In brief
The microbiological safety of plant raw materials is assessed by four main parameters: TAMC (total aerobic microbial count), TYMC (total yeast and mould count), and the presence of the specific pathogens Escherichia coli and Salmonella spp. The reference framework is the European Pharmacopoeia (Ph. Eur.) chapter 5.1.4 and USP <2021>.
What is monitored
TAMC (Total Aerobic Microbial Count)
The total count of aerobic microorganisms (bacteria) in one gram of sample, expressed in CFU/g (colony-forming units per gram). It indicates the general microbiological cleanliness of the material.
TYMC (Total Yeast and Mould Count)
The total count of yeasts and moulds in one gram of sample, in CFU/g. A high TYMC is related to the risk of mycotoxin formation - which is why TYMC is an important preventive indicator.
Specific pathogens
- Escherichia coli - an indicator of faecal contamination; in plant raw materials for distribution, absence in a defined amount of sample (e.g. 1 g) is typically required,
- Salmonella spp. - a pathogenic bacterium; as standard, absence in 10 g of sample is required.
Optionally, depending on the intended use of the material, other pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus cereus) are also tested.
Limits under EuPh 5.1.4
The European Pharmacopoeia sets limits according to the category of use of the raw material. For oral use of herbal raw materials (category B) the indicative limits are:
- TAMC: ≤ 107 CFU/g (i.e. a maximum of 10 million CFU per gram),
- TYMC: ≤ 105 CFU/g (i.e. a maximum of 100 thousand CFU per gram),
- absence of Salmonella in 25 g,
- absence of E. coli in 1 g.
For herbal raw materials with an assumed higher-quality processing (category A), the limits are stricter (TAMC ≤ 105 CFU/g). The specific classification of kratom into a category depends on the intended use stated in the documentation.
Causes of contamination
The main sources of microbiological contamination in the kratom chain:
- Harvest - contact with soil, insects, birds,
- Drying - drying in an unclean environment, insufficient ventilation, contact with contaminated surfaces,
- Fermentation - if it takes place in unsatisfactory conditions, it supports mould growth,
- Storage and transport - damp, high temperature, contaminated bags,
- Secondary contamination during packaging - contact with personnel, insufficiently disinfected tools.
Prevention of contamination is primarily a matter of hygiene discipline throughout the production line, not just the final analysis.
The detection method
Standard microbiological analysis uses cultivation on selective agars:
- TAMC - Tryptic Soy Agar (TSA), incubation 30-35 °C, 3-5 days,
- TYMC - Sabouraud Dextrose Agar (SDA), incubation 20-25 °C, 5-7 days,
- E. coli - MacConkey Agar / EMB with confirmation by biochemical tests,
- Salmonella - selective enrichment (RV broth) + plating on XLD/Hektoen agar + serological confirmation.
Modern laboratories also use molecular methods (PCR, MALDI-TOF) for faster identification.
Frequently asked questions
Can kratom be sterilised by irradiation?
Some types of gamma irradiation are used for the microbiological decontamination of spices and plant raw materials. However, the effect on the content of alkaloids in kratom has not been sufficiently studied; in addition, in the EU the irradiation of food is subject to separate regulation (Directives 1999/2/EC, 1999/3/EC).
What does TAMC mean?
Total Aerobic Microbial Count - the total count of aerobic (oxygen-requiring) microorganisms in one gram of sample, expressed in CFU/g.
Is salmonella a common finding in kratom?
With standard hygiene, no. Cases of detection appear in raw material processed under unsatisfactory conditions. The standard is a test for absence in 25 g of sample.
How is TYMC related to mycotoxins?
TYMC measures the presence of moulds; the mere presence does not mean the presence of mycotoxins, but a high TYMC increases the risk of their formation. Both parameters are assessed together.
References
- European Pharmacopoeia, ch. 5.1.4. Microbiological quality of non-sterile pharmaceutical preparations and substances for pharmaceutical use.
- USP <2021>. Microbial Enumeration Tests - Nutritional and Dietary Supplements. United States Pharmacopeia.
- USP <2023>. Microbial Procedures for Absence of Specified Microorganisms - Nutritional and Dietary Supplements.
