Variability of lactic acid production, chemical and microbiological characteristics in 24-hour Parmigiano Reggiano cheese.

The achievement of a sufficient acidity level by starters at early stages of manufacture is essential for a good quality Parmigiano Reggiano (PR) cheese. In this work, the chemical parameters and microbial characteristics of 18 PR cheeses during the moulding phase were analysed to determine how the microbial growth takes place conditioning acidification performances. Based on the mean values of lactic acid content, two groups of cheeses were observed. High numbers of culturable thermophilic bacteria and in particular Lactobacillus helveticus able to metabolise galactose but also grow faster in the cheese appeared to be essential conditions to achieve adequate lactic acid content. On the other hand, low acidification and residual galactose, as observed in the second group, may be associated with a lower amount of metabolically active L. helveticus and higher relevance of Streptococcus thermophilus contents in the cheese. While culturable thermophilic bacteria were fundamental for higher lactic acid production, non-culturable cells did not seem to contribute to the acidification. [ABSTRACT FROM AUTHOR]