To clarify the reason for the effectiveness of radiative heat transfer in the color development of a food surface, the heat-receiving rate of food was compared with that of metal.
Cookies and iron plates were heated at 200°C with two heat-transfer modes : radiative (RAD) and convective (CON). The moisture loss of the cookies and the surface temperature of the iron plates were measured to calculate the heat-receiving rate. The results show that the heat-receiving rate of a cookie heated with RAD was higher than that of a cookie heated with CON and of an iron plate heated with either mode. To clarify this phenomenon, the emissivity of the cookie's surface was measured. The emissivity did not change as the baking time progressed, and therefore had no influence on the effectiveness of the radiative mode.