Selection,Identification And Property Of Lactic Acid Bacteria Fermenting Walnut Milk

Walnut milk is a kind of nutritious drinks,which is the source of a variety of vitamins,proteins and trace elements.Besides,compared with other beverages,walnut milk promoting the absorption of calcium and iron has good diet.What's more,walnut milk on cranial nerve,arteriosclerosis,high blood pressure,coronary heart disease and aging have good health benefits.The suitable lactobacillus for walnut milk fermentation were obtained by strain screening.and then get a walnut and lactic acid bacteria fermentation food dual advantages of functional walnut milk fermented beverages.A new kinds of fermented milk beverages with walnut were developed.The beverages combined the advantages of walnut and lactobacillus drink.Main screen lactobacillus were isolated from kefir starter,The identifications were carried out for lactobacillus through clustering form,16 S rDNA PCR and RFLP technology.Then,the optimum conditions which were temperature,pH value,tolerance,growth curve,produce acid salt concentration rate and other physiological and biochemical experiments for lactobacillus subspecies and Enterococcus italicus were studied to understand the fundamental properties of the lactic acid bacteria species;Walnut milk fermentation performance was studied.The acid-producing content of walnut milk,the number of living bacterium,the type of organic acids,sugars,aroma substance changes,and the evaluation of the sensory characteristics were analyzed for the mixed fermentation with two strains of lactic acid bacteria.Those researches provided theoretical basis for the development of the fermented walnut milk.This topic 62 lactic acid bacteria strains were obtained directly from kefir starter.Six types of morphology divided from the lactic acid bacteria were observed by colony morphology and microscopic morphology.Then using 16 S rDNA PCR and RFLP technique combined with molecular identification and sequencing,four types of molecules were divided,such as Leuconostoc lactis,Enterococcus durans,Enterococcus italicus and Streptococcus thermophilus.This study selected Lactobacillus subspecies and Enterococcus italicus.The optimum conditions of the two lactic acid bacteria were: the optimum growth temperature 35?,the optimum growth pH value 6.5,best inoculation volume 108 mL.The plant of lactobacillus optimization was: the best culture temperature 36.52?,pH 6.70,quantity 0.98×108/mL.Enterococcus italicus optimization was: the best temperature 37.82?,pH 6.50,quantity 1.02×108/mL.When Lactobacillus subspecies and Enterococcus italicus were cultivated under the same conditions,the growth rate of plant lactobacillus subspecies was faster,pH dropped further,produce acid content was more than that of Enterococcus italicus.Low pH value below 4.5 could play a bacteriostatic action;The basic biochemical characteristics of two strains of lactic acid bacteria were obtained by biochemical experiment.The viable counts of lactic acid bacteria in the fermented walnut milk were: plant lactobacillus subspecies 6.43×108 cfu/mL,Enterococcus italicus 2.98×108 cfu/mL,The viable counts of lactic acid bacteria accorded with the requirements in dairy products.The pH value of the fermented walnut milk was 3.44.The acidity was 44.205 oT.High performance liquid chromatography(HPLC)was used to detect organic acids and sugar after the end of the fermentation.The results were: tartaric acid 0.646 5 g/L,pyruvic acid 0.022 g/L,lactic acid 5.622 3 g/L,acetic acid 0.416 5 g/L,fructose 1.905 g/L,glucose 2.435 g/L,sucrose 37.651 g/L,cottonseed sugar 0.39 g/L.Gas chromatography mass spectrometry was used to determinate the fragrance material in the fermented walnut milk.The results showed that the main compones of fragrance in the fermented walnut milk were b benzoin,hexyl alcohol and caproic acid substances.The quality of the fermented walnut milk products was evaluated by the sensory evaluation.The results showed that the colour of fermented walnut milk was unanimous with milk white,and there was not visible foreign material.With walnut milk flavor and fragrance,the taste and smell of fermented milk;Sweet and delicious,smooth thick;Organizations: fine and homogeneous,stratification,no precipitation.