Kilning
Kilning is where germination stops and malt begins. Green malt — the fully germinated but still-wet grain coming off the germination bed — is loaded into a kiln and dried with controlled heat until moisture drops to storage levels. The process takes between 16 and 24 hours for base sorghum malt, and the temperatures involved are low enough to preserve enzymatic activity while still developing the flavor compounds that define pale lager malt character.
For Bard's, kilning decisions were made by Missouri Malting under their proprietary process. But the principles behind those decisions — and the flavor outcomes that result — are not proprietary. They are well-documented in malting science and visible in the finished malt that arrived at Left Hand Brewing.
What This Page Is Built to Answer
- What is kilning doing to the grain?
- What temperature parameters apply to base sorghum malt?
- How does kilning temperature affect enzymes and flavor?
- What does freshly kilned sorghum malt look like, and how does it change in storage?
What Kilning Does
Kilning accomplishes three things simultaneously:
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Stops germination — Heat denatures the growth hormones and signals that would otherwise drive the grain to continue sprouting. If kilning were skipped, the grain would continue to consume itself.
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Removes moisture — Sorghum malt must be dried to approximately 5% moisture or below for stable storage. Above that level, residual moisture accelerates enzyme degradation and supports microbial activity during storage.
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Develops flavor — Even at low kilning temperatures, Maillard reactions (heat-driven interactions between sugars and amino acids that produce color and flavor) begin between reducing sugars and amino acids in the grain. The flavor contribution of a pale sorghum lager malt — its light grain character, mild sweetness, and clean finish — is shaped at the kiln.
Kilning Is a Flavor Decision
This is the most important reframe in malting: kilning decisions are flavor decisions, not enzyme preservation decisions.
Bard's brewing process used external enzymes — Termamyl, Neutrase, Fungamyl — to handle starch gelatinization and conversion in the mash. The enzymatic capacity of the malt mattered, but it was supplemented rather than relied upon exclusively. This means Missouri Malting's kilning choices could prioritize the flavor character of the finished malt without being constrained by the need to maximize diastatic power.
For standard pale lager malt, lower kilning temperatures (50-55°C) preserve more enzymatic activity and produce a lighter, cleaner flavor profile. Higher temperatures sacrifice some enzyme activity for increased Maillard development — toasty, biscuit, and nutty notes — which works for amber or specialty malt applications.
Temperature Parameters for Sorghum Base Malt
Research documents two commonly cited kilning protocols for base sorghum malt:
| Protocol | Temperature | Duration | Enzymatic Activity | Flavor Character |
|---|---|---|---|---|
| Agu 2005 | 50°C | 16 hours | Maximum preserved | Light grain, clean, pale |
| EtokAkpan 2004 | 55°C | 24 hours | Slightly reduced | Light grain with mild warmth |
| Specialty/amber malt | 65–80°C | Variable | Significantly reduced | Toasty, biscuit, nutty |
| Crystal/caramel malt | 100°C+ (stew first) | Variable | Destroyed | Caramel, toffee, sweet |
| Roasted malt | 150–230°C | Variable | Destroyed | Chocolate, coffee, dark |
Sorghum dries more slowly than barley. Sorghum's hull structure and kernel density mean moisture migration out of the kernel takes longer, which is why kilning durations for sorghum tend to be longer than barley equivalents for the same temperature.
Freshly Kilned vs Aged Malt
Freshly kilned sorghum malt from research studies showed a diastatic power of approximately 68.1°WK (degrees Windisch-Kolbach — the standard unit for measuring enzyme activity in malt) immediately after kilning. That same malt, measured after 6 months of storage, showed a 29% reduction in diastatic power — approximately 48°WK.
| Malt Age | Diastatic Power | Wort Turbidity | Notes |
|---|---|---|---|
| Freshly kilned | ~68.1°WK | ~4.9 EBC | Baseline — highest enzymatic activity |
| 2 months | Moderate decline | ~0.95 EBC | Turbidity drops significantly |
| 6 months | ~48°WK (−29%) | Lower | Substantial DP loss — age management critical |
This means malt age is a real variable. A brewer receiving malt from a toll maltster does not always know how long it has been sitting in the warehouse. For Bard's, the Missouri Malting agreement specified that malt should be shipped within 21 days of final processing — a provision that controlled for age-related quality decline.
What Can Go Wrong
Kilning too hot — Premature enzyme deactivation produces malt with insufficient diastatic power for brewing. If external enzymes are the primary conversion tool, this matters less — but it still affects wort quality, protein solubility, and flavor.
Kilning too cool or too short — Insufficient drying leaves the malt above the target moisture threshold. Wet malt cannot be stored safely and will degrade rapidly during shipment or in the warehouse.
Uneven drying — If kilning is uneven across the bed, some malt is under-dried while other portions are over-kilned. The resulting blend has inconsistent moisture, color, and enzyme activity.
Extended storage before use — Diastatic power drops 29% over 6 months. Malt stored for an extended period before reaching the brewery will underperform relative to freshly kilned baseline values.
Source Notes / Confidence
- Strongly supported: 50°C/16h protocol (Agu 2005); 55°C/24h protocol (EtokAkpan 2004); freshly kilned DP of 68.1°WK and 29% decline over 6 months (archive research)
- Strongly supported: Sorghum dries more slowly than barley (referenced in malting literature)
- Strongly supported: Bard's external enzyme protocol (Termamyl, Neutrase, Fungamyl) from Bard's brewing process documents
- Partially supported: Maillard reaction onset at low kilning temperatures (standard malting chemistry — applies to all malting grains)
- Needs review: Missouri Malting's specific kilning protocol (proprietary; research parameters used as baseline)