Effect of High-Pressure Processing on the Microbiology, Proteolysis, Biogenic Amines and Flavour of Cheese Made from Unpasteurized Milk

Abstract

Cheese varieties with long ripening periods are prone to form biogenic amines and develop off-flavours. High-pressure processing (HPP), which inactivates microorganisms and enzymes, may be useful in preventing those defects. On this aim, cheeses made from unpasteurized milk were treated at 400 or 600 MPa, after 14 or 21 days of ripening, and their characteristics were compared to those of untreated control cheese throughout a 240-day period. Lactic acid bacteria declined by 2 log units in 400 MPa cheeses and by 6 log units in 600 MPa cheeses after HPP, while Gram-negative bacteria were below detection level in all the HPP-treated cheeses. Aminopeptidase activity was significantly lower in HPP cheeses than in control cheese from day 21 onwards. Hydrolysis of αs-casein was enhanced in 400 MPa cheeses, but not in 600 MPa cheeses, while a more pronounced hydrolysis of β-, κ- and para-κ-caseins was recorded in all the HPP cheeses from day 60 onwards. Levels of hydrophilic and hydrophobic peptides were higher in HPP cheeses than in control cheese on day 60 and thereafter. Total free amino acids were at lower concentrations in 600 MPa cheeses than in the rest from day 60 onwards. The concentration of total biogenic amines was lower in all the HPP cheeses than in control cheese from day 60 onwards. Flavour quality and flavour intensity of cheese made from unpasteurized milk were not significantly affected by HPP.