Interrelationship between microbial numbers and other parameters in the spoilage of vacuum-packed cooked ring sausages

The spoilage process of 60 vacuum-packed cooked ring sausages stored at 8° C was studied by determining the number of bacteria, sensory properties, pH and the headspace gas composition. Lactobacilli (cfu determined on Rogosa SL agar incubated anaerobically) multiplied in samples during storage and became the main microbial population of the sausages being also responsible for the spoilage. All variables examined showed a change as a function of lactobacilli.
The change in these variables can be used as indication of deterioration. The judges began considering the samples unfit for human consumption after the lactobacilli count had reached 107 cfu/g. The probability that a lactobacilli count of 107 cfu/g caused spoilage of vacuum-packed cooked ring sausage was approx. 10%. Above the level of 108 lactobacilli/g a sharp decrease in pH from 6.3 down to approx. 5.4, was observed.
The CO2 concentration in the vacuum-packs was constant, being under 10% until the lactobacilli count exceeded 6.4 × 106 cfu/g, after which the CO2 concentration increased sharply up to 40–60%.