Chemical composition, hygiene characteristics and coagulation aptitude of milk for Parmigiano Reggiano cheese from herds yielding different milk levels

The aim of the research was to compare milk quality parameters among herd characterized by different levels of milk production. The trial involved 1080 bulk milk samples collected from 30 dairy herds producing milk for Parmigiano Reggiano cheese. Herds were grouped in 3 classes (10 herds per class) according to their production level (kg/cow/lactation):from 6000 to 7999 (L), from 8000 to 9999 (M) and from 10000 to 12000 (H). The average herd size were 64, 69 and 64 in the L, M and H, respectively. Samples were collected monthly in each herd during 3 years period and the following parameters were assessed on each sample: fat and crude protein (CP), titratable acidity (TA), total bacterial count (TBC), somatic cells (SCC), coliforms bacteria (CB) and Clostridia spores. Least mean values were obtained by ANOVA univariate using the herd class (L, M or H) as fixed factor. Fat was higher in L milk than in the M and H ones (3.60 vs 3.28 vs 3.30 g/100g; P0.001 respectively). CP resulted lower in L milk compared to M and H milks (3.17 vs 3.37 vs 3.43 g/100g; P0.001 respectively). The TA was higher in M milk and lower in L and H ones (3.25 vs 3.22 vs 3.23 °SH/50ml; P0.01 respectively). These differences, although statistically significant, probably were not significant from a cheese-making perspective. The parameters of SCC, TBC and CB resulted higher in L milk and lower in H milk. Milk produced in H herds showed a better microbial quality, with less SCC, TBC and CB values. No differences were observed for Clostridia spores in the 3 types of milks.