A Sound Way To Sort Out The Unopened Pistachios

28 November 2004


A bag of pistachio nuts always contains a few unopened specimens, largely because the process used to sort the open from closed nuts is far from perfect. But now a Kansas-based inventor, Tom Pearson, has come up with a sound way to separate the two - by creating a machine that can tell the difference between the noises made when opened and closed nuts clatter onto a steel tray. Unopened nuts make a shorter ringing sound when they drop onto the tray, compared with their open counterparts, and these unwanted specimens are blown away with a puff of compressed air. Capable of sorting 25 nuts a second, the new machine is slower than the existing technique, which relies on opened nuts being caught by a series of needles as they are spun in drum, but the new technique is 97% accurate, compared with 90% for the needle method. This could save companies up to half a million pounds a year, and a lot of frustrated customers !


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