Introduction to the Freezing Process

The focus of this book is on the freezing of solid or non-moving liquid foods. A detailed description of the physical process is given so that it can be properly understood and mathematically modelled. First the freezing of a small droplet of water is described, then that of a larger mass of water, and then of a real food. In the first case clear distinctions can be made between the precooling, phase change and subcooling stages. In the second case the distinctions are less clear due to the internal temperature profile, while in the third a further complication is caused by the gradual nature of ice formation. The concept of a freezing plateau is explained. Methods to calculate the freezing times can be classified into analytical, approximate, empirical and numerical methods.