The use of reflectance for monitoring phenolic maturity curves in red grapes

A new laboratory method is discussed for monitoring phenolic quality in grape during maturation in the vineyard. Spectroscopy on whipped grapes was used to determine an index of phenolic maturity (Phenolic Maturity Trend - PMT) derived from the elaboration of the reflectance signals from six light emitting diodes in the spectral range 525-880 nm. The PMT index allows the trend of the overall maturity of polyphenols in grape berries to be qualitatively defined in laboratory and supplies information equivalent to that obtained with the traditional methods used to identify polyphenols. Since the method does not require polyphenol extraction, many more analyses can be done daily.