Thermal properties of food materials

THERMAL PROPERTIES THERMAL PROPERTIES OF FOOD OF FOOD Properties controlling the transfer of heat in a specified food Thermal properties of foods and beverages must be known to: Perform the various heat transfer calculations, required in the design of storage and refrigeration equipment Estimate the process times for refrigerating, freezing, heating, or drying foods and beverages. Thermophysical properties of foods encompass a wide range of parameters associated with heat transfer operations in food processing. Important thermal Important thermal properties of foods properties of foods 1. Specific heat capacity (Cp) The amount of heat needed to raise the temperature of one gram of a substance by one degree Celsius. Unit- J/kg K (SI system) Heldman (1975) proposed the following equation to estimate the specific heat of foodstuffs based on their mass fraction (water, protein, fat, carbohydrate, and ash). Source: https://www.sciencedirect.com/topics/food-science/thermal-property-of-food 2. Thermal conductivity (k) It is the ability of a material to conduct heat. Unit- Watts per meter-kelvin (SI system) It determines how fast heat can be evenly transferred to the entire food mass, which in turn affects the quality of the final product. The thermal conductivity of a food product depends mainly on its chemical composition, molecular structure, and the temperature at which it is processed. 3. Thermal Diffusivity (α) It is rate at which heat is diffused out of the materials. It is the ratio between thermal conductivity to volumetric heat capacity. Unit- m²/s(SI system) 4. Boiling Point Rise and Freezing Depression Boiling point elevation is the raising of a solvent's boiling point due to the addition of a solute. Freezing point depression is the lowering of a solvent's freezing point due to the addition of a solute. As the boiling point of a solvent increases, its freezing point decreases. Ex; Addition of salt to ice. The solute (salt) reduces the freezing point of the ice, which allows the ice to melt at a lower temperature. The increase in the boiling point Δ Tb = Tb – Tb0 is known as the elevation of boiling point. The elevation of boiling point (ΔTb) is directly proportional to the lowering of vapour pressure (Δp). Source: https://thefactfactor.com/facts/pure_science/chemistry/physical-chemistry/elevation-of- boiling-pointand-freezing-point-depression/7943/ In general, thermophysical properties of a food or beverage are constant when its temperature is above its initial freezing point. below However, the initial thermophysical properties vary greatly because of the complex processes involved during freezing. freezing point, the Because the thermophysical properties of ice and water are quite different, thermophysical properties of frozen foods vary dramatically with temperature. Source: https://www.cae.tntech.edu/~jbiernacki/CHE