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A method for selectively counting Bacillus bulgaricus in yogurt

A Bacillus bulgaricus, counting method technology, applied in the field of dairy microorganisms, can solve the problems of many components and high cost of MRS solid medium

Active Publication Date: 2019-05-07
INNER MONGOLIA AGRICULTURAL UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Currently recognized as the most effective method is Tharmaraj N, Shah N P. In Selective enumeration of Lactobacillus delbrueckiissp.bulgaricus, Streptococcus thermophilus, Lactobacillus acidophilus, bifidobacteria, Lactobacillus casei, Lactobacillus rhamnosus, and propionibacteria[J].Journal of Sci3, Dair2 The method disclosed in 86(7):2288-2296, that is, the pH value of the MRS solid medium is adjusted to 4.58, and anaerobic culture is carried out at a temperature of 45°C for 72 hours. The growth of bacilli is less affected, and the disadvantage of this method is that the MRS solid medium has many components, the cost is high, the anaerobic conditions required for the culture conditions are also very strict, and the culture time is 72h and it is also long, so in practical applications There are certain deficiencies

Method used

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  • A method for selectively counting Bacillus bulgaricus in yogurt
  • A method for selectively counting Bacillus bulgaricus in yogurt
  • A method for selectively counting Bacillus bulgaricus in yogurt

Examples

Experimental program
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Effect test

Embodiment 1

[0079] The implementation steps of this embodiment are as follows:

[0080] Prepare MRS liquid medium: mix 10g soybean peptone, 4g yeast powder, 1g Tween 80, 5g sodium acetate, 0.2gMgSO 4 ·7H 2 O, 5g beef extract, 20g glucose, 2g K 2 HPO 4 , 2g triammonium citrate and 0.05g MnSO 4 4H 2 O was dissolved in 1000 mL of distilled water, and the pH value was adjusted to 6.80 with inorganic acid or alkali, and then sterilized at 121° C. for 15 minutes to obtain the MRS liquid medium. According to 1.5% of the mass of the MRS liquid medium, adding agar to the MRS liquid medium can obtain the MRS solid medium.

[0081] Prepare AST liquid medium: mix 10g tryptone, 10g sucrose, 5g yeast powder and 2g K 2 HPO 4 Distilled water was dissolved in 1000 mL of distilled water, and the pH value was adjusted to 6.80 with inorganic acid or alkali, and then sterilized at a temperature of 121° C. for 15 minutes to obtain the AST liquid medium. According to 1.5% of the mass of the AST liquid m...

Embodiment 2

[0094] The implementation steps of this embodiment are as follows:

[0095] MRS liquid medium, AST liquid medium and strain activation were prepared in the manner described in Example 1.

[0096] Yogurt preparation: Combine activated Streptococcus thermophilus and Lactobacillus bulgaricus in pairs, inoculate 200 μL of each into 10 mL of skim milk, and ferment in an incubator at 42°C for 3 to 4 hours until curdling. Take 0.5mL of curd and transfer it to 4.5mL of sterile saline with a concentration of 0.85% by weight, dilute with a 10-fold gradient, and take 1mL of a dilution of 10 -6 , 10 -7 Transfer the bacteria liquid into the plate, adopt the pouring plate counting method, and count each strain with the following culture medium, count three parallel samples for each culture medium, and the number of viable bacteria is expressed in cfu / mL.

[0097] A. Conventional MRS agar medium, pH 6.80, aerobically cultured at 37°C for 48 hours, used to count the total number of viable b...

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Abstract

The invention relates to a method for selectively counting Bulgarian bacillus in yogurt. The method comprises the following steps: selecting a selective counting culture medium suitable for Lactobacillus bulgaricus growth, adding waterless sodium acetate for inhibiting Streptococcus thermophilus growth, regulating the pH value of the counting culture medium, and regulating the counting culture temperature. By using the selective counting culture medium and culture conditions thereof, the viable count of the Streptococcus thermophilus can be lowered from 10<8> cfu / mL to 10<6> cfu / mL or below, and the viable count of the Lactobacillus bulgaricus has no significant difference from the control group (P>0.05). The method has the advantages of fewer culture medium components, lower cost and simple and feasible culture conditions, and overcomes the defects in the prior art.

Description

【Technical field】 [0001] The invention belongs to the technical field of dairy microorganisms. More specifically, the present invention relates to a method for selectively enumerating Bacillus bulgaricus in yogurt. 【Background technique】 [0002] The Food and Agriculture Organization of the United Nations and the World Health Organization (FAO / WHO) define yogurt as milk and dairy products (sterilized milk or concentrated milk) that have been processed under the action of Lactobacillus bulgaricus (L.bulgaricus) and Streptococcus thermophilus (S.thermophilus). For curd-like milk products obtained by lactic acid fermentation, these microorganisms must be present in large quantities in the final fermented product. [0003] Lactobacillus bulgaricus (L.bulgaricus) and Streptococcus thermophilus (S.thermophilus) play an extremely important role in yogurt, mainly reflected in the following two aspects: [0004] 1) The number of live bacteria of Streptococcus thermophilus and Lacto...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C12Q1/06C12R1/01
CPCC12Q1/06
Inventor 王俊国岳林芳萨如拉丹彤包秋华张和平
Owner INNER MONGOLIA AGRICULTURAL UNIVERSITY