Assessment of technological maturity parameters and anthocyanins in berries of cv. Sangiovese (Vitis vinifera L.) by a portable vis/NIR device

In grape berries the balance between technological parameters such as soluble solids and titratable acidity and phenolic maturity such as anthocyanins concentration, is a key factor for obtaining quality wines. Grapevine berries are commonly harvested on the base of technological maturity parameters determined by traditional analysis methods, often without considering properly phenolic maturity. We investigated the potential use of a portable and non-invasive device based on visible and near infrared (vis/NIR) spectroscopy (Cherry-Meter), which provides an Index of Absorbance Difference (IAD) based on two wavelengths peaks (560 and 640 nm), to measure soluble solids concentration (SSC), titratable acidity (TA), firmness (DI) and anthocyanins (total and monomeric) in cv. Sangiovese grapes. Berries were separated in ten IAD classes according to the Cherry meter data ranging from 0.4 to 1.8, and then analyzed for technological parameters and anthocyanins by using conventional methods. Linear and non-linear regression analysis showed that IAD values were significantly correlated to SSC (R2 = 0.92), TA (R2 = 0.87), DI (R2 = 0.89), and monomeric and total anthocyanin concentration (R2 ranging from 0.68 to 0.97). A Principal Component Analysis (PCA) was applied to analyze relationship among IAD classes, obtaining four different clusters based on increasing level of maturity defined by means of technological parameters and anthocyanins concentration. This is the first approach demonstrating that the use of IAD values obtained from Cherry-Meter could be useful for monitoring both technological maturity parameters and anthocyanin concentration and composition of grape berries.