The fermentation process that turns must into wine is traditionally monitored manually by enologists, with little aid from automation tools so far. This supervision requires the enologist to follow a daily routine consisting of must sampling and subsequent analysis at least twice a day during the whole fermentation span and for every single fermentation tank, which is awkward and time-consuming, especially in regions like La Mancha (Spain), where production takes place at a massive scale. In order to contribute to the automation of both the fermentation and the maceration supervision, an optoelectronic system has been developed. It was devised to record both the refractive index n and the chromatic characteristics of the fermenting must. The former, closely related to the fermentation kinetics, is obtained through measurements of a laser beam displacement; whereas the latter, which is essential for the maceration, relies on absorbance measurements in the visible spectrum. Additionally, the system measures the temperature, necessary to reference the data to 20°C. It comprises a frame that holds a laser diode, a PSD (position sensitive detector), three LEDs, six photodiodes and a temperature sensor, plus some conditioning electronics and a data acquisition board. Several fermentations have been monitored off-line with the reported system, reaching a resolution of 0.00046 RIU (refractive index unit). Data show a slight increase in n during the last stage of the fermentation, which does not have a match in the density measurements and could therefore be used as an alert to automatically detect the fermentation end.

Date Published: 17 May 2013
PDF: 11 pages
Proc. SPIE 8763, Smart Sensors, Actuators, and MEMS VI, 87630I (17 May 2013); doi: 10.1117/12.2016935

Published in SPIE Proceedings Vol. 8763:
Smart Sensors, Actuators, and MEMS VI
Ulrich Schmid; José Luis Sánchez de Rojas Aldavero; Monika Leester-Schaedel, Editor(s)