The relative ability of acetic, benzoic, citric, lactic, propionic, and sorbic acids to inhibit the growth of six common meat spoilage bacteria ( Brochothrix thermosphacta , Carnobacterium piscicola , Lactobacillus curvatus , Lactobacillus sake , Pseudomonas fiuorescens , and Serratia liquefaciens ) was compared under otherwise optimum conditions (BHI or MRS broths; 20°C). Because of their low solubility in the growth media, benzoic and sorbic acids could only be used in low concentrations (below 0.15% [wt/vol]) and did not efficiently inhibit bacterial growth. All other acids totally inhibited growth at concentrations ranging from 0.1 % to 1% (wt/vol). On a weight basis, acetic acid was found to be the most inhibitory, followed by propionic. lactic, and citric acid, while the order of efficiency was reversed (citric> lactic> propionic> acetic) when the acid concentrations were expressed on a molar basis or when the acid effectiveness was evaluated relative to the concentration of undissociated molecules. Overall, the lactobacilli were the bacteria most resistant to the action of organic acids, followed by P. fiuorescens and S. liquefaciens , while B. thermosphacta and C. piscicola were considerably more sensitive.
The microbiological quality of goat milk collected at Quebec farms was observed over a one-year period. Microbial counts increased during the summer period. Only one farm had a total aerobic count of >10 5 CFU/ml in >50% of samples taken from storage tanks. Coliform counts were <10 3 /ml even when the total aerobic count was 10 6 /ml. No relationship between somatic cell counts and bacterial counts was found. Exponential bacterial growth began after a lag of at least 3 d at 0–4°C. Good hygiene, rapid cooling and refrigeration, as well as frequent collection by refrigerated vehicles, ensured the production of good quality milk.