Proteolysis during ripening of traditional montenegrin white brined Pljevlja cheeses

Abstract

Pljevlja cheese is known traditional Montenegrin product that belongs to brined cheeses group. Due to its high nutritional value and long tradition of production and consumption, Pljevlja cheese is a candidate for receiving the sign of protected origin (PDO). The objective of this study was to analyze composition and proteolysis of Pljevlja cheeses, supplied from 10 producers that produce cheese by traditional technology. Collected cheese samples were analyzed in duplicate for dry matter by the oven drying method, fat by Van Gulik, total protein by Kjeldahl and sodium chloride by Volhard method. The level of proteolysis was monitored by urea polyacrylamide gel electrophoresis (Urea PAGE) and water-soluble nitrogen content (WSN) according to the method of Kuchroo and Fox. All analysis were done at first, 20th, 40th and 60th day of cheese ripening. The differences among cheeses parameters during ripening were determined by LSD test at a 0.05 statistical level using Statistica software (Stat Soft. Inc., Tulsa, USA). Parameters of proteolysis increased during 60 days of ripening and ranged from 7.45 to 14.23% for water-soluble nitrogen (WSN) as a percentage of total nitrogen (WSN/TN) and from 8.38 to 11.13% for nitrogen soluble in 5% phosphotungstic acid as a percentage of WSN (PTAN/WSN). Degradation of as casein was more pronounced than of β casein but still not very extensive during all ripening period. Preliminary results of this study indicate that high salt content of cheeses was the main cause of limited proteolysis, observed in all Pljevlja cheese samples. Also, the high variability of the gross composition and proteolysis parameters of Pljevlja cheeses are due to the lack of standardized cheese-making technologies. It is necessary to continue with additional research on chemical, microbiological and sensory analysis, together with proteolysis, in order to obtain enough relevant data that could be useful for achieving the constant quality of Pljevlja cheese, i.e. to create the necessary preconditions for the development of its standard, as a final aim.