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.