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Sorghum Seed Standard 2 (draft): A Sorghum for the Barley Process

A future specification for breeders: a sorghum that could replace barley in the same process. Its starch gelatinizes low enough for a standard mash, and its malt carries enough enzymes of the right types to convert that mash on their own, with no added enzymes and no cereal cook. The same thirteen properties as Seed Standard 1, plus enzymes.

Status: proposed, draft v0.3, never ratified by anyone. A hypothetical specification: it describes a target to breed toward, ahead of today's grain. It covers non-tannin (Type I) sorghum. The standard in use today, with external enzymes, is Seed Standard 1.

The standard​

Report every value with its unit, method, moisture basis and germination length.

#PropertyTargetReport it asBasis
1Tannin classNon-tannin (Type I), confirmed by assayA bleach test for a pigmented testa; ISO 9648 to quantify tannin. Colour is not the testTannin and non-tannin sorghum; GFB-SME
2ExtractAs high as the line givesExtract from the malt's own enzymes in a standard mash, with method, grind and moisture basis. The GFB-SME reference mash adds enzymes, so it would hide what this standard measuresGFB-SME
3ProteinDeclaredTotal protein, % d.b. GFB-MSS Profile B proposes 11–14%; the sorghum research direction is protein digestibility, because kafirin cross-linking restricts FANGFB-MSS; Kafirin and protein digestibility
4FANAs high as the line givesmg/L at a stated wort gravity, or mg/100 g malt, with the method. The 25 Madison cultivars ran 59–140 ppm across 3- and 4-day germinationMadison screening
5ColourDeclaredMalt colour and wort colour, each with its unit and method. Pale sorghum malt ran 0.9–2.1 SRM across six lab reportsReading a certificate
6Gelatinization temperatureSubstantially complete at or below 149°F (65°C) — the conclusion temperature, inside the barley-malt mash zone of about 136–149°F (58–65°C), so a standard mash opens the starch without a cereal cook. The target is the mash zone, not barley's starch figure, which is lower. It binds the conclusion temperature, not onset: today's sorghum already shows onset at 61.75–65.51°C while completing at about 154–178°F (68–81°C), so a line can meet an onset target and still need a cereal cook. Ceiling: 69.6°C (157°F), the midpoint of thermal inactivation for sorghum malt α-amylase — above it, half that enzyme is gone while the top of today's starch range is still closed1Onset, peak and conclusion temperature, each stated separately, with the method named (DSC or viscometric). The conclusion temperature is the one this target binds. "Sorghum's comparatively high starch-gelatinization temperature is a documented constraint in brewing, separate from its enzyme deficit"Gelatinization; K-State results
7Haze and filtrationFree-running wortWort filtration rate and viscosity first; turbidity in formazin units, with the instrument declared, secondGFB-SME
8Grain conditionTest weight ≥ 56 lb/bu; moisture ≤ 14%; no desiccant before harvestGrade, test weight, and moisture with its basis; kernel hardness and size declared; harvest-aid declaration from the growerGFB-MSS, Part 3
9Germination≥ 90% within 3 days, ideally ≥ 95% and evenGerminative energy, with the method and temperature; water uptake at steep-out declaredGFB-MSS, Profile B
10MycotoxinsDON ≤ 0.5 ppm; aflatoxin ≤ 5.0 ppbMethod and limit of detectionGFB-MSS, Part 3
11Gluten statusGluten-free, on each lotThe test's method and threshold, lot-matchedLot Reporting Standard
12Identity and supplyNamed, or declared anonymousGenotype or pedigree, growing locations and crop year, the check cultivars grown alongside, and whether seed is available to repeat the work. "Anonymous grain is a different, lesser class of result"GFB-SME
13FlavourDescribedAt the pilot-brew stage, in sensory lexicon terms. Line screening leaves it outBlue Milo #4 and Ivory 7
14EnzymesEnough, of the right types, to convert a standard mash with no added enzymes. The screened floor: diastatic power ≥ 30, ideally ≥ 40 °ASBC; α-amylase ≥ 62, ideally ≥ 78 DU, both at 3-day germination; β-amylase reportedEach in the unit its method uses: SDU under SABS 235, or °ASBC. Never convert between themGFB-MSS, Profile B

Rows 6 and 14 are one target, not two. Neither is worth anything on its own, and that is the whole point of this standard. A sorghum whose starch opens inside the mash zone but whose malt carries no enzymes still needs a dosed conversion plan. A sorghum with barley-grade diastatic power whose starch does not finish gelatinizing until 81 °C still needs a cereal cook — and the cook destroys the enzymes the line was selected for, because sorghum malt α-amylase is half inactivated at 69.6 °C1. The distance between where the starch opens and where the enzymes die is why conversion is external today, and closing it takes both rows moving at once. A line that moves one and not the other has not got halfway; it has changed which workaround it needs.

Malt it the declared way. Use the GFB-SME reference schedule so results compare: a 26-hour steep at 75°F (24°C) and germination at 75°F (24°C), to a 1:1 acrospire, about 72 hours at bench scale. Declare the kiln. "Where the goal is preserving enzymes, sorghum malt is kilned cooler. That is the correct choice for a malt that must convert its own starch" (GFB-SME).

Read the enzyme targets as rankings. They come from the Madison screening: α-amylase at its 3-day median and upper quartile, and diastatic power at the screening's own working line of 30. They rank a line against published material; they don't prove the malt will convert a mash by itself. Three cautions come with them:

  • Germination length moves the numbers. A fourth day raised α-amylase in all 25 Madison cultivars, by 19.2 DU on average, and Beta 1995 germinated for five days. The 3-day targets are a reference point, and shorter than some schedules in use.
  • Diastatic power hides β-amylase. Report it on its own.
  • Methods don't agree yet. The site's two α-amylase datasets differ by roughly five to ten times, so compare only within one method.

Rank against check cultivars. Grow named check cultivars alongside the lines under test, and rank each line against them as well as within the set. Cultivars "respond differently to the same schedule" (GFB-SME).

How it differs from Standard 1​

Standard 1: today's processStandard 2: the barley process
ProcessExternal enzymes and a 190°F (88°C) liquefaction step: the process Gluten Free Brewer uses todayA standard single-infusion mash, as barley malt is brewed, with no added enzymes and no cereal cook
GelatinizationDeclared; the liquefaction step clears the whole rangeSubstantially complete at or below 149°F (65°C) — the conclusion temperature, inside the barley-malt mash zone of about 136–149°F (58–65°C)
EnzymesNot required; listed with the barley numbers to ignoreEnough, of the right types, to convert that mash on their own
ExtractFine-grind extract, as the certificate reports itExtract from the malt's own enzymes
Protein9–12%, ideally 9–10.5%, for extractDeclared; protein digestibility is the research direction
Malted howProduction malt, judged on the certificate and a brewhouse trialA declared reference micro-malting, kilned cooler to keep enzymes
OutputBuy, trial, or passA rank against named check cultivars, and a line to breed toward

What would move this to v0.4​

  1. Craig's review of the fourteen properties and the differences.
  2. One α-amylase method the site's datasets agree on, so the enzyme targets stop being method-bound.
  3. A gelatinization value — onset, peak and conclusion — with its method, for each screened line, and a line whose conclusion temperature falls inside the barley-malt zone.
  4. A line that converts a standard single-infusion mash with no added enzymes.
  5. A laboratory running the reference schedule on a named set of North American lines, with check cultivars.
  6. Review by a sorghum breeder and a cereal chemist.

Version history​

  • v0.3, amended 2026-10-22. Gelatinization (row 6) now binds the conclusion temperature rather than a bare band. Today's sorghum already meets 58–65 °C on onset (61.75–65.51 °C by DSC) while completing at 68–81 °C, so an onset target specified almost nothing — a line could satisfy it and still need a cereal cook. Adds the sorghum malt α-amylase thermal-inactivation ceiling of 69.6 °C, labelled as literature-derived from purified enzyme at pH 4.8 and not measured on sorghum malt in a mash, with Ask 21 carrying the request for the real figure. Rows 6 and 14 are now explicitly stated as one target rather than two, which is the destination this standard exists to name. DR-0096.
  • v0.3, amended 2026-10-19. Grain condition (row 8) adds no desiccant before harvest, with a harvest-aid declaration from the grower, matching GFB-MSS Part 3. Board #253 (seed silo).
  • v0.3 — 2026-09-28. Named for what it is: a hypothetical future specification, a sorghum that could replace barley in the same process. Gelatinization now targets the barley-malt mash zone; enzymes target converting a standard mash with no added enzymes.
  • v0.2 — 2026-09-28. Checked against what sorghum malting research and barley breeding programs measure. The same thirteen properties as Seed Standard 1, reported for research, plus the enzyme specification: β-amylase added, SDU accepted. Protein made declared; extract from the malt's own enzymes; filtration and viscosity lead the haze row; germinative energy and grain descriptors named; ranking against check cultivars moved into the reporting rules.
  • v0.1 — 2026-09-28. First draft. Seed Standard 1's twelve properties, with GFB-MSS Profile B's targets, the GFB-SME reference malting, and the Madison screening's enzyme data.

Sources​

Each outside source is named beside the claim it carries on this page; the footnote holds the full citation.

References​

  1. Kumar, R.S.S., Singh, S.A. & Rao, A.G.A. (2005). Thermal stability of α-amylase from malted jowar (Sorghum bicolor). Journal of Agricultural and Food Chemistry 53(17):6883–6888. A purified 47 kDa α-amylase from malted jowar (sorghum); midpoint of thermal inactivation (Tm) 69.6 ± 0.3 °C, inactivation following first-order kinetics at pH 4.8, the enzyme's pH optimum. Of the three cereal amylases compared — barley, ragi and jowar — jowar's was the most thermostable. Tm falls to 66.3, 58.1 and 48.1 °C with 0.1, 0.5 and 1 M NaCl respectively, and rises to 77.3 °C with sucrose. Read it as a ceiling, not a mash figure: this is purified enzyme in buffer at pH 4.8, not malt in a mash at pH 5.2–5.6, and a midpoint states where half the activity is gone rather than what survives a 60-minute rest. doi:10.1021/jf0501701 ↩ ↩2

Research needed