Effect of High Pressure Processing on the Lipolysis, Volatile Compounds, Odour and Colour of Cheese Made from Unpasteurized Milk

Cheeses made from unpasteurized milk were high pressure processed (HPP) for 14 or 21 days after manufacture at 400 or 600 MPa, in order to prevent excessive accumulation of flavour compounds, in particular free fatty acids (FFA) and volatile compounds (VC). They were compared with untreated control cheese throughout a 240-day period. On day 60, cheeses treated at 400 MPa had esterase activity values 57.1-58.0 % lower than control cheese while cheeses treated at 600 MPa had values 82.3-82.8 % lower, with no significant differences between total FFA concentrations of cheeses. However, on day 240, total FFA concentrations were 6.5-9.0 % lower in 400 MPa cheeses than in control cheese and 15.0-16.9 % lower in 600 MPa cheeses, with more marked differences for short-chain FFA and less marked for hexadecanoic and octadecanoic acids. Fifty-two of the 70 VC found in cheese were significantly influenced by HPP. On day 240, total alcohols reached the highest levels in control and 400 MPa cheeses, total aldehydes, ketones and hydrocarbons in 600 MPa cheeses, and total sulphur compounds in 400 and 600 MPa cheeses. Levels of total volatile acids, esters, ethers, benzenic compounds and terpenoids in 240-day cheese were not affected by HPP. Odour quality and intensity were not significantly influenced by HPP. Higher L* values were recorded for 600 MPa cheeses and higher a* values for control and 400 MPa cheeses. Principal component analysis on the groups of volatile compounds highlighted the different evolvement of volatiles in control, 400 and 600 MPa cheeses during ripening.