Technical Terms Dictionary
TOTAL PLATE COUNT
(quote: Swiss Handbook of Foods / ISO 4833:2003)
The total plate count TPC (aerobic, mesophilic organisms) defines how many aerobic (oxygen-loving), mesophilic (moderate-temperature-loving) micro-organism colonies such as bacteria, yeast and mould fungi will grow in 72 hours on an agar plate that was normed for microbiological testing at a controlled temperature of 30 °C.
Precisely defined amounts of the sample will be mixed in petri dishes with nutrient solution and kept in an incubator at 30 °C. After 3 days, the colonies grown on the samples will be counted, thereby determining the number of aerobic, mesophilic organisms per g or per ml of sample.
The result will be given in colony forming units (cfu/g or cfu/ml).
Apart from the undesirable, pathogen organisms, the total plate count or plate count also includes the desirable micro organism such as lactic acid bacteria in fermented foods (yoghurt or cheeses). The count of aerobic, mesophilic organisms can therefore be used to determine the hygienic status of these foods.
A high total plate count generally points to a poor microbial quality of a non-fermented product. For specific details, further tests will have to be done.
However, drawing the reverse conclusion is not that simple, as it does not necessarily mean that a product with a low total plate count is good - for determining that, further testing of indicator organisms is needed.
Guideline values for a few products
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