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 which will increase their chance of producing viable grain, with the optimum grain size, protein and colour, that achieves the premium malting grade.
This is the most important quality characteristic for malting barley. Grain with less than 98 per cent germination is unsuitable for malting. Barley that cannot germinate is classified as feed. Poor germination can result from overheating the grain during grain drying and inappropriate storage.
Importance of protein
Grain protein generally relates to the level of malt extract in the grain, affecting the operating efficiency of the malthouse and brewery. The higher the level of protein the lower the level of malt extract and the less alcohol that can be produced. In addition, beer made from high-protein malted grain can develop cloudiness and has a shorter shelf-life. Low protein is just as undesirable, reducing the stability of the beer head and cling of the beer foam to the side of the glass. Low protein also limits the growth of yeast during the fermentation process, hence the conversion of sugars into alcohol. The optimum protein for malting barley is 10- 11.5 per cent.
Factors affecting protein
Nitrogen supply from soil and plant residues and moisture during grain filling have the greatest effect on protein. N supply depends on
- soil type
- organic carbon levels
- crop rotation.Protein is also affected by
- sowing date
- nitrogen fertiliser
- seeding rate.Managing protein
- Avoid sowing after a long-term pasture phase.
- Avoid waterlogged soils.
- Maximise yield by targeting optimum
- sowing date and seed rate and minimising disease.
- Very early sowing reduces protein in highyielding situations.
- Avoid paddocks with very low nitrogen.
- Apply nitrogen fertiliser around seeding or before the end of tillering.How much nitrogen fertiliser is required? This depends on:
- supply of nitrogen from soil + plant
- rainfall and mineralisation
- target yield.
Importance of grain size
Plumper grain means more extract. Consistent grain size means a uniform rate of modification in the malthouse, and uniform milling in the brewery.
Factors affecting grain size and screenings
- timing of moisture supply during grain filling
- high temperatures after flowering
- to a lesser extent, plant density outside of optimum range.Managing screenings
- Select a soil type that allows moisture to be available during grain filling.
- Sow at the ideal time for maturity of variety.
- Manage leaf and root diseases.
- Achieve target plant density.
- Do not over-fertilise.
Importance of colour
Discoloured grain can indicate fungal activity. There is a strong market preference for bright grain.
Factors that cause staining:
- high humidity or moisture during late grain fill
- delayed harvest of crop after maturity.Managing staining:
- Match variety to sowing date.
- Harvest crop as soon as mature and at appropriate moisture.
Skinning results from over-threshing during harvest and excessive movement of grain during handling. Husk is important during all stages of processing. The husk protects the embryo during grain movement, surrounds the modified starch after malting, and is used as a filtration aid during brewing.
Growers interested in participating in a TOPACTIVE workshop should contact their local adviser. Advisers interested in running a TOP ACTIVE workshop should contact either Mark Stanley, PIRSA Rural Solutions, 08 8688 3400. email firstname.lastname@example.org; or Roslyn Jettner, AGWEST, 08 9892 8444, email Ijettner@agric.wa.gov.au.
More information about TOPACTIVE is available on the web site http://topcrop.grdc.com.au