Australian Stonefruit Grower Magazine Issue 2 August 2016 | Page 36
Research
The DA-Meter, from
theory to practice
By Christine Frisina and
Dario Stefanelli
DA-Meter
technology will
increase consumer
satisfaction as a
result of consistent
fruit maturity.
T
he DA-Meter is a new technology that provides a rapid non-destructive method
for assessing fruit maturity from orchard to market. Being non-destructive,
the DA-Meter can monitor fruit maturity as it develops in the orchard to predict
the optimum harvest date. Different maturity classes can be identified to optimize
harvest timing to supply local and export markets of choice. In the packhouse, it will
be possible to grade fruit according to its shelf life potential. Overall, the DA-Meter
technology creates increased consumer satisfaction resulting from the supply of fruit
with consistent maturity.
The DA-Meter uses spectroscopy to measure chlorophyll ‘a’ in the mesocarp
(just below the skin) of the fruit through the difference in absorbance between 670
and 720 nm (index of absorbance difference, IAD). The best way to determine the
physiological maturity of the fruit is to correlate IAD values with the fruit ethylene
production rate. The correlation between the IAD and ethylene is cultivar dependent,
but once the correlation is performed correctly, the resulting maturity classes should
be independent of factors such as location, agronomical practices and growing season.
These factors will influence the date in the growing season at which the fruit will reach
a certain value but the relative ethylene production at the specific IAD value will not
change.
Calibrating the DA-Meter for optimal maturity
determination
The main challenge in determining fruit maturity classes is the correlation between
IAD value and ethylene production as it requires sophisticated instrumentation,
such as a gas chromatograph (GC) to measure ethylene. In general, this equipment is
only available in fruit research laboratories. However, the correlation with ethylene
production and the identification of the maturity classes is fundamental to the use of
DR DARIO STEFANELLI
is is Team Leader at Fruit
Physiology, Agriculture
Research Division, Victorian
Department of Environment
and Primary Industries.
He can be contacted on
03 9032 7373 or via email:
[email protected]
the DA-Meter and if not done will reduce the accuracy and effectiveness of the DAMeter.
To enable owners of DA-Meters access to ethylene analyses, DEDJTR scientists
developed a procedure for the collection of ethylene produced by the fruit that
can then be sent to a central laboratory for measurement with GC (see video:
Introduction to Ethylene Sampling for Optimal Ripening Prediction with DA
Meter and the ethylene sampling protocol below). The procedure uses preevacuated vials for the easy and rapid collection of ethylene samples from fruit.
Growers and other handling chain participants can collect the ethylene and ship it
to a DEDJTR laboratory for analysis. Central processing of the ethylene samples
36
Australian Stonefruit Grower | august 2016
summerfruit.com.au