| Cholesterol is an important substance in the body,but long-term high cholesterol level in the blood can cause atherosclerosis and could be a critical factor in cardiovascular disease.Salad dressing is a popular food in recent years,especially popular among young people.However,as a high-calorie,high-fat and high-cholesterol food,a large intake of salad dressing may have adverse effects on human blood lipids and lipid metabolism organs.Therefore,exploring and developing a low-fat,low-cholesterol salad dressing has gradually become a trend.This study aims to screen safe lactic acid bacteria with efficiently cholesterol-degrading ablity from common fermented products.The strains with good cholesterol-degrading properties were screened by the methods of cholesterol-lowering ability determination,acid and bile salt resistance and strain identification,and were applied to the preparation of low-fat salad dressing.The microbial and cholesterol components of low-fat salad dressing were determined in the experiment.This paper provides a basis for the application of excellent lactic acid bacteria and the development of new products.1?15 strains of Gram-positive bacteria with calcium-dissolved circles were initially screened from the Chinese traditional fermented taro and sour beans sampled in Hedong Village,Meijiang Town,Ningdu County,Ganzhou City,Jiangxi Province by the method of casting plate and plate scribing.Physiological and biochemical characteristics analysis and 16S rRNA gene sequence alignment and phylogenetic tree constructing were performed to determine its taxonomic status.The experiment found that 8 of the suspected lactic acid bacteria isolated and screened were 99%similar to Lactobacillus plantarum.5 strains were similar to Lactobacillus brevis and 2 strains were similar to Lactobacillus casei,with similarity of 99%respectively.2?Cholesterol degradation experiments were carried out on 15 experimental strains,among which A02f1 and A03d1 had the highest degradation rates of cholesterol,37.8%and 35.8%,respectively.The 15 strains were tested for acid resistance,bile salt resistance and salt tolerance.The excellent strain A03d1 was screened,and the number of live bacteria grown in strong acid environment for 2 h reached 8.89±0.01 Lg CFU/mL.;the number of live bacteria cultured in the bile salt environment for 2 h reached 6.87±0.04 Lg CFU/mL.Strain A03d1 has good acid and bile salt resistance and can grow in 8%NaCl concentration.After physiological and biochemical identification and 16S rRNA identification,strain A03d1 was identified as Lactobacillus plantarum.3?Formulations of low-fat egg-free salad dressing and low-fat egg-containing salad dressing were optimized by single factor and orthogonal experiments.The best formula for low-fat egg-free salad dressing is 30%vegetable oil,7.5%white vinegar,22%sweet potato powder,11%white sugar,1%salt,0.4%seasoning,3%starch,23%water,0.3%xanthan gum,0.35%monoglyceride,and 0.35%sucrose ester.The best formula of low-fat egg-containing low-fat salad dressing is 30%vegetable oil,7.5%white vinegar,24%sweet potato powder,11%white sugar,1%salt,and 0.4%seasoning,3%starch,the amount of egg yolk added was 23%,0.3%xanthan gum,0.35%monoglyceride,and 0.35%sucrose ester.The shelf life of the salad dressing was quickly predicted by the accelerated shelf life test(ASLT)method,and the peroxidation value of the main influence index was used as the evaluation index.The shelf life of the egg-containing salad dressing at normal temperature of 25°C was 190 days.The shelf life of egg-free salad dressing is 217 days.The selected excellent strain A03d1 was added to the low-fat salad dressing,and after 35 days at room temperature(25?),the number of live bacteria of the lactic acid bacteria in the salad dressing reached 10~6CFU/g,indicating that it is feasible to add lactic acid bacteria to the salad dressing. |
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