High-pressure differential scanning calorimetry: Evaluation of phase transition in pork muscle at high pressures

High-pressure (HP) differential scanning calorimetry (DSC) was used to investigate phase-transition behavior of water in pork muscle at elevated pressures. Fresh pork (rib portion) muscle samples (0.62-0.72 g, vacuum-packaged in polyethylene pouches) were tested through isothermal pressure-scan (P-scan, 0.3 MPa/min) and isobaric temperature-scan (T-scan, 0.15C/min) techniques. By using P-scan testing procedure, the relationship between phase-transition temperature (T) of frozen pork and the weighted-average pressure during the phase-change period ((P) over bar (1-2)) was found to be T = -1.17 - 0.102 (P) over bar (1-2) (P) over bar (2)(1-2) (R-2 = 0.998, n = 10). Comparing with similar temperature pressure relationship classically established for pure water, it was observed that the depression of phase-change temperature was much more pronounced in pork muscle than in pure water, and the degree of depression increased with an increase in pressure level. The ice content was evaluated with P-scan at various constant calorimetric temperatures and compared with similar data from conventional DSC Differences between the two were statistically insignificant (P > 0.05). T-scan tests demonstrated phase-transition behavior at constant pressure, but results were not very satisfactory. Overall, HP DSC seems a powerful technique for phase-transition characterization of water in real foods during HP process.