The name ‘malting’ is most likely derived from the Anglo-Saxon words ‘metan’ (to melt or dissolve something) and/or ‘malled’ (broken into fragments). This is a reference to the softening of kernels that accompanies grain germination at early brewing stages where malted barley is milled into a coarse flour. Malting, together with baking and brewing, represent the earliest manifestation of biotechnological processes that date back to 5000 BC in Sumerian times.1
How does it work?
To make malt, seeds (viable grains) are allowed to partially germinate under controlled conditions. The process encompasses four operations:3,4
1. Steeping. Grains are mixed with water in a stainless steel tank to evenly hydrate the kernels, resume metabolic activity and encourage germination. Important variables to monitor:
- Grain swelling (weight gain)
- Temperature (ambient conditions)
- Steep water replacement or “refreshing” (control microbial activity and eliminate extraneous materials)
- Aeration of steep water (compressed filtered air).
- Air-rest period between draining and re-flooding the grain bed
- Dissolved oxygen in steep water
- Steep water (potable with proper hardness and free from extraneous matter)
2. Germination. Steep water is drained and hydrated grains are recovered and allowed to germinate under controlled conditions. Mechanical agitation is important to avoid developed rootlets. Convective air currents can be applied to improve grain bed drying.
In this phase, enzymes required for the degradation of starches, β-glucans, arabinoxylans, proteins, are synthesized. The manifestation of these changes is the appearance of rootlets and the acrospire and loss of the physical integrity of grains. As a result, grains become friable.
3. Drying (kilning). Heat is applied to ensure enzymatic activity has ceased and immature or green malt is converted into its finished form.
4. Milling (to malted flour or powder).
Grains intended for malt need to meet critical specifications, including:5
- High percentage of germination (High proportion of grains capable of germinating is essential as the process requires high levels of enzymes)
- High diastatic activity
- High germ viability
- Germination vigor and uniformity
- Low dormancy (time that takes for seed to germinate should be as short as possible)
Products from malting
- Diastatic malt: one form of malted barley flour (also available as a liquid or syrup) that is often added to correct amylase enzyme activity and to adjust/quicken fermentation. Diastatic malt is naturally rich in fermentable sugars and provides α-amylase to break down starch.2
- Non-diastatic malt (also known as roasted malt): Thermally-inactivated malted barley flour that can provide color and flavor. It is usually added to whole wheat and artisan bread. The greater the heat input during kilning, the darker the color and the stronger the flavor of the product.2
Considerations for bakery applications
The malting process renders a significant level of enzyme activity and a wide variety of sugars can be carried into the dough if using malted grains or diastatic malt.
Aspects such as dough softening and side-wall collapse in the baked good (keyholing in severe cases) can appear if formulating bread with excessive amounts of malted grains or diastatic malt.2
Malt syrup or malt extract is considered a GRAS food additive (color and flavor).
- Boulton, C. “M.” Encyclopedia of Brewing, John Wiley & Sons, Ltd, 2013, pp. 388–416.
- Cauvain, S.P. “Raw Materials.” Baking Problems Solved, 2nd edition, Woodhead Publishing, Elsevier Ltd., 2017, pp. 40, 112.
- Swanston, J.S., and Wilhelmson, A. “Malting, Brewing, and Distilling.” Barley: Chemistry and Technology, 2nd edition, AACC International, Inc., LLC, 2014, pp. 193–212.
- Rosentrater, K.A., and Evers, A. “Malting, Brewing, Fermentation, and Distilling.” Kent’s Technology of Cereals. An Introduction for Students of Food Science and Agriculture, 5th edition, Woodhead Publishing, Elsevier Ltd., 2018, pp. 730–784.
- Serna-Saldivar, S.O. “Physical and Morphological Properties of Cereal Grains.” Cereal Grains: Laboratory Reference and Procedures Manual, CRC Press, Taylor & Francis Group, LLC, 2012, pp. 1–22.