Microbial testing checks how many living microorganisms a sample carries and whether specific harmful ones are present. Count-based tests include total aerobic microbial count (TAMC) and total yeast and mould count (TYMC), reported in colony-forming units per gram (CFU/g). Pathogen tests look for organisms such as Salmonella, Shiga-toxin-producing E. coli and pathogenic Aspergillus species, usually reported as detected or not detected in a set sample mass.
In practice
A COA might show TYMC 2,000 CFU/g against a limit of 10,000 CFU/g: pass. Mould counts rise with slow, humid drying, dense buds, poor airflow and storage at high water activity. Labs use either culture plating or DNA-based (qPCR) methods; the two can give different counts on the same sample, so check the method. Limits vary by jurisdiction; check local rules.
Units and formula
CFU/g (colony-forming units per gram), often written as powers of ten, e.g. 10^4 CFU/g = 10,000 CFU/g.
Don't confuse with
- Mycotoxins: toxic chemicals some moulds leave behind, which can persist after the mould is killed.
- Visible mould: a lab count can fail before anything is visible.
- Water activity: a risk indicator for growth, not a microbe count.
