Improvement of raw sausage fermentation by stress-conditioning of the starter organism Lactobacillus sakei.

Effective growth and high acidification activity during meat fermentation are key characteristics of starter lactobacilli to ensure hygienic safety and sensory quality of the product. In this study, we demonstrated that the performance of Lactobacillus sakei in sausage fermentation can be improved by preinoculation treatments with sublethal heat, cold, and salt stress. Sausages were produced and inoculated with stress-treated cells of L. sakei 23 K (pLPV111) and the isogenic mutant of the class III heat-shock repressor CtsR, which was previously shown to exhibit improved growth in fermenting sausages. The pH values of sausages fermented with stressed cells attained defined threshold values in a distinctly shorter time than those inoculated with unstressed cells. In particular, the cold-stressed cells (4 degrees C) reduced the pH to 5.0 within approximately 40 hours compared with approximately 70 hours for untreated cells. This enhanced acidification activity of the cold-stressed cells was consistent with an increased growth rate. Growth studies in culture medium showed that stress-treated cells with improved performance did not exhibit this advantage when exposed to curing salt, one of the major stressors at the beginning of sausage fermentation. Preinoculation stress treatment is a promising way to improve the effectiveness of meat starter lactobacilli.