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.
Point of Reflection – Reconvene
Welcome back. So, what were your thoughts?
If we look back to our table showing adjunct composition, we can see that whole wheat kernels contain around 3% lipids. Lipids destroy foam and can lead to off-notes in the finished beer, due to oxidation. Wheat also contains large proteins, pentosans, and some β-glucans that can increase wort viscosity, leading to slower wort separation as well as filtration problems later in the brewing process. Raw barley flour causes the same problems, however β-glucans are the problematic component rather than pentosans. The use of exogenous β-glucan and pentosan degrading enzymes can help minimise their impact on wort separation and beer filtration. Addition rates are usually kept low, with flour typically making up less than 15% of the grist weight.
If bought in, the wheat flour will have been produced by roller milling and sieving, to produce material that is nearly pure endosperm tissue. As we saw in the percentage composition table earlier, this changes the flour’s composition by reducing protein, lipids, and ash. By using air classification further reductions in protein can be achieved with the protein-enriched material used in biscuit manufacture. Wheat starch is produced in a very complex process where the flour is mixed with water and the various components are separated out using decanters and centrifugal screens.
Air classification is a system that separates (classifies) particles on the basis of their size, shape, and density. The powdered product falls through the classifier by gravity against an upward flow of air. Finer and lighter particles are held up by the flow of air and are removed towards the top of the classifier. Larger and more dense particles fall through the stream of air and are removed from the bottom.
As you can imagine, wheat starch is expensive to buy so it is not commonly used in breweries today.
As we discovered earlier, flour is a hazardous substance to work with. On top of the explosion risk, the inhalation of flour causes allergies, disease, and potentially permanent harm to the respiratory system. Handling flour is significantly harder than handling grains or grits, and requires specially designed hoppers, usually equipped with vibrating feeds to ensure that the flour can flow. Likewise, flour needs dedicated pneumatic and vibrating conveying systems to move it around the brewery.
If you lack the facilities needed to cook the grits or handle flour, you can use another group of solid adjuncts called pre-gelatinised cereals. We will discuss these next.