June 1997, Volume 20, Issue 6

Everything You Always Wanted to Know About Malt (but were afraid to ask)

by Scott A. Kaplan

grtscott@nh.ultranet.com

http://www.nh.ultranet.com/~grtscott/homebrew.html

Seacoast Homebrewers Club (SHC) of Portsmouth, NH

This would have been helpful for the Grain Round Table discussion. Better late than never. - Editor

Purpose of malting:

To convert insoluble starches into soluble starches within the grain kernel. Malting activates Proteolytic and Diastatic enzymes which will reduce long protein chains into smaller chains and component amino acids and reduce soluble starches into simpler, fermentable sugars (mono-, di- and trisaccharides) and longer unfermentable dextrins. Malting is the process of sprouting the grain kernel to a desired level of modification.

Grain Structure:

The barley kernel consists of a hard, starchy endosperm encased in the husk. The germ is located near the base of the kernel, and the acrospire will grow from it. The acrospire is the portion of the growing kernel that will eventually push up and remain above ground. It grows along the dorsal side of the kernel, just below the husk.

Types of Barley:

Two types of barley are used in brewing: two-row and six-row. Two-row barley has only two rows of kernels fertile along the head of the stalk, while six-row has six rows of fertile kernels. Six-row barley will yield more per acre of crop than two-row and have a higher diastatic power, but it also has a thicker husk and a lower extract rate than two-row. Two-row will also have a lower nitrogen and protein content.

Modification:

Modification is the ratio or percentage of the length of the acrospire (growing portion of the kernel) to the original length of the kernel. Thus, an acrospire that has grown to 3/4 the length of the kernel indicates approximately 75% modification. The degree of modification determines the starch content, protein content, enzyme activity, nitrogen complexity and type of mash schedule required.

Malting Process:

The grain is selected, cleaned and sorted. Barley used for malting will generally be the "pick of the crop", and the kernels used will generally be plump, well formed and able to remain on a 3/32 inch screen.

Once selected, the grain is placed in a container (cistern) of water where it is allowed to steep for two to three days at 50-60 ° F until a moisture content of 40-45% is reached. The water is changed frequently to wash off any bacteria that may be present which would later sour the mash.

The water is then drained and the grains cast into a heap on a malting floor to set for several hours. Once germination begins, the temperature of the grain will rise. The "piece" of germinating grain is then raked and spread out to dissipate the heat and allow oxygen access. Germination normally takes between six and ten days, depending on the desired amount of modification.

Once the grain has reached the desired modification it is loaded into a kiln for drying and roasting; time and temperature determine the final malt grade. Pale malts are low kilned, 130-180 ° F until dry. Extended kilning develops darker colors typical of Vienna and Munich malts. Darker malts are kilned at temperatures in the 200 ° F range, and chocolate and black patent are kilned up to 400+ ° F. Crystal and Carapils malts are not dried before the temperature is raised; they go straight to 150 ° F where diastatic enzymes convert the soluble starches into sugars. These malts are essentially mashed within their own husks, then dried and roasted to the desired color level.

Malt Characteristics:

Percent Moisture - Pale malt will generally have a moisture content of 2-4.5%. Moisture content should be kept low during extended storage to prevent spoilage.

Extract - The measure of soluble carbohydrates extractable from the malt.

Diastatic Power - The measure of potential enzyme activity, expressed in degrees Lintner. American 6-row malt is about 150 ° L (good for high adjunct mashes, up to 40% of the grist). American 2-row is about 120 ° L (can support some adjunct mashing). European lager malt is about 90 ° L (cannot support adjunct mashes).

Beta Glucan Content - A gum-like substance which causes stuck mashes. 75-150 ppm is the acceptable range.

Modification - Again, this is the ratio of the acrospire length (growing portion of the kernel) to the original length of the kernel.

Sieve Assortment - The measure of grain size and uniformity. Helps determine the roller separation for roller mill malt crushers.

Protein Content - Protein content is usually expressed by a malt's nitrogen content (in percent by weight). Total protein content can be determined by multiplying the nitrogen percentage by 6.25 since nitrogen makes up about 6.25% of protein's weight. A protein content of 9-11% is ideal (1.6% nitrogen max.). Soluble proteins affect fermentation and head retention, chill haze and colloidal (permanent) haze, and storage and stability. High protein malts like American 6-row require a protein rest to degrade proteins into soluble fractions, or else dilution with adjuncts like corn and rice.

Kilning:

Kilning, combined with degree of modification, determines the type and character of the malt. Examples:

British Pale is kilned at 130-180 ° F.

Crystal, Carapils and Caravienne (Dextrine malt) are fully modified to 50% moisture then kilned at 150-170 ° F, essentially mashing starches internally, then heated to final color roasting temperature.

Chocolate and Black Patent are undermodified (less than 50%) then dried and roasted at 420-450 ° F for 1-2 hours. These malts have no diastatic power as it is destroyed by the high roasting temperature.

Kilning affects sugars (especially in crystal malts), proteins (undermodified dark malts), enzymes (Dextrine and dark malts), color and flavor. Note that a small amount of dark malt will contribute a very different flavor profile than a larger amount of lighter malt, despite the fact that each may contribute the same amount of color to the resulting brew.

Malt Components:

Starches - Converted to simple and complex sugars by action of alpha and beta amylase enzymes during the mash. Mash temps of 154-158 ° F favor alpha amylase and will promote a more dextrinous, less fermentable wort. Mash temps of 149-154 ° F favor beta amylase and will promote a less dextrinous, more fermentable wort.

Sugars - Monosaccharides such as glucose, fructose, mannose and galactose. Disaccharides such as maltose, isomaltose, melibiose and lactose. Trisaccharides such as maltotriose, which are generally not fermentable by ale yeasts, but will sustain lager yeasts during prolonged cold conditioning. Oligosaccharides are longer chain sugars, also called dextrins, which are not fermentable.

Gums and Hemicellulose - Includes beta-glucans which must be reduced by proteolytic enzymes (protein degrading) to promote head retention and avoid haze.

Cellulose and Tannins - These are husk components. Avoid leaching tannins from husks by sparging below 170 ° F, not oversparging, and maintaining slight acidic sparge water.

Proteins - Serve as food for the kernel during germination and are reduced by proteolytic enzymes into less complex albumins and amino acids (essential for yeast nutrition).

B-vitamin Peptides - Essential for yeast nutrition and growth.

Polyphenols - Contributes "off" flavors.

Lipids/Fatty Acids - Also contribute "off flavors".

Phosphates - Naturally acidify the mash and provide yeast nutrients.

Color Prediction:

The color of the resulting brew can be approximated by the following formula: (lbs. of grain)*(Lovibond rating)/gallons in boil=Color. For example, 10 lbs. of 3L British Pale malt in a 5 gallon boil would be (10)*(3)/5=6L. For grists with more than one kind of malt, simply add each grain's contribution together to get the final figure. This figure is only an approximation; several other factors contribute to color, especially caramelization during extended boils, and high gravity worts.