An analysis of factors influencing precision of thermal property values during freezing

Abstract

An unfrozen water fraction prediction equation is proposed that compensates for both unfreezable water ( M b) and the equivalent molecular weight of solids ( MW s) during the food freezing process. The parameters ( M b and MW s ), when obtained from published unfrozen water content data, demonstrate that the proposed equation describes the data very well. When unfrozen water content data is not available, MW s can be obtained from the initial freezing point ( T f) of the food product, and M b can be obtained using calorimetric methods. The precision of MW s is shown to be very dependent on the precision of T f for a frozen food with medium (75%) to high (95%) moisture content. The precision of the input variables required in the proposed equations (temperature, M b, MW s, solids content) along with other physical parameters of the unfrozen food product (density, specific heat, and thermal conductivity) were investigated in an effort to determine the predictability of the frozen food density, apparent specific heat, enthalpy, thermal conductivity and unfrozen water content.