Identification of low molecular weight compounds produced or utilized by pychrotrophic meat spoilage organisms

Meat Juice Medium (MJM), an aqueous extract of meat, was inoculated with Pseudomonas aeruginosa and incubated for 7 d at 4$ sp circ$C under shaking conditions (100 rev.min$ sp{-1}$). Two predominant compounds produced during spoilage of MJM were detected using HPLC. These compounds with retention times (RT) of 21.48 and 32.04 min were tentatively identified as acetic and butyric acids, respectively. These compounds were also produced when MJM was replaced with Brain Heart Infusion Broth medium. In later experiments, the effect of glucose supplementation on the rate of MJM spoilage was examined. Glucose 0.5% (wt/vol) was added to the MJM, inoculated with P. aeruginosa and incubated at 30$ sp circ$C under shaking conditions (100 rev.min$ sp{-1}$). HPLC of samples after 1d of incubation indicated the presence of 8 predominant compounds including acetic and butyric acids. Their concentrations were, in general, higher in control samples of MJM without added glucose. Using HPLC, TLC, Pyrolysis/GC/MS, FTIR and GC-MS methodologies, the compounds with RT of 8.91, 9.67, 11.96, 13.33, 17.74, 21.48, 26.07 and 32.04 min were tentatively identified as cadaverine, 2-keto gluconic acid, fructose, lactic acid, acetic acid, methanol and butyric acid. In contrast to the results of previous researchers, cadaverine was produced in large amounts while no putrescine was produced by P. aeruginosa. During the spoilage period, the levels of glucose, fructose and total carbohydrate were monitored. Addition of glucose to MJM delayed slime production by 4 days and increase to maximum pH of 8.3 by 7 days. Results suggest that addition of glucose to MJM delays spoilage by P. aeruginosa