiment and laser scanning confocal microscope analysis showed that the spreadable soy-cheese had three types of particles:large protein particles containing a small number of small fat particles,large protein particles containing large fat particles,and small protein particles containing smaller fat particles.SDS-PAGE showed that both 11S and7S globulin were involved in the protein network structure of the spreadable soy-cheese.11S-B peptide chain and 7S-?subunit are more likely to form a protein network containing small fat particles.The interaction of 11S-B peptide chain,7S-?'and?subunit is strong,so the protein network is not easy to be destroyed and the particles are larger.The effect of enzymatic hydrolysis on the quality of the spreadable soy-cheese was studied because the structure of soy-cheese was relatively rough compared with milk cheese.It was found that the use of 0.3%papain in the enzymatic hydrolysis of soymilk for 15 min significantly reduced particle size,hardness and spread work of the product.The fineness of the product was close to the commercial milk spreadable cheese,and the emulsification stability of the product is good.This study also investigated pH value,microbial colony number and sensory analysis of the spreadable soy-cheese during storage.The results showed that those indicators of the spreadable soy-cheese did not change significantly within 60 days.