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Stabilization of Acidified Milk Drinks Induced by Polyanionic Polysaccharides

Author: LiuJunLiang
Tutor: ZhangHongBin
School: Shanghai Jiaotong University
Course: Materials Science
Keywords: acidified milk drinks carboxymethylcellulose (CMC) carboxymethyl curdlan(CMc) corn fiber gum(CFG) stabilization
CLC: TS275
Type: Master's thesis
Year: 2012
Downloads: 82
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Abstract

Acidified milk drinks are popular worldwide for its good taste and healthy function, and they also have a good development in China. However, the sedimentation of milk protein and floating of milk fat at low pH is a key factor on production and research of acidified milk drinks. Therefore, there are many works focused on the interaction between polysaccharides and milk protein and the stability of acidified milk drinks induced by polysaccharides. Current works focused on acidified milk drinks induced by pectin, soluble soybean polysaccharide and propylene glycol alginate, few studies are about other polysaccharides. Most researchers have adopted the skim milk system as research object, few researchers studied the whole milk system. In this paper, we choose acidified whole milk system as our research object and studied the stabilization of acidified milk drinks induced by sodium carboxymethyl cellulose (CMC), carboxymethyl curdlan (CMc), corn fiber gum (CFG).CMC in aqueous solution is mainly used in application that exploits its rheological property. So the rheology of CMC aqueous solution was studied firstly. CMC aqueous solution shows pseudoplastic behavior. The shear viscosity of CMC solution decreases with increasing the shear rate and the storage modulus G’ and loss modulus G’’ are highly dependent on frequency. The electrosorption of CMC onto casein micelles will take place when the pH of CMC/casein micelle mixture is at and below 5.2. The steric repulsion and the electrostatic repulsion provided by CMC onto casein micelles? surface are the main reason of stability of casein micelles at low pH. The adding amount, molecular weight and degree of substitution of CMC have influence on the stability of acidified milk drinks. The higher adding amount, the higher molecular weight, the higher degree of substitution, the stability of acidified milk drinks will be better. Compared with the skim milk system, the particle size of whole milk is larger. But the changes of particle size and zeta potential are familiar with each other, indicating the presence of milk fat does not affect the structural changes of milk protein or CMC adsorption on casein.CMc and CMC have similar chemical structure, so their chemical properties should also be similar with each other. We got CMc with degree of substitution of 0.87 by carboxymethylation of curdlan. CMc aqueous solution also showed pseudoplastic behavior. The solution viscosity decreases with increasing shear rate and increases with increasing concentration. CMc can also adsorb on the surface of casein particles and provide steric repulsion and electrostatic repulsion to stabilize the casein particles when pH of CMc/casein micelle mixture is at and below 5.2. High adding amount, high molecular weight will be beneficial to the stability of acidified milk drinks. Compared with the CMC, CMc has a worse stabilizing effect of acidified milk drinks. That?s because CMC is harder than CMc.Different from CMC and CMc, the viscosity CFG solution isn?t dependent on shear rate and CFG has similar characteristics with Newtonian fluid. In addition, CFG can not adsorb on the casein particles and provide steric repulsion and electrostatic repulsion as CMC and CMc. CFG can not be used as a stabilizer of acidified milk drinks.

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