Application of photoacoustic spectroscopy to the optical study of pigments in corn pericarp: spectral separation of optical absorption centres

The optical absorption centres in corn pericarp biopolymers have been studied by photoacoustic spectroscopy and the phase-resolved technique. The results show that the optical absorption spectra of these samples are formed by the superposition of two absorption bands, one of these corresponding to the cellulose of the epidermis and the other to o-glucoside pigments of flavonoid type which are bound to hemicellulose sugars. A spatial separation was obtained of the materials responsible for these absorption bands as a function of the Ca(OH) 2 concentration used in the alkaline cooking process which is the result of hemicellulose dissolution in these biopolymers.