Japanese drinkers seek a pearler of a barley
By Chris Greenwood
One of the most popular alcoholic drinks in Japan is a spirit known as shochu. It is a fermented and distilled spirit with an alcohol content of about 25 percent, and is produced from barley.
At the University of Adelaide, a joint GRDC/SA Grain Industry Trust funded research project at the School of Agriculture and Wine is investigating the cultivation of barley in Australia for use in shochu.
Photo: Lucrative market: shochu is an opportunity for Australian barley growers.
Australian barley growers have an opportunity to tap into this lucrative market and the research is attempting to establish the critical management and quality factors to help them do this.
Before shochu production, the barley is pearled (the outer layer removed) to allow the penetration of a special mould, "koji", which begins the process of enzymatic conversion of starch to sugars, thus allowing yeast fermentation.
Pearling quality is therefore very important in determining shochu quality, and inferior-grade barley can significantly reduce financial returns to the processor.
Since grain uniformity is a key quality trait for the pearling of barley, it is crucial to know how management factors can influence this quality trait.
Barley destined for the shochu market in Japan needs to meet a minimum malting grade 1 specification (see Table 1).
The management of varieties to achieve malting quality is well established, but grain uniformity (hardness, size and weight) is not a key specification for malting quality.
The varieties favoured by shochu producers are Schooner from SA and Stirling from WA. Each variety imparts a unique flavour to the final liquor.
The value of this market for the malting barley industry in Australia has been recognised with specific segregation at selected grain receival facilities on the Yorke and Eyre peninsulas for Schooner that meet the stricter quality requirements.
In addition, growers are being encouraged to continue to grow superior-quality Schooner in these areas through a premium of approximately $12 a tonne over malting grade 1. So far, the main conclusions of the research, carried out by Dr Nigel Long and Jenny Washington, are that barley grain hardness and uniformity are influenced by both genetics and environmental factors.
Uniform or synchronous tillering is likely to be a key to improving the grain uniformity of barley for pearling.
Pearling quality is strongly influenced by environmental conditions, so preliminary results from studies in 2002 are difficult to interpret, given the drought conditions in that period.
The general advice for growers is to maintain management systems that aim for malting quality.
The researchers note that to improve grain uniformity without compromising shochu and malting quality, the impact of nitrogen management regimes and seeding rates on tillering and tiller development needs to be further evaluated.
Advanced breeding lines from the South Australian barley breeding program (Waite campus, University of Adelaide) and the Victorian barley breeding program (Victorian Institute for Dryland Agriculture) are in the process of being analysed for pearling quality and hardness.
For more information:
Dr Nigel Long, 08 8303 7286, and Jenny Washington, 08 8303 7456, School of Agriculture and Wine, Faculty of Sciences, University of Adelaide
GRDC Research Code: UA00030 (2002-2005), program 1
Later seeding and the subsequent delay in flowering significantly reduces uniformity. Later flowering means that grain filling proceeds when moisture is more limiting and temperatures and evaporative loss is increasing. Consequently, the duration of grain filling is reduced, significantly affecting grain yield and resulting in smaller grain and poorer uniformity. Starch deposition is impaired, and grain protein is higher and may exceed malting and shochu specifications.
Current advice for malting barley is to aim for 70 percent of grain yield potential and a protein content of eight percent. At this stage there is no evidence to suggest that nitrogen management for shochu quality should be any different.
Crucial because of grain protein considerations for growing barley for malting and/or shochu. Paddock selection should be based on historical grain protein records, with areas traditionally producing lower protein grain ideally suited for shochu/malting quality.
Typically, barley is 1-2 percent higher in grain protein than wheat under similar management conditions.
A disciplined monitoring program and a timely and appropriate treatment response will minimise the loss of yield potential and quality.
In the study there was nothing to suggest current practices undermine grain uniformity, therefore aim for 145 plants per square metre, which is the recommended density for barley in most areas of SA. However, too low a seeding rate may lead to over-tillering.
Variation in grain hardness between tillers contributes most to the variation in grain hardness, rather than variation within the ear of tillers.
Environmental factors conducive to good shochu and pearling quality are the same as for good malting quality. Moderate temperatures and good rainfall during grain filling, and soils with good moisture-holding capacity, favour improved grain uniformity.
There is evidence to suggest that late seasonal rainfall may adversely affect grain hardness, and therefore pearling quality, even though visual pre-harvest sprouting has not occurred and germination was not affected (see graph below).
The effect of total November to December rainfall (mm) on pearling quality (sound kernels) of Schooner over four diverse environments and four seasons (two reps each). The sound kernel measurement is calculated from the plump (>2.0mm) unbroken kernels remaining after pearling.