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.
Adjunct Composition
As with any raw material, it is important that we can determine the composition of the adjuncts we use, and understand how this composition affects the brewing process and the beer produced. In this section, we will detail the components of adjuncts and discuss how these affect our brewing processes and our final product.
The composition of an adjunct depends on the cereal in question and the degree to which it has been processed. For example, the table below shows that wheat starch has a fraction of the amount of protein found in unprocessed wheat. We will discuss the figures in the table in more detail later in the lesson.
Table: Percentage composition of non-starch components of solid cereal adjuncts
|
Adjunct |
β-glucan |
Pentosans |
Protein |
Lipids |
|
Barley |
3.5 |
10 |
11 |
3.5 |
|
Wheat |
0.5 |
8.5 |
12 |
3 |
|
Wheat flour |
0.1 |
1 |
9 |
1 |
|
Wheat starch |
0.1 |
0.6 |
0.5 |
0.4 |
|
Maize |
0.2 |
1.6 |
9.8 |
4.9 |
|
Maize grits |
0.1 |
1.5 |
9 |
0.4 |
|
Rice grits |
0.1 |
0.5 |
7 |
0.5 |
|
Sorghum |
0.3 |
2.5 |
11 |
5 |
It is important to understand that the figures above are typical figures, and there is variation between varieties of the same cereal (and even between grains of the same variety of a cereal!). Before using any raw material, we must set a specification and check that our analysis of what is supplied matches that specification.
Cell wall material – β-glucan and pentosans
β-glucan and pentosans are long chain carbohydrate molecules that form gums when hydrated. As they are gums, these cell wall components can cause filtration problems in the brewing process. During malting, the cell wall materials are broken down and become soluble. Filtration difficulties, both in the brewhouse and during beer filtration, arise when high molecular weight β-glucan molecules are present in the wort. Depending on their concentration, they can increase viscosity significantly. Downstream there is a risk of glucan haze formation in the beer.
Pentosans, which are relatively plentiful in wheat, rye, and triticale, give similar problems to β-glucans both during wort separation and later on in beer filtration.
Proteins
The bulk of proteins in all cereals are found in the endosperm, where they are stored as the building blocks of new plants. The majority of wheat’s storage protein is made up of glutens (80%) compared to barley (5-8%).
Gluten is derived from the Latin, gluten, and means ‘glue’. Gluten is the composite of storage proteins in grains such as wheat, barley, and rye. The storage proteins are divided into prolamins and glutelins. The prolamins group can be further classified into gliadins, hordein, secalins, and avenins. The glutelins in wheat are called glutenin.
Barley’s storage protein is mainly hordein, which makes up around 37% of the total barley protein fraction.
Not all proteins behave the same during brewing, and this is evident when comparing barley and wheat. Wheat does not necessarily contain more protein than barley, but wheat contains a greater proportion of higher-molecular-weight proteins, which are more soluble in wort than the hordein in barley. Wheat glycoproteins are associated with good foam stability and are associated with haze formation in the finished beer.
The article below discusses brewing with oats and sorghum.
https://onlinelibrary.wiley.com/doi/full/10.1002/jib.152
You will also see from the table that maize grits contain a relatively high proportion of protein. More, perhaps, than you would expect from a source of starch. Due to its structure, maize protein is significantly less soluble during mashing. So, maize does not contribute as much protein (haze potential, foam stability) or FAN to wort as barley and wheat.
Lipids
‘Lipids’ is a catchall term for fats and oils. All cereal grains contain some amount of lipids for use as an energy store and to support the growth of the new plant. Using adjuncts with high lipid levels can adversely affect both beer flavour and foam stability. Lipids oxidise during beer production and storage, generating off-flavours such as E-2-nonenal, which is detected as a papery or cardboard aroma and flavour.
Lipids are foam negative. Have you ever experienced your perfect foam disappear after you have taken a sip with oiliness on your lips? Foam is stabilised by molecules with hydrophobic (water hating) parts. The hydrophobic part of the molecule associates with the gas bubble helping to hold it in the foam structure. While the hydrophobic parts hate water, they tend to love lipids! As a result, they interact with any lipids present rather than the gas bubbles in foam. When you sip beer with your lips covered in lipstick or grease from the potato chips you are eating, they deposit lipids in the beer, in turn stealing the hydrophobic foam stabilisers from the foam, causing it to collapse. You will learn more about the complexities of foam stability and lipids later in the course.
Maize is comparatively high in lipids, but these lipids are largely confined to the embryo. The embryo and seedcoat of maize are removed during processing into grits and flour, so maize does not pose a risk of adding excessive levels of lipid.