Study On The Set Yoghurt Processing Technology Of Goat Milk

The Goat milk is rich in protein, fat, lactose, minerals and vitamins, the nutritional composition are similar to the human milk, It is perceived as the competitive milk. The goat yoghurt has unique flavour, smooth state and was popular with consumers, the goat milk has the characteristics of low acidity, smaller casein micelle and fat globule which effect the quality of goat yoghurt during the process,such as leading poor texture, increasing the whey separates and prolonging the curd time.Effect of processing technology, storage characteristics and the the composition of milk on the quality of goat yogurt were study using goat milk powder as material.This paper mainly contains three parts:the processing technology of goat yogurt, the storage characteristics of goat yogurt and the effects of milk composition on the quality of goat yogurt.In the first part, The factors affecting quality of goat yoghurt including sterilize conditions, fermentation temperature, sugar additions, solid concentration in milk, starter culture (strains ratio, addition), and postfermention conditions were evaluated. On the single-factor test basis, the milk solid concentration,bacteria ratio,additions of starter culture were selected which has a great effect on the goat yoghurt. The Box-Behnken model was employed in optimize processing parameters. The results showed that the optmium parameters were milk solids concentration 12.3%, starter culture addtion 3.52%, starter culture strains ratio 0.89:1. The acidity was 104°T, the viscosity was 400 mPa-s, the water holding capacity was 28.20% and the number of alive lactic acid bacteria was 1×109cfu/mL in the final yogurt products.In the second part, the aim of the study was to analyse the effect of different storage conditions including storage temperature, milk solid concentration and starter culture on physical and chemical indicators (pH, titratable acidity, viscosity, water holding capacity), the number of alive lactic acid bacteria and quality during goat yoghurt storage.The results showed that it has the best quality of goat yogurt When the goat yoghurt was manufactured of the milk solids concentration 12%, mixed ration of Lactobacillus bulgaricus (Lb800) and Streptococcus thermophilus (St499) 1:1, starter culture addtion 3%,and storage temperature 4℃.In the third part, the effect of the composition of milk (casein, whey protein and lactose) on the quality of goat yogurt was studied. The results showed that the sensory quality of goat yogurt was improved by the addition of casein and whey protein, but it is insignificance on the quality of goat yogurt by the addition of lactose.