Effect Of Stabilizers On Acidified Milk Drinks

Acidified milk drinks are fond of consumers for their rich nutrition and pleasant flavor. But their qualities suffer from defects, such as flocculation, whey separation and sedimentation during their production procedure. And this affects their developments gravely. The key to improving the stability of acidified milk drinks is to make caseins stable under acidity condition. Adding stabilizers can increasing the stability of the drinks.At present, the stability of acidified milk drinks is investigated using mainly quality measurements (e.g. viscosity, sedimentation, whey separation). However, such methods often destroy the acidified milk drinks'matrix prior to or during the measurements. So they have limitations.Instruments such as laser granulometer, nuclear magnetic resonance spectrometer, Zeta potential analyzer was used in this research. Changes of the drinks'physical and chemical indices after adding the stabilizers were determined. Effect of the interaction between caseins and stabilizers in the acidified milk drinks on the drinks'physical and chemical indices was researched . In addition, the mechanism of interaction between stabilizers and caseins was investigated. And the research field of the stability of acidified milk drinks was expanded in this research. The rationale for much better solving the problem of acidified milk drink unstable was laid down.Seven stabilizers which were pectin, sodium carboxymethyl cellulose (CMC),guar gum, xanthan gum, locust bean gum, soluble soybean spolysaccharide and propylene glycol alginate (PGA)were studied. Effect of them on acidified milk drinks'stability were studied by Centrifugation .Four stabilizers which were pectin, CMCsoluble soybean spolysaccharide and PGA were selected. Effect of their contents on the drinks'indices which were sedimentation rate, viscosity, particle size distribution, water molecular mobility and Zeta potential were investigated.The results showed that the stabilizers would affect the characters of the acidified milk drinks.The stabilization of the stabilizers on the drinks were showed in macroscopic that the sedimentation rate of the drinks were reduced, and the viscosity of the drinks rose with the amounts of the stabilizers increasing. The stabilization of the stabilizers on the drinks were showed in macroscopic that the particle size distribution of the drinks were diminished, water molecular mobility of the drinks were to slow down, the Zeta potential absolute value of the drinks were to heighten with the amounts of the stabilizers increasing. In these stabilizers, pectin affected the drinks'Zeta potential obviously, and CMC affected the drinks'water molecular mobility, Soybean soluble polysaccharide affected the drinks'particle size distribution strongly and PGA affected both the drinks's water molecular mobility and particle size distribution obviously.The results showed that the stabilizers which were pectin, CMC, soybean soluble polysaccharide and PGA stabilized the acidified drinks well. The drinks were unstable due to the aggregation of caseins through bridging when the stabilizers'contents were 0.05%. The sedimentation rate of the drinks were reduced with the contents of the stabizers increasing.The drinks were stable when the stabilizers additional amounts that pectin was 0.40%, CMC was 0.40%, soybean soluble polysaccharide was 0.40%, PGA was 0.30% ,respectively.The technological parameters in the handle procedure of the acidified milk drinks would affect the interaction between the stabilizers and caseins .Factors which affect the stability such as homogenization pressure, homogenization temperature, acidified temperature, pH, sterilization temperature and sterilization time were determined when the content of pectin and CMC was 0.40%, respectively. The results showed that the drinks were stable when the homogenization pressure was 20~30MPa and the homogenization temperature was 60℃.The acidified temperature and pH also affected the stability of the drinks. The effect of acidified temperature was obvious, the effect of pH was little. The drinks were more stable under higher pH condition. The stability of the drinks was affected by sterilization temperature and sterilization time too. The results showed that sterilization time had more effect on the drinks's stability than sterilization temperature, So high-temperature short-time sterilizing method was suggested.