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.
Water and Inorganic Ions
Water constitutes over 90% of almost all beer produced. Through the substances dissolved in it, water plays a definitive role in beer flavour. It has many ions that create direct flavour effects. They also create indirect effects such as influencing reactions in wort production and fermentation.
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Beer usually has a pH of between 4-4.5. Certain conditions may reduce the pH to below that, for example:
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Using water with low alkalinity and low pH
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Yeast that produces a high amount of organic acids
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Bacterial contamination
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Use of darker acidic malts
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As pH decreases, it will impart an acidic flavour that can become unpleasant.
Ions in water are purported to affect flavour, for example:
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Sodium at low levels, imparts sweetness. If sodium exceeds 150 mg/L in beer, it imposes harsh, salty and sour notes.
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Potassium, above 500 mg/L, will also taste salty.
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Magnesium, at > 15 mg/L, will contribute astringent and bitter flavours.
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Iron gives an unpleasant metallic flavour to beer at very low levels, detectable at 0.05 mg/L in some more delicately flavoured beers.
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Some feel that chloride provides enhanced mouthfeel and has a smoothing effect on beer texture at 200-300 mg/L. Above this level, some feel it gives an overly full mouthfeel.
- Some also feel that sulphate has a mouth-drying or astringent effect on the beer palate and can enhance perceived bitterness at 200-400 mg/L.