Pre-germination or chitting in malting barley
Pre-germination, or chitting, is the premature sprouting of grain before harvest. Pre-germination can occur when mature barley is still in the field during prolonged wet weather before harvest.
Barley should retain 95% germination energy to be selected for malting. Pre-germination reduces barley’s capacity to maintain a high level of germination energy during long-term storage. Pre-germinated barley can produce good quality malt but must be malted soon after harvest while the grain still retains a high level of germination energy.
Barley initially accepted for malting may be rejected after several months in storage if it loses the germination capacity needed to produce good quality malt.
Detecting and measuring pre-germination in barley
A germination energy test is routinely used to select barley for malting. Testing for germination energy does not detect pre-germination in barley. A visual inspection of barley can identify severely sprouted grain, but the early stages of germination may not be visible on the kernel.
Rapid visco analysis, or RVA, is a fast and objective test for detecting and measuring the degree of pre-germination in barley. Alpha-amylase is one of the enzymes produced very early during germination. Since the level of alpha-amylase in sound grain is very low, the content of alpha-amylase can be used as a marker for germination. Rapid visco analysis indirectly estimates the amount of alpha-amylase in barley by measuring the viscosity of ground barley in water. The results are expressed as viscosity in rapid visco units (RVU) or in centipoise (cP).
Interpreting rapid visco analysis results
Samples with final viscosity values higher than 120 rapid visco units are considered sound and will likely retain germination energy after storage. Samples with rapid visco analysis values between 50 to120 rapid visco units are considered moderately pre-germinated. Samples with rapid visco analysis values lower than 50 rapid visco units are heavily pre-germinated and are at high risk of losing germination energy during storage. Samples with rapid visco analysis values lower than 50 rapid visco units should be malted as soon as possible.
|Risk of germination energy loss in storage||Rapid visco analysis viscosity (RVU)|
|Low||Higher than 120|
|Intermediate||50 to 120|
|High||Lower than 50|
A rapid visco analysis test is a management tool that can help predict whether barley is at risk of losing the required 95% germination energy for malting. In addition to rapid visco analysis values, storage conditions (temperature and relative humidity) and the initial moisture content of the grain must be considered to accurately predict safe storage time for malting barley.
A rapid visco analysis test can help grain and malting companies make decisions about managing stored barley that has been selected for malting. It can also be used to reduce risk in marketing for producers, marketers, grain companies and malting companies.
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