Quality Factors for Malting, Brewing and other End-uses

Barley is primarily used for animal feed. It is fed to beef cattle, dairy cattle, swine and poultry. In most cases, the whole barley kernel is rolled, ground, or flaked, prior to being fed. Feed efficiency improves with removal of hulls, grinding, or breaking of bran layer (efficiency = weight gain / weight fed).

• Dry rolling: cheap, but dusty
• Steam rolling: same efficiency, but better palatability
• Fine grinding: hammer mill for impact grinding
• Pelleting: force material through die

The second most important use of barley is for malt. Malt is used in beer, liquor, malted milk and flavorings in a variety of foods.

Barley is also used for food. Pearling barley involves removal of the hull by using abrasive rollers with paddles moving through a perforated steel cylinder.

U.S. Barley Grades are Based on:

• Row number (2 vs 6)
• Malt vs feed use
• Test weight (50# bu for 2-row)
• Discount schedule
• Plumps: retained on 6/64” screen
• Thins:
  • through 5/64” screen for 6-row
  • through 5.5/64" screen for 2-row

Generally higher test weight and greater % plumps indicate better feed value and better malt quality.

Barley for Malting

Two-rowed barleys are favored for malting throughout most of the world, but in the USA and Mexico, six-rowed barleys are used extensively for this purpose. Thus, there are no absolute definitions of malting and brewing quality, due to differences in malting and brewing practices and consumer preferences.

The American Malting Barley Association (AMBA) provides specific quality guidelines for breeders in the US market: http://www.ambainc.org/ni/index.htm

Contract production for malting: specifications are given to growers for grain quality, plump kernels, and protein content.

The Malting Process

Source: http://www.howtobrew.com/section2/chapter12.html

The starch, protein and nucleic acid molecules that are stored in barley grains are not good nutrients for brewing yeast nor do they support the fermentation reactions performed by brewing yeasts. These large and structurally complex compounds must be partially or, in some instances, fully degraded into their component sugars, amino acids, and nucleotides before the yeast can use them. When barley seeds germinate, hydrolytic enzymes are synthesized or converted to active forms that can readily degrade these large compounds.

Malting is controlled sprouting - A complex interaction of genes involved in germination, growth and development.

Steps in Malting:

1. Steep: raise moisture to 42-44% uniformly through kernel
• If too short – poor malt
• If too long – mold and bacteria grow
2. Germination : on beds with forced air and 100% RH 15 °C temp.
   Releases alpha-, beta- amylase, glucosidase, dextrinase.
   These enzymes are temperature stable during drying (kilning).
3. Kilning : reduces moisture and dries malt
4. Browning : adds flavor and color
5. Optional bleaching : reduces color

Changes in Kernel Composition and Enzymes During Malting

During malting, the acrospire (the plant shoot) grows along one side of the kernel. As it grows, pre-existing enzymes are released and new enzymes are created in the aleurone layer which "modify" the endosperm (the protein/carbohydrate matrix starch reserve) for the acrospire's use.

Malted barley is the source of the sugars (principally maltose) which are fermented into beer. The grain partially germinates, releasing enzymes in the aleurone layer (outermost layer of the endosperm). New enzymes are created that break down the endosperm's protein/carbohydrate matrix into smaller carbohydrates, amino acids and lipids, and open up the seed's starch reserves. The endosperm is composed of large and small starch granules that are packed in a protein matrix. The cell walls within the matrix holding the starch granules are primarily composed of beta-glucans (a type of cellulose), some pentosans (gummy polysaccharide) and some protein. The degree to which the enzymes unpack the starch granules (i.e. breakdown the endosperm) for use by the growing plant (or brewers) is referred to as the "modification." It refers to all of the polymer-degrading processes that occur during malting.

One visual indicator that a maltster uses to judge the degree of modification is the length of the acrospire which grows underneath the husk. The length of the acrospire in a fully modified malt will typically be 75-100% of the seed length. Drying is used to stop the malting process when the proper balance between resources converted by the acrospire and resources consumed by the acrospire has been achieved.

The purpose of malting is to create these enzymes, break down the matrix surrounding the starch granules, prepare the starches for conversion, and then stop this action until the brewer is ready to utilize the grain. After modification, the green malt is gently dried with heat (kilning) and the acrospire and rootlets are knocked off by tumbling. The kiln drying of the new malt denatures many of the enzymes, but several types remain, including the ones necessary for starch conversion. The amount of enzymatic starch conversion potential that a malt has is referred to as its " diastatic power".

Beta glucans are the soluble dietary fiber component of barley and oat bran. B-glucan is thought to have serum cholesterol reducing properties and occurs in highest amounts in the endosperm of barley and oats. B-glucan also is important for the malting industry and indicates how well the endosperm is modified. High levels of b-glucan cause a viscous wort that may cause problems with filtration or hazy beer. Thus, lower levels of b-glucan are preferred for brewing.

Brewing

Steps in Brewing

1. Malted barley is soaked in hot water to release the malt sugars
2. The malt sugar solution is boiled with hops for seasoning
3. The solution is cooled and yeast is added to begin fermentation
4. The yeast ferments the sugars, releasing CO₂ and ethyl alcohol
5. When the main fermentation is complete, the beer is bottled with a little bit of added sugar to provide the carbonation.

Mashing - the hot water soaking process that provides the right conditions for the enzymes to convert the grain starches into fermentable sugars. The basic light colored malts such as pale ale malt and pilsener malt need to be mashed to convert the starches into fermentable sugars.

Adjuncts - fermentables not derived from malted barley.

Extract efficiency - typical amount of fermentable and non-fermentable sugars obtained from the grain.

German or US specialty beers use straight barley malt. Most brewers use adjuncts of rice, corn, wheat, or other grits to provide an additional carbohydrate source. Hops are added for ‘bitters’. Yeast is Saccharamyces carlsbergensis, occasionally S. cerevisiae.

The malt is treated with water under appropriate conditions (“mashing”) to obtain an extract (wort)that must perform several critical functions.

1. The extract must provide adequate nourishment to the yeast so that fermentation can occur.
2. The extract must provide sufficient fermentable sugars to enable the yeast to produce the desired levels of alcohol.

A high quality malt will contain the right amount of hydrolytic enzymes and metabolites to fulfill these requirements and will have the right degree of friability to allow many of its components to be readily solubilized during mashing. During malting and mashing, the barley starch should be almost completely degraded into sugars that can be utilized by the brewing yeasts, whereas only about 45% of the barley protein should be solubilized. Too much protein solubilization is thought to result in beers with poor foaming characteristics. When insufficient protein hydrolysis occurs, the remaining proteins may interact with polyphenols to form beer haze precipitates.

Four amylolytic enzymes are generally thought to participate in converting the starch in malted barley into fermentable sugars: these are a-amylase, b-amylase, a-glucosidase and limit dextrinase. During brewing, amylase enzymes digest amylose (linear starch) and amylopectin (branched starches) into hexose sugars. The sugars are a nutrient source for the yeast to facilitate fermentation. Sufficient sugars are needed to obtain the desired alcohol level.