Determination of tocopherols and phytosterols in sunflower seeds by NIR spectrometry

The objective of this work was to develop a near-infrared reflectance spectrometry (NIRS) calibration estimating the tocopherol and phytosterol contents in sunflower seeds. Approximately 1000 samples of grinded sunflower kernels were scanned by NIRS at 2-nm intervals from 400 to 2500 nm. For each sample, standard measurements of tocopherol and phytosterol contents were performed. The total tocopherol content was obtained by high-performance liquid chromatography coupled with a fluorescence detector, while the total phytosterol content was assessed by gas chromatography. For tocopherol, the calibration data set ranged from 175 to 1005 mg/kg oil (mean value around 510 +/- 140 mg/kg oil), whereas for the phytosterol content, the calibration data set ranged from 180 to 470 mg/100 g oil (mean value of 320 +/- 50 mg/100 g oil). The NIRS calibration showed a relatively good correlation (R-2 = 0.64) between predicted by NIRS and real values for the total tocopherol content but a poor correlation for the total phytosterol content (R-2 = 0.27). These results indicate that NIRS could be useful to classify samples with high and low tocopherol content. In contrast, the estimation of phytosterol contents by MRS needs further investigation. Moreover, in this study, calibration was obtained by a modified partial least-squares method; the use of other mathematical treatments can be suitable, particularly for total phytosterol content estimation.