Barley: The Whiskey Grain

Whiskey is one of the most fascinating liquids for human life. It is also called aqua vitae in latin which means "water for life". Whiskey can be prepared from maize (corn), barley, wheat, rye, etc. Whiskey with the raw material content of at least 51% maize (corn) is known as Bourbon Whiskey. Similarly, if the rye content is at least 51%, it is known as Rye Whiskey. The whiskey made in Scotland with 100% barley is known as Scotch whiskey or simply Scotch. Barley is arguably the most important grain in the whiskey industry.

Barley is an exciting grain to learn about. The more you learn about it, the more you love this grain. Barley falls under Poaceae Family of Plantae kingdom. General two-row barley used in malt distilling, which generally is used to prepare Scotch whiskey, is Hordeum distichon whereas Hordeum vulgare is used for grain distilling, generally used for bourbon and rye whiskey. Any grain which contains starch could be used to prepare whiskey but why has the barley got so much attention? Because it deserves attention. It is one of few grains which has a lot of enzymes to breakdown the starch into glucose. Glucose could be fermented by yeast to produce ethanol and carbon dioxide as primary products.

Above is a picture of Barley kernel with the section exposing its internal parts. Barley has four major parts: 1. Husk 2. Embryo 3. Aleurone layer 4. Endosperm

1. Husk: The outermost layer of the barley grain is the husk. It safeguards the grain from physical damage during harvesting, transportation, and malting process. The husk is composed of silica, cellulose, fiber, lignin, pentosans among others. It accounts for nearly 10% of dry grain weight. Husk has an important role to play during mashing process in brewing and distilling.
2. Embryo: The embryo produces plant growth regulators or hormones, such as Gibberellic Acid which is responsible for the production and release of endosperm degrading enzymes from the aleurone layer at the onset of germination. It constitutes approximately 2-5% of the barley dry weight.
3. The Aleurone Layer: This layer is the driving force for enzyme production. This tissue is very thin - three cells thick. During the malting process, the germinated embryo produces gibberellic acid (GA) into the aleurone layer, encouraging the release of enzymes. This begins the modification of the endosperm during malting but also during mashing, which increases sugar production. Enzymes associated to aleurone layer are alpha-amylase, limit dixtrinase, endoprotease. It is 8 -15% of dry grain weight.
4. Endosperm: Its the largest portion of barley kernel with about 75% of dry weight of barley. Endosperm is a non-living tissue unlike the embryo and aleurone layer. It is mostly composed of starch, which is compartmentalized in starch granules in the protein matrix. Starch granules are of two types, large A type (10-25 micrometer) which is about 10% of total amount of starch but 90% weight of starch, small B type (1-5 micrometer) which is the remaining 10% weight of starch and 90% of total amount of starch of the kernel. The protein content is about 9%.

In brewing and distilling, starch is the most important component of the barley kernel; however, all the other components play an important role in order to achieve well-modified malt. Modification of the endosperm involves enzymes from the grain breaking down the cell walls then removing the protein matrix to expose the starch.

The enzymes present in the grain are:

• α-Amylase
• Endo (1,3) (1,4) glucanase
• Phytase
• Lipase
• Pentosanase

Barley can widely be categorized into two groups: a) two-row barley b) six-row barley. Two-row barley is used mostly for malt distilling to produce Scotch whiskey as these have uniform shape and size with more starch content. Six-row barley is more suitable for grain distilling as a source of enzyme source as these contain more protein and less starch which could be an important source of nutrients for yeast during fermentation.

Since barley has a lot of enzymes and starch as well, this can be used for whiskey production and as an enzyme and nutrient source for yeast in grain distillings like corn, rye, or a mixture of corn, rye, and barley. 100% malt whiskey has a more profound taste and nature whereas bourbon whiskey has a sweeter taste because of corn and rye whiskey is of spicy nature. This diverse use makes barley one of the most important grains for the alcohol and whiskey industry.