Dairy maturation of milk used in the manufacture of Parmigiano-Reggiano cheese: effects on physico-chemical characteristics, rennet-coagulation aptitude and rheological properties.

The aim of this research was to study the effects of dairy maturation on the physico-chemical characteristics and technological properties of milk used for Parmigiano-Reggiano cheese manufacture. Three different operating conditions (CF1, CF2 and CF3) were considered. Full cream milk from the evening milking was stored on the farm and delivered to the cheese factory in churns (CF1) or in thermoregulated tanks at a temperature not lower than 18 degrees C (CF2 and CF3). The natural creaming (10-12 h overnight) was performed in a traditional large flat vat containing 10-12 hl (CF1 and CF2) or in thermoregulated large flat vats containing 60 hl at about 15 degrees C (CF3). Twenty-four, 24 and 22 maturation trials were performed in CF1, CF2, and CF3, respectively, during 2 consecutive years. A significant increase (P<or=0.05) in pH during the maturation of milk was observed in CF1 and CF2. The increase of pH was higher (P<or=0.05) in CF1 than CF2 and CF3. The values of titratable acidity were higher (P<or=0.05) in partially skimmed evening (PS) milk than in full cream (FC) milk in each operative condition. The increase observed in CF2 was higher than those reported in CF1 and CF3. Compared with FC milk, PS milk showed lower values (P<or=0.05) of casein and casein number and higher contents (P<or=0.05) of whey proteins and, particularly, proteose-peptone. The increase of proteose-peptone--per 100 g SNF or 100 g casein--was significantly higher (P<or=0.05) in CF1 than in CF2 and, in particular, than in CF3. A higher increase (P<or=0.05) of resistance to compression was observed in CF1 with respect to CF3. CF2 variation was not different with respect to either CF1 or CF3. Variation of the difference between PS and FC milks (PS-FC) in pH, TBC and fat were clearly lower in CF3 than CF1. This means that the control of milk temperature throughout the whole maturation phase offers a greater control of both microbial development and extent of creaming.