Shelf-life of vacuum-packed cooked ring sausages at different chill temperatures

Microbiological and sensory changes in 313 vacuum-packed cooked ring sausages from 28 different production runs and stored at 2, 4, 8 or 12°C were monitored as a function of time. The sensory scores started to decrease at a level of approx. 10⁷ lactobacilli/g. The judges began considering the samples unfit for human consumption when the lactobacilli counts were between 10⁷ and 10⁸ cfu/g; above a level of 10⁸ cfu/g most of the samples were deemed unfit. At 2°C, however, spoilage did not always seem to be microbiological, and four out of six different production runs were deemed unfit without any marked increase in microbial counts. In such cases, the judges described the sensory defects as a ‘musty’ rather than a sour aroma and taste. The sausages were deemed unfit ehen the lactobacilli were in a stationary growth phase which was considerably later than the point when the bacterial counts exceeded 10⁷ cfu/g. The mean length of this delay was 30, 19, 16 and 7 days at 2, 4, 8 and 12°C, respectively. The average shelf-lives were 55, 43, 29 and 17 days at 2, 4, 8 and 12°C, respectively. The dependence of shelf-life on temperature can be formulated as follows: Shelf-life = 10^{(1.835 − 0.048 × temperature)}.
The maximal shelf-life of this product including nonmicrobiological spoilage, is assessed as approx. 10–11 weeks. A lactobacilli count > 10⁷ cfu/g indicates that either the spoilage process has started or the product is already spoiled. When the lactobacilli count exceeds 10⁸ cfu/g it is highly probable that the sausage sample is unacceptable.