Food Hygiene Microbiology Test Coliform Count Determination 5

Microbe. 1. Detection of coliform bacteria.

The first method is coliform MPN counting and the second method is coliform plate counting.

Lauryl sulfate tryptone (LST) broth: weigh and dissolve in 1000ml of distilled water, heat and boil until completely dissolved, and divide it into test tubes with inverted fermentation tubes, 10ml per tube, 121 autoclaved for 15min and set aside. Double the ingredients except distilled water.

Brilliant green lactose bile salt (BGLB) broth: weigh 30g and dissolve it in 1000ml distilled water, and autoclave it for 115 15min for later use.

Sterile saline: Weigh and dissolve in 1 L of distilled water. Aliquot in 250ml Erlenmeyer flasks, 121 autoclaved for 15min and set aside.

Crystal violet neutral red bile salt agar (VRBA): weigh and dissolve in 1L distilled water, shake well, heat and boil for 2min to cool to 50, and pour the plate.

Sterile 1 mol L NaOH: Weigh 40 g of sodium hydroxide and dissolve it in 1 000 ml of distilled water, and autoclave at 121 for 15 minutes.

Sterile 1 mol l HCl: pipette 90 ml of concentrated hydrochloric acid, dilute to 1 000 ml with distilled water, and autoclave at 121 for 15 min.

2. Detection of coliform bacteria The first method is the coliform bacteria MPN counting method.

Weigh the lactose bile salt fermentation medium and dissolve it in 1000ml of distilled water, heat and boil until it is completely dissolved, and then pack it in a test tube with an inverted fermentation tube, 10ml per tube, and 115 autoclaved for 15min for later use. Double the ingredients except distilled water.

Eosin blue agar plates: weigh the eosin agar and dissolve it in 1000ml of distilled water, heat and boil until completely dissolved, divide and autoclave at 115 for 15min and then set aside.

Lactose fermentation tube: weigh the lactose fermentation medium and dissolve it in 1000ml of distilled water, heat and boil until completely dissolved, and divide it into a test tube with an inverted fermentation tube, 10ml per tube, 115 autoclaved for 15min and then set aside.

Sterile saline: Weigh and dissolve in 1 L of distilled water. Aliquot in 250ml Erlenmeyer flasks, 121 autoclaved for 15min and set aside.

Gram staining is specified in GB T4789-2003 Part 2.

National Food Safety Standard Food Microbiology Test Coliform Bacteria Count

Detection process of fecal coliform bacteria in cosmetics testing projects:

10g ml sample + 90ml sterilized normal saline 10ml + 10ml double lactose bile (containing neutralizer) medium fecal coliform bacteria, 48h culture.

Note: In the cosmetics testing project, if the sample contains oily components, such as essential oils, liquid paraffin, Tween 80, and normal saline should be added to homogenize the sample before treatment, so that the sample can be evenly dispersed.

What kind of microorganism is fecal coliform? Let's take a closer look:

Coliform bacteria: Coliform is not a bacteriological taxonomic designation, but a term used in the field of hygienic bacteria, which does not refer to a specific group of bacteria or genus of bacteria, but refers to a group of bacteria with certain characteristics associated with fecal contamination, which are not identical in biochemical and serological aspects.

Definition (GB2010): aerobic and facultative anaerobic gram-negative non-bacillus capable of fermenting lactose, acid and gas production under certain culture conditions.

Fecal coliforms: a kind of coliforms, also known as heat-resistant coliforms, culture temperature: , fecal coliforms are the microbial items that must be detected in cosmetics testing projects.

Escherichia coli: (escherichia.)Coli) is commonly known as E. coli. Pathogenic E. coli is divided into 5 categories according to different biological characteristics:

Pathogenic Escherichia coli (Epec),

Enterotoxigenic Escherichia coli (ETEC),

Enteroinvasive Escherichia coli (EIEC),

Enterohaemorrhagic Escherichia coli (EHEC),

Enteroadhesive Escherichia coli (EAEC).

Testing services that may interest you:

(1) Coliform bacteria.

It is people who copy and move.

A normal microflora in the gut of the attacker and is only present in the intestines of humans and animals.

2) Coliform bacteria usually exist at the same time as animal intestinal pathogens, but the number is different, and the animal intestinal pathogenic bacteria are not resistant to the outside world.

The ability of the environment is similar, and the survival time in the in vitro environment is about the same or slightly longer than that of enteric pathogens, and some enteric pathogens are difficult to detect in food.

3) Culture, separation, and identification are relatively easy to accommodate.

For the above reasons, coliform bacteria are often used to raise the possibility of contamination of food with feces, intestinal pathogens.

1) Escherichia coli culture process should be considered: nutritional conditions, temperature, pH and other conditions Escherichia coli has the advantages of small size, simple structure, easy selection of mutation types, easy culture, and fast reproduction, so it is often used as experimental materials for genetic research (2) In the process of microbial culture operation, in order to prevent contamination by miscellaneous bacteria, it is necessary to sterilize the culture medium and petri dish Ultraviolet rays can denature proteins and damage DNA structure, so they are used to destroy bacteria in the air (3) Count the number of viable bacteria by dilution coating plate method, It is necessary to dilute the sample to be tested moderately to avoid overlapping of the bacteria and affecting the counting (4) Preliminary identification or classification of bacteria can be carried out according to the shape and size of the colony (5) The used medium and its culture must be discarded after sterilization to prevent the spread of the culture and cause bacterial contamination Therefore, the answer is: (1) temperature pH short life cycle (2) sterilization damage to DNA structure (3) moderate (4) identification (classification) (5) sterilization.

(1) Escherichia coli bai

The culture process should consider the nutritional conditions, temperature, acidity and alkalinity of E. coli with body.

Small internal volume, simple structure, easy selection of mutation types, easy to cultivate, fast reproduction, etc., so it is often used as experimental materials for genetic research (2) In the process of microbial culture operation, in order to prevent contamination by miscellaneous bacteria, it is necessary to sterilize the medium and petri dish Ultraviolet rays can denature proteins and damage DNA structure, so they are used to destroy bacteria in the air (3) The number of viable bacteria should be counted by dilution and coating plate method, and the samples to be tested should be moderately diluted to avoid overlapping bacteria and affect the counting (4) It can be based on the shape of the colony(5) The used medium and its culture must be sterilized before being discarded to prevent the spread of the culture and cause bacterial contamination

So the answer is: (1) Temperature.

pH has a short life cycle.

2) Sterilization. Damage DNA structure (3) Moderate (4) Identification (classification) (5) Sterilization.