The effect of NaCl and metabolic profile of propionibacteria on eye formation in experimental Swiss-type cheese

The influence of three brining times (0, 1, and 3 d) and two propionibacteria (PAB) cultures (Prop A and Prop B) on eye formation was investigated in experimental Swiss-type cheeses by comparing PAB counts, biochemical parameters, eye numbers, diameters and volumes. Prop A was strongly inhibited with increasing NaCl content. As a result, eye volume decreased considerably, as well as eye diameter especially towards the cheese surface. Prop B exclusively converted l-lactate and was much less affected by increasing NaCl content, hence, eye formation changed less. The salt sensitivity of the cultures also influenced the spatial distribution of the eyes. The width of the eyeless border zone was mainly affected by three factors: CO₂ diffusion to the outside, propionic acid fermentation, and body firmness. The study clearly showed that strain-specific salt sensitivity of PAB is an important feature that strongly influences eye formation in Swiss-type cheeses with different salt content.