The natural microflora of cold-smoked fish at the end of shelf-life are lactic acid bacteria (LAB). Some of these display a capacity to inhibit spoilage as well as several strains of pathogenic micro-organisms, e.g. Listeria monocytogenes which is isolated frequently from cold-smoked salmon (CSS). Eight batches of sliced vacuum-packed CSS from Norway, Scotland and Spain were collected at retail. Packs were stored at 5 degrees C and examined for chemical and microbiological characteristics, at purchase date and at expiration date. pH, water activity and salt content were similar to available data on lightly preserved fish products. There was a consistent pattern in the development of the microflora on CSS; the initial level of LAB was low on freshly produced CSS (10(2) cfu g(-1)); however, storage in vacuum packaging at refrigeration temperature was elective for LAB. At the end of the stated shelf-life these micro-organisms, represented mainly by Lactobacillus spp., attained ca.10(7) cfu g(-1) while Enterobacteriaceae counts were consistently lower (10(5) cfu g(-1)), which indicates the ability of LAB to grow and compete with few carbohydrates available and in the presence of moderate salt concentrations. L. monocytogenes was not found in any sample. Forty-one percent of LAB strains isolated exhibited inhibitory capacity against Listeria innocua, in a plate assay. A majority of the inhibitory effects were non-bacteriocinogenic, but nevertheless were very competitive cultures which may provide an additional hurdle for improved preservation by natural means.
The 5-year incidence of dental caries in a random sample of 60-, 70- and 80-year-old inhabitants of Goteborg was related to salivary and microbial conditions. Of the 208 persons examined at baseline, 148 (71%) participated in the follow-up examination; 69, 51 and 28, respectively, in the different age groups. The study revealed that 27% of the participants had not developed any carious lesions during the 5-year period and that the incidence of coronal and root caries increased with age. In the 60-year-olds, 2.5% of the susceptible coronal and root surfaces, respectively, had decayed, while the corresponding figures for the 80-year-olds were 8.8% for coronal surfaces and 9.8% for root surfaces. In all, 18% had an unstimulated saliva secretion rate of below 0.1 ml/min and 14% had a stimulated secretion rate of or = 10(6) CFU/ml in saliva and the corresponding figures for > or = 10(5) lactobacilli counts were 22, 31 and 43%. In the stepwise regression analysis, it was found that age, salivary levels of mutans streptococci and lactobacilli and number of teeth were the best predictors of the incidence of root caries. In conclusion, these observations indicate that there is an increased risk of dental caries with age owing to unfavourable microbial and salivary conditions.