Thermophysical Properties of Channel Catfish at Freezing Temperatures

Freezing is the most common method used to preserve and minimize loss in quality of catfish during storage. Since freezing is a heat transfer process, the design and selection of freezing equipment require knowledge of thermophysical properties such as freezing temperature, enthalpy of freezing, unfreezable water and specific heat. Channel catfish thermophysical properties at freezing temperature were determined using differential scanning calorimetry. Using the combination of Raoult’s law and Classius-Clapeyron equations, the amount of unfreezable (bound water) was estimated to be 0.129 g H2O g. During freezing (or melting), the specific heat increased from about 1.5 J g °C to about 30.6 J g °C. It was found that freezing of catfish occur over a wide temperature range with the peak and incident freezing temperatures occurring at temperatures of -1.88 °C and -6.10 °C, respectively. About 250 J g of heat have to be removed from catfish when it is to be frozen to -40 °C. The implication is that any system that will be designed to freeze catfish must be able to remove 250 J g of heat.