Study On Processing Of Probiotics Rice Milk

Probiotics milk beverage is rich in protein and probiotics and usually fermented by started culture that is applied to milk.The yield of rice is high in our country.Rice or broken rice are rich in protein and starch,which are good raw materials for producing fermented rice milk beverage.The product is hard to have a good flavor when fermented by the sarted culture applied to yougurt,as the growth charactertic of microoganism is concerned with the property of matrix.In the study,rice flour was the main raw material,and the growth charactertic of commercial yoghurt starter and Lactobacillus ZSM002were studied.The thick rice milk beverage and thin rice milk beverage were developed,which could provide new applications for rice.The main findings are as follows:1.The characteristic of strains and the starter cultureThe commercial yoghurt starter and Lactobacillus ZSM002 showed different adaptabilities for medium that was rice milk-based.According to the curve of acid production,the production rate of Lactobacillus ZSM002 was higher than that of commercial yoghurt starter.When the mixing ratio of commercial yoghurt starter and ZSM002 was 3:2,the highest production rate and titratable acidity were obtained.The ratio of 3:2 for commercial yoghurt starter and ZSM002 was thus selected as the mixing ration of mixed culture in the following experiments.2.The rice milk beverage and stabilizerThe thick rice milk beverage and the thin milk beverage were developed.The optimum fermentation conditions of the thick rice milk were as follows:the addition of sugar was 9%,the optimum ratio of rice to water was 1:10,the addition level of skim milk and bacteria content was 10%and 3%,the addition level of stabilizer was 0.2%(Propylene glycol alginate 60%,sucrose fatty acid ester 0.2%,pectin 38%and xanthan gum 1.8%),respectively.The fermentation was under 37℃for 10 h.The thin rice milk was hydrolyzed by mesophilicα-amylase and glucoamylase.The optimum conditions obtained from orthogonal experiments were as follows:mesophilicα-amylase was 3 U/g(flour),glucoamylase was 22 U/g(flour),the ratio of rice to water was at 1:5,and the saccharification was under 60℃for 30 min.The optimum fermentation conditions of the thin rice milk were as follows:the addition of sugar was 7%,the bacteria content was5%,the addition level of stabilizer was 0.2%(Propylene glycol alginate 0.5%,sucrose fatty acid ester 13.8%,pectin 50%and xanthan gum 35.7%),and the fermentation process was under 37℃for 10 h.The thick rice milk beverage was sticky,and had a soft lactic acid flavor.Meanwhile,the thin rick milk beverage had a good flowability.3.The quality characteristics of rice milkRheological property of rice milk beverage was studied.The results showed that two kinds of rice milk beverage were both pseudoplastic fluid.Under the external force of low frequency(0.01Hz-10Hz),the liquidity of rice milk was enhanced.The rice milk beverage contained rich volatile substances.The thin rice milk totally had 48 kinds of compounds,including 16 kinds of amine,4 kinds of acids and acid derivatives,7 kinds of alkanes and alkyl derivatives,3 kinds of alcohols,4 kinds of ketones,7 kinds of aldehydes and 7 kinds of hetercycles compounds.The thick rice milk totally had 25 kinds of compounds,including 6 kinds of amine,4 kinds of acids and acid derivatives,3 kinds of alkanes and alkyl derivatives,2 kinds of alcohols,3 kinds of ketones,3 kinds of aldehydes and 4 kinds of hetercycles compounds.when stored in 4℃for 7 days,the acidity and the viable count of the thick rice milk was 34.2~0T and 2.8×10~7cfu/m L,the thin rice milk was 43.5~0T and 1.1×10~8cfu/m L.The rice milk beverage maintained a good taste after storage.