Effect of high-pressure treatments on proteolysis, volatile compounds, texture, colour, and sensory characteristics of semi-hard raw ewe milk cheese

•Semi-hard raw ewe milk cheeses were treated at 200-500 MPa for 10 min on day 7.•Formation of free amino acids increased in cheeses high pressure (HP) treated at 200-400 MPa.•HP treatments of cheese retarded the formation of some volatile compounds.•Sensory characteristics of HP-treated cheeses were mostly unaffected.

High pressure (HP) offers potential industrial applications in cheese preservation, but it is essential to provide knowledge concerning their effects on the ripening process and sensory characteristics. In this study, we investigated the effect of different HP treatments (200-500 MPa at 14 °C for 10 min on day 7) on proteolysis, texture, colour, volatile compounds and sensory characteristics of semi-hard raw ewe milk cheese. HP treatments did not affect pH or dry matter values of 60-day-old cheeses. Treatments at pressure levels up to 400 MPa led to significant (P < 0.01) increases in the total free amino acids (FAA) content at 60 days, compared to control cheese, although the cell-free aminopeptidase activity was lower. HP retarded the formation of some volatile compounds in cheeses, the number of compounds affected by HP being higher as the pressure level increased. Cheeses pressurized at 300-500 MPa had lower levels of 2-butanone, 2-butanol, 2-propen-1-ol, 1-butanol and acetic acid than control cheese, cheeses pressurized at 400-500 MPa lower levels of 1-propanol, 2-pentanol, and butyric and hexanoic acids, and cheeses pressurized at 500 MPa lower levels of ethanol, 3-methyl-1-butanol and 3-methyl-2-buten-1-ol. All HP-treated cheeses showed higher fracturability values, and higher Hue angle and lower a* values than control cheese. Despite the differences detected by instrumental analyses between HP-cheeses and control cheese, few significant differences were found between the sensory characteristics of HP-cheeses and control cheese. Only the pressurization of cheese at 500 MPa affected significantly (P < 0.01) some of the sensory characteristics, with a negative effect on taste intensity but a positive effect on aroma quality.In summary, HP treatments at 200 and 300 MPa showed the mildest effects on the characteristics of semi-hard raw ewe milk cheese. HP treatment of this cheese variety at 300, 400 and 500 MPa prevented late blowing defect caused by Clostridium tyrobutyricum (Ávila et al., 2016, Food Microbiol. 60, 165-173). Thus, it may be concluded that HP treatment at 300 MPa is the most adequate procedure, able to prevent late blowing with minimum changes in cheese characteristics.

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