Innovative sensor monitors fruit cargo

A sensor developed at Switzerland-based research facility Empa looks and acts like a piece of fruit – but is actually a spy. Empa is looking for investors to bring the product to market at a price of less than CHF50 a sensor.

In a news release Empa noted that fruits can quickly perish, with the refrigeration inside cargo containers not always guaranteed and existing methods for measuring the temperature not sufficiently reliable.

Despite frequent inspections some fruit is damaged or may even perish during a journey. Although existing sensors measure the air temperature in the freight container, it is the core temperature of the individual fruit that is decisive for the quality of the fruit, said Empa. Previously it had only been possible to measure the core temperature by inserting a sensor through the skin and into the centre, but this could be unreliable if a fruit was taken from the top of the container, because fruit that is closer to the outside of the transport container is better refrigerated than fruit on the inside.

Empa said that sometimes whole container loads had to be destroyed because the temperatures on the inside of the container did not meet the prescribed guidelines. “The USA and China, in particular, are extremely strict regarding the importation of fruit and vegetables,” said Empa, adding that “if the cargo has not been stored for three weeks at a certain minimum temperature, it is not authorized for sale in either of these countries. Refrigeration maintains the freshness and quality of the fruit; it also kills any larvae which can nest in the fruit. It is therefore essential to prove that the refrigeration has actually penetrated all the fruit in the whole consignment for the required period of time”.

Empa’s artificial fruit sensor is the same shape and size as the relevant fruit and also simulates its composition. It is packed in with the real fruit and travels with it. On arrival at the destination, the data is extracted from the sensor. From this, the researchers hope to gain information about the temperature during transportation. In insurance terms this is important information because it might help assign liability in the case of mass spoilage. The sensor can be used to establish the point in the storage and transport chain at which something went wrong.

Project leader Thijs Defraeye from the Laboratory for Multiscale Studies in Building Physics said: “We analysed the sensors in the Empa refrigeration chamber in detail and all the tests were successful”. However, the same sensor does not work for all fruits. “We are developing separate sensors for each type of fruit, and even for different varieties.” There are currently separate sensors for the Braeburn and Jonagold apple varieties, the Kent mango, oranges and the classic Cavendish banana.

A desirable feature would be to be able to receive the data from the cargo container live and in real time, so that appropriate countermeasures could be taken in the event of abnormal data – thereby potentially saving the fruit cargo. That would require a wireless or Bluetooth connection. “However, our current fruit sensor cannot do that yet. And the price of the product would, of course, go up,” said Defraeye.