| Fermented dairy products is the favorite traditional fermented food for people. As the important part of fermented dairy products, probiotics have a lot of functionality, such as enhancing the immunity of the body, lowering serum cholesterol etc. To research the functional milk which has a preventive effect on hyperlipidemia in this paper, ten strains of probiotics were studied. The tolerability, cholesterol and triglyceride degradation ability were researched and the lipid lowering mechanism was explored. Besides, the fermented milk and fermented milk beverages were also researched in this paper. The main results are as follows:The probiotic characteristics of probiotic strains were determined:To study the optimum growth conditions, the growth temperature and pH value were measured. And the ability of acid production, artificial gastric juice and bile salt tolerance were determined. The results showed that the strain growth conditions were not the same with others; With the passage of time, the rate of acid production were different, LC and LP grew faster and produced acid ability is stronger; the pH value tended to be stable after 22 h; the survival rate of LAR, BA, LA and EF incubated in the artificial gastric juice were 78.41%,76.50, 66.02% and 60.24%, respectively, the survival rate of the rest of the strains were lower than 50%; when the bile salt concentration was 0.3%, the survival rates of LC, LP and LG were 54.18%,46.13% and 31.36%, respectively, the survival rates of the rest strains were less than 30%.The ability of reducing blood lipid was studied:Cholesterol micelles or triglyceride micelles were added into culture medium to screen the probiotics with degradation ability in vitro. The results showed that the strains had significant specificity in the degradation ability of cholesterol and triglyceride. The cholesterol degradation rate of LC was superior to other strains, the cholesterol degradation rate of LC was 48.13%, besides, the degradation rate of LB was 45.62%, and the others were less than 35%. The triglyceride degradation rate of LR was better than other strains, the degradation rate was 46.6%, and the others were less than 35%. After simulating the environment of human body, The cholesterol degradation rates of LC, LAR and LP were 20%,22% and 11.35%, respectively, and the others were less than 10%. The degradation rate of LC was better than other strains, the degradation rate of was 23%, the second was LR, and the the others were less than 10%.The lipid-lowering mechanism was preliminary studied:The strains which had strong ability of reducing blood lipid were selected as the research object, the degradation mechanism was studied from two aspects:the absorption of the strains and the non-cell supernatant. The results showed that cholesterol degradation rate of LC was 48.13%, the bacteria had no degradation effect. Compared with the cholesterol degrading ability of LC, who play an important role in the degradation is all the cell-free supernatant. The lipid-lowering substance is protein and polysaccharide with the degradation rate of 15.88% and 30.64% in the cell-free supernatant; the triglyceride degradation rate of LR was 46.6%, the bacteria’s degradation rate was 20.1%, no-cell supernatant was 26.5%, the lipid-lowering substance is lipid, polysaccharide substances, and the degradation rate was 24.35%,2.15% in the cell-free supernatant, respectively. During the growth of probiotics glycerol was decomposed rather than as a carbon source. The glycerol degradation rate of LC supernatant was 12.73%, the active substance were lipid and protein substances and the degradation rate was 9.37%,3.36% in the cell-free supernatant.The fermented milk and the lipid-lowering properties were studied:The best fermented condition for LP fermented milk were that the inoculation amount was 6%, the fermentation temperature was 33℃, the fermentation time was 28 h. Under these conditions, the cholesterol degradation rate reached 19.22% and the product acidity was 85℃. The best fermented condition for LC fermented milk were that inoculation amount was 4%, the fermentation temperature was 39 ℃, the fermentation time was 26 h. Under these conditions the cholesterol degradation rate reached to 25.40% and the acidity was 86℃. At this time, the degradation rate of glycerin was 12.46%.The fermented milk beverage and the lipid-lowering properties were studied: The fermentation time, fermentation temperature, inoculation amount, milk amount, sugar amount and fruit amount were used as a single factor to sensory evaluation respectively, the number of viable bacteria, acidity, lipid-lowering ability as an indicator of the fermented milk was research. The results showed the best fermented condition for LC fermented milk beverage production were that the added amount of fruit was 20%, the added amount of milk was 65%, sucrose content was 8%, inoculum amount was 6%, fermentation temperature was 33 ℃, the fermentation time was 22 h, the bacteria number reached to 6.3×109 cfu/mL, cholesterol degradation rate reached to 22.47%; when the LP fermented milk beverage, the added amount of fruit was 15%, the added amount of milk was 60%, sucrose content was 10%, inoculum amount was 5%, fermentation temperature was 37 ℃, the fermentation time was 14 h, the bacteria number reached to 7.2x109 cfu/mL, triglyceride degradation rate reached to 29.06%; at this time, the measured glycerin degradation rate was 14.73%.The lipid-lowering properties of fermented milk and fermented milk beverages in the ripening process after cold storage were studied:The number of viable bacteria, acidity and lipid lowering ability of fermented milk and fermented milk beverage were determined under the condition for 0 d and 15 d at 4℃. The results showed that the viable count of LC fermented milk and LP fermented milk reached to 8.5×108 cfu/mL,6.7×108 cfu/mL, the acidity of 116 °T, 108 °T, lipid-lowering capacity were 24.47%,17.48% when refrigerated for 15 d; When refrigerated for 15 d, the viable count of LC fermented milk beverage and LP fermented milk beverage reached to 6.3×108 cfu/mL,2.7×108 cfu/mL, the acidity of 110 °T,103 °T, lipid-lowering capacity were 26.12% and 19.98%, respectively. |
PDF Full Text Request