“Quesucos de Liébana” cheese from cowʹs milk: biochemical changes during ripening

The changes in chemical composition, main physico-chemical parameters, classical nitrogen fractions, caseins and their degradation products, and some fat characteristics were studied during the ripening process of 10 batches of Quesucos de Liébana cheese, a traditional variety made in the north of Spain. The values of the different compositional and physico-chemical parameters at the end of the ripening did not differ significantly from those found in other cowʹs milk cheeses elaborated with similar technology. The presence of residual lactose at the end of the ripening process is outstanding. The total soluble nitrogen increased by a factor of 2 at the end of the ripening compared to the values shown at the beginning. However, non-protein nitrogen increased very little. The final values of the different nitrogen fractions show that this cheese undergoes a proteolysis moderate in extension but not very intense and that the rennet is the main agent of the proteolysis produced during ripening. Using PAGE techniques, it was possible to show that, throughout ripening, 56% of αs-casein and 11% of β-casein turned out to be degraded. The TBA number and acidity index of the fat values show that the processes of lipolysis and fat autooxidation during the ripening of this cheese are not very intense.