Lesson 6 - Wort Clarification, Cooling and Oxygenation Final SAQ

**Describe what trub is. How is it formed? Why is it important to control trub levels? Explain how you can improve the collection of trub using a whirlpool.

Response:

Trub (hot break) is a complex mixture of various compounds from our raw materials (malt, adjuncts, hops and water). The majority of trub is made up of protein (40-70%) as denatured protein, or as complex compounds with polyphenols (via hydrogen or covalent bonding). Other trub compounds from the raw materials include tannins (5-10%) and spent hops (10-20%). There is also lipid material (1-2%) and various precipitated salts (3-5%). These proportions obviously vary depending on the raw materials and the brewing processing techniques used, such as pH, times and temperatures.

Trub formation will also depend on the pH and gravity of our wort, but in particular on the type of hops that we are using. The design of the whirlpool will be set up according to the type and relative proportions of hop pellets and extract being used; a whirlpool alone cannot handle the use of whole hops.

We know that trub flocs come from the vigorous wort boil. Thus, we must maintain the integrity of these flocs in our wort clarification process. We do not want to break them up into smaller pieces. Small trub particles are much more difficult to separate from the wort, and thus clarification will lead to excess wort loss. These particles will also cause processing problems (low filterability). They can be responsible for hazes and off-flavours, such as hydrogen sulphide (), ‘stewed vegetables’, and staling (due to the oxidation of the lipid components). This is not a nice ‘cocktail’ of off-flavours and we can usually quickly detect this trub contamination taste in our beers.   

Due to its simple and effective design, the whirlpool is a popular method of wort clarification. To make improvements in the collection of trub, we can use Stokes’ Law to improve the whirlpool’s ability to rapidly settle all particulate matter in the wort.

Using Stokes’ Law we can improve particle settling by having:

• Large particle sizes.
• High particle density.
• Low wort viscosity.
• Short settling distances.

We can ensure that we have the following conditions in a whirlpool, to maximise the collection of the hot break:

• Correct tangential entry (typically 30^°).
• Slow wort entry velocities.
• No eddy currents formed.
• Multiple wort draw-off points.
• Correct timing and efficient clear wort draw off.
• Effective trub removal system so as not to remix the separated trub.
• Minimum use of pipe bends.