Measuring device for measuring a surface layer on an object to be measured, particularly on a foodstuff

A measuring device for measuring a surface layer on an object to be measured, comprising:

• a) at least one excitation source for exciting luminescence in the surface layer on the object to be measured that is to be monitored, so that the surface layer emits luminescent radiation, and
• b) at least one optical sensor for detecting the luminescent radiation which is emitted by the surface layer, and
• c) an evaluation unit for qualifying and/or quantifying at least one of the surface layer and the object and for generating a corresponding output signal,
• d) wherein the evaluation unit determines at least one of the following at peaks of the luminescent radiation:
• d1) a wavelength of each peak and a wavelength correspondence between, on the one hand, wavelengths of the peaks of the luminescent radiation and, on the other hand, given characteristic wavelengths, wherein the characteristic wavelengths are wavelengths of peaks in a fluorescent radiation of porphyrins, and
• d2) an intensity of each peak and an intensity ratio of the peaks of the luminescent radiation.