Migration And Change Of Soybean Milk Composition During Film Formation And Its Influence On Film-Forming Characteristics

Yuba is a typical representative of traditional soy products in my country.It is loved by consumers because of its delicious taste and rich nutrition.However,the production technology of yuba,a traditional soybean product in my country,is relatively weak,and the quality of yuba has problems such as uneven quality and low yield.Yuba is a soy protein-lipid network membrane formed on the surface of heated soy milk,which can be continuously uncovered from the heated soy milk,and then dried and stored.The quality of yuba is directly determined by the composition and characteristics of soy milk in the process of exposing bamboo,and the composition of the slurry is dynamically changing during the process of exposing bamboo.Therefore,in view of the quality problems of traditional yuba in my country,this article studies the migration and changes of soy milk components and the changes in the film-forming characteristics of yuba during the process of exposing bamboo,and analyzes the factors and mechanisms affecting the quality changes of yuba during the film-forming process,hoping to be an industrial production process The dynamic control of the medium slurry and the improvement of the quality of yuba provide references.The main research results of this experiment are as follows:1.During the film formation,the percentages of protein,solids,soluble protein and carbohydrates in soy milk gradually increase and change significantly(p<0.05).This is mainly due to the continuous evaporation of water during the process of Jiezhu.;The free fat content in soybean milk decreased in the early stage of Jiezhu,and slightly increased in the later stage of Jiezhu,which was caused by the formation of complexes between more fat and protein in the early stage of Jiezhu.The protein/solids,soluble protein/solids,free fat/solids in soy milk gradually decrease,while carbohydrates/solids gradually increase.With the film formation,the content of free amino acids and reducing sugars in soy milk increased,and the content of free amino acids/total solids gradually increased.The content of reducing sugars/total solids increased slightly in the early stage of Jiezhu,and significantly increased in the middle and late stages of the film formation.decline.During the film formation,the migration rate of the main components in the slurry is: water﹥protein﹥fat﹥carbohydrate.The water migration rate was relatively stable in the early stage of Jiezhu,and decreased in the later stage of the film formation;the migration rate of protein first increased and then did not change significantly,the migration rate of free fat first increased and then decreased,and the migration rate of carbohydrates showed an increasing trend.The protein,fat,and carbohydrate exhibited heterogeneous migration.With the film formation,soy milk L* gradually decreases,b* gradually increases,a* does not change significantly,p H value gradually decreases,apparent viscosity gradually increases,soy milk particle size first increases and then decreases.In the process of uncovering bamboo,the content of soymilk protein 7S decreased;the content of free sulfhydryl groups,total sulfhydryl groups and disulfide bonds in the protein gradually decreased,and the content of α-helix and β-turn in the protein secondary structure did not change significantly.,The content of random curls increased significantly,and the content ofβ-sheets gradually decreased.The surface hydrophobicity of the protein gradually increases,and the protein aggregates to a certain extent.2.During the film formation,the film forming rate of yuba increases,but the film forming time decreases first and then increases.The main nutrient protein and fat content of yuba gradually decrease with the increase of the number of uncovering the film,and the carbohydrate content gradually increases.The moisture content of undried yuba is different,and the moisture content of yuba after a certain period of drying is also different.The mechanical properties and tensile strength of yuba did not change significantly in the early stage,but significantly decreased in the later stage,the elongation at break gradually decreased,and the mechanical properties became worse;the dry matter loss rate of yuba increased,and the boiling resistance and rehydration became worse.The degree of non-covalent binding of protein in yuba membrane first gradually increased,and then stabilized.There was no significant change in the disulfide bond content in the yuba film.During the film formation,the color and taste of the yuba first increase and then decrease.The weighted average of the sensory quality of yuba is the highest in the fourth film,and the sensory quality is the best.The microstructure of the yuba changes greatly with the progress of the yuba,the yuba film has fewer holes in the early stage,and the pore size is also smaller,the distribution is uneven,and the film holes increase in the later stage of the yuba.A systematic cluster analysis of the yuba shows that the first,second,third,and fourth yuba are classified into one category,which is the first grade;the fifth and sixth are the second grade;the seventh yuba is the first category and the third grade.The quality of the three grades of yuba gradually declined.3.The moisture content in the undried yuba has a significant positive correlation with the yuba protein and water migration rate,a significant negative correlation with the film formation time,a very significant negative correlation with the solid content of the slurry,and no yuba fat and carbohydrates.There is a significant correlation.That is,the main factors affecting the moisture content of fresh yuba are the solid content in the slurry,the protein content of the yuba,the water migration rate during the film formation process and the film formation time.After timed drying,the moisture content of the yuba has a very significant negative correlation with the protein and fat content of the yuba,and a very significant positive correlation with carbohydrates.That is to say,the higher the carbohydrate content,the more difficult it is to dry and remove the moisture in the yuba.In actual production,the drying time can be adjusted according to the formation stage of the yuba film.The protein content of yuba has a very significant positive correlation with the protein/total solids in the slurry,soluble protein/total solids,and fat/total solids,and a significant negative correlation with carbohydrates/total solids;the fat content of yuba and protein/ Total solids,soluble protein/total solids,fat/total solids are extremely significantly positively correlated,and carbohydrates/total solids are significantly negatively correlated;the carbohydrate content of yuba is related to protein/total solids,soluble protein/total Solids,fat/total solids have a very significant negative correlation,and carbohydrates/total solids have a very significant positive correlation.The yuba L* and the slurry L* have a very significant negative correlation with the free amino acid and reducing sugar content in the slurry,and a very significant positive correlation with the p H of the slurry.That is to say,the main factors affecting the color of yuba during the film formation are the p H value of the slurry,the content of free amino acids and reducing sugar in the slurry.The dry matter loss rate of yuba is extremely negatively correlated with protein and fat content.The tensile strength of yuba is significantly positively correlated with protein and fat content.The elongation at break and protein and fat content of yuba are both extremely positively correlated.Related.The dry matter loss rate of yuba has a very significant positive correlation with protein a-helix,protein hydrophobicity,and protein size,a significant negative correlation with β-sheet,a significant positive correlation with β-turn,and no correlation with free sulfhydryl content.The tensile strength has a very significant negative correlation with the a-helix and protein hydrophobicity of the yuba,a significant negative correlation with the β-turn angle,and no correlation with the content of free sulfhydryl groups and particle size.The elongation at break is significantly negatively correlated with the a-helix of the yuba,the hydrophobicity of the protein and the particle size,but has no correlation with the content of free sulfhydryl groups.The film formation rate has a very significant positive correlation with slurry protein,soluble protein,carbohydrate,solid content and apparent viscosity,and has the largest correlation coefficient with slurry solid content.The protein,fat content and brightness value L* of yuba have a significant positive correlation with the sensory index color,luster,taste and shape of yuba.