Screening Efficacy Evaluation And Product Development Of Lactic Acid Bacteria Strains

China's traditional dairy products have a long history and are rich in lactic acid bacteria strains.However,the screening of good strains,the preparation process of direct-acting starter and the development of probiotic products based on it are relatively backward.Based on this,this paper is from traditional milk.Separation and identification of lactic acid bacteria strains in products,fermented foods,and commercially available active lactic acid bacteria products,and evaluation of probiotic effects by acid resistance,resistance to bile salts,tolerance to artificial gastrointestinal fluids,and ability to degrade cholesterol in some strains.The good strains were studied for the preparation process of direct-type starter,and finally217-1 was used as the starting strain to develop compound fruit and vegetable enzymes with obvious antioxidant capacity.Through the research of this article,we have provided important theoretical basis for the study of traditional dairy products rich lactic acid bacteria resources,the establishment of a standardized evaluation system of probiotic strains,the development of direct-acting starter with independent intellectual property rights and the development of functional fermented foods.The specific conclusions are as follows:1.Screening and identification of lactic acid bacteriaWe selected traditional dairy products,fermented foods,and commercially available active lactic acid bacteria products to screen the active lactic acid bacteria.During the screening process,we summarized the morphological,physiological and biochemical experiments of the strains.The lactic acid bacteria have the characteristics of catalase-negative,acid-producing and Gram-positive.Then we used the 16S rRNA sequencing method to identify the 20 strains of lactic acid bacteria screened to the level of species,laid the foundation for the development of lactic acid bacteria resources.2.In vitro probiotic evaluation of dominant lactic acid bacteriaWe selected 8 strains of lactic acid bacteria with higher biomass from 20 strains of lactic acid bacteria screened for the determination of a number of probiotic functions such as acid tolerance in vitro,bile salt tolerance,artificial gastrointestinal fluid tolerance,and cholesterol degradability.The purpose is to understand the acid-tolerant,bile-alkali-resistant and cholesterol-degrading ability of different lactic acid bacteria,so as to screen out the excellent lactic acid bacteria 217-1,217-3 which have both extreme environmental tolerance and good prebiotic effect.Fermentation preparation and Jiaosu production.3.Optimization and activity determination of lactic acid bacteria lyoprotectantTo ensure the activity of lactic acid bacteria in direct-acting starter.We selected strains 216-1,217-3,and 217-8 with strong tolerance as experimental strains.Using common lyoprotectants such as sodium glutamate,trehalose,and skimmed milk powder as materials,better culture conditions were obtained through single-factor tests and optimization of lyoprotectant formulations was performed through orthogonal tests.The specific culture formula was:skim milk powder 14%,trehalose5%,and sodium glutamate 0.4%.After the direct-acting starter cultured with this formula was preserved in the refrigerator for 56 days,the viable cell count of the strain could still reach about 10~8.Among the many direct-stretched starters developed,protection is at a high level.In order to develop a direct investment fermentation agent with independent intellectual property rights.4.Development of Compound Fruit and Vegetable Jiaosu with Antioxidant Activity and Evaluation of Their Probiotic EffectTo develop a complex biological fruit and vegetable Jiaosu product with high biological activity for research purposes.By tracking the changes in the pH value and the number of live bacteria in the fermentation process,the fermentation time of the compound fruit and vegetable Jiaosu was determined.Then,the probiotic effect of compound fruit and vegetable fruit Jiaosu was evaluated by testing indicators of probiotic elements in the composite fruit and vegetable Jiaosu.According to the experimental results,the fermentation time of the composite fruit and vegetable Jiaosu was 14 days.After fermentation,the polyphenol content was 0.554 mg/mL,riboflavin was 0.0514 mg/mL,procyanidin was 1.975 mg/mL,and the total sugar content was13.31 mg/mL.Therefore,it was found to have strong free radical scavenging capacity.Based on the experimental data,we can conclude that this product can potentially regulate intestinal balance in the human body,improve the body's antioxidant capacity and immune level,and promote the digestion and absorption of nutrients.It also shows that our self-developed composite fruit and vegetable Jiaosu is a The type of Jiaosu with great potential.