Studies On The Effects Of Gellan Gum On The Microstructure Of Casein-Stabilizers And Its Application In Acid Milk Drinks

The microstructure of gellan and the effect of gellan on the microstructure of casein-stabilizers in acid milk drinks(AMDs)were studied by using confocal scanning laser microscopy(CSLM);The influence of gellan on the suspension,stability of AMDs with fruit pulp were investigated;The effect of stabilizers including CMC,SSPS and HMP on AMDs were researched by zeta potential measurement.The impact of gellan on the zeta potential,particle size of AMDs were studied.Through FITC labeling of gellan and CSLM observing,the results showed that 0.006-0.01%low acyl gellan systems with 10mM CaCl₂ could form a weak gel network,while high acyl gellan could not form the similar network;Ca²⁺and K⁺ had the similar influence on gellan's microstructure.However in order to achieve the maximal network denseness,K⁺ concentration needed to add was as much as 25 times of that of Ca²⁺;Adjust of pH by adding acids could affect gellan system's microstructure.The casein particles distributed uniformly in AMDs applying CMC,SSPS as stabilizer.The stability effect of SSPS,CMC were better than that of HMP.The stabilizers such as CMC,SSPS added as stabilizers in AMDs were adsorbed onto the surface of casein micelles by electrostatic attraction and then the negatively charged casein-stabilizers complexes were dispersed by electrostatic repulsion. Then we keep adding gellan to drinks,which resulted in casein particles aggregate and gathered casein particles in gellan network.Ultimately it causeded acid milk system unstable.Different adding gellan technologies influenced the microstructure of casein-stabilizers and the stability of acid milk system.Five technologies were designed according to the order of adding gellan,the results attested that the AMDs using technology No.4 was less stable than that of technology No.3;Storage had a negative effect to the microstructure of casein- stabilizers,causing the AMDs more unstable; The gellan concentration influenced the stability of AMDs,increasing the gellan concentration resulted in milk system less stable.The results of applying gellan in AMDs testified that technology No.3 and technology No.5's AMDs had good suspension stability;It could improve the suspension to add gellan at the base of stabilizers.The viscosity,sedimentation and suspension of the milk were enhanced along with increasing gellan concentration.The addition of 0.02-0.03%gellan in the AMDs were suitable to suspend furit pulp. High addition of gellan may affect its stability in milk system.Calcium lactate,calcium carbonate,potassium chloride influenced the stability of AMDs.Adding low concentration calcium could improve the suspension of AMDs,but the suspending effect of calcium carbonate was better than that of calcium lactate.0.02-0.04% calcium added in the AMDs were necessary to suspend furit pulp. Adding potassium chloride and calcium lactate had the similar suspending effect.To achieve the same suspending effect,the potassium chloride concentration need to add 10 times of that of calcium salt.The results of applying zeta potential measurement in AMDs showed that zeta potential's absolute value was improved along with increasing the stabilizer concentration.It proved that stabilizer could enhance the stability of AMDs,and the effect of SSPS,CMC to the AMDs' stability effect was better than that of HMP.Sterilization treatment aroused a decrease in the numeric value of the zeta potential, which indicated that the stability of AMDs was reduced.Different technologies of adding gellan,gellan concentration and different type gellan mixed rates would affect the zeta potetial and the mean particle size of AMDs.The zeta potential's absolute value and the mean particle size of the AMDs preparing with technology No.3 or technology No.4 were larger than that of technology No.1,which showed that some gellan was adsorbed on the surface of the casein particles and increased their electrostatic charge.Sterilization treatment of adding gellan's AMDs caused a increase in the numeric value of the zeta potential.The measurement of the mean particle size could be used as an indicator of the effect of gellan on the stability of AMDs,while zeta potential measurement couldn't.