The DA meter is an instrument that, by means of absorbance properties enables measurement of the chlorophyll content in fruit. The chlorophyll content is a precise index of the fruits ripening state, is very accurate and is not affected by any environmental factors.
Fresh fruit orchards and pack houses have used the DA meter to better understand fruit ripening in the field and enabled growers to better grade fruit on ‘maturity’ rather than just colour as is currently the case. Fruit can be more reliably separated into three categories, namely: ready to process, ideal for short term storage, ideal for long term storage. Each variety has a specific ripening pattern and requires calibration for the unit to be used effectively. For peach processors the DA meter offers the opportunity to better understand the maturity of fruit in the orchard to better manage picking times, then to differentiate fruit into maturity categories once in the factory to prioritise processing based upon maturity to maximise processed fruit yield. The operation of the DA meter is now well understood as described in: ‘A new Index based upon spectroscopy to characterise the progression of ripening in peach fruit” Post Harvest Biology and
Technology 49 (2008) 319-329. Units are now commercially available in Australia for use on some fresh fruit cultivars. No work has been completed for canning peach varieties and to become effective a separate calibration and development of the specific DA index for that variety needs to be done. Absorbance properties vary for individual fruit varieties but once the initial calibration is completed the DA index can be applied for this variety in subsequent seasons without the need for re-calibration.