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Scientists invent a sniffing method to detect rotten avocados

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A team of UK scientists are working to invent a type of portable sniffing device that can detect whether avocados are rotten without breaking the skin and damaging the fruit – ensuring customers do not buy fruit that is already past its best.

Avocados are fashionable, very nutritious, and have a high commercial value worldwide. But the fruit must be eaten at just the right time because it can go off very quickly, creating a lot of expensive waste.

This is because the fruit is prone to developing various disorders in the flesh, such as fungal decay, grey pulp and vascular browning. The main problem with these internal disorders is that it is not possible to detect them from the outside – which leads to many unhappy consumers.

The likelihood of various flesh disorders occurring in avocados is estimated to be as high as 15-20%, or every 1 in 5 fruit, which equals to around £40 million worth of poor quality fruit being thrown away every year in the UK alone – and around £1.5 billion globally.

But now, a multi-disciplinary research team is working on developing a high performance machine, which will be able to detect these disorders in avocado using its aroma. The research project has been funded by the UK STFC Food Network+ and it is applying a mixture of new and well-known scientific techniques to try to address the challenges of the global food supply chain. The team has identified a range of chemical markers that indicate whether the fruit is of poor quality. Ultimately, based on the heritage of developing instruments for space missions, the aim is to develop affordable, portable devices that can identify these markers and can be used by anyone at all stages in the value-chain.

The lead scientist, Dr Marcin Glowacz, a Post-Harvest Technologist at the Natural Resources Institute/University of Greenwich, said: “If these poor quality fruit could be identified prior to reaching the consumer they could be used for other purposes, for example in new product development and so reduce any negative environmental impact, rather than entering the market. Removing them from the supply chain before they reach the consumer would also have a positive impact on society, i.e. changing consumer behaviour so that people do not have to worry so much about the internal quality of the fruit, especially considering its premium price.”

Dr Glowacz is developing this new sniffing technology by working with space instrumentation expert Dr Geraint Morgan and his analytical colleagues Dr Simona Nicoara and Dr Sonia Garcia-Alcega of The Open University.

In partnership with the UK’s RAL Space research and technology facility, Dr Morgan was part of the team at The Open University that developed the Ptolemy instrument for the European Space Agency’s Rosetta mission that landed on a comet in 2014. Ptolemy was a shoe-box sized gas analyser that confirmed that the ‘building blocks of life’ are present on comets by sniffing and analysing the gases given off by it. Lessons learnt from this and other space missions will be applied to help to develop the avocado sniffer.

Preliminary results are promising and suggest that the detector would be sensitive enough to separate and detect numerous compounds and thus able to profile the differences between avocado fruit of different ripening stages and those with these disorders.

A longer-term experiment will need to be carried out to gather more statistically relevant data to build on these findings.

Dr Morgan, who works with Dr Simon Sheridan of Applied Science and Technology Solutions Ltd to commercialise his space technology research, said: “It is our theory that once the marker compounds associated with these flesh disorders are identified, it should be feasible to develop a small, robust, low power, portable system – based on the lessons previously learnt from the development of the Ptolemy instrument on the Rosetta mission – that is affordable and fit for purpose for the food industry.”

Find out more about the other projects being supported through the Food Network here.

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