The near-infrared (NIR) transmittance spectra of flue cured tobacco (Nicotiana tabacum L.) in various physical states have been obtained. The spectra have been discussed with reference to moisture content, leaf thickness, brown pigmentation, and certain dynamic spectral characteristics. Apparent absorption caused by light scattering was found to be a function of leaf thickness. Brown pigmentation influenced the NIR spectra only in the short wavelength region from 0.6 to 1.3 µ. The primary difference between cured and yellowed tobacco was the intensity of the water absorption bands, with the yellowed leaf exhibiting the strongest band due to its higher moisture level. In addition to strong water absorption bands, the spectra of green leaves have a chlorophyll absorption band at .675 µ. The time dependent behavior of the spectra during curing was discussed with reference to developing analytical instruments for monitoring certain optical attributes of the leaf.

(Full article published with kind permission from "Tobacco International")