Microbiological Changes in Smoked and Charred Baltic Herrings during Storage

The microbiological quality of smoked and charred Baltic herrings from two different processing plants was studied after preparation and after storage for 24, 48 and 96 h at 4 and 20°C. One of the processing plants used traditional processing methods and the other a modern processing technology. No significant increase in aerobic plate counts (APCs) was observed during storage of smoked herrings at 4°C; after 96 h the mean APC was 1.7 × 10² CFU/g. The mean APC of charred herrings increased markedly at 4°C within 48 h, and after 96 h was 2.4 × 10⁴ CFU/g. At 20°C the mean APCs of smoked and charred herrings increased markedly within 24 h, and after 96 h were 1.0 × 10⁸ and 1.7 × 10⁹ CFU/g, respectively. At 20°C, high coliforms and fecal streptococci counts were found in some samples and high Staphylococcus aureus counts in 2 samples. The microbiological quality of smoked herrings was better than that of charred herrings both after processing and during storage. Bacterial numbers of smoked herrings prepared in a modern steel oven were lower than those of herrings prepared in a traditional tiled oven. The mean APC of charred herrings was, however, higher when the modern continuous-operating line was used compared to the traditional method. On the continuous-operating line, heavy bacterial contamination occurred during the salting stage. The salting procedure was therefore changed by cooling the brine. When chilled brine was used, the mean APC of charred herrings was lower than the corresponding mean for the traditional method.