Résumé:
The evolution of psychrotrophic microbial flora during refrigerated storage at low temperatures was studied on three commodities namely different foods (poultry carcasses, cheeses and milk), according to three studies from different laboratories.
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In the first study Meurier et al., 1972 have enumerated the psychrotrophic flora of poultry carcasses in an industrial slaughterhouse in Brittany marketing fresh gutted chicken. The samples taken by swabbing the flora made it possible to highlight its decrease in the population of carcasses after scalding and the passage through the wax, then its increase close to plucking, evisceration and during the manipulations carried out at the end of the chain.
In the same study, a qualitative analysis of psychrotrophic germs encountered in poultry arches was presented. This study resulted in the isolation and identification of 2,591 strains, which highlighted the critical importance of hygienic conditions during the gutting and finishing of carcasses. It is at these posts that the number of Pseudomonas increases very significantly.
According to Dumont et al. 1977, a study was carried out on the influence of the contamination of milk by psychrotrophic bacteria on the organoleptic qualities of soft cheese, in addition to an accentuated lipolysis, it was noted a very strong increase in the contents in methyl ketones and secondary alcohols. The degradation of seed proteins stops at an intermediate state as evidenced by the bitterness observed.
And finally Mottar's study (1984) on two strains of psychrotrophic bacteria gram (-) Pseudomonas P 104 and Flavobacterium P 108, which are capable of producing extremely thermostable exocellular proteinases, are isolated from refrigerated mixed milk.
The heat resistance of proteinases produced by isolated microorganisms is high enough to fully resist UHT treatment.
