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Challenge testing


A challenge test is the deliberate addition of specific microorganisms to monitor their growth in a product.


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A challenge test is the deliberate addition of specific microorganisms to monitor their growth in a product.


In this challenge test, a known number of microorganisms are injected into a sealed modified atmosphere pack.


Self–sealing foam pads are used to maintain the atmosphere, and packs are kept under conditions that mimic the intended storage.


The contents of the pack are diluted in a suitable diluent, and samples are blended in a stomacher.


A dilution series is created from the sample, and thoroughly mixed.


1 ml of each dilution is places in a Petri dish, to which is added agar.


Plates are incubated at an appropriate temperature for the organisms under investigation.


The number of colonies is then counted.