The pH-unrelated influence of salt, temperature and manganese on aroma formation by Staphylococcus xylosus and Staphylococcus carnosus in a fermented meat model system

The influence of manganese (0.01–0.1–1.0 μg/g), temperature (15–24 °C) and salt (3–4% w/w) on volatile formation in model minces inoculated with Pediococcus pentosaceus and either Staphylococcus xylosus or Staphylococcus carnosus was studied in a full factorial experiment. In order to study the direct, pH-unrelated effect of the parameters, data were analysed by use of multiple linear regression and partial least-squares regression both before and after transformation of the volatile responses into pH-orthogonal (pH-unrelated) responses. By using the pH-orthogonalised data, the overall interpretability of the experiment was increased, and new cause-and-effect relations were suggested. Approximately 50% of the total variance in volatile levels was due to differences caused by S. xylosus and S. carnosus, and another 30% was related to differences in pH development. The remaining 20% covered pH-orthogonal effects of manganese, temperature and salt plus the experimental noise. From this, it was concluded that most of the variation in volatile profiles caused by manganese, temperature and salt was in fact directly or indirectly caused by changes in lactic acid bacterial activity and pH.