Coliform bacteria counts are generally used in the field of food microbiology in the most likely number (EMS) method is used. The reason why this method is preferred is that the number of coliform bacteria allowed in foodstuffs is too low to be detected by standard culture methods using solid media. Nevertheless, solid media is used in some studies.

For microbiological analysis of foodstuffs, the most preferred solid medium for total coliform count is Violet Red Bile (VRB) Agar medium. In addition, other solid media are used for this purpose. Specifically for the counting of damaged coliform bacteria on solid media, the sample to be analyzed is seeded on the Tryptic Soy Agar medium by spreading and VRB Agar medium is poured onto it as a second layer after about 10 minutes.

The biggest evaluation error in the use of solid media in coliform bacterial analyzes is the identification of the developing bacterial colonies and the interpretation of the analyzed food as health-appropriate or non-health-friendly.

According to the current legal regulations, foodstuffs should be free from harmful bacteria for human health. However, legal regulations also allow the presence of a certain number of coliform bacteria in the analysis using the Most Probable Number (EMS) method. This means that some coliform bacteria, although not suitable for human health, are considered to be small in number. In fact, this is a contradiction in the Food Codex.

In authorized laboratories, studies are carried out for the determination of coliforms on solid media within the scope of microbiological analyzes. During these studies, standards and test methods issued by domestic and foreign organizations are followed. A few standards to consider are:

 

• TS ISO 4832 Microbiology of food and animal feed - Horizontal method for counting coliforms - Colony counting technique
• TS EN ISO 9308-1 Water quality - Detection and enumeration of Escherichia coli and coliform bacteria - Part 1: Membrane filtration method for low bacterial soil flora waters