Cheeses with a propionic acid (PA) fermentation can vary in terms of NaCl-content between 0.3 and 1.7%. Though propionic acid bacteria (PAB) are relatively NaCl-sensitive, their sensitivity is strain dependent. The influence of three different NaCl treatment-levels on two PAB cultures (Prop A and Prop B) was investigated in experimental Emmental-type cheeses by comparing the chemical and biochemical composition, proteolysis parameters and the eye formation. The number of eye nuclei was standardized by microfiltration and addition of hay powder to the milk. Gas formation was monitored during the whole ripening period. At low NaCl-concentrations, Prop A metabolized the two lactate-isomers completely. However, PA fermentation was inhibited with increasing NaCl-content. As a result, PA content and eye volume decreased considerably. Prop B converted only L-lactate and was hardly affected by increasing NaCl-content, therefore, PA content and eye volume varied only slightly. The eye number differed between the cheeses made with the two experimental cultures Prop A and Prop B. In contrast to the eye volume, the cheeses made with Prop B always had more eyes than the cheeses with Prop A. The faster CO2 formation by Prop B favoured the formation of eyes. As expected, the distance of the outermost eyes to the cheese rind increased in all cheeses with growing NaCl-content. The dimension of this eye-free zone was mainly affected by the three factors CO2 diffusion to the outside, PA fermentation and body firmness. Overall, the study clearly showed that depending on the applied PAB culture, NaCl content strongly influences quality and eye formation.
