Evaluation of quality and nutraceutical content in blueberries (Vaccinium corymbosum L.) by near and mid-infrared spectroscopy

Blueberries (family Ericaceae; genus Vaccinium corymbosum L.) are interesting fruit for potential 2 health benefits due to their bioactive compounds (anthocyanins, flavonoids, polyphenols and 3 ascorbic acid). The blueberry quality indices and nutritional properties are generally determined by 4 instrumental techniques (LC-MS; HPLC) that are time and chemical consuming, laborious and 5 expensive. 6 The aim of this work was to examine the potential of MIR and NIR spectroscopy to evaluate both 7 ripening indices and nutraceutical properties of two cultivar of blueberries, (‘Brigitta’ and ‘Duke’) 8 grown in Valtellina (northern Italy) harvest 2005 and 2006, collected weekly from mature green to 9 full ripe berry. Fruit from each ripening class was analysed for total soluble solids (TSS), total 10 phenols, total flavonoids and total anthocyanins, ascorbate and spectroscopic analysis, such as FT- 11 IR and FT-NIR. The spectral datasets were correlated with technological ripening parameters and 12 with nutraceutical compounds by using Partial Least Squares (PLS) regression algorithm both in 13 full cross validation and test set validation. The PLS analysis for quantitative prediction of TSS 14 gave good calibration models in near (RMSECV=0.50% and RMSEP=0.65%) and mid infrared 15 region (RMSECV=0.30% and RMSEP=0.36%). The calibration models developed in near infrared 16 region were able to evaluate the content of total phenols (RMSECV=0.14 mg catechin/g and 17 RMSEP=0.18 mg catechin/g), total flavonoids (RMSECV=0.20 mg catechin/g and RMSEP=0.25 18 mg catechin/g) and total anthocyanins (RMSECV=0.25 mg malvidin/g and RMSEP=0.22 mg 19 catechin/g). The models developed in medium infrared region proved to be well correlated with 20 analytically determinated phenolic compounds. The predicted results by the regression models 21 developed for ascorbic acid in near and mid infrared region were not as good as those obtained for 22 the phenolic parameters. 23 3 On the whole, near and mid infrared spectroscopy gave promising results as they were rapid and 1 non destructive methods to evaluate at the same time, technological ripening indexes and 2 nutraceutical compounds of blueberries. These techniques could be valid and simple tools to reduce 3 the analytical time and cost of monitoring blueberry quality.