Study On The Synthesis Evaluation Method Of Milk System And Its Stability

The dairy products refered to the products which was processed by the fresh dairy cattle (sheep) milk or its products. The property of the dairy products was investigated according to the rheological characteristics of dairy products, The research took yogurt as an example to analyze the rheological behavior of yogurt, and a reasonable evaluation system was established by structural state of the yogurt. Furthermore, The stability of milk was researched by single factor test and mixed test. It was supposed to afford a reference and guidance for enterprises with different production conditions and capabilities.1 A preliminary research on the rheological properties of popular stirred yogurt on marketThe rheological properties of stirred yogurt was investigated by taking the popular stirred yogurt on market. The results showed that: six samples could produce thixotropic loop in the processes of acceleration and deceleration. The apparent viscosity decreased during rotor running up and increased in the process of speed down. When the shear rate was 16s-1, the relation of the speed of rotator and corresponding apparent viscosity adapt to power law. We could further find that the stirred yogurt was a kind of positive thixotropic liquid. The order of their thixotropic was No 5ï¹¥No 4ï¹¥No 2ï¹¥No 1ï¹¥No 3ï¹¥No 6.2Study on fuzzy synthesis evaluation method of yogurt qualityIn order to obtain colour, flavor and texture quality preference, combination determining weights method was employed by sensory evaluation experiment on the popular stirred yogurt on market. Particle size; WHC; hardness; AV were chose as objective index, measuring each index, distributing their weightiness, using the fuzzy synthesis evaluation method, and finally different yogurt were graded according to the graded criterion. Yogurt comprehensive assessment set was B=(0.7551, 0.7845, 0.8359, 0.7787, 0.6818, 0.8622). If yogurt comprehensive evaluation value bj was higher, the quality of yogurt was better; if bj was lower, the quality of yogurt was poorer. Based on the experiment results, the order of the quality of yogurt was No 6ï¹¥No 3ï¹¥No 2ï¹¥No 4ï¹¥No 1ï¹¥No 5. 3 Influence of stabilizers on the stability of milk system3.1 Influence of emulsifier on the stability of milk systemThis study mainly investigated on influence of emulsifier on the stability of milk system and its mechanism was discussed. The results showed that compound emulsifier can significantly increase emulsifying effect of milk system and the optimum HLB value was in 9.0. In this case, the adsorption amount of emulsifier molecules on milk fat globnles was largest, and the fat globule membrane was also the most stable. When the addition of compound emulsifie was 0.12%, the increasing surface area of milk fat globnles could be completely covered by the protein and emulsifie molecules. At this point the interface membrane had a high intensity and a best stability.3.2 Influence of thickeners on the stability of milk systemThe stability of milk was researched by single factor test and mixed test. Based on the centrifugation precipitating rate, viscosity and granularity, the influence of stability of milk was elaborated. The results showed that PGA was more suitable for neutral milk system. When the dose of PGA was 0.10 %, the milk system had the best stability. PGA was mixed with Xanthan Gum or pectin or Guar Gum respectively, they had a synergistic effect. When PGA to Xanthan Gum equals to 3:7, the milk system had the best stability. 3.3 Influence of stabilizers on the stability of yogurtBy the compound experiment, it could draw a conclusion that when the addition of PGA, pectin and gelatin was 0.091%, 0.068% and 0.079% respectively, the WHC of yogurt was 21.20%, which fitted well with predictive value.