PROTEOLYTIC PATTERNS OF CACIOTTA AND MONTEREY JACK HARD GOAT MILK CHEESES AS EVALUATED BY SDS-PAGE AND DENSITOMETRIC ANALYSES

Protein degradation characteristics of Caciotta and Montery Jack hard goat milk cheeses aged for different storage time and under different temperature conditions were evaluated with SDS-PAGE and an advanced Bi o-Image Whole Band Densitometric analysis. Two replicates of three var ieties of cheeses (Caciotta, Monterey Jack, and a cow milk Cheddar as a reference control) were assigned to three temperatures (4, 13 and 22 degrees C) and four storage times (0, 8, 16 and 24 weeks) in order to study the effects of different time-temperature treatments on PAGE pa tterns of cheese proteins and water soluble nitrogen (WSN) contents of cheeses. Initial fresh Caciotta and Monterey Jack goat cheeses had di stinctive alpha(s2)-casein PAGE bands, whereas cow milk Cheddar cheese displayed an almost absence of the alpha(s2)-CN but clear and intensi ve alpha(s1)-CN bands. Caciotta and Monterey Jack goat cheeses showed some peculiar proteolytic patterns of alpha(s1)- and alpha(s2)-caseins at 8 weeks aging compared to cow milk Cheddar cheeses, which might be attributable to the specific physicochemical characteristics of the t wo hard goat cheese varieties. Densitometric integrated intensity show ed that the initial (0 week) goat cheeses had the greatest p-casein va lues, and then continuously declined as the storage time progressed. T he extent of protein degradation in all 3 varieties of cheeses was als o shown by the increase in WSN and the concomitant reduction in beta-c asein as aging advanced. The elevations of WSN in the two goat cheeses were significantly greater (P < 0.01) than those in cow milk Cheddar. All main factors (variety, temperature and time) and their interactio ns had significant effects on proteolysis of the cheeses. It was concl uded that the rates of protein degradation in Caciotta and Monterey Ja ck goat cheeses were greater than in cow milk Cheddar. Protein degrada tion of the cheeses were also synergistically affected by storage time and temperature treatments. (C) 1998 Elsevier Science B.V.