Lesson 3 - Warm and Cold Maturation SAQ

** Answer BOTH parts of this question:

A brewer wants to produce a barrel-aged ale however has minimal space and capacity to hold casks.

a)    What are the three processes of barrel maturation that the brewer wants to achieve?

b)    What alternative methods of wood ageing should the brewer consider?

Response:

a)     The primary purpose of wood ageing is to achieve the following:

• Subtractive maturation – this involves the removal of negative and harsh flavours such as sulphur compounds.

• Interactive maturation – this involves the development of flavours often involving oxygen, via reactions such as ‘esterification’, for example, the conversion of aldehydes (harsh flavour) to acetals (fruity notes).

• Additive maturation – this involves numerous reactions:

  • Develop wood-derived flavours – beer extracts wood and converts them into more mellow, spicy, smooth and fruity attributes

  • Beer will take on character from previous contents of the cask

  • Beer may continue to ferment and develop a broader flavour profile, e.g. spicy or sour

  • Colour generation from the previous fill or reaction with the charred internal layer of the barrel

b)    A brewer can consider alternative methods to simply filling barrels and leaving the beer to mature for a period of time. This process can be accelerated to deliver similar results at a significantly faster rate. Methods may include:

• By using a smaller barrel, the higher surface area of wood to beer will mean the wood chemistry will occur at a faster rate, achieving wood ageing character quicker.

• A brewer may wish to add wooden staves or wood chips directly to the maturation vessel. These can be suspended in a hygienic nylon bag; the main downside, however, is the restricted contact surface area with the beer can mean a lower extraction efficiency,

• Wood chips can be added to a small extraction tank connected to the maturation vessel. Beer is pumped from the main vessel, through the extraction tank and back again. This agitation promotes wood character extract efficiency and therefore accelerates the wood ageing process. To mitigate staling of the beer, the vessels and lines are flushed with deaerated water or CO₂ before introducing beer, to purge out any oxygen.