**6.1.1 The pre-enrichment**

It's a non-selective phase that uses a rich medium in which the sample is diluted to one tenth (1 / 10) and for which the incubation period is about twenty hours at 35 ° C or 37 ° C (Humbert et al ., 1998). The pre-enrichment allows bacteria to sublethal to recover all of their potential at the end of incubation. The media used are liquids, most often using buffered peptone water or lactose broth (Humbert et al., 1998). For dairy products can be used Ringer's solution or phosphate buffer solution.
