Setting up of simplified handheld optical systems to estimate ripeness of grapes and blueberries from Valtellina (SO, Alps region)

User-friendly devices could assist growers in the field in determining the optimal harvest date in accordance with the desired ripeness of berries. At the same time, simple devices in the oenological sector are important to support wine growers in monitoring ripening progress of grapes and to plan harvest time. In order to explore the technical feasibility of such a system, this study focused on defining simple ripeness indices for grapes and blueberries by identifying the main spectral changes accompanying their ripening process, with special attention paid to the last and most relevant stages. Non-destructive analyses were carried out on grapes and blueberries from Valtellina (SO, Alps region) using a portable commercial vis/NIR spectrophotometer. Measurements were accompanied by weekly samplings, with picked fruits divided into ripeness grades according to commercial growers’ classification. Chemometric analyses were performed in order to extract the maximum useful information from spectral data and to select the most significant wavelengths. Correlations between the spectral data matrix and the main ripening parameters were carried out. Regarding blueberries, three main wavebands are able to maximize the differences among fully ripe, close to ripeness or unripe samples. Therefore, spectral values at 680, 740, and 850 nm were used to create a blueberry ripeness index. Similar wavelengths were selected for grape: 670 nm, 730 nm and 780 nm. Principal component analysis and multiple linear regression were applied on the three wavelengths in order to verify their effectiveness obtaining good results. The results demonstrated the feasibility of a simplified, low-cost handheld device for ripeness assessment of grape and blueberries directly in the field and a possible functional scheme was proposed.