HIGH-PRESSURE EFFECTS ON LIPID OXIDATION

Rendered pork fat (0.44 water activity, A(W)) was subjected to high-pressure treatment of 800 MPa for 20 min at 19 degrees C prior to storage at 4, 25, and 50 degrees C. In all cases, high pres sure-treated samples oxidized more rapidly (had a shorter induction period) as shown by the peroxide value (PV), 2-thiobarbituric acid value, and ultraviolet absorbance. The effect was less marked at lower pressures. In contrast, at all water activities outside the range of 0.40-0.55, the PV of the high pressure-treated pork fat was lower than control samples stored similarly, and the PV of rancid fat decreased slightly on pressure treatment at 19 degrees C, but not at higher temperatures. This effect may explain the observed inhibition of oxidation at most water activities. At 0.40-0.55 A(W), other factors, such as the liberation of transition metals, may override the destruction of peroxides.