Electronic Nose Measures Ripeness of Fruit

Summer’s a fine time for picking mangoes, but choosing ripe ones can be difficult—whether you’re a consumer or a food service plant selecting mangoes for processing. However, this summer—thanks to scientists at the U.K.’s University of Leicester—we’re a lot closer to being able to determine ripeness scientifically.

According to research published in the journal Metabolomics, the University of Leicester’s scientists have developed a process for what they call “real-time profiling of mango ripening” using an “electronic nose” to sniff out mango ripeness. By measuring volatile organic compounds in the “headspace” of the fruit, and noting the increase of ester compounds (which smell like pear), they were able to tell whether a mango was ripe without touching or tasting it.

Lead scientist Professor Paul Monks, of the Department of Chemistry at the University of Leicester, says “There is the potential to rapidly scan individual fruit for ripeness in a non-invasive way. We have already been contacted by three major fruit operations interested in how they could use the ideas, so there has been interest out there.”

While Professor Monks says the relation between volatile compounds and ripeness was already known, “the innovation we brought to the table was in terms of looking at ripening as a dynamic process and using technology that allows the translation of the biomarkers [through] small e-nose type devices that would allow it to translate into the commercial sphere.”

The work of Professor Monks and his team follows the development of an e-nose called the zNose, which was used in experiments to identify melon ripeness. Simona Vallone, PhD, who studied the zNose project, noted in 2012 that mangoes were similar to melons in that their skins do not reliably indicate ripeness. Professor Monks and his associates’ paper notes that their development could work in concert with existing research into “headspace analysis,” such as that using the zNose, while also updating that analysis to recognize that the patterns that indicate fruit ripeness are subject to distinct changes over time.

Professor Monks suspects that the discovery will soon prove enormously beneficial to fruit wholesalers, who wish to be able to consistently deliver ripe fruit to store shelves.

“Mangoes are one of the most important and popular tropical fruits, with India producing approximately 40 percent of the world’s supply, notes Professor Monks.

The U.K. alone imports more than 60,000 tons of mangoes—representing revenues of over $100 million. In that kind of market, the capacity to predict and identify ripeness counts a great deal. One possible result that the study imagines is that “small, handheld electronic noses” could be employed in fruit picking operations to “determine the optimum point to harvest mature, green mangoes.”

“The signatures we have at the moment are for a given cultivar of mango and different cultivars have different signatures,” says Professor Monks. “Having said that, I think that it would be possible to train a device with a range of signatures to detect ripeness.”

However, the University of Leicester’s team believes the usefulness of the “electronic nose” extends well beyond the produce aisle. Professor Monks has been working for some time on a project to “explore breath analysis as a medical diagnostic”—a process that he says means the work he and his team have made on using the “nose” to identify mango ripeness in fact stretches much further, all the way “from fruit to your personalized health.”