A Study of the Physico-Chemical, Electrophoretic and Rheological Properties Throughout Ripening of Sao Jorge (PDO) Raw Cow?s Milk Cheese

摘要

Texture is an important quality parameter that determines the identity of a cheese and greatly affects its consumer preference and acceptance. In the present study, the texture (rheological properties), physicochemical and proteolysis profiles of Sao Jorge cheese at 90, 120 and 210 days of ripening were evaluated. The moisture content ranged between 36-37%, the pH values lay between 5.20 and 5.45 with highest values found consistently in 120 days samples (p>0.05)and the instrumental hardness varied between 550 and 700 g. As cheeses aged, the total protein varied from 25.89 g/100 g in 90 days cheeses to 27.41/100 g in 210 days samples; the protein electrophoretic patterns showed a consistence between cheese age and a lowering in intensity of bands associated to intact casein and conversely an increase in intensity and number of bands associated to the water-soluble extracts components, commonly used as index of cheese ripening. It was concluded that Sao Jorge cheeses of 120 days are markedly different from their counterparts of 90 and 210 days, being characterized by a slight higher moisture, higher pH value, higher stress-strain slope, lower hardness and a lower resistance to compression, indicative of a more fragile structure. This is the first systematic report on the evolution of texture in Sao Jorge cheese.