Measuring Weather Damage in Grain
Rainfall events just prior to harvest can stimulate grain to germinate or sprout while still in the head. This act of germination causes an increase in enzymes, such as alpha amylase, that break down starch and proteins, the natural biochemical process of a seed mobilising its starch energy reserves. Of the various enzymes produced, the starch degrading enzyme, α-amylase has a greatest effect on reducing the physical quality and functional properties of the grain and of products made from the grain.
The further along the germination process the grain has travelled (amount of sprouting) the greater the amount of amount of α-amylase formed. If badly sprouted wheat is milled, the flour can cause product problems such as sticky, doughy bread which won’t slice in mechanical slicers, or noodles which are too stretchy and lack firmness. The quality of malting barley can also be severely affected by sprouting. Partial sprouting of malting barley reduces the evenness and vigour of the seeds, crucial characteristics needed for the malting process.
Weather damaged grain is segregated when delivered to grain receival points and is usually only sold on for use as feed grain. Farmer are severely penalised in terms of price for delivering weather damaged grain with the differential between milling grade and feed grade potentially 50% of the value.
The extent of weather damage to wheat is usually measured via a method call Falling Number, details of which can be found here. The Falling Number test has been controversial for the grain industry despite being the accredited and accepted method. This is because of the perceived lack of inconsistency of results and between machines, as well as the large number of other factors that influence the results. The current testing methods do not correlate well with the effect that weather damage has on the end user (the baker or noodle manufacturer).
In any one season at least one region of our grain belt suffers from a late season rain event and subsequent weather damage. Falling Number machines are usually sent to the grain depots in these districts when weather damage is suspected.
A rapid test which can be used by growers to measure rain damage before harvest, so as to avoid pockets of badly damaged grain, or to segregate weather damaged grain on farm, would be an ideal outcome. The test would need to be repeatable, cost effective and correlate with the effects of weather damage on end-products of the grain (for example flour, bread, noodles).
Between 2003 and 2009 the GRDC invested significant funds in the search for a replacement for the Falling Number machine. A number of avenues were examined including Infrared spectral analysis, enzyme assays and physical grain characterisation. To this point no success has been achieved using any of these techniques. A new technology able to be used at receival points that accurately predicts the likelihood the grain will display weather damaged characteristics later in the value chain is needed.