A toasting appliance includes a toasting chamber, a heating element for heating a foodstuff located within the toasting chamber, an optical system having a first light source for illuminating the foodstuff with light having a first wavelength and an optical receiver for detecting light reflected from the foodstuff. A second light source is provided for illuminating at least the optical receiver with light having a second wavelength different from the first wavelength. A controller varies the intensity of the light emitted from the second light source during a toasting operation.