Developing a handheld NIR sensor for the detection of ripening in grapevine

It has already been proven that near infrared (NIR) reflectance spectroscopy can be used to measure the maturity of grapes by the determination of the sugar and acid content. Until now, winegrowers frequently collect a random one hundred berries sample per plot, to measure these parameters destructively for the estimation of the ideal harvest time of the gained product. Meanwhile, inexpensive sensors are available, to build convenient instruments for the non-destructive, low-priced and fast control of ripening parameters in the vineyard. For this, a small handheld device including a NIR sensor (1350nm – 2600 nm) was built from a Raspberry Pi 3 single-board computer and a NIR sensor. Spectra of individual berries, sampled from Riesling (Vitis vinifera, L.) were collected. Corresponding reference data were determined with high performance liquid chromatography (HPLC). Samples were taken from different fruit as well as cluster zones and from the beginning of v´eraison until after harvest, to ensure a broad range of ingredients and the ripening properties of different berries from the vine. This study is the first that systematically investigates the ripening parameters of a whole vineyard with a handheld sensor. The sensor can be used in viticulture practice to detect the ripening progress and determining the ideal harvest time effective, simple, and nondestructively.