Thirty percent of all our food is wasted, for one thing because we store it incorrectly. For example, ripe fruit quickly rots if it is kept for too long. This is not a disaster if it happens at home, but if you are a fruit grower with a warehouse full of apples, pears and other fruit then you’ll want to keep the damage to a minimum. Happily, we are getting better and better at this, for example thanks to a device that measures the gases that fruit ‘exhales’. Frans Harren, associate professor of Molecular and Laser Physics at Radboud University, is an expert at measuring gas traces in the air. He and his colleagues have developed a promising prototype of just such a device.Frans Harren has been studying ways to measure traces of gases in the air for some twenty-five years. He does this using lasers in Radboud University’s Trace Gas Facility. “In the beginning we could only conduct measurements with large lasers and only in our lab. Now there are solid-state and fibre lasers available which we can use in mobile devices to carry out reliable measurements in the field,” he says. In a fruit grower’s cold store, for example.Harren and his colleagues developed a prototype of a mobile trace gas detector that can also be used to measure low concentrations of gases on location. This was not easy, because to make accurate measurements you need light that can measure a wide range of wavelengths simultaneously (the spectrum of an infrared lamp), but that also has the narrow focus of a laser beam. Fortunately, such white light lasers are now available. Harren and his colleagues used these to develop their trace gas detector. The device containing all the measuring equipment and lasers is no larger than a small refrigerator.The measuring system from the inside (above) and from the outside (below).Sleep stateThis measurement system has to provide feedback to the control system of the cold store. The Radboud researchers have now established QCAP (Quality Control of Fresh Agro Products), a project in which they are working closely with the company Storex (a large supplier of storage facilities for fruit and vegetables). ‘Controlled atmosphere’, says their logo – because that’s what it’s all about. “Fruit is stored under low temperatures, low oxygen levels and controlled CO2 concentrations,” says Harren. “This is what allows you to store apples all year round. You want to put them in a sleep state and keep them in that state for as long as possible, so that they ‘breathe’ as little as possible (hence the low oxygen) and do not ripen, ferment, rot and lose moisture.”Not all apples are alike, however: the time of picking and the field they grew in can influence the optimal storage conditions of different batches. This is why a fruit grower wants to be able to monitor and adjust the conditions in storage. But how do you go about that? “One of the project’s advisors is a potato farmer, and he related how he would walk through his storage sheds and test the condition of the potatoes with his nose,” says Harren. “We’re actually doing the same thing – only in a much more sophisticated way.”The trace gas detector measures the gases that the fruit releases very precisely and without the need to open a door or hatch, which could upset the delicate balance in the cold store. The detector measures ethylene, ethanol, acetaldehyde, methanol and acetone, among others. The degree to which these gases are present reveals the state of the fruit: ethylene is released at the first signs of ripening, which are often still invisible to the eye. Ethanol and acetaldehyde are released during fermentation, and methanol and acetone are a sign of rotting.Commercial application“We have built two prototypes which we are currently testing extensively in fruit testing stations in northern Germany and Belgium,” continues Harren. “We’re also going to run a test on potatoes in England.” If all goes well, the next step will be a commercial application. “On average, a fruit grower in Europe loses €60,000 a year on unsalable goods. We will have to come up with something that will pay for itself within one or two years.”QCAP was established with the support of Interreg, a European programme dedicated to spatial development and cross-border cooperation in Europe.