Effect of high‐pressure treatments on microbial loads and physicochemical characteristics during refrigerated storage of raw milk Serra da Estrela cheese samples

Abstract

This work studied the effect of high pressure processing (HPP) at 400, 500 and 600 MPa during 10, 5 and 3 min, respectively, on samples ewe cheese manufactured from raw milk, during storage (100 days) at 5°C. Total aerobic mesophilic and lactic acid bacteria were slightly affected, decreasing by about 1.0 and 0.82 log CFU g À1 , respectively, immediately after HPP treatment at 600 MPa for 3 min, while Enterobacteriaceae, yeasts and moulds, and Listeria innocua were reduced to below the quantification limits. Lactic acid bacteria decreased further during storage, showing increasing inactivation as the pressure level increased. Physicochemical parameters (water activity, moisture content, pH and titratable acidity) were generally not affected by HPP, while lipid oxidation increased throughout storage, with HPP samples showing lower values (50-66%) at 100 days of storage. The results indicated that HPP has potential to improve cheese microbial safety and shelf-life, with a lower lipid oxidation level than nonpressurised cheese.

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

“…Lactobacilli and lactococci (Figure 1A,B) were found at a similar order of magnitude independently of the cheese treatment and packaging system; in Ch C +V cheeses, viable cell numbers were found at 8.37 and 8.29 log cfu g −1 , respectively, at the beginning of storage (0 months), and these remained relatively constant (p ≥ 0.05) throughout the 10 months of storage (exception for lactococci viable cell numbers that increased to 9.30 log cfu g −1 at 3 months of storage (p < 0.05)). Similar values were reported in the literature, never below the 8 log cfu g −1 at 30-60 days of ripening [13,14]. The HPP treatment caused a significant reduction in lactobacilli and lactococci viable cell numbers (p < 0.001) of about 3.8 and 2.5 log cycles, respectively, values close to those previously obtained for Serra da Estrela cheese (450 and 600 MPa/6 min) (submitted data) and in Casar cheese (400 and 600 MPa/5 min) [15].…”

A Review of the Preservation of Hard and Semi-Hard Cheeses: Quality and Safety

“…When high pressure treatment is applied to milk, microbiological quality comparable to that of pasteurized milk can be achieved [ 55 ]. Thus, thermal milk pasteurization can potentially be replaced by HHP treatment for cheesemaking [ 56 ]. However, milk HHP treatments can modify the physico-chemical structure of proteins, causing the fragmentation of casein micelles and denaturation of whey proteins, mainly due to the generation of non-covalent disruptions [ 57 , 58 , 59 ].…”

“…Medium and long FFA content did not vary with any of the HHP treatments [ 45 , 65 ]. Inácio et al [ 56 ] reported a significant reduction in the microbial count of Enterobacteriaceae , Listeria innocua , molds and yeasts in raw milk ewe’s cheeses treated with high pressure. HHP treatment (400–600 MPa) applied to cheese at 45 ripening days did not significantly modify its physico-chemical characteristics, although lipid oxidation was reduced in comparison with non-pressurized cheeses after 100 ripening days.…”

Serra da Estrela cheese: A review

“…Like other raw milk cheeses, Serra da Estrela cheese can enable spoilage microorganisms’ growth during ripening and cheese storage. To try avoiding this, a new food processing technology, that is, high pressure processing (HPP), was tested for its efficacy to simultaneously reduce the risk of pathogenic and spoilage microorganisms development without jeopardizing the desired LAB metabolic activity (Inácio, Fidalgo, Santos, Queirós, & Saraiva, ). Serra da Estrela cheese samples with 45 days of ripening were treated at 400–600 MPa pressures during 3–10 min and the effect of HPP after pressure processing and during storage (100 days at 5°C) was studied.…”