A tablet comprised of uniaxially compressed powdered copper was developed to measure the pressure within a High hydrostatic pressure (HHP) processing system. The density of the tablet increased proportionately as HHP increased between 400 and 600 MPa (P-0.001). Tablet density increased as time-at-pressure increased between 1, 5 and 10 min (P-0.012) when held at
constant HHPs between 400 and 600 MPa. No significant increase in tablet density was found when tablets were HHP processed at 7, 15 or 24 8C between 400 and 600 MPa (P)0.29). The change in density of the tablet placed in the geometric center of a large food product, such as a ham, indicated that the ham received approximately 9 MPa less pressure than the HHP system
delivered (P-0.017), challenging the assumption that all foods follow the isostatic rule. This finding may have implications when determining the microbial lethality for large food items pasteurized or sterilized using a HHP process. The indicator may also serve as a HACCP verification tool for HHP-processed foods.