Investigation of underlying factors in split and secondary fermentation defects in rindless block Swiss-type cheeses

Factors associated with split and secondary fermentation defects in Swiss-type cheeses include seasonality of milk supply, interactions between lactic and propionic acid bacteria and variability in cheese composition. Swiss-type cheeses produced from a seasonal milk supply were sampled on two days per month of the production year (season), at three different times during the manufacturing day (time of day), at internal and external regions of the cheese block (area) and at four ripening time points (ripening: d 7, post hot room, d 14 post hot room and 3 months in a cold room). Compositional, biochemical and microbial indices were determined, and the results were analysed as a split-plot with a factorial arrangement of treatments (season, time of day, area) on the main plot and ripening time on the sub-plot. Cheese salt levels were not equilibrated within the 60 kg cheese block 3 months post exit from hot room. Season (and interactions) had a significant effect on pH and salt-in-moisture levels (p<0.01), on mean counts of L. helveticus, propionic acid (p<0.05) and non-starter lactic acid bacteria (p<0.001), on levels of primary and secondary proteolysis (p<0.01; as measured by nitrogen soluble at pH 4.6 and in 5% phosphotungstic acid) and on cheese firmness. Levels of proteolysis increased significantly during hot room ripening but also during cool room storage. Rheological parameters (e.g. springiness and cohesiveness) were significantly affected by interactions between ripening and sampling area within cheese blocks. Trends identified will enable seasonal manipulation of manufacture protocols to minimise compositional and biochemical variability and to reduce the occurrence of split and secondary fermentation defects.