Use of near infrared hyperspectral tools for the screening of extractable polyphenols in red grape skins

Abstract

Hyperspectral images of intact grapes were recorded at harvest time using a near infrared hyperspectral imaging system (900–1700 nm). Spectral data have been correlated with red grape skin extractable poly- phenols (total phenolic, anthocyanins and flavanols) by modified partial least squares regression (MPLS) using a number of spectral pretreatments. The obtained results (coefficient of determination (RSQ) and standard error of prediction (SEP), respectively) for the developed models were: 0.82 and 0.92 mg g-1 of grape skin for extractable total phenolic content, 0.79 and 0.63 mg g-1 of grape skin for extractable anthocyanin content, 0.82 and 0.45 mg g-1 of grape skin for extractable flavanol content. The obtained results present a good potential for a fast and reasonably inexpensive screening of the extractable poly- phenolic compounds in intact grapes. Moreover, the heterogeneity of extractable polyphenols within the ripeness stage has been also evaluated using the proposed method.