VIS-NIR wave spectrometric features of acorns (Quercus robur L.) for machine grading

The study is intended for engineers and small-scale forestry owners because it offers a simple solution for acorns quality improvement by machine grading before sowing. Visible diffuse reflectance spectra of single whole acorns (Quercus robur L.), damaged acorns, acorns pericarp, whole and damaged acorn seeds were scanned with spectrometer USB 4000 (Ocean Optics Inc., USA) from 450 to 900 nm at 1 nm intervals. Near infrared reflectance spectra of single acorns material were scanned with spectrometer NirQuest512 (Ocean Optics Inc., USA) from 900 to 2100 nm at 1 nm intervals. English oak acorns cannot be divided from damaged acorns and acorns pericarp in the visible wavelength range. Hard-to-release damaged acorns with shell cracks are eliminated in the NIR-reflectance at a wavelength range from 1400 to 1500 nm or from 1900 to 2000 nm. After the elimination of damaged acorns, good whole acorns can be grading from the acorns rotten seed and acorns pericarp (only one the inner side of a shell) at a wavelength range from 1600 to 1700 nm. The results of this study are limited to these specific samples and cannot be interpreted for acorns of all Quercus species. (paper)