Grains, Malting, Grain Roasting
This is the first in a series of post we’re calling The Brewer’s Notebook. This series of posts will be a compilation of information relating to beer brewing, from published references as well as empirical data collected in the labs at Area 51 (home of the Toxic Brew Company). These articles will include information regarding the beer brewing process, brewing chemistry, and the art of brewing beer. This information is intended to be useful for reference, but experience and experimentation is the ultimate teacher. This first post will focus on grains, malting and grain roasting.
The following is a list of some of the upcoming topics for future posts in The Brewer’s Notebook series:
Grains
2-row: Has 2 rows of grains, most brewing grains are made from 2-row due to its larger kernel size which leads to a larger ratio of usable to non-usable content (higher yield and better taste); lower nitrogen, and lower protein content.
6-row: has 6 rows of grains: used mainly for animal feed due to its general larger yield per acre of land, but some used for brewing due to the higher enzyme content and thus higher diastatic power for use to help break down adjuncts. Due to the larger protein content a protein rest is usually desired, and since it has more husk content it can be used more effectively with larger amounts of wheat. Though rice hulls are often necessary to overcome the large amount of sticky gluten in wheat.
Malting:
The wet grains are allowed to germinate, which, in the process, produce the necessary enzymes needed to convert the proteins and starches into fermentable sugars. The germination process is halted by heating and drying of the gains. Stopping the germination process at different times via kilning determine the degree of modification (malting).
Roasting Grains:
Grains are roasted to impart flavor and color, some are roasted malted, some are roasted unmalted, some are roasted wet, and some dry.
To get a porter/stout with a white head one must use roasted unmalted barley, to get those tasty caramel malts (crystal, caraviene, caramunich, Special B, etc) one must roast those after soaking in water which helps convert the starches to sugars. Just as there are almost an unlimited variety of roasted grains there are an unlimited combination of procedures/variables used in the process, from fully modified grains, to non-modified grains, wet vs dry, temperature profiles including ramp rates, multiple temperature holds, and different kilning times. Each produces a unique flavor profile dependent on the chemistry that takes place. The 3 main overall processes are:
The Maillard Reaction:
Probably the most complicated set of reactions during grain roasting which involving non-enzymatic browning where different nucleophilic amino group of an amino acids and the carbonyl group on a reducing sugar react with the help of heat (more so over 300F) to produce a very complicated set of byproducts that are still not fully understood. The reaction has been used since well before documented history in such acts as browning meat over a flame, but the reactants and by-products are so numerous that it is very hard to characterize. Melanoidins are one of the most important byproducts and are responsible for some of the dark colors and toasty flavors and are heavier molecules that can have atomic masses ranging from a few hundred to over 100,000 g/mole. Melanoidins from roasting grains have even been shown to increase the antioxidant behavior of Barley tea. Other byproducts include aldehydes (furans, thiophenes, polysulfides, thiols) which can contribute to the desired smells (furfural which is an aromatic aldehyde has an almost almond smell), Diacetyl (buttery flavor…also produced and consumed in the fermentation process), acrylamide which is shown to be harmful, and many more. Some of the byproducts, harmful and beneficial are volatile and will evaporate during the process or upon the weeks of rest the grains should undergo after roasting. One amino acid reacted with Glucose or Fructose can be shown to produce over 20 different aroma-active compounds and countless other volatile and non-volatile compounds, malted barley has many hundreds of possible amino acids and though maltose is the main reducing sugar there are many more available.
Caramelization:
Basically the polymerization (process of small chains forming larger chains, in the process becoming a furfuryl, a type of furan) of sugar molecules to form sweet compounds that are often too large for the yeast to act on (why some darker caramel malts can impart almost overpowering sweetness, but things like sucrose (a disaccharide made from glucose (also called dextrose) and fructose) just gets converted to alcohol and CO2 without imparting almost any sweet taste. Generally speaking, caramels do not contain Nitrogen where their close relatives Melanoidins do.
Thermal Degradation (Pyrolysis):
Once the heat is high enough, carbon based molecules break down into smaller units, release volatile compounds and eventually turn into black dust (mostly carbon residue)
All these competing processes are happening during grain roasting and the fine balance is what gives the desired end product. Industry and most people will say that letting the grains rest for few weeks is a must to let the not-so-nice volatile compounds escape and let the flavors mellow, especially for the darker and smoked grains, some people that roast their own use the grains freshly roasted but it is not commonly recommended. Roasting grains can also be done over smoking wood (beachwood is a classic, Peat fire is what makes a Whiskey malt). Grain roasting also lowers the pH of the grain and eventual mash.
Many methods are used to actually kiln/roast the grains used by homebrewers to industrial grain producers:
Conventional oven: Uneven roasting, but what most people have to work with: stirring of grains every 30 min or so is recommended, slightly lower temperatures for longer times helps more evenly roast the grains, does not scale very well.
Drum roaster: Rotating, and heated Container, perforations allow volatiles the ability to escape: fairly even roasting, and fairly scalable.
Perforated floor & Fluidized bed: Air Driven through the grain at varying temperatures and speeds. Best process control if done with the right equipment, poor man’s version you hear about is the air popcorn popper, but has very limited control and one temperature…HOT. Pros: much quicker roasting, more even heating. Cons. More air born debris generated, temps, times, flowrates, not usually published.
As a rough guideline (depends on layer thickness, type of heating container, etc):
Grains Roasted Dry
- Dortmunder -195-200F ~1 hour
- Vienna Malt – 160F for 2-3hours
- Toasted Malt – 350F for 10-15 minutes until gold and aromatic
- Munich Malt – 210-240F for 1-2 hours (or 350F for 20 minutes)
- Amber Malt – 280-300F for 1 hour or desired color
- Biscuit – 300-340F for 30-60 minutes
- Chocolate – 350-400F for ~1 hour
- Roasted Barley – 400-450F 1-2hrs
- Black Patent – 400-450F for 60-90 minutes
Wet Roasted after 24 hour soak (Kiln @ ~50%water content)
- Crystal Malt – Kiln at 180F for 1 hour, raise temp to 250-350F, roast until desired flavor/color, ~ 1-2hrs.
- Carramunich- Kiln at 160F for 90 min, raise temp to 250F, ~ 1hr.
- Caraviene-Kiln at 180F for 1 hour, raise temp to 300F, ~1hr.
- Special B- Kiln at 160F for 30 min, raise temp to 325F, ~1hr
- Shane Juhl | Toxic Brew Company
References:
-Area 51 labs (home of The Toxic Brew Company)
-Papetti et al, Isolation of an in Vitro and ex Vivo Antiradical Melanoidin from Roasted Barley, J. Agric. Food Chem. 2006, 54, 1209-1216
-Lee et al, Investigation of the Aroma-Active Compounds Formed in the Maillard Reaction between Glutathione and Reducing Sugars, J. Agric. Food Chem, 2010, 58, 3116-3124
-Hayase et al, Volatile Components Formed by Thermal Degradation of Nondialyzable Melanodins Prepared from Sugar-Amino Acid Reaction Systems, Agric. Biol. Chem., 45 (11), 2559-2567, 1981
-http://homebrewandchemistry.blogspot.com
-BJCP beer brewing study guide