The TGC – Total Germs Count is an essential microbiological test that measures the actual microbial load present in a batch of cosmetic products. Unlike the challenge test, which is used to prove the effectiveness of the preservative system, the DGT evaluates the microbiological cleanliness of the finished product. This analysis is essential to ensure compliance with the hygiene and quality requirements imposed by both European Regulation (EC 1223/2009) and the Swiss Cosmetics Ordinance (OCos/OSAV).
The procedure begins with the collection of a representative sample from the batch. This sample is then diluted and spread onto selective culture media suitable for the growth of bacteria, yeasts, and molds that may be present. After controlled incubation (usually 24–48 hours for bacteria and 3–5 days for fungi), the visible colonies are counted one by one. The number of colonies (CFU – colony-forming units) is used to calculate the total microbial load of the product and to verify that it remains below regulatory thresholds (e.g., <10 CFU/g for products without preservatives, or <100 CFU/g for products containing an effective preservative).
The DGT thus provides a direct picture of several critical factors:
- Manufacturing quality : it reveals any contamination introduced during the production process.
- Site hygiene : it reflects the level of cleanliness of the premises, equipment, and staff.
- Compliance with GMP (Good Manufacturing Practices, ISO 22716): it confirms that health control procedures are being properly implemented.
Because it measures the microbiological reality of each batch, the DGT must be performed. on each batch produced. This repetition ensures that the entire production process complies with safety and stability requirements. However, the challenge test is only performed once per formula, as it only tests the preservative's ability to control hypothetical contamination.
By integrating the DGT results into the Product Information File (PIF) or the Product Information File (PIF), manufacturers provide Swiss and European authorities with tangible proof of the microbiological compliance of their products, thereby strengthening consumer confidence and facilitating market entry.