When water turns to ice at 0 °C its temperature does not change, yet it releases 334 kJ/kg of heat; that is latent heat. It equals the heat needed to warm the same water from 0 °C to 80 °C. Since most foods are mostly water, their latent heat of freezing is between 200 and 300 kJ/kg: freezing meat removes three to four times more heat than cooling the same meat from 20 °C to 0 °C.
The refrigeration cycle itself runs on latent heat: as the refrigerant evaporates in the evaporator it takes latent heat from the room, and as it condenses in the condenser it gives latent heat to the outside air. The greater a refrigerant’s latent heat of vaporisation, the less refrigerant has to be circulated for the same capacity; this is one of the reasons ammonia (R717) is preferred.
In a blast freezer latent heat is the heart of the calculation: when bringing 1,000 kg of product from +4 °C to −18 °C, most of the product load is the latent heat removed during freezing. The cooling load calculator adds latent heat automatically when the room temperature is below the product’s freezing point and shows it separately in the result.