ten times dilution

pouring method

Coating method

medium, conditions

Inverted culture: medium weight loss less than 15%

Select a plate with appropriate bacterial colony count, 30 to 300 CFU for bacteria, and 10 to 150 CFU for mold/yeast.

Methods: naked eye observation, colony counter

Identify colonies: Colonies are too small or similar to sample particles - dye reduction method, TTC (red tetrazolium, chromogenic medium), bacterial characteristics

high productivity

Small error

Internationalization: Approval from official bodies

Fast: 6-14 hours can estimate accurate results within 24 hours 3-5 days to confirm mold and yeast counts

Automatic spiral inoculation, counting system

Counting method: There are more colonies in the middle and less around them. Calculate the number of colonies per unit area.

The measurement results are highly correlated with SPC

blue to white

Dark blue turns to pink, white

Colorless to red

In biological materials with resistance, inductance and capacitance, the impedance that hinders the measurement of current is called impedance.

Principle: Microorganisms change the electrical properties of the culture medium, and the electrically inert substrate decomposes into electroactive molecules and ions. The conductivity of the culture medium increases and the impedance decreases.

Changes in conductivity over time

Microorganisms have different impedance curves

The culture medium is put into a special measuring tube. After inoculation with microorganisms, electrodes are inserted into the culture medium to directly measure changes in the electrical properties of the culture medium.

key factors, culture medium

Microbial metabolism produces carbon dioxide, etc., to reflect the metabolic activity of microorganisms

advantage

ATP participates in the luciferin-luciferase system, causing luciferin to emit light, and the amount of light emitted is proportional to ATP

Calculate cell number based on luminescence intensity

It can automatically measure and detect quickly. The results are consistent with the SPC method, saving time.

application

The amount of radiation is proportional to the number of bacteria

Detection time is inversely proportional to the number of microorganisms

radioactive energy counter

Check for stomach problems by blowing air

Food microbiology testing

rRNA accounts for 80% of total RNA

Many segments are highly conserved

biological evolution timer

phylogenetic map

Polymerase chain reaction, cell-free cloning, a molecular biology technique that amplifies specific DNA fragments outside cells

Detection of pathogenic bacteria: specific fragments, conservation

Principle: Under the catalysis of DNA polymerase, the parent strand DNA is used as the template, and specific primers are used as the starting point for extension. Through denaturation, annealing, extension and other steps, the process of in vitro copying of daughter strand DNA complementary to the template DNA is carried out.

reaction components

advantage

Principle: The instrument fixes the biochemical reaction culture medium necessary for bacterial identification on the card. After the culture, the instrument judges the displayed reaction and uses the numerical method to make the determination.

Gram-negative bacteria card, Gram-positive bacteria card, yeast card

API bacterial identification system

Antigenicity: Immunogenicity and Reactogenicity

Heterogeneity: protein, sugar, nucleic acid (chemical composition), 5-10ku poor immune effect (molecular weight)

Known Antibodies Identify Antigens

The granular antigen binds to the corresponding antibody, and after a certain period of time in the presence of a dielectric, small agglutinated pieces appear with the naked eye.

Enzymes bind to antibodies or antigens

specific reaction between antigen and antibody

Enzyme-catalyzed substrate color development, qualitative or quantitative analysis with naked eyes or instruments

Specificity ➕ Enzyme signal amplification

solid support

Enzyme labeled antigen or antibody

substrate for enzyme action

Direct method, indirect method, sandwich ELISA: determination of particle antigen

Competition method: determination of small molecule antigens such as mycotoxins

sandwich ELISA (sandwich ELISA)

Can detect multiple samples at the same time, can be automated, simple to operate, and commercialized

n: The number of samples that should be collected for the same batch of products

c: The maximum allowable sample value exceeding the m value

m: Limit value of acceptable level of microbial indicators

MThe maximum safety limit value of microbiological indicators