15B-5 |
Primary protein degradation of Fynbo cheese at different ripening temperatures |
G. A. Sihufe, S. E. Zorrilla, and A. C. RUBIOLO. Instituto de Desarrollo Tecnológico para la Industria Química, Universidad Nacional del Litoral - CONICET, Güemes 3450, Santa Fe, S3000GLN, Argentina Various biochemical changes occur during cheese ripening, such as proteolysis, that contribute to the development of characteristic flavor and texture. Temperature is an important factor that affects biochemical processes during ripening. Moreover, increasing the temperature has proved to be useful for accelerating the ripening, but cheese quality can be affected. Our objectives were to study primary casein degradation of Fynbo cheese at different ripening temperatures and determine characteristic kinetics parameters. Twenty-one Fynbo cheeses (12 cm diameter x 6 cm height, initial composition: 50% w/w moisture, 16% w/w fat, and 30% w/w protein) were brought from a factory and salted for approximately 10 hr at 12 °C in a solution of 190 g/L NaCl. Cheeses were ripened at 5, 12, and 16 °C and sampled at 1, 5, 10, 20, 30, 60, and 90 days. Two different zones (central and external) were considered because salt and moisture change with cheese position and may affect proteolysis. Primary casein degradation was studied by urea-polyacrylamide gel electrophoresis (PAGE). Quantitative analysis of electrophoretic fractions was performed by scanning photographs at 632.8 nm. Different casein fractions were considered in a basic electrophoretic pattern (as1, as1-I and b caseins). Significant differences were observed between levels of proteolysis for different temperatures and cheese zones. Casein degradation was major for higher temperatures and central zone. Results showed that b-casein in Fynbo cheeses was more resistant to proteolysis than as1-casein, remaining practically constant during the first month of ripening. Considering first-order kinetics for as1-casein degradation, the kinetics constants values were in the range of 0.2 to 2 x 10-2 day-1 (r>0.86). The activation energy for this reaction was approximately 28 Kcal/gmol. These results indicated that ripening temperature accelerate significantly the primary proteolysis of Fynbo cheese and can be useful information for controlling and optimizing the ripening temperature.
Session 15B, Dairy Foods: Chemistry, microbiology and sensory analysis of various cheeses
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