Anthocyanin Assessment During Grape Reception In Winery Using a Fluorescence Optical Sensor.

Grape block selection at harvest is a matter of great interest for winery to optimise their wine production. Indeed, the grape quality characterisation during reception would allow choosing in real time the best winemaking process for each grape container. Moreover, it can help winery to remunerate viticulturists according to reliable criteria. Nowadays, grape block assessment is mainly based on vine development, cultural practices and technological maturity. For red varieties, the grape phenolic maturity is little taken into account. However, anthocyanin content is an important criterion which contributes to sensory characteristics of wines, particularly in terms of colour. Phenolic maturity depends on the environmental conditions of the year such as irradiance, temperature or water availability. Anthocyanin content among blocks can thus vary extremely. Recently, a non-contact hand-held optical sensor, the Multiplex^®, was introduced to estimate anthocyanin content on grapes in less than a second. The measuring principle of this device is based on the chlorophyll fluorescence screening method.

The aim of the present study was to characterise 1700 grape containers belonging to the winery of “Union de Producteurs de Lugon” during the 2009 grape reception according to their anthocyanin content thanks to the use of the Multiplex sensor. The container content characterisation obtained with Multiplex allowed us to fill in real time 6 fermenters with two different anthocyanin potentials: low or high. At the end of alcoholic fermentation, the anthocyanins content and the color intensity of the six fermenters were analysed. The 3 fermenters with a high anthocyanin potential determined by Multiplex showed as expected higher content in anthocyanins (+15%) and the color intensity was also more important (+ 26%).

This fast approach will allow wineries to identify in a few seconds the anthocyanin potential during grape reception to determine its best winemaking process.