Analysis of total glucosinolate content and individual glucosinolates in Brassica spp. by near-infrared reflectance spectroscopy

This study was conducted to lest the applicability of near-infrared reflectance spectroscopy (NIRS) for estimating the total glucosinolate (GSL) content in samples of intact seed from a wide range of Brassica species, and to develop calibration equations to estimate simultaneously the percentage of individual GSLs. A total of 290 samples from 15 different Brassica species were scanned by NIRS and analysed for glucosinolate content by high-pressure liquid chromatography (HPLC). A calibration equation for total GSL content was developed using 270 samples of 14 species in a range between 6 and 193 mu mol/g seed, resulting in an r(2) of 0.99 in calibration and cross-validation, and 0.95 in independent validation with 20 samples of Brassica rapa, a species not represented in the calibration. Furthermore, calibration equations to estimate the relative amount (mol/mol) of progoitrin, sinigrin, and gluconapin were successfully developed (r(2) > 0.85 in cross-validation) and validated with samples from species not included in the calibration. It was also possible to discriminate between entries with high and low values of glucoiberin, 4-hydroxyglucobrassicin and glucoerucin.