Food Specific Heat (Choi-Okos)
Compute a food's specific heat by the Choi-Okos equations, cp = 4.18·Xwater + 1.55·Xprotein + 1.71·Xfat + 1.42·Xcarbohydrate + 0.91·Xash (kJ/kg·K), from the component mass fractions. Since water has a very high specific heat, wetter foods heat and cool more slowly. It is essential in computing the heat loads of cooking, refrigeration and freezing. Enter the water, protein, fat, carbohydrate and ash fractions.
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Food specific heat (Choi-Okos)
How much energy does it take to heat or cool a food? That depends on its specific heat (cp), which shifts with composition. The Choi-Okos equations work out the cp by summing the contribution of each component, weighted by its mass fraction: cp = 4.18·Xwater + 1.55·Xprotein + 1.71·Xfat + 1.42·Xcarb + 0.91·Xash (kJ/kg·K). Note that water carries the largest coefficient by far (4.18) — hence moist foods (fruit, vegetables, meat) show a high cp and heat up or cool down slowly, demanding more energy and more time, while dry or fatty foods respond faster. The cp feeds straight into thermal load calculations for cooking, pasteurization, refrigeration and freezing (above the freezing point; below it, the latent heat of ice dominates). It stands as a fundamental property in the design of heat exchangers and cold rooms across the food industry. Enter the water, protein, fat, carbohydrate and ash fractions.
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Compute the product cooling heat load in a cold room, Q = m·cp·ΔT, from the product mass, its specific heat and the desired temperature change. It is the sensible-heat portion to remove to lower the product temperature — one of the components of the room's total load (which also includes wall transmission, infiltration, lighting, motors and people). It defines the refrigerating capacity needed. Enter the mass, the specific heat and the ΔT.
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