Lesson 2 - Speciality Malt

Speciality malt is more expensive than base malt and usually provides less extract. The extra money that we spend on it therefore needs to be justified by other benefits! In this section we cover some of these benefits and other speciality malt effects on the brewing process. 

Colour

The most obvious effect of speciality malt on beer is colour. This varies depending on the type of malt used and its contribution to the grist. Beer brewed with pale malt has a pale straw colour unless it is very strong. As the colour of the malt increases, so does beer colour (also measured as EBC). The table below shows the colour value for some beer styles. This is for illustrative purposes only. Not every example of each style is the colour indicated.

Table: Beer colour

All darker beer styles get their colour from the use of speciality malt. Different malts provide different types of colour. Some of the kilned speciality malts provide a redness to beer and one producer sells a caramel malt called Carared^® specifically designed to produce red beer. Highly roasted malts can produce red hues at low use rates and black colour when used above a few per cent.

Flavour

The three forms of non-enzymatic browning that form colour and flavour in speciality malt are:

1. Maillard reaction ‒ when subject to high temperatures, reducing sugars react with molecules with amino groups leading to a cascade of colour and flavour forming reactions.
2. Caramelisation ‒ when subject to very high temperatures, low moisture levels, and either high or low pH, sugars are broken down by heat and their breakdown products take part in a cascade of colour and flavour forming reactions.
3. Pyrolysis ‒ very high temperatures break down sugars forming new compounds and polymers of new compounds.

Pyrolysis requires temperatures above 200°C so only contributes to the very highly roasted malts like chocolate and black malt and roasted barley.

Caramelisation also requires quite extreme conditions to proceed at any significant rate. It requires low levels of moisture and is favoured by either high >9 or low <3 pH. Therefore, caramelisation is only likely to contribute to highly coloured crystals and the highly roasted products above, even then, probably not substantially.

This leaves us with the Maillard reaction which accounts for the flavour of pretty much everything else, and contributes to the flavour of highly roasted malts. The malty, bready and biscuity flavour from the kilned speciality malt can only come from the Maillard reaction. With high concentrations of its reactants and with most crystal malt roasted at around its optimum temperature, conditions are perfect for the Maillard reaction. Caramelisation has a higher optimum temperature. Because the name caramel malt is used, many people (some of whom have published articles stating it as a fact) assume caramelisation is the main source of flavour, when in fact it is likely to be a minor contributor. No scientific work has been done on the reaction pathways that form the key odorants of speciality malt. However, the flavour compounds that have been found to define crystal malt aroma are Maillard products. The sensory descriptors for these include, sweet, caramel, toffee, jam/conserve, candyfloss/cotton candy, molasses, fruity and roasty.

With the exception of the highly roasted malts and roasted barley, coloured speciality malts are generally associated with a fuller/richer/sweeter mouthfeel. Extracts produced from them are usually less fermentable than those produced from base malts, so residual extract may contribute to this. We know that heating malt produces compounds that do not ferment, but the compounds in question are not well established. Pyrodextrins are resistant to hydrolysis by amylase enzymes and can be produced by heating pure starch, usually with acids. The heat and catalysis by the acid changes the structure of the starch polymer so that the enzymes can no longer bind to it. The Maillard reaction has also been demonstrated to change starch or its breakdown products, such that they are resistant to enzymatic hydrolysis. It is likely that something similar happens to barley starch, especially if stewing is taking place and the granules are disrupted. The non-fermentable extract is often called dextrins but may not be purely incompletely degraded starch because changes during processing mean it is no longer starch.

For non-barley malts, it makes sense that as they are made from different cereals, they will provide different flavour compounds. Many descriptors are used for these malts but compounds responsible for them have not been identified. Poetic licence is often used by suppliers, beer enthusiasts and brewers promoting their products, so their effects on beer flavour are best established in your brewery.

Flavour stability

Some crystal malts are sold on the basis that they promote beer colloidal and flavour stability. There is also anecdotal evidence that beers brewed with speciality malts have longer shelf lives. Darker speciality malts’ effects on flavour stability were put down to reductones and melanoidins which can act as antioxidants. Recent scientific work has cast doubt on their long term effectiveness at preventing oxidation throughout shelf life. Also, some of the heat derived flavour compounds found in highly coloured malts have been shown to play a part in stale beer flavour. This is either as stale flavour compounds or their precursors. Any ingredient that has been subject to high thermal load seems likely to reduce flavour stability. 

Foam

We have seen earlier in the lesson that wheat, roasted malts and some caramel malts have been found to promote foam stability. Other speciality malts have no effect or can reduce it. Foam is very complex and not well understood, so in many cases we don’t know why. Some speciality malts have been found to be high in triglycerides and oxidised lipids, both of which damage foam. 

Wort pH

Melanoidins are known to lower wort pH and other acidic compounds are produced by non enzymatic browning. As a general rule, the darker the malt, the greater its contribution to reducing mash pH. Unlike with pale malts, suppliers do not usually quote wort pH on malt analyses reports for speciality malts. It is something that they routinely measure, so they can provide the information on request. What is reported is only an indication of the effect it will have on mash and wort pH because it is likely to be a small proportion of the grist. Also, mash and wort are a complex pH system with many compounds changing pH and resisting pH change. For any degree of accuracy, mash and wort pHs for different grists and water compositions must be determined on pilot brews.