Study On The Technology Of Mulberry Lactic Acid Bacteria Fermented Beverage

Fructus Mori is the fruit spike of the mulberry tree in the mulberry family,also known as mulberry fruit,mulberry jujube,etc.It is widely planted in temperate to subtropical regions.Mature mulberry juice is full,with suitable acidity and sweetness,high nutritional value and rich bioactive substances,earning it the reputation of"the best health fruit of the 21st century"in the Chinese medical community.In addition,mulberry also has pharmacological effects such as anti microbial,anti hyperglycemic,anti hyperlipidemic,and anti-inflammatory effects.China has the highest planting area of mulberry trees,so its mulberry varieties are diverse and resources are abundant.However,due to the extremely difficult transportation and storage of mulberry,as well as the relatively single processing method and limited precision processing products,a large amount of mulberry resources are wasted.Fermentation of mulberry juice with lactic acid bacteria is one of the important ways to solve the problem of mulberry resource utilization.Fermentation not only improves the drinking taste of mulberry beverages,but also produces a large amount of beneficial lactic acid bacteria metabolites for the human body.This project mainly focuses on the process research of mulberry lactic acid bacteria fermented beverage.Through five basic studies,including strain selection,mulberry fermentation variety selection,basic process parameter optimization,live bacterial count process parameter optimization,fermentation beverage seasoning and stability process optimization,the optimal production process conditions have been determined.The experimental results of each part are summarized as follows:(1)Selection of fermentation strains.Four lactic acid bacteria,Lactobacillus plantarum,Lactobacillus paracasei,Enterococcus faecalis and Streptococcus thermophilus,were selected for freeze-drying treatment to test their fermentation characteristics.The evaluation criteria were the number of viable bacteria,p H,total acid and reducing sugar content.The results showed that Lactobacillus plantarum was identified as a fermentation strain,and the freeze-dried survival rate of this strain was 84.15%.At 24 hours of fermentation,the number of viable bacteria was 68*10~7 CFU/m L,the p H value was 3.1,the total acid content was 14.53g/L,and the reducing sugar content was 4.27%.(2)Selection of fermented mulberry varieties.Five different mulberry varieties and their fermentation broth in Shandong Province,namely Baiyu,Dashi,Black Pearl,Moyu,and Black Pearl ZQ,were selected for nutritional composition and antioxidant capacity determination.Soluble solids,p H,titratable acid,juice yield,total sugar,total phenol,flavone,anthocyanin,vitamin C,DPPH removal capacity,ABTS removal capacity,and iron reduction capacity were taken as the judgment indicators.The results showed that Black Pearl was identified as the mulberry fermentation variety.Its fresh fruit soluble solids were 16.5 Brix%,p H value was 5.32,titratable acid was 4.85 g/kg,juice yield was 66.31%,total sugar was13.24%,total phenol was 2.55 mg/g,total flavonoids was 3.91 mg/g,anthocyanin was 1.89mg/g,vitamin C was 5.88 mg/g,and DPPH removal capacity was 68.44μmol/L,with a ABTS clearing ability of 82.53μmol/L,iron reduction capacity of 91.68μmol/L.The soluble solids of fermentation broth are 8.9 Brix%,p H value is 3.45,titratable acid is 21.12 g/kg,total sugar is 4.74%,total phenol is 2.65 mg/g,total flavone is 3.94 mg/g,anthocyanin is 1.74 mg/g,vitamin C is 3.94 mg/g,and the ability to remove DPPH is 70.04μmol/L,with a ABTS clearing ability of 83.33μmol/L,iron reduction capacity of 90.61μmol/L.(3)Optimization of the basic process for mulberry lactic acid bacteria fermented beverage.The experiment selected five factors:material to liquid ratio,initial p H,fermentation time,fermentation temperature,and bacterial powder input.The Box Behnken response surface optimization experiment was conducted using the number of live bacteria and total acid content as judgment indicators.The optimal basic fermentation process parameters were determined as follows:material liquid ratio of 1:2,initial p H of mulberry natural p H,2.6%of bacterial powder input,fermentation time of 27 hours,fermentation temperature of 37℃.Under these conditions,the total acid content measured was 24.19 g/L,and the number of viable bacteria was 84.56*10~7 CFU/m L.(4)Optimization of the number of live bacteria in mulberry lactic acid bacteria fermented beverages.On the basis of basic fermentation technology,glucose,pectinase,cow’s milk powder,sheep’s milk powder,yak’s milk powder,and camel’s milk powder were selected as factors and conditions for the experiment.The Box Behnken response surface optimization experiment was conducted using the number of live bacteria as the judgment indicator.The optimal process parameters for optimizing viable bacteria were determined as follows:glucose addition of 6.60%,pectinase addition of 0.40%,and milk powder addition of 15.50%.Under these conditions,the number of viable bacteria measured was 72.98*10~8 CFU/m L,which increased by 8.63 times compared to the basic fermentation process.(5)Optimization of Flavoring and Stability Process for Mulberry Lactic Acid Bacteria Fermented Beverage.The experiment selected mulberry juice,blueberry dehydrated osmotic sugar solution,composite sweetener,and composite acidity as seasoning experimental factors,and conducted orthogonal experiments using sensory evaluation as the judgment index.Indeed,the optimal seasoning formula for mulberry lactic acid bacteria fermented beverages is 11%mulberry juice addition,6%high permeability blueberry dehydrated osmotic syrup addition,12%composite sweetener addition,and 6%composite acidity addition.Under this formula,the sensory score of mulberry lactic acid bacteria fermented beverages is 88.63.Pectin,sodium carboxymethyl cellulose and sodium alginate were selected as the stability test factors,and the stability rate was used as the judgment index for the orthogonal experiment.The optimal stability formula of mulberry lactic acid bacteria fermented beverage is 0.20%pectin,0.08%sodium carboxymethyl cellulose and 0.05%sodium alginate.Under this formula,the stability rate of mulberry lactic acid bacteria fermented beverage is 96.43%.