Millet

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General

Millet is the umbrella name for a group of small-seeded grasses within the subfamily Panicoideae. It is a close relative to, though distinct from, sorghum (also a member of Panicoideae). The millet group includes foxtail, pearl, kodo and proso. The most important millet variety for brewing is proso (Panicum miliaceum, also known as common millet, broomcorn millet, white millet, red millet, or kashfi millet).

Phylogenetic tree of millet and other grasses

History

China, Africa ... Broomcorn (Proso) millet adapted by nomadic farmers ~8,000-10,000 years ago in Northern China. It was intensively cultivated there as the staple crop. ~3000 years ago it began to spread across Eurasia.[1]

Millet

Fermented drinks with millet include Boza, Oshikundu. See Traditional Gluten-Free Beers

Varieties (species) used in brewing

In North America, Grouse Malt House provides the majority of malted millet to brewers. Grouse uses Proso millet (Panicum miliaceum L.) sourced from Colorado growers. Of different millet species, Proso millet may be better adapted to brewing given it's relatively higher amylose to amylopectin ratio (28% amylose compared to 24% in Kodo, 21.1% in Pearl, 17.5% in foxtail, and 16% in finger millet).[2] Worldwide, the vast majority of Proso millet is grown in India, China, and the former Soviet Republics.

With little to no Proso cultivation in Africa, African brewing tradition makes use of other millet species ...

Malting

  • Deculming (removing the small, dried rootlets from the kilned malt) is an important step that can reduce perceived grain bitterness from the mashing process.

Brewing

Gelatinization

Heat and water in tandem help break down the bonds of starch molecules, essentially unraveling them so that they are more accessible to enzymes for conversion to sugar. The temperature range for gelatinization can vary by millet variety, growing region and conditions, and malting process.[3] The temperature range cited by a number of gluten-free brewing resources is significantly higher than that of barley and wheat, leading to additional impacts for enzyme denaturing and mash schedule recommendations. Endogenous amylase enzymes denature above x• C and therefore many gluten-free brewers combine a high temperature gelatinization mash step followed by the addition of exogenous enzymes (including some that are active at these higher temperatures).

There is also some indication that gelatinization of malted millet is effective at a lower temperature range (Zarnkow, Yerger), with potential impacts for endogenous vs exogenous enzyme usage and mash schedule variables. Some possible benefits of lower mash-in temperatures include activation of proteases and cellulases that help prepare grain (and other materials) for amylolytic activity by breaking down proteins and cell wall substances. High gelatinization temperatures (especially combined with mash pH > 5.6) could potentially leach tannin from grain husks, however in practice this has not been reported as a problem by advocates of the high temperature mash-in process.

Author Range (C) Range (F)
Briggs [4] 54 - 80 129 - 176
Lavery [5] 75 - 85 167 - 185
Ubwa [6] 76 - 86 169 - 187
Zarnkow [7] 64 - 71.6 147 - 161
Kiss [8] 78 172

Proteins and diastatic power

Carbohydrate composition

Malted millet is reported to be high in endogenous glucosidase enzymes. If those intrinsic enzymes are not denatured early in the mashing process (i.e through high gelatinization temperatures) malted millet wort may be much higher in glucose (relative to maltose and maltotriose) compared to a malted barley wort. Using exogenous enzymes to replace the naturally occurring ones may result in a different carbohydrate matrix (di- and tri-saccharides such as maltose and maltotriose).

One impact of a wort high in glucose content is a tendency for yeast to produce more esters (especially ethyl acetate and isoamyl acetate). This tendency is exaggerated at higher original gravities.[9]

Variety research and breeding trials

Millet species describe major botanical groupings and include proso, finger, foxtail, kodo, etc. Varieties or cultivars are more narrowly defined instances within the species. Those varieties may have commercial names or accession numbers to distinguish between them. Varieties are distinct and uniform in their growing characteristics. As a point of reference, in conventional barley malting and brewing, lists of malting barley varieties are published annually with analysis on malt quality and brewhouse performance.[10] By comparison, limited information is available about variety-specific millet suitability for malting and brewing.[11]

Individual varieties of Proso millet include Dawn, Minco, Minsum, Rise, Cerise, Horizon, Sunrise, Huntsman, Earlybird, Sunup, Dawn, and "172-2-9" [12][13]

The Sustainable Seed Systems Lab at Washington State University (Pullman, WA) conducts research on barley, quinoa, buckwheat and millet varieties with respect to food and brewing applications. The lab has applied for a Sustainable Agriculture Research and Education (SARE) grant to conduct research on buckwheat and millet with the following objectives:

  1. Determine nutritional and malt quality, as well as food functionality, to bolster marketability (existing varieties grown in Washington and Idaho)
  2. Conduct researcher and farmer-led millet and buckwheat variety trials that would identify improvements to variety baseline
  3. Characterize millet and buckwheat varieties for flavor, threshability, nutritional quality, and malt and food functionality to determine end-use suitability
  4. Utilize outreach, education, and networking tools to support supply chain development and product awareness.

Although breeding trials of new varieties can have a twelve year runway, there is potential to utilize new research about existing varieties to find varieties more suited to malting and brewing.[14]

External References

References

  1. ↑ Millet cultivation across Eurasia: Origins, spread, and the influence of seasonal climate
  2. ↑ Sorghum and millets in human nutrition, FAO Food and Nutrition Series, No. 27
  3. ↑ Martin Zarnkow, personal correspondence (2019)
  4. ↑ Briggs et al, Brewing Science and Practice, 2004, chapter 2 "Malts, adjuncts and supplementary enzymes"
  5. ↑ Lavery, All Grain Gluten Free Brewing Tutorial (2006), https://www.glutenfreehomebrewing.com/lavery_brewing_tutorial.php
  6. ↑ Ubwa et al, Studies on the Gelatinization Temperature of Some Cereal Starches (2012), DOI:10.5539/ijc.v4n6p22
  7. ↑ Zarnkow et al, "The Use of Response Surface Methodology to Optimise Malting Conditions of Proso Millet (Panicum miliaceum L.) as a Raw Material for Gluten-Free Foods (2007)
  8. ↑ Kiss et al, "Optimization of Technological Processes for Gluten-Free Beer Production"
  9. ↑ Chris White with Jamil Zainasheff, Yeast: The practical guide to beer fermentation (2010), p. 12
  10. ↑ Canadian Malting Barley Technical Centre recommended variety lists and variety quality overviews
  11. ↑ Evan Craine presentation on Sustainable Seed Systems Lab to Zero Tolerance Homebrew Club, May 31, 2020
  12. ↑ Santra, Proso Millet Varieties for Western Nebraska, University of Nebraska-Lincoln Extension (2013)
  13. ↑ Berglund, Proso Millet in North Dakota (2007)
  14. ↑ Evan Craine presentation on Sustainable Seed Systems Lab to Zero Tolerance Homebrew Club, May 31, 2020
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