Pressurization is accompanied by a uniform transient temperature increase. Upon depressurization, the temperature returns back to close to its initial value. Heat compression represents magnitude of transient temperature increase in the product per 100 MPa pressure application.
Each food component has specific heat of compression values (example, water ~3ºC/100 MPa, fats and oils ~6ºC-8ºC-/100 MPa). Heat of compression of water and water like substances (such as protein and carbohydrates) value increases with increasing initial temperature. Heat of compression of fats and oils do not change with initial product temperature.
Table 1. Heat of compression values of selected foods determined at initial sample temperature of 25 ºC
a Substances exhibited decreasing temperature rise with an increase in pressure (Adapted from Rasanayagam et al., 2003; Kesavan et al., 2002; Ramaswamy et al., 2005)
Table 2. Estimated compression heating factors (ºC per 100 MPa of water for various initial temperatures)