Lesson 6 - Beer Flavour and Stability
In this lesson we will discuss beer flavour and beer flavour stability. This will include the effects raw material has on beer flavour, followed by a discussion on common taints, their flavours and consumer reaction. We will examine the flavour changes that occur during beer storage: focussing on oxidation reactions, the species of oxygen involved, and how we can utilise antioxidants to protect against aged beer flavour change. Finally, we will summarise the selection of raw materials and process optimisations available to improve beer flavour stability.
Barley and Other Malts
Malted barley is the largest contributor by weight after water. Kilning removes the green malt flavour and introduces new flavours.
The majority of beer produced globally uses pale malt as the main fermentable source, which confers the typical biscuit flavour associated with malt. Speciality malts employ higher curing temperatures. This causes increased flavour and colour through the complex Maillard reactions between sugars in the grain, and amino acids.
Certain dark beers, for example, stouts and porters, are characterised by the chocolate malt, black malt and roasted barley flavours.
Table: Malt types and their contribution to beer flavour
|
Product |
Colour EBC |
Descriptors (based on usage) |
|
Pale malt |
2-3 |
Biscuit-like, malty |
|
Pale Ale malt |
4-6 |
Light malty, slight sweetness |
|
Vienna malt |
6-9 |
Malty, toasty, almond, hazelnut |
|
Munich malt |
10-20 |
Rich, malty flavour, light caramel, honey, bread-like |
|
Amber malt |
40-70 |
Baked biscuit flavour |
|
Brown malt |
90-120 |
Mild coffee/biscuit notes – less sweet than crystal malt |
|
Low Chocolate malt |
350-550 |
Moderate coffee |
|
Chocolate malt |
900-1,100 |
Coffee and mild burnt toast |
|
Roasted malt |
1,200-1,500 |
Smoky, strong coffee, burnt toast |
|
Crystal malt |
10-400 |
Sweetness. The toffee, caramel notes will increase with colour, full bodied |
|
Roasted barley |
1,200-1,500 |
Sharp, astringent, burnt |
|
Wheat malt |
2-4 |
Adds fullness to mouth feel |
|
Rye malt |
5-10 |
Spicy but also flavours like bready and honey are common |
|
Sorghum malt |
6-10 |
Sour and fruity flavours |
During wort boiling, more flavour is imparted by the Maillard reaction. However, many flavour compounds are evaporated, such as dimethyl sulphide (DMS), which gives a canned sweetcorn flavour to the beer. If boiling is too short or not vigorous enough, or the whirlpool stand is too long, DMS levels above the flavour threshold can persist through to the packaged beer. There are some large beer brands across the world where DMS is an important part of their flavour profile.
Malt contains around 3% lipids of various length chains. As longer chain fatty acids are largely insoluble in wort, they are precipitated out in the mash, as well as during boiling and subsequent cooling. However some long-chain unsaturated fatty acids, such as the 18-carbon linoleic acid, are dissolved and can take part in beer staling reactions, which we will discuss later.
Another important component of both malt and hops are polyphenols. If present in enough quantities in the finished beer, they add astringency – described as a drying mouthfeel. The polyphenol content is limited by good wort separation practices such as not collecting weak worts. This tends to pull the polyphenols from the husk, where they are concentrated.