This chapter summarizes the major methodologies and the key issues related to mathematical modeling of freezing, thawing and chilling processes for foods. Refrigerated food is popular worldwide because refrigeration is the technique that best preserves the quality characteristics of fresh food. The main industrial food refrigeration processes include freezing, thawing and chilling. Heat and mass transfer during freezing, thawing, and chilling generally comprises heat conduction and diffusional mass transfer within the solid food, and convection, radiation, and/or evaporation/sublimation heat and mass transfer between the food surface and the external medium. For freezing and thawing an extra difficulty is how to predict the ice fraction of foods during phase change. For most foods, nucleation and supercooling are quite short term phenomena and have relatively little effect on freezing rate. Pressure shift freezing has been gaining attention as a freezing method for high quality or freeze-sensitive foods. In pressure shift freezing, the food is cooled under very high pressure to sub-zero temperatures.