Effect of the somatic cell count on the manufacture of the prato cheese. / Efeito da contagem de celulas somaticas do leite na fabricação do queijo prato.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

Mastitis is defined as an inflammation of the udder and is characterized by an increased of somatic cell count in the milk. The inflammatory process causes alterations in the milk composition and its enzymatic activity, resulting in milk products of inferior quality. The objective of this work was to evaluate the effect of somatic cell count (SCC) in milk on its composition, and the effect of the treatment (SCC and clotting time) on the serum and Prato cheese composition, as well as on the cheese yield and ripening. Initially, two groups of animals were selected to obtain milk with low (<200.000 cell/ml) and with high (>600.000 cell/ml) SCC. The milk was submitted to three treatments to obtain Prato cheese: (1) from milk with low SCC and clotting time of 35 minutes; (2) from milk with high SCC and clotting time of 35 minutes; and (3) from milk with high SCC and adjusted clotting time. Milk, serum and cheese compositions were evaluated. Cheese yield and recovery of constituents of milk to cheese were calculated. The cheeses were evaluated after 5, 12, 19, 26, 33, and 40 days of ripening according to pH, moisture, nitrogen fraction, texture and eletrophoretic profiles. The ratios of width (SNpH4.6/TN*100) and depth (SN-12%TCA/TN*100) of ripening were calculated. The complete experiment was repeated three times and a randomized block design was used with a single factor: either SCC or treatments (SCC and clotting time). The milk with high SCC showed a smaller concentration of true protein, and a higher concentration of non-protein nitrogen. The cheeses obtained from the milk with high SCC presented higher proteolysis than the cheeses with low SCC. The protein recovery was higher for the cheese with low SCC and the lactose recovery was higher for the cheeses with high SCC. For these SCC levels, no significant difference in cheese yield was observed. However, the treatments affected pH, moisture and the ratios of width and depth of ripening of the cheeses. The cheese with high SCC presented higher pH, moisture and more intense proteolysis, followed by the cheese with high SCC and adjusted coagulation time and the cheese with low SCC. The treatments affected the texture profiles: the cheese with high SCC without adjusted clotting time was less firm than the others; the cheese with low SCC had more elasticity than the cheese with high SCC without adjusted clotting time. The cheese with low SCC had the most cohesiveness. All the cheeses with high SCC presented more intense proteolysis of the as1- e B-caseins fractions during ripening. In conclusion, the cheeses with high SCC, regardless of the coagulation time, had higher pH and moisture, more intense proteolysis and an alteration of the texture profile, all of which can compromise the typical sensorial quality of the product.

ASSUNTO(S)

prato cheese proteolise somatic cell count contagem de celulas somaticas mastite ripening queijo prato mastitis proteolysis maturação

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