Effects of Radiant Characteristics of Heaters on Crust Formation and Coloring Processes of Food Surface

Studies on Radiative Heating Condition of the Food Part I

Abstract

Under the fixed heat flux condition of radiative heating, the effects of radiant characteristics of heaters on crust formation and coloring processes at surfaces of white bread and wheat flour batter have been evaluated using five heaters of different kinds. The radiative heat flux from the heater to the sample surface was maintained constant throughout the experiments to examine the combination effects of the wavelength characteristics of the heaters and the absorptivities of tested foods for radiant heat. Results showed that the crust formation and coloring rate were dependent on the wavelength characteristics of the heater used, and that the radiant heating with shorter wavelength led to a greater heat sink into the food samples forming the relatively wet crust layers compared with the dry layers formed by heating with longer wave. The coloring rates with the infrared heaters emitting the longer wave were faster than those by the shorter one because of the greater increasing rates of temperature at the food sample surfaces. These results confirmed that both crust formation and coloring rates at a heated food surface were mainly interpreted in terms of the variation of wavelength characteristics of radiant heaters.