The effect of some gram-negative bacteria on the ripening and quality of dry sausage

Abstract

The possible use of gram-negative bacteria as starter cultures in dry sausage was studied by inoculating the following gram-negative bacteria into dry sausage both alone and with Lactobacillus plantarum: Aeromonas x, Aeromonas 19. Vibrio costicolus, Achromobacter 22, Achromobacter guttatus, Achromobacter X, Escherichia coli, or Proteus vulgaris. Sausage without any inoculation and sausage containing Micrococcus sp. + Lactobacillus plantarum were used as references. Aeromonas x and 19 strains had a very favourable effect on the quality of dry sausage when inoculated together with lactobacilli. Both strains reduced nitrate, and the colour formed during the first 3 days. The pH value of Aeromonas + Lactobacillus sausages decreased so quickly that the consistency of these sausages developed within one week and was at least as good as, and often firmer than in Micrococcus + Lactobacillus sausages. The consistency of Aeromonas 19 + Lactobacillus sausages was better at the 0.05 significance level than that of Micrococcus + Lactobacillus samples. The aroma and flavour of Aeromonas + Lactobacillus sausages were as good as or better than those of Micrococcus 4- Lactobacillus sausages. The aroma and flavour of Aeromonas 19 + Lactobacillus sausages were significantly better (significance level 0.001) than Micrococcus-f Lactobacillus sausages. The flavour of Aeromonas x + Lactobacillus sausages was better at the 0.05 level than Micrococcus + Lactobacillus sausages. The number of bacteria, roughly the number of lactobacilli. was often significantly higher in Aeromonas + Lactobacillus sausages (range 2—4 x 108/g between 3 and 21 days of ripening) than in Micrococcus + Lactobacillus sausages (range 8 X 107 1.5 X 108/g between 3 and 21 days of ripening). For this reason the former sausages ripened more quickly than the latter. Vibrio 21 and three Achromobacter strains did not thrive in dry sausage and disappeared during the first 7 days of ripening. When inoculated together with lactobacilli, Escherichia coli had almost as favourable an effect as micrococci on the quality of dry sausage. Inoculations of E. coli alone and Proteus vulgaris, both alone and with lactobacilli, did not improve the quality of dry sausage. P. vulgaris actually had a detrimental effect. Conclusion The investigation has proved that gram-negative bacterial strains Aeromonas x and 19 inoculated with lactobacilli improve the quality of dry sausage and that, especially with the Aeromonas 19 + Lactobacillus inoculum, better dry sausage was obtained than with micrococci and lactobacilli.