TWIST TEST FOR MEASURING FRUIT FIRMNESS

A new test for measuring in-situ crushing strength of flesh of a range of fruits and other crops is described. The device consists of a blade on a spindle, which is pushed into the fruit and rotated about the axis of the spindle. The resisting moment is measured by an offset arm arrangement. The tester can measure fruit properties in-situ at any depth, including the core of the fruit. This has advantages for fruit that ripen from the centre, or where internal properties are more important than those close to the surface. Each full test can be completed in under 15 s. The tester is easier to use and more reliable than a conventional penetrometer. Some typical experimental results conducted on kiwifruit and apples harvested at various stages of growth and maturation are presented.