An E-Tongue That Whines About Bad Wine

Vinophiles are well-known for their love and appreciation of the subtle qualities of fine wines. Accordingly, fault monitoring is a critical aspect of wine manufacturing that seeks to maintain high levels of quality and ensure that the final product meets the expectations of discerning consumers. Spoilage in wine can be caused by numerous factors like the introduction of microbes, including those from the genera Wickerhamomyces, Acetobacter, Lactobacillus, and Pediococcus. These microorganisms can lead to chemical changes in the wine that alter its flavor and aroma, often resulting in unpleasant tastes and smells.

These changes not only impact the sensory experience of wine but can also tarnish the reputation of the wine producer. Faulty wine can lead to customer dissatisfaction, damaged brand image, and substantial financial losses. Therefore, it is important for manufacturers to detect spoilage as early as possible to prevent contaminated products from reaching consumers.

However, there is a delay between the introduction of these microorganisms and any signs of spoilage that can be noticed by humans. This period can last several weeks, during which time the affected wine may be bottled, shipped, and even purchased by customers before problems become evident. This poses a major challenge for winemakers, as tainted products can hit the market despite their best efforts to detect them.

A big part of the problem is that the human senses of taste and smell are not able to detect the minute quantities of chemicals that appear in the earliest stages of contamination. For this reason, researchers at Washington State University have developed a different way to assess wine quality that relies on a sensing instrument referred to as an “e-tongue”. These instruments are equipped with an array of chemical sensors that can detect the presence of trace organic and inorganic compounds in liquids at very early stages of contamination.

In their work, the team leveraged an off-the-shelf Astree II electronic tongue unit that is commonly utilized to evaluate the taste fingerprint of liquids. They intentionally introduced four different microorganisms into a white wine, then assessed the samples after varying time intervals. The assessments were made both by the e-tongue and a trained panel of human experts.

The experiments revealed that the e-tongue could detect spoilage of the wine within a week. The humans, on the other hand, could net recognize the signs of spoilage until 35 days had passed — a full four weeks after the e-tongue. It was further noted that the e-tongue was even quicker to spot the microorganisms than was possible with a petri dish culture.

This study may not perfectly represent the ability of humans to detect spoilage, as the microorganisms were not prepared in a food-grade laboratory, so the inoculated wines were only assessed for aroma changes and not tasted. But in any case, the e-tongue proved to detect spoilage very early on, so it may have a bright future in wine manufacturing quality control. Looking to the future, the ability of the instrument to generate a chemical fingerprint of a wine batch might provide winemakers with additional insights to help them further improve their products.