Water Distribution in a Bread under Toasting by Radiative Heaters

Distribution of water concentration in a bread under toasting by radiative heaters has been studied experimentally and the effects of the radiative characteristics on it has been discussed. A white bread was employed whose water content was 45.0%. Three kinds of electric heaters, whose radiative characteristics were different each other, were used. After toasting of predetermined period, the bread was divided by three parts; the crust layer, the upper half part of the crumb, and the lower half part of the crumb. The water content of these parts were measured by a constant pressure drying method. The experimental results show that as the toasting time is increased, the water content of upper and lower parts of crumb decreases, takes a minimum, increases, and then goes beyond the initial water content of the bread. In this process, the water content of the upper part changes faster and the extent of value change is larger than that of the lower part. The radiative characteristics of the heaters affects the water distribution history in the bread. If the bread is toasted by the heater with longer wave length, the water content both of crumb parts becomes higher, and the difference of these values are larger.