| High fat intake will bring some potential health hazards to humans,more and more studies on low-fat cheese,choose the right fat substitute to improve the lack of fat due to the taste,texture and other aspects of the lack of research Hot spots.Starch in other dairy products is more common,but in the application of natural cheese and less research,and pea starch and fat globules are relatively similar to the microstructure,has its special functional properties,as a fat substitute applied to natural cheese And other dairy products have great potential.However,the curd process of natural cheese is the process of row of whey,starch will be discharged with the whey,therefore,need to prove the pea starch and casein in the coagulation before the interaction,the two composite stability and stability mechanism,For the pea starch as a fat substitute in the application of natural cheese to provide pre-based basis.At present,the research on the application of starch in fermented milk at home and abroad is more mature.The basic research on the use of pea starch in natural cheese processing is less,and the interaction and stability of pea starch and main protein casein in cheese also less.In this paper,casein and pea starch were compounded under heating,and the Zeta potential and particle size were measured at different pH,temperature and casein concentrations.The effects of pH and temperature on pea starch and cheese The results showed that the microstructures of casein and pea starch complex under different pH conditions were observed by laser confocal microscopy.Finally,the change of viscosity characteristics of the two complexes was determined by RVA.The interaction and stability of casein with pea starch were expounded,which provided the theoretical basis for its application as a substitute for fat in natural cheese.The main contents and results are as follows:(1)The effect of pH and temperature on Zeta potential and particle size of casein solution was studied.The following conclusions were obtained:The zeta potential of casein solution was positive when pH was below casein PI(pH 4.2),Zeta potential was too small,The particle size is large,it is observed that the solution is unstable and flocculation occurs,which may be due to the decrease of pH to reduce the steric hindrance and electrostatic repellency between casein particles,so that the casein particles are aggregated and the system is lost The Zeta potential of casein solution increases with the increase of pH,and the particle size decreases with the increase of pH,and the solution stability increases.(2)The effects of pH,temperature,casein concentration and starch type on zeta potential and particle size of casein and pea starch complexes were studied.The results showed that pH had a significant effect on the zeta potential of pea starch/casein complex(p<0.05).Meanwhile,the Zeta potential of pea starch and casein complex increased significantly with the increase of casein concentration(P<0.05).Meanwhile,the starch type had significant effect on the Zeta potential of the complex.The pH value,temperature,casein concentration and pea starch type could affect the stability of casein/pea starch complex at pH 4.6 or higher.When the other conditions were the same,the Zeta potential value of the pea starch and casein complex was the highest when the pH was 4.2(casein isoelectric point below)and the pH was greater than the casein isoelectric point(pH 4.6)The results showed that the mixture of amorphized pea starch and casein had the strongest stability at the casein concentration of 3%and heat treatment at 73?for 2 min.The Zeta potential was-19.97 mV and the particle size was 18.79?m.(3)Study on the microscopic distribution of pea starch and casein complexes The following conclusions are drawn:At the neutral pH,for the complexes of three pea starch and casein under laser confocal microscopy,amorphized pea starch and casein The distribution of the complex is uniform and dispersed,the casein particles are relatively small,the solution stability is strong,the original pea starch and casein complex is the second,and the pregelatinized pea starch and casein complex casein distribution is not uniform,Gathered to form a relatively large particles,the system instability.At the acidic pH,the distribution of casein in the complex of the original pea starch,the pregelatinized pea starch and the amorphous pea starch and casein was more dispersed than the neutral pH,and the solution stability was stronger.(4)To study the viscosity characteristics of pea starch and casein,the conclusion is that the paste viscosity of the original pea starch is 75.2 ?,the peak viscosity is 7576 cp,the minimum viscosity is 4432.5 cp,the final viscosity is 6205 cp.The viscosity of the pregelatinized pea starch was 66.8 ?,the peak viscosity was 8864.5 cp,the valley viscosity was 4912 cp,the final viscosity was 7769.5 cp,the decay value was 1095 cp,the regenerative value was 2857.5 cp The viscosity of amorphized pea starch was 72.4 ?,the peak viscosity was 5118.5cp,the valley viscosity was 3186.5cp,the final viscosity was 4653cp,the attenuation value was 1932cp,the return value was 1467cp.The addition of casein changed the viscosity characteristics of pea starch,reduced the peak viscosity,valley viscosity and final viscosity of raw pea starch,pregelatinized pea starch and amorphous pea starch,and with the increase of casein concentration The peak viscosity,valley viscosity and final viscosity of pea starch and amorphized pea starch were significantly decreased(P<0.05).The reason why the casein affects the viscosity characteristics of pea starch may be that the addition of casein causes the pea starch molecules to be more dispersed in the aqueous solution,the electrostatic repulsion between the pea molecules is weakened,and the starch molecules are not easily rearranged and aggregated,Change,peak viscosity,valley viscosity,the final viscosity decreased,so that the mixed solution showed different from the previous viscosity characteristics.(5)The effect of pH and temperature on Zeta potential and particle size of casein solution was studied.The following conclusions were obtained:The zeta potential of casein solution was positive when pH was below casein PI(pH4.2),Zeta potential was too small,The particle size is large,it is observed that the solution is unstable and flocculation occurs,which may be due to the decrease of pH to reduce the steric hindrance and electrostatic repellency between casein particles,so that the casein particles are aggregated and the system is lost The Zeta potential of casein solution increases with the increase of pH,and the particle size decreases with the increase of pH,and the solution stability increases.(5)Through this experiment,we can get the stability mechanism of pea starch and casein:When the pea starch and casein,the casein PI and the ionic strength is very low,the starch can form complex with casein particles,At this time two kinds of macromolecules show a certain compatibility.The reason for the stabilization of the starch and casein mixture at low pH may be due to the electrostatic repulsion of the modified starch and casein colloidal particles,so that the solution shows a uniform and stable state.When the pH value of the solution increases,the casein colloid is negatively charged,the stability of casein and pea starch complex decreases,probably when the pH is higher than casein PI,the two macromolecules are mutually exclusive,both in the aqueous solution The electrostatic repulsion between the casein particles decreases,the solution appears to flocculate,the system is unstable,but with the increase of pH,the electrostatic repulsion between the casein particles gradually increases,and the solution instability is weakened. |
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