A possible approach to assess acidification of meat starter cultures: a case study for some wild strains of Lactobacillus plantarum

BACKGROUND. The performances of four autochthonous isolates of Lactobacillus plantarum were assessed to study the most important variables acting on acidification and propose a possible step-by-step approach for the validation at lab-scale. This main topic was addressed through three intermediate steps: (i) evaluation of acidification in liquid and solid media, as a function of salt, nitrites, nitrates, lactose, pepper and temperature; (ii) assessing acidification in a pork-meat preparation; iii) designing a protocol to improve the performances at sub-optimal temperatures. The concentration of the ingredients and the temperature were combined through a 3k-p Fractional Factorial Design. Acidification and viable count were assessed and modeled through a multi-factorial ANOVA. RESULTS. In model systems acidification was affected by lactose and was maximum (ΔpH of ca. 2.8-3.0) in the combinations containing 0.4% lactose, 250 mg/kg nitrates or 150 mg/kg nitrites, 5% salt, and at 30°C. Solid media caused a higher acidification. In the pork meat preparation, the effect of salt and nitrites was significant. At 10°C the strains could not reduce pH, but this ability could be induced using an adaptation step. CONCLUSIONS. Acidification was affected by lactose in the model system, whereas in meat preparation the other variables were significant. In addition, a protocol to improve acidification at 10°C was optimized.