Thermal Properties of Unfrozen Foods
Food processing operations such as blanching, cooking, pasteurization, and sterilization involve temperature-dependent biochemical or chemical changes. The safety and quality of foods depend critically on correct temperature regimes; for example, in canning the classical problem is ﬁnding the optimum heating regime that inactivates any microorganisms while still preserving nutritional quality (avoiding overprocessing and destruction of vitamins). In water-containing foods, heat transfer is often accompanied by a signiﬁcant water transfer. Thus the quality and safety of foods depend critically on the entire temperature history and the state and distribution of water in the food. Other physical properties and variables such as pressure, ﬂow, electric ﬁelds, and water activity also critically inﬂuence processing of foods.