Malting Barley Quality Specifications
Malt is an important ingredient in beer that provides a source of starch and enzymes necessary to produce fermentable sugars which yeast then turn into alcohol. Malt also provides color, flavor, an foam compounds which contribute to the final character of beer. Malt is also used to produce spirits and many food products, especially bread and packaged cereal.
Malting is the process that turns barley (or other grain) into malt. It involves soaking (or steeping) the grain in water to rehydrate the kernels; germination under cool, humid conditions and then drying (or kilning) to introduce flavor and stabilize the final malt.
Strict quality specifications must be met for barley acceptable for malt production. Maintaining tight controls on these quality factors ensures food safety and final product consistency in the brewery, distillery or kitchen. A premium is paid to growers for high quality malting barley.
High quality malting barley should have the following characteristics:
- Pure lot of an acceptable variety
- Plump and uniform kernels
- Less than 5% of peeled, broken, or damaged kernels
- Germination of 95% or higher
- Protein content between 9.5% to 12.5% (dry basis)
- Moisture content below 13.5%
- Free of disease and low DON content
- Clean and free of insects, admixtures, ergot or foreign material
Malting barley varieties are bred specifically for characteristics that promote good malting and brewing performance, such as high enzymatic activity, as well as good agronomic performance and disease resistance. Each malting barley variety behaves differently during the malting process. For this reason is important to segregate varieties when they are grown, stored, shipped and processed. Using a high quality, certified seed can help ensure varietal purity. Barley of different varieties must not be blended or co-mingled prior to malting.
Plump and uniform kernels are desirable as plump kernels contain higher levels of starch, which will produce more beer from a given weight of malt. Plumpness is assessed by sieving over a 6/64” slotted screen with greater than 80% kernel retention being ideal for a two rowed barley. Six rowed varieties are generally less plump than two rowed.
Peeled and Broken
It is important that the husk on malting barley grain remains in-tact. The husk protects the shoot growth during the malting process, and helps regulate the uptake of water resulting in even modification. Broken kernels will not germinate, or may grow in an abnormal manner, resulting in a poor quality malt. Care must be taken in threshing and handling to not damage or peel the grains. No more than 5% of the kernels should be peeled or broken.
This specification is critical to malting quality since barley must be alive in order to be processed into malt. Some malting barley varieties can exhibit dormancy, where live kernels fail to germinate under ideal conditions. A Germination Capacity test can be conducted, using hydrogen peroxide, where dormancy is suspected. Pre-harvest sprout damage, or pre-germination, can occur when mature barley is exposed to wet conditions prior to harvest. Pre-germinated grains are at risk of losing germination rapidly over time, especially under poor storage conditions (hot and humid). Sensitivity to water can also occur when grain is adversely affected by environmental conditions during ripening in the field. Germination ability for malting is assessed using standardized tests develop by the malting industry under various controlled laboratory conditions using petri dishes.
The protein content of the barley grain affects the chemical composition and enzyme levels of the finished malt. If the protein is too high, this reduces the starch content and amount of extract available to the brewer. High protein grain also takes up water slowly and is harder to modify in the Malthouse. If the protein to too low, there may be insufficient enzymatic activity to modify the barley kernel and break down starch for brewing. Grain with a higher protein content can be suitable for producing malt for distilling or higher color specialty malt ingredients. The protein level in the grain is determined both by agronomic practice, and by the environment. Hot, dry growing seasons tend to result in higher protein grain at harvest. Cool, wet seasons typically result in lower protein grain at harvest. Excessive nitrogen fertilization application can increase protein levels, although can varieties respond differently.
Moisture content of malting barley must be < 13.5% to maintain quality in storage. In humid climates with a lot of rain, harvesting at 17-18% moisture and low temperature drying at 40°C (100°F) is recommended to avoid environmental risk in the field. Excessive air drying can damage germination rate. Low moisture will reduce the risk of mold growth and ensure long term preservation of germination ability. Barley should be stored in bins with good air circulation to prevent ‘hot spots’ which can cause heat damage and mold problems.
Mycotoxins and Disease
Fusarium head blight (scab) is a fungal disease that occurs in barley resulting in damage to the kernels and reduced yield. The fusarium fungus can also produce mycotoxins such as deoxynivalenol (DON) which make the barley unsuitable for malting and brewing. Typically grain with DON levels over 1.0 ppm is not acceptable for malting to ensure suitability for different end markets (beer, spirits & food).
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Check out the recommended crop management best practices for growing malting barley in Pennsylvania
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