Polysaccharides & Proteins

element: Barley / DATE: 22/03/2016

Producing the prime raw ingredient for single malt whisky is a tricky juggling act. There’s more to it than meets the eye.

A farmer, paid per ton for the barley he grows, obviously wants as much barley per acre as his land can grow. The distiller seeks as many litres of alcohol per ton of that barley that he can extract from it. While the maltster, in the middle, has to juggle the two parties’ interests in transforming that green barley in to useable malt.

Yet counterintuitively, the interests of both the distiller and the farmer are almost intractable: to grow more barley the temptation is to add more fertiliser, but that means more proteins and proteins reduce alcohol yield.

At harvest green barley is roughly 78% carbohydrate, 10% protein, 10% water, 1% fat, 1% other minerals.

Carbohydrate is a ‘folder’ of organic compounds that includes ‘files’ of sugars, starch and cellulose. Like a night storage heater, these can be broken down to release energy at a later stage such as for spring growth.

A long-chain carbohydrate, made up of smaller monosaccharides, is a polysaccharide. Starch happens to be a storage polysaccharide, found as both amylose and amylopectin.

Starch is too complex for yeast to digest. Enzymes in the proteins free up the starch and then break it down into its fermentable component, glucose.

At harvest, the starch, protein and moisture levels are critical. If the moisture is excessive the grain will rapidly rot. If the protein is too high there’ll be less starch and so less alcohol. Not only are the economics compromised but the machinery can become gummed up with Beta Glucan gloop, another long-chained polysaccharide that differs from glucose; the wrong sort of sugar.

There is delicate balance to be struck: if a farmer seeks more yield from his field, the temptation is to increase the fertiliser; but that raises proteins reducing starch thus sugars and the distiller’s alcohol. For the distiller, the proteins need to be nearer the 9% mark.

Agronomic advice provided by the maltster throughout the season addresses this conundrum, ensuring optimum conditions for the crop addressing all parties’ interests.

The farmer’s cultivation methods throughout the growing season, as well as his land’s natural soil fertility, are key. The relationship between land, farmer, maltster and distiller is a complex and sensitive one.

Polysaccharides

WD_Polysaccarides_Diagram_01-03

Starch

Composition
A, B – Granules

Structure
Amylose (linear)
Amylopectin (branched)

Enzymes
Alpha – Amalyase
Beta – Amylase
Limit dextrinase

Cell Walls

Composition
Beta – Glucans
Arabinoxylans
Cellulosics

Enzymes
Solubilisation
Hydrolysis
Removal

Protein

WD_Protein_Diagram_01-04

Proteins
Structural proteins
Functional proteins
Hydrolytic enzymes
Enzyme inhibitors

Protein Derivatives
Soluable nitrogen
Amino Acids (FAN)
Short chain polypeptides

See other Barley elements