Malting Barley Requires Care When Drying, in Storage
Malting barley germination will be lost if the allowable storage time is exceeded.
Malting barley needs special care when drying and storing it, according to North Dakota State University Extension.
The allowable storage time (AST) is cumulative, so if the barley is stored for 15 days at 17% moisture and then dried to 13% moisture, the remaining allowable storage time is only 135 days, rather than the 270 days of storage time if the barley had dried to 13% before harvest. Germination will be lost before mold growth is visible.
| 11% | 12% | 13% | 14% | 15% | 16% | 17% | 18% | 19% | |
|---|---|---|---|---|---|---|---|---|---|
| 80° F | 230 | 175 | 115 | 70 | 40 | 20 | 11 | 9 | 6 |
| 70° F | 560 | 420 | 270 | 175 | 100 | 50 | 30 | 20 | 15 |
| 60° F | * | * | 660 | 430 | 260 | 130 | 65 | 45 | 25 |
| 50° F | * | * | * | * | 630 | 350 | 140 | 100 | 60 |
- Allowable Storage time exceeds 700 days.
- Source: Drying Cereal Grains by Brooker, Bakker- Arkema and Hall
Malting barley germination also will be lost if adequate airflow is not provided to barley being dried by natural-air or low-temperature drying so that it is dried within the allowable storage time.
The minimum recommended airflow rates and drying times to dry the barley within the allowable storage time are 1.25 cubic feet per minute per bushel (cfm/bu) to dry 18% moisture barley in about 16 days, just barely shorter than the AST of 18 days; 1 cfm/bu to dry 17% moisture barley in about 19 days, just barely shorter than the AST of 25 days; and 0.75 cfm/bu to dry up to 16% moisture barley in about 23 days, less than the AST of about 50 days, based on typical August weather conditions.
Use a fan selection program or table, such as one available from NDSU Extension, to determine whether you have adequate airflow. You also can have the fan supplier verify the airflow rate.
The time required to complete drying, and the allowable storage time will be longer at cooler temperatures because the cooler air holds less moisture. Drying grain at 60 degrees will take about 30% longer than it does at 70 degrees.
Adding supplemental heat to a natural-air drying system will reduce the moisture content of the grain but only reduces the drying time slightly. Warming the air by 5 degrees will reduce the relative humidity by about 10% and the barley moisture content by about 1.5 percentage points. The air normally will be warmed 3 to 5 degrees by the fan operating at a static pressure of about 5 to 6 inches associated with drying barley, so typically, little additional heat is needed.
Adding more heat than is required results in the barley being dried to a moisture content lower than desired. The equilibrium moisture content for barley is about 12% at 70 F and 60% relative humidity, which are average conditions for August. North Dakota’s September air conditions of 58 F and 70% relative humidity will be 63 F and 60% relative humidity if the fan heats the air 5 degrees. This air will dry barley to about 12% moisture content.
It's recommended to limit the plenum temperature in a high-temperature dryer to a maximum of 110 F when drying malting barley to maintain germination.
