The total number of colonies is checked

The total number of colonies is the total number of bacterial colonies grown per gram (per milliliter) of the test under certain conditions (such as aerobic conditions, nutrient conditions, pH, culture temperature and time). Colonies are growth-producing organisms that grow on solid media and are made up of tens of thousands of identical bacteria. When the sample is diluted to a certain extent and mixed with the medium, each of the bacterial cells capable of growing and reproducing can form a visible colony on the plate under certain culture conditions. Basic Information Specialist classification: Infectious disease inspection and classification: pathogenic microorganism inspection Applicable gender: whether men and women apply fasting: not fasting Tips: Glassware used in the inspection. Such as petri dishes, straws, test tubes, pipette tips, etc. must be completely sterilized, and washed before sterilization, no bacteriostatic substances remain. Normal value no Clinical significance Only reflect the number of aerobic and mesophilic bacteria; Psychrophiles, thermophiles, special nutritional needs and dead bacteria cannot be reflected; Reflecting the sanitary quality of food, as well as the hygiene measures and management of food during production, transportation and marketing; does not represent the degree of harm to human health. Hygienic significance of the total number of colonies Food clean state sign Strip fish ≤104/g first freshness; ≤106/g second freshness; Predicting the shelf life of food Beef with a total number of colonies of 105/cm2 can be stored for 7 days at 0 °C; Beef with a total number of colonies of 103/cm2 can be stored for 18 days at 0 °C. Precautions 1. Glassware used in the inspection. Such as petri dishes, straws, test tubes, pipette tips, etc. must be completely sterilized, and washed before sterilization, no bacteriostatic substances remain. 2. Used as a liquid for sample dilution, with a blank control for each batch. If several colonies appear on the agar control plate, look for the cause. 3. The dilution of the sample is usually treated with sterile saline, if the food with high salt content is diluted. It is advisable to use distilled water. Inspection process For the determination of the total number of colonies, the test sample is generally prepared into several different 10-fold incremental dilutions, and then 1 mL of each dilution is taken out and placed in a sterilized dish and mixed with the nutrient agar medium at a certain temperature. After a certain period of incubation (usually 48 hours), the number of colonies formed in each dish was recorded, and the total number of bacterial colonies contained per gram (or per ml) of the original sample was calculated based on the dilution factor. The basic operations generally include: dilution of the sample - pouring the plate - culturing for 48 hours - counting report. The methods for determining the total number of colonies at home and abroad are basically the same, from sample processing, dilution, pouring to counting, and counting reports are not significantly different, but only slightly different in some specific requirements, such as some countries in the sample dilution and pouring culture, The flow rate of the liquid in the pipette, the amplitude of the oscillation of the diluent, the time and the number of times, and the time of placement are all specified. Not suitable for the crowd No special people. Adverse reactions and risks No complications.