280 Meat refrigeration Table 13.6 Specific gravity Mean specific gravit Lean meats(also liver) Bones beef, fresh: humerus femur 1.33 1.44 Source: Morley, 1972a at-2°Cand rising to ca 13Wm-1°lat-30°C airer and Zaritzky 1983) 13. 2.4 Density a knowledge of the density of meat components is important in heat con duction analysis since density (p)appears in the general transient heat con duction equation. Table 13.6 shows the mean specific gravities during hilling of lean meats, fats and bones. It can be seen that the density of bone is much greater than that of lean and fat and that there is a fairly large variation in density between differ ent bones 13.3 Mathematical models Computer programs are now available such as COSTTHERM and FoodProp that will accurately predict the thermal properties of food from their compositional properties. In general a knowledge of the initial freez ng point of the product is required to obtain accurate data in the freezing range. Programs are under development that will automatically predict the itial freezing point. 13. 4 Conclusions 1 The thermal properties of meat are both a function of its composition and its temperature 2 At temperatures above-1.5C: the thermal conductivity of lean meat is roughly two and a half times of fat. the specific heat of fat is also very variable with temperature 3 At temperatures below -15C:at -2 °C and rising to ca. 1.3 W m-1 °C-1 at -30 °C (Barrera and Zaritzky, 1983). 13.2.4 Density A knowledge of the density of meat components is important in heat con￾duction analysis since density (r) appears in the general transient heat con￾duction equation. Table 13.6 shows the mean specific gravities during chilling of lean meats, fats and bones. It can be seen that the density of bone is much greater than that of lean and fat and that there is a fairly large variation in density between differ￾ent bones. 13.3 Mathematical models Computer programs are now available such as COSTTHERM and FoodProp that will accurately predict the thermal properties of food from their compositional properties. In general a knowledge of the initial freez￾ing point of the product is required to obtain accurate data in the freezing range. Programs are under development that will automatically predict the initial freezing point. 13.4 Conclusions 1 The thermal properties of meat are both a function of its composition and its temperature. 2 At temperatures above -1.5 °C: • the thermal conductivity of lean meat is roughly two and a half times that of fat; • the specific heat of fat is also very variable with temperature. 3 At temperatures below -1.5 °C: 280 Meat refrigeration Table 13.6 Specific gravity Mean specific gravity Lean meats (also liver) 1.07 Fats 0.92 Bones beef, fresh: humerus, femur 1.33 tibia 1.41 radius 1.44 cannon bones 1.56 Source: Morley, 1972a