Things to consider before shortening your boil time



In search of a shortened brewday many new all-grain homebrewers will ask us if once the sterilisation of the wort is achieved, if there is any other good reason to continue this for an hour, or longer?


When making the decision on how long to boil your wort for, it’s important to understand that the purpose for the boil is sevenfold. In addition to sterilising and killing off any unwanted wild yeast or bacteria that would spoil the beer (which can be achieved in under 30mins), the boil can play a significant impact on the colour, bitterness, flavour, intensity and overall character of your beer.


The additional factors that reducing boil time may impact include:  


Hop Utilisation:Whilst there are many factors that affect hop utilization (hop form, wort gravity, batch size, time of hot stand to name a few) boil time and intensity plays a big part. Essentailly the longer and more intense the boil is, the more alpha-acids isomerization occurs and the more IBU’s are contributed to the wort. If you wanted to achieve the same level of bitterness with a shorter boil, you’d have to adjust your recipe and use more hops.


Halting enzyme activity: Dependant on your mash schedule there may be continued action of enzymes that need to be deactivated by heat. Giving your wort to a strong boil will stop the enzyme activity meaning that the composition of sugars in the wort will remain fixed. This is important as active enzymes will alter the fermentability of your wort.


Unpleasant aroma and flavour compounds: One of the major reasons for boiling wort is to remove the unwanted compounds that would otherwise create off flavours in your finished beer. During the evaporation stage of a long and vigorous boil, compounds such as dimethyl sulphide (DMS) and Aldehydes are driven off with steam.

Reductone compounds are also produced during the boil, these delay the onset of stale flavours and the production of oxidised chemical hazes.

Beer Clarity: There are a number of materials in malt, particularly proteins, that are suspended in wort. These proteins combine with unoxidised polyphenols to create chill haze in your beers. Sufficient boiling, and the reduction in pH this causes, helps these proteins gather into larger chunks. These proteins can then form during the hot break and will settle out during the cold break.

Wort Concentration: The longer the boil, the greater amount of evaporation will occur. A specified length of boil is required to hit your target recipe, if you want to reduce the boil time, there are several adjustments to the recipe you’ll need to make to ensure that you are still hitting the same gravity.  

Colour and flavour additions: Throughout the boil there’s several things happening that increase the colour of your wort, this includes the maillard reaction, the caramilisation of sugars, possible charring (i.e. if your brewpot has a thin bottom) as well as some oxidation. In some cases the darkening of colour, if significant enough, can also impart a rich caramel flavour into the wort. As with all of these, the longer the boil, the more significant the effect.

I hope this gives you some further insight into some of the additional variables to consider when thinking of adjusting your boil schedule. If you have any questions about anything above please pop them into the comments below.