Lesson 4 - Adjunct Composition and Application
This lesson explores adjuncts, which are sources of fermentable extract other than malted barley. It investigates the different cereals that we can use as a starch source within the brewhouse and examines how these same cereals can produce liquid adjuncts. It also considers other sources of fermentable sugars that we can add either directly into the kettle or later in the brewing process.
Other Liquid Adjuncts
Brewers who are targeting a market based on offering a large number of varied brands will use some of the more exotic liquid adjuncts to their advantage. A wide range of liquid adjuncts are available to provide novel flavours or to help market the beer.
Sucrose-based liquid adjuncts
Here is a brief summary of sucrose-based adjuncts.
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Molasses is a by-product in the manufacturing of sugar from sugar cane or beet. The molasses is in effect the residue of the plant material left behind as the juice is purified and hence contains higher concentrations of the non-sugar components of the beet or cane like minerals and vitamins. It has a dark colour, a distinctive flavour and is 75% fermentable material. Molasses contains around 47 mg/kg of iron, which as you will learn in the Water unit, can cause off-flavours and a number of other problems with beer. Care must therefore be taken when incorporating it into a recipe.
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Invert sugar is made by heating a sucrose solution with an acid. This causes the hydrolysis of the sucrose molecule, producing fructose and glucose. It is possible to achieve the same result using the enzyme invertase, although this is less common. ‘Invert’ refers to the change in rotation of light passed through the sugar as a result of hydrolysis. A mixture of fructose and glucose rotates light in the opposite direction to sucrose. Syrups of different levels of inversion are available. All are completely fermentable, but a highly inverted syrup may provide excessive levels of glucose to the wort. Different grades (colours) of invert are available, which are made from sugars with differing levels of molasses. The greater the proportion of molasses, the higher the colour.
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Not strictly a liquid adjunct, Belgian candi (candy) sugar consists of solid crystals of sucrose, coated with a coloured sugar product that has been produced by heating. An 80% Brix (described later) sucrose solution is heated to 50°C and held until the appropriate amount of colour has formed. This can be up to five days. During the heating process, crystals form in the sugar. The crystals are removed and sold separately. The coloured syrup left behind is called candi concentrate and this is used to coat sucrose crystals to produce the candi sugar product. Different candi sugars are available, from light candi sugar at 225 EBC, to dark candy sugar at 1900 EBC. A liquid product is also available, in which the candi concentrate is added to a sucrose syrup. As well as producing colour by caramelisation, the heating process also hydrolyses (inverts) the sucrose molecule so that the products contain fructose and glucose as well as sucrose.
There is a wide range of commercial sucrose-derived sugars, where the molasses content, degree of inversion, and heat applied are varied in order to produce a unique product. They are available as granules or syrups.
Honey
Honey contains 95% fermentable sugars, 38% fructose, 30% glucose, 8% various disaccharides, and 3% dextrins. Aromas vary according to the type of honey and the specific plants from which the bees harvested the nectar. To minimise the amount of honey aroma lost by evaporation, we need to add honey after wort cooling.
Honey contains melibiose, which is a disaccharide of glucose and galactose. Ale yeast cannot ferment melibiose, while lager yeast can. Bees actually secrete invertase into honey to hydrolyse sucrose.
Others
Other syrups can be used to add interesting attributes to beer flavour, or at least to the marketing material for the brand. Agave nectar, derived from the plant used to make tequila, and maple syrup, are notable examples.