High-resolution low-cost optoelectronic instrument for supervising grape must fermentation

In a globalized world, the quality–cost ratio for wine is a key factor for winemakers in order to be competitive. Therefore, the fermentation process of grape must should ideally be continuously supervised to achieve a wine that meets the expected quality standards, avoiding undesirable states which may contribute to raise the cost. However, the traditional procedure followed by winemakers to monitor the fermentation process is not automated as winemaking is monitored manually by enologists, who must extract and analyze fermenting must samples at least twice a day from each fermentation tank during the whole fermentation process. An optoelectronic device has been developed in order to contribute to the automation of the wine fermentation process. It is capable of measuring both the fermentation kinetics and the maceration of wine during the whole fermentation by means of refractometric techniques and absorbance measurements in the visible spectrum, respectively. Moreover, as the refractive index is not measured by enologists during the fermentation (they rely on density measurements instead), it has been validated as an indicator for monitoring the fermentation kinetics according to both predictions derived from analytical calculations and from experimental data obtained in several fermentations with the optoelectronic device and other analytical techniques. The system consists of a laser diode and a PSD (position sensitive detector) for refractive index measurements, LEDs and photodiodes for color measurements, and a temperature sensor useful to reference the data to 20 °C. It also comprises a frame holder, some conditioning circuits and a data acquisition board.