Varietal purity of malting barley
Malting barley must be grown, stored and shipped in pure single-variety lots if top quality malt and beer is to be produced.
Barley varieties differ in their chemical characteristics during the malting process. They contain different levels of important enzymes and other characteristics that are critical for the maltster to produce high quality malt. When malting a particular variety, the maltster will adjust the processing schedule to suit each variety. When a lot contains either a wrongly declared variety or a mixed batch, the malting process is poorly regulated, over modification of the malt can occur and beer processing is affected.
Feed barley varieties are so declared because they are unsuitable for malting. They lack some of the critical enzymes that are required or have characteristics that make them unsuitable, such as high levels of beta-glucans that clog up the filters in the brewery.
Before sowing, ensure you know that your barley is pure and of the correct variety.
If visual cues are not enough then the grain will need to be tested at an accredited laboratory for varietal purity. The most common method used to determine varietal purity is based on mass spectrometry analysis of protein profiles in grains, but newer methods such as DNA microsatellites and DArT technology are also available and being used.
Testing
- AGWEST Plant Laboratories offer a mass spectrometry test that compares the protein profile of a combined sample or of 30 individual seeds or of 150 individual seeds. Those tests range from $135 to $694 to conduct. Higher levels of accuracy can be obtained by analysing more seeds, but the price also increases as more seeds are done. They also offer a DNA microsatellite test for $298.
Grain quality
Buyers of malting barley prefer grain that has a high germination rate, large kernel size, good hectolitre weight, correct protein level and bright grain with intact husk that is free of mould or weather staining. Feed barley buyers prefer grain that is clean, bright, plump with good hectolitre weight and low in moisture. Grain growers must produce barley with a high grain quality to receive the maximum price per tonne for their grain.
When producing malting barley there are some factors, such as seasonal conditions, that influence quality but cannot be controlled by growers. However, there are factors that growers can manage that will increase their chance of producing viable grain with the optimum grain size, protein and brightness that achieves the premium malting grade
Germination
Germination is the most important quality characteristic of malting barley. In order to be made into malt the barley grain must germinate. Grain with less than 98% germination is unsuitable for malting. During the malting process, maltsters germinate the grain under controlled conditions. The germination process is required to prepare the grain for brewing. Varieties of barley that cannot germinate are classified as feed. The germination of grain is not critical for feed barley.
Factors affecting germination
The factors that influence germination percentage are:
- Weather conditions at harvest - Wet conditions at harvest may initiate germination (pre-harvest sprouting). They may also induce secondary dormancy though the growth of mould and fungi and therefore delay the earliest time at which a variety is suitable for malting.
- Crop growth stage when harvested - If the crop is harvested before physiological maturity (before flag leaf and peduncle have turned from green to yellow), then the sample will have a large proportion of immature grains. These immature grains will have a much lower germination percentage than mature grains.
- Grain drying conditions - If the grain is dried to temperatures above 43C then the germination percentage will decrease.
- Grain storage conditions - Poorly stored grain can be subject to large temperature and moisture gradients which may affect the viability of the embryo and hence the germinative ability of the grain. In addition poorly stored grain is at greater risk of insect infestation.
Variety
Some varieties are more susceptible to weather damage at harvest than others due to their inherent dormancy and sensitivity to pre-harvest sprouting and should not be left standing in the paddock for too long after maturity.
Acknowledgements: This information comes from the 'Barley production in Western Australia' site, first compiled by Roslyn Jettner and Pam Burgess from contributions by officers of the Department of Agriculture and Food, Western Australia then updated in 2006 by Richard O'Donnell, Alaina Smith and in 2013 by Blakely Paynter.