Dear colleagues,

I perform microbial limit tests using poured plates . With some products (lactose, starch) it is difficult to distinguish the colonies. I know there`s the recomedation of using MPN in this cases, but I wonder if it is possible to use poured plates adding  TTC to the culture medium to stain the colonies and differentiate them from the product being tested. Has anybody validated this method? I`ve heard about possible inhibitory effect of TTC. Could someone refer me any paper on this topic? 
Any help would be appreciated, thanks in advance,

Laura Acevedo
Microbiological Quality Control Manager
Laboratorio LIBRA
Montevideo-Uruguay
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