Lesson 3 - Wort Boiling Theory SAQ

*Indicate whether the following statements are true or false. If false, please give the correct answer.

a)    Enzymes are denatured below boiling temperatures.

b)    Boiling destroys all microorganisms in wort.

c)    It is best to achieve the evaporation of at least 15% of the wort volume during the boil to ensure that all the necessary changes occur.

d)    Reactions involving amino acids and reducing sugars are the only source of flavour during the boil.

e)    DMS can form after wort boiling is complete.

Response:

a)    True. Of all the malt enzymes α-amylase is the most heat stable but even that is denatured at 80°C. Most are denatured at mashing off temperatures (76-78°C). But also false! Some commercial enzymes are more heat stable and require the heat from the boil to denature them.

b)    False. The boiling process destroys all vegetative bacterial and fungal cells. However, some spores may survive. Thankfully, spore forming organisms are not normally beer spoilers.

c)    False. 15% is excessive. Evaporation is not an objective of wort boiling but some level of evaporation is required to achieve the boiling objectives. About 4% is a good target and is achieved in most modern wort boiling systems. Excessive boiling is a waste of water, money and energy and can lead to poor flavour stability and poor foam stability.

d)    False. Flavour is also contributed by the hops in the form of bitterness and aroma. Adjuncts such as dark candi sugar and invert sugar can contribute flavour. Finally, caramelisation of the wort sugars can also make a small contribution to flavour.

e)    True. SMM can be converted into DMS after the boil during wort clarification, and yeast can convert DMSO to DMS during fermentation.