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Electronic tongue knows its Merlot from its Pinot Noir, tells you when to harvest


An electronic tongue created by a university and a local winery can tell you when your Chardonnay or Merlot vines are ripe for picking. 

A team from the Universitat Politècnica de València has been trialling the voltammetric tongue with the help of winery Torre Oria, using it to test the acidity and sugar content (measured in Brix degrees) of eight types of grapes used in wine making — Macabeo, Chardonnay, Pinot Noir, Cabernet Sauvignon, Shyrah, Merlot and Boba. The “tongue” itself consists of eight metallic electrodes housed in a stainless steel cylinder that help pick up the three main parameters used in wine making: Brix degrees, pH and Total Acidity.

Whether or not a grape is ready for harvest depends on what type of wine is being produced. Sweet wines, for instance, are one of the last to be harvested as they are left to ferment on the vine to increase the sugar content. It also depends heavily on the grape type. Merlot, for instance, has a high sugar content so needs to be harvested earlier so as to limit the fermentation process since the sugar levels will rise as the grape ferments, and the acidity levels will fall. Getting the balance right between these two levels is key to creating the wine with the right flavour, alcohol content and aroma.

Typically, these can be measured in a number of ways. A refracatometer can be used to measure the weight of sugar in a handful of grapes, while simple litmus tests can be used to measure pH levels. Measuring the Total Acidity, pH and sugar levels needs to be done onsite not back at a lab, for the sake of timeliness. Hence, the Valencia team believes its electronic tongue could be the solution as it’s both cheap and portable. 

“The latter is especially useful to assess the degree of ripeness as with current methods of analysis further assessment in a laboratory is usually required,” says Ramón Martínez Máñez, coauthor on a paper describing the technique published in Food Research International

The team measured the eight grape types over a period of one month in vineyards across Valencia. Statistical analysis of the measurements identified a strong correlation between the electrochemical data gathered by the tongue, and separate Total Acidity, pH and sugar content levels taken the ordinary way.

“These results suggest the possibility of employing electronic tongues to monitor grape ripeness and of, therefore, evaluating the right time for harvesting,” writes the team, which hopes to transfer the method to post-harvesting winemaking techniques as well. The balancing act does not end with the harvest, but continues as the wines are stored in vats for further fermentation. The correct temperature needs to be maintained — too high and the alcohol content will drop, too low and the tannins and colour will be sub-par — and all the usual measurements monitored on a daily basis.

“These devices allow performing a continuous monitoring of the process, which would result in greater control over the product, and ultimately an increase in competitiveness,” Inma Campos, a researcher working with Máñez, commented. 


A team at the Universtat Autonoma de Barcelona has already created an electronic tongue that, rather than telling you when the grape is ready, tells you which type of cava you have submerged its biosensors in. Another being developed at Washington State University can measure how metallic, savoury, sweet or bitter a wine tastes, and is currently working its way through 60 reds in the university’s labs. It’s a way off measuring the subtle differences in a wine as perceived by humans, such as the aptly named mouthfeel factor. Which is why the final marker at harvest is still a wine’s physiological attributes: the grower plucks it, has a feel, and sticks it in their mouth to apply their years of experience the old fashioned way.