Using Hops In The Brewhouse
Geterbrewed have been working on hop blog posts recently to try and provide more knowledge around the use of hops. Many modern day craft brewers are going for the juice bomb affect with loads of late whirlpool hopping, hop stands at different temperatures then huge x amount per litre dry hops, in comparison to that on the opposite side of that parameter our research has showed that many traditional german breweries add 60/70% of their hops at first wort. Some brewers add hops in the mash, first wort, the kettle, the whirlpool and the fermenter, so what works best for you?
There is much more to brewing with hops than simply just working out the IBU’s when hops are added, its important to recognise how the hops will affect the finished beer.
There is multiple types of alpha acids, the main types that brewers are interested in are: Humulone, Co Hululone and Adhumulone.
The above alpha acids are isomerised in wort by heat and each are transferred into two forms, the result being six iso alpha acids (cis-iso-humulone, trans-iso-humulone, cis-iso-cohumulone, trans-iso-cohumulone, cis-iso-adhumulone and trans-iso-adhumulone)
Alpha acids aren’t really soluble in beer and aren’t bitter whereas iso-alpha acids are intensely bitter, at least four times more bitter than alpha acids. So Iso alpha acids provide bitterness, they stabilise beer foam and they inhibit the growth of bacteria.
Hop Scientists have identified that higher percentages of co-humulone produce a harsher bitterness hence the demand for hops with low amounts of co-humulone, this has to be balanced as low level co-humulone hops wouldn’t be efficient in achieving high levels of bitterness.
Co-Humulone and Humulone levels vary between 20-50% each in different hop varieties while Adhumulone will be 10-15%. These alpha acids are important for flavour stability in packaged beer. Traditional hopped beers are made up of 68% cis alpha acids (perceived bitterness) and 32% trans alpha acids (these alpha deteriorate much faster) Many factors will affect the degradation of these alpha acids but cold storage of your packaged beer will slow this down greatly.
Some brewers are starting to brew with pre isomerised hop extract, Geterbrewed recently started to sell Isohop in 1 litre format for this purpose. This acheives a 55% utilisation as apposed to 30%. Isohop contains a higher % of Cis- Isomers and are in turn more stable.
Beta acids generally are not soluble but some research has shown oxidation reactions with beta acids create halipinic acid in the boil and perceived bitterness because of its transformation. Oxidation reactions occur due to hops not being stored correctly .
Lots of variables will affect perceived bitterness levels in beer for eg some malts will add bitterness like roasted malt. It can be said that been brewed with more calcium sulphate in the water will be recognised on the taste as having a crisper hop character while those beers higher in calcium carbonate exhibit a harsher bitterness.
The temperature a beer is served at may highlight or suppress the bitterness, with colder temperatures being the suppressant. The level of polyphenols also affects the perception of bitterness.
IBU utilisation is complex to measure and results from different locations will vary greatly depending on what formula you use to calculate. Tinseth formula would be the most popular.
IBU categorisation was created to help brewers brew a beer with a consistent bitterness level. So how do they measure this? By acidifying and extracting a sample of beer with iso-octane, then take an absorbance reading at a specific wavelength with ultra violet light, this is a high tec lab test not one we as brewers can routinely carryout in the brewhouse.
The home-brew community use calculators like Brewersfriend to work out IBU’S.
There is many variable to affect the utilisation of hops, for eg change the length of the boil and the hop utilisation will change, other factors affecting utilisation include:
- Type of hop- eg pellets are 10% more efficient than leaf and BBC enhanced t90 pellets are 30% more efficient than leaf
- Shape/size of the kettle – how the hops move around during the boil
- The gravity of the wort – the higher the og the lower the utilisation
- The temperatures during the boil
- The pH, salts & minerals in the water
Hop utilisation equals the quantity of iso alpha acids found in finished beer. Brewers can expect to lose about 50% of iso alpha acids on the hot side and a further 20% during fermentation and packaging.
Different hops require different boiling times, experimentation with blending hop varieties and splitting the addition times are best practice in our opinion to build layers of hop flavour into your beer. Longer post boil stands will result in more hop flavour, aroma and perceived bitterness.