Ever walk into a homebrew shop and wonder how or why there
are so many varieties and types of malt? I know when I first started home
brewing I was amazed by the dozens of choices I had; black malt, chocolate
malt, caramel malts, biscuit, Vienna, and victory malts . Dark specialty malts
are especially important ingredients for the production of several beer styles
(e.g. stouts and porters). Most of these specialty malts owe their existence to
one reaction, the Maillard Reaction (Figure 1).
Figure 1. Black malt (Patent Malt)
The Maillard Reaction is responsible for many of our
favorite flavors in food. Think about coffee, a nice seared steak, the crust on
your favorite bread, or most importantly your favorite porter. The Reaction is often called the “browning
reaction” and it isn’t only about the color but the flavor it produces in a complex
set of reactions involving sugars, amino acids, and heat.
The reactive carbonyl group (having one oxygen atom
double-bonded to a carbon atom) of the sugars found in malt reacts with the
nucleophilic amino group (organic molecule with a nitrogen base that tends to
donate a pair of electrons to form a bond) of the amino acid (building blocks
of proteins), and forms a complex mixture of molecules responsible for a range
of odors and flavors (Figure 2). This process is accelerated in an alkaline
environment (e.g., lye applied to darken pretzels) and the type of the amino
acids involved also determines the resulting flavors (1).
Figure 2. Example of Carbonyl groups of a simple sugar
The temperature and duration of the roast largely determines
the level of the reaction. Malts used primarily for coloring beer are produced
on a kiln using elevated curing temperatures, while caramel malts and roasted malts
are attained from roasting green malt and pilsner malt in a device similar to
that used for coffee roasting (2). The longer the kilning process the less
aromatics that are present in the finished malt and the more dry burnt flavors are
added to beer. The darker malts also have no enzymes available to help in mashing
(conversion of starches to fermentable sugars) which includes black malt (Black
Patent), chocolate malt, and caramel (crystal malts). The next post will cover how these malts are used to create a stout.
- Maillard reaction. (2013, October 30). In Wikipedia, The Free Encyclopedia. Retrieved 23:49, November 26, 2013, from http://en.wikipedia.org/w/index.php?title=Maillard_reaction&oldid=579509781
- Coghe, S. et al. 2006. Development of Maillard Reaction Related Characteristics During Malt Roasting. J. Inst. Brew. 112(2), 148–156, 2006
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