Valutazione del Grana Padano grattugiato attraverso determinazione per elettroforesi capillare di frazioni caseiniche e di loro peptidi di degradazione

Patterns of proteolysis in the rind and interior of Grana Padano cheeses were assessed by capillary electrophoresis. An alphas2-casein fraction was very stable in the rind, but was degraded during the 1st few days of ripening, even just below the rind. A peptide, alpha-s1-casein (f80-199), was formed only at trace levels in the rind, but accumulated progressively in the remainder of the cheese during ripening. The ratio between peak areas of these 2 components was 400x higher in the rind than in the remainder of the cheese. When a whole Grana Padano cheese was grated, this ratio was <7. A calibration curve was produced showing that values for this ratio increase with increasing amount of added rind in the grated product. Ratios >7 may also be due to presence of non-ripened cheese, or cheese types other than Grana Padano or Parmigiano Reggiano. Samples of commercial grated Grana Padano cheese were analysed for presence of rind in excess of that naturally present in an intact cheese. Most samples labelled as Grana Padano or Parmigiano Reggiano had ratios <7; a few had ratios of 7-8. Some samples labelled as grated hard cheese had much higher ratios.