Thermophysical Properties of SweetPotato Puree at Freezing and Refrigeration Temperatures

The thermophysical properties (initial freezing point, unfreezable water, enthalpy of freezing, and specific heat) of alginate-restructured sweet potato (SP) puree at freezing and refrigeration temperatures were determined using differential scanning calorimetry. Restructuring of SP puree increased the amount of unfreezable (bound) water in the puree from 0.44 g H₂O/g solids to about 0.56 g H₂O/g solids and reduced the freezing point from ?2.5 to ?3.2°C. During freezing (or melting), the specific heat increased from about 1.9 to 90 kJ/kg. After freezing, the specific heats of restructured and nonrestructured SP puree were respectively 3.695 and 3.404 kJ/kg. Between 358 and 403 kJ/kg of heat have to be removed when SP puree (at 20°C) is to be frozen to ?40°C.