Strain Screening And Its Fermentation Type Walnut Beverage Processing Technology Research

Walnut milk belongs to vegetable protein drink,made from walnut kernel,pure water as the main raw material and processed by modern technology,which has special aroma of walnuts.The product has what the walnut kernels have,which has good health care effect on cranial nerve,arteriosclerosis,high blood pressure,coronary heart disease and aging.Lactic acid bacteria is widely used in food industry and regarded as a functional food,which can improve the flavor of food and nutrition quality,extend the shelf life,adjust the balance of intestinal flora,antibacterial,antitumor,lower cholesterol,prevent constipation,improve lactose discomfort,anti-aging and other important physiological health care function.This study was entrusted by Hebeiyangyuan Co.,Ltd.in order to obtain functional walnut milk fermented beverages,containing walnut and lactic acid bacteria fermentation food dual advantages.The composition of Hebeiyangyuan Co.,Ltd walnut was studied,the results indicated that the protein and fat accounted for 89.28%in walnut kernel,the total sugar content was low,the fermentable sugar content was 11.96 mg/g.,Walnut milk pulping process were optimized based on the soluble protein dissolution rate as examining index by the response surface method.The results indicated that the optimum conditions for walnut milk pulping as follows:the best material-water ratio 1:7,pulping temperature50℃,pulping time 12 min.Under the optimal conditions,the soluble protein dissolution rate was 4.57%.Thermal sterilization method was used to sterilizate with 85℃for 15min.The reserach included the choice to walnut milk strains of lactic acid bacteria fermentation and domestication.First the adaptability of lactic acid bacteria was studied in walnut milk,the results showed that the growth of lactic acid and produce acid was inhibited when MRS liquid medium was completely replaced by walnut milk.Through gradual domestication method after inoculating culture,the quantity of acid and the number of bacteria would be improved in the walnut milk.The produce acid quantity of Plant lactobacillus subspecies increased 27.2%and the bacterial count increased 6.9%;The produce acid quantity of Italy enterococcus increased 27.5%;the domestication effect of Thermophilic streptococcus and Bulgaria lactobacillus was not obvious.The expansion of lactic acid bacteria culture screened out,fermentation technology,optimum formula and product indicators were studied.The results showed that the expanding culture conditions of Italian enterococcus as follows:the amount of glucose in the walnut milk 2%,Vc content 0%,the inoculation quantity 7%,cultivate temperature34℃;Plant lactobacillus subspecies expanding culture condition was:the amount of glucose in the walnut milk 5%,Vc content 0.15%,the inoculation quantity of 7%,the temperature 34℃.The suggested optimum fermentation conditions were the following:fermentation temperature of 37℃,fermentation time of 12 h,inoculum size of 1.0×10⁸mL^-1,inoculation ratio for Plant lactobacillus subspecies:Italy enterococcus=2:3 and sucrose concentration of 4 g/100mL;Mixing formula:xanthan gum 0.14%,sodium carboxymethyl cellulose 0.09%,sodium alginate 0.1%,sucrose ester 0.1%,glyceryl monostearate 0.1%,cane sugar 5.31%,0.02%milk essence and walnut essence 0.04%;20MPa under homogeneous 2 times,which could improve walnut milk quality and stability.Made of walnut milk presented milk white,luster and uniform color,no visible foreign material,which had walnut milk flavor and fragrance,the taste and smell were similar to fermented milk;fermented walnut milk was homogeneous and had no stratification or precipitation.The determination of index for walnut milk products was obtained as follows:Fat 5.96%;Protein 1.35%;pH 4.41;Titratable acidity 40.11°T;Lactic acid bacteria surviving 9.8×10⁸ CFU/mL.In this study,the change of various index for fermented walnut milk,which was in the process of storage were measured and analyzed.The results showed that the number of bacteria,pH value,opacity,sensory score decreased with the extension of storage time,and with the higher the storage temperature,these index reduced faster.Centrifugal sedimentation rate and centrifugal creaming rate increased with the extension of storage time,and with the higher the storage temperature,the two index rose faster.The fermented walnut milk was more conducive to the stability of the system under the low temperature storage,so the low temperature should be chosen to transport and storage in the process of actual production and transportation.