Investigating the refrigerated performance shelf-life of high pressure treated, reduced sodium, low moisture part skim Mozzarella cheese

Abstract Text: Physical, or performance, properties of low moisture part skim (LMPS) Mozzarella cheese are acceptable for only a relatively short time period (e.g. 4-6 wk) when stored under refrigeration conditions (4^oC). During longer term storage (such as for exporting), cheese becomes soft and pasty due to physicochemical changes in para-casein matrix and ongoing protein breakdown, which results in poor shredding properties for unmelted cheese. We proposed that the performance and sensory properties of reduced Na LMPS-Mozzarella cheese could be extended by decreasing microbial and enzymatic activity with the application of high hydrostatic pressure (HHP). Camel chymosin was also used as a coagulant to help reduce cheese proteolysis. Average composition of reduced Na (1.0±0.1% NaCl) LMPS-Mozzarella cheeses were 48.6±0.7% moisture, 22.6±0.4% fat, and 24.4±0.7% protein. Cheeses were divided into three groups randomly after manufacture and stored at ~4^oC. One group was non-pressurized and kept as control. Two wk after manufacture, the two groups of cheese samples were HHP-treated at 500 or 600 MPa for 3 min. Analysis was performed at 2, 4, 6, 8, 12, 16, and 20 wk after cheese manufacture. Texture profile analysis (TPA) and dynamic low-amplitude oscillatory rheology was used to monitor cheese functionality during ripening. Quantitative descriptive analysis was conducted with 9 trained panelists to evaluate texture and flavor attributes using a 15 point scale. Pressure treatments at 500 and 600 MPa resulted in ~1 and ~2 log reduction in starter culture numbers at 2 wk of ripening, respectively, compared to control cheese. High pressure treatment of LMPS-Mozzarella cheese resulted in an initial (at 2 wk of ripening) increase (P < 0.05) in pH values; however, by 4 wk of ripening we did not observe any statistical difference in pH values between control and HHP-treated samples. At 2 wk of ripening, pressure treatment significantly (P < 0.05) decreased cheese hardness; however, by 16 wk the 600 MPa HHP-treated cheeses exhibited significantly (P < 0.05) higher TPA hardness values compared to control. Sensory panels also indicated that by 16 wk of age, the 600 MPa HHP-treated sample was significantly (P < 0.05) firmer than the control. Pizza panels indicated that 600 MPa HHP-treated cheese was significantly (P < 0.05) chewier and exhibited lower blister quantity and higher strand thickness compared to control. Pressures of 600 MPa produced LMPS-Mozzarella cheese with acceptable performance on pizza for a greatly extended refrigerated storage period.

Keywords: High pressure, reduced sodium, camel chymosin