The total number of colonies refers to the unit weight (g), volume (mL) or surface area of a food sample after being cultured under strictly prescribed conditions (sample processing, sterile medium and its pH value, culture temperature and time, counting method, etc.). (cm2), the total number of bacterial colonies generated.
The genera Escherichia, Citrobacter, Enterobacter and Klebsiella of the Enterobacteriaceae are collectively referred to as coliforms. They all come from the intestines of humans or warm-blooded animals, do not form spores, and are gram-negative bacilli that ferment lactose to produce acid and gas at 35-37 °C. These bacteria are resident bacteria that live in the intestines of humans and warm-blooded animals, and are excreted in the stool. The higher the number of coliform bacteria in food, the greater the degree of food contamination by feces. Therefore, the use of coliform bacteria as a hygienic index of fecal-contaminated food to evaluate the quality of food has extensive significance.
Pathogens are bacteria that can cause people to get sick. A pathogenic bacteria test may be performed when the coliform test is positive and the food may be suspected to be contaminated with pathogenic bacteria. Food microbiology testing pathogens generally refer to "enteric pathogenic bacteria and pathogenic cocci", mainly including Salmonella, Shigella, Staphylococcus aureus, and pathogenic Streptococcus. Pathogenic bacteria are not allowed in detected in food.
For different foods and different occasions, a certain reference flora should be selected for testing. For example, Vibrio parahaemolyticus is used as the reference flora for seafood, Salmonella, Staphylococcus aureus, Proteus, etc. are used as the reference flora for eggs and egg products, and Bacillus cereus, Proteus, mold, etc. are used for rice and noodles. As a reference flora, canned food uses thermostable Bacillus as a reference flora, etc.
Since there are many molds that can produce toxins that can cause food poisoning and other illnesses, toxin-producing molds should be tested. Such as Aspergillus flavus, Aspergillus parasiticus, etc., Penicillium citricium, Penicillium island, etc., Fusarium moniliformes, Fusarium graminearum and so on.
Food microbiology testing indicators should also include viruses, such as hepatitis virus, swine fever virus, chicken Newcastle disease virus, horsetail virus, foot-and-mouth disease virus, rabies virus, swine vesicular virus, etc. Listed as microbiological test indicators, such as Trichinella, Cysticerccus, Porcine sporozoite, Ascaris, Paragonimiasis, Toxoplasma, mites, Fasciola chinensis, Branch fluke sinensis, etc.
The food microbiology testing items carried out in the United States mainly include: plate count of aerobic bacteria, fecal coliform, Escherichia coli, coagulase-positive Staphylococcus, Salmonella, Vibrio cholerae, Vibrio parahaemolyticus, monocytogenes, Listeria, Vibrio vulnificus, Clostridium botulinum, paralytic shellfish toxin, neurogenic shellfish toxin, amnestic shellfish toxin, and histamine.