Microbiological and lipolytic changes in high-pressure-treated raw milk cheeses during refrigerated storage

Abstract

High-pressure processing (HPP) has been used to control microorganisms and enzymes and avoid over-ripening in cheese. Excessive lipolysis is associated with over-ripening in cheese. However, little information about the effect of high pressure on microorganisms and lipolysis in mature cheese is available. For this reason, microbiological and lipolytic changes during refrigerated storage of pressurised Torta del Casar cheese (a raw ewe's milk cheese) were studied. Mature cheeses (60 days of ripening) were high-pressure treated (200 or 600 MPa for 5 or 20 min) and stored at 6°C. Cheese samples were analysed at day 60, just after high-pressure treatment, and during the refrigerated storage (at days 120, 180 and 240). Enterobacteriaceae counts were significantly reduced after high-pressure treatment, thus increasing the food safety of this cheese. In particular, Enterobacteriaceae showed a significant (p<0.01) decrease of 2.18 and 2.46 log units in cheeses treated at 200 MPa for 20 min at days 120 and 180, respectively; however, treatment at 600 MPa for 20 min only caused reductions of 2.09 and 1.79 log units at days 120 and 180. Free fatty acids content was not significantly influenced by high-pressure treatment, although it increased with time of storage.

Evaluating the Quality of Cheese Slices Packaged with Na-Alginate Edible Films Supplemented with Functional Lactic Acid Bacteria Cultures after High-Pressure Processing

“…Most of the studies deal with fresh cheeses, or cheeses made from raw (unpasteurized) milk. For example, Rodríguez-Pinilla et al [ 32 ] studied the effect on microbiological and lipolytic changes during the refrigerated storage of pressurized (200 or 600 MPa for 5 or 20 min) Torta del Casar cheese (a raw ewe’s milk cheese). The results showed that the safety of the product was enhanced after HPP, while free fatty acid content was not significantly influenced by HPP [ 32 ].…”

“…For example, Rodríguez-Pinilla et al [ 32 ] studied the effect on microbiological and lipolytic changes during the refrigerated storage of pressurized (200 or 600 MPa for 5 or 20 min) Torta del Casar cheese (a raw ewe’s milk cheese). The results showed that the safety of the product was enhanced after HPP, while free fatty acid content was not significantly influenced by HPP [ 32 ]. The study of Stefanini and Vignalu [ 34 ] evaluated the shelf-life of a fresh Ricotta cheese after HPP (600 MPa for 3 min) stored in modified-atmosphere packaging (MAP), in comparison with cheeses stored in MAP without HPP treatment.…”

“…To date, HPP has been applied in a variety of cheeses in an effort to increase their microbiological quality and/or safety. More specifically, some of the studies that have been carried out have elaborated on the application of HPP to enhance the safety of Queso Fresco cheese inoculated with Listeria monocytogenes [ 29 ], to extend the shelf-life of different starter-free fresh cheeses [ 26 , 30 , 31 , 32 ], to inactivate starter bacteria and spoilage yeasts in a fresh lactic curd cheese [ 33 ], and to evaluate the combination of HPP along with modified-atmosphere packaging in the extension of ricotta cheese shelf-life [ 34 ]. The pressure levels that are usually applied to cheeses are above 500 MPa for a relatively short time (5 min); however, different combinations of pressure levels and time can be found in the literature.…”

Comparing Different Packaging Conditions on Quality Stability of High-Pressure Treated Serra da Estrela Cheeses during Cold Storage

“…Highpressure processing (HPP) has been studied and applied as an alternative non-thermal process to conventional thermal pasteurization, with a 2-3-fold shelf-life extension for dairy Foods 2023, 12,1935 2 of 17 foods compared to the raw counterparts [4], and with low impact on quality. Several studies have revealed the advantage of HPP application at the optimum organoleptic ripening time of cheeses, ensuring the effective inactivation of microorganisms and thus improving safety [5,6]. For example, studies performed with Torta del Casar cheese [5,6] demonstrated that HPP treatment of 600 MPa/5 min at 60 days of ripening caused 2.3 and 2.5 log cycle reductions in Enterobacteriaceae and Pseudomonas spp.…”

“…Several studies have revealed the advantage of HPP application at the optimum organoleptic ripening time of cheeses, ensuring the effective inactivation of microorganisms and thus improving safety [5,6]. For example, studies performed with Torta del Casar cheese [5,6] demonstrated that HPP treatment of 600 MPa/5 min at 60 days of ripening caused 2.3 and 2.5 log cycle reductions in Enterobacteriaceae and Pseudomonas spp. viable cells numbers, respectively [5].…”