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Effects of Temperature on Dry Hopping

For many homebrewers who are just starting out, dry hopping can be a difficult technique to get right. There are a lot of variables such as hopping rates, time in contact with beer, gravity of beer when adding the hops and temperature of beer when adding them. When you get dry hopping right it gives your beer the freshest possible hop aroma and taste and can really improve your beer. Getting it wrong however can impart harsh, vegetative flavours that mute the overall flavour of the beer. We caught up with Chris Neish from the UK office who has been experimenting with the effect beer temperature has on dry hopping.
Currently I’m quite happy with my dry hopping technique. I usually vary my amounts depending on the starting gravity of my beer but I almost always add the hops when the beer reaches ~1.020 and leave them in contact with the beer for three days. Until recently I had not considered the temperature at which I add the hops to the beer as usually I would just throw them in at whatever fermentation temperature I was at (typically around 20 degrees).
However, I’m interested to see what effect, if any, adding hops at varying temperatures has on the overall flavour and aroma of the end beer. I decided for this experiment I was going to brew one beer, split this into three separate fermenters and ferment them all at the same temperature until the beers reached 1.020 at which point I would dry hop them and move one fermenter to the fridge, one onto a heat pad and leave the other at ambient temperature.
For the beer, I decided to do a hoppy black saison using 50g of Mosaic and 50g of Citra at the end of the boil, and then dry hopping each 6.5 L batch with 34g of Mosaic and 34g of Citra. The beer was fermented with the Mangrove Jack’s Belgian Ale Yeast.
The beer fermented with no problems. I had a start gravity of 1.057 and all three beers finished at 1.007. When the beers reached a gravity of around 1.020 I moved one fermenter into the fridge at 12°C, put one on a heat pad at 26°C and left one in an ambient temperature room at 20°C. I added my dry hops and left the beers to continue to ferment for a further 3 days before bottling the beer.
Fermenter at ambient temperature
Fermenter at room temperature
Fermenter on heat pad
Fermenter on a heat pad
Fermenter in fridge
Fermenter in the fridge
When it came to tasting, all the tasters tried the beers blind, referring to them only as A, B and C. Beer C was the stand out favourite for all tasters with everyone citing the great hop aroma and flavour that came through. Beer B had a similar aroma and flavour but slightly muted compared to Beer C. Beer A was easily the worst of the three, with a very poor hop aroma and flavour. The strong citrus fruit flavours that were present in the first two were really dull in the third. An interesting observation though was that as B warmed up, the hop aroma became much more pronounced (though everyone still agreed C was the best).
This was an interesting experiment as it went against what I thought would have been the results. C, which was the favourite, was the beer that was dry hopped in the fridge at 12°C. B was dry hopped at room temperature and A was dry hopped on the heat pad. The lack of aroma and flavour in A can probably be easily explained by delicate volatiles being driven off by the heat. With C, it’s a bit more difficult to understand what’s going on. Tests have shown that alpha acids dissolve faster at higher temperatures (20°C) but when compared to 4°C the temperature influence is minimal, with most of the dissolving being complete just one day after dry hopping in both cases.
So adding dry hops to your beer when it is chilled will not negatively affect the level of alpha acids which are dissolved and based on the results of this experiment, dry hopping at cooler temperatures can give a better aroma and flavour. There is also research to suggest that dry hopping cold can help with the end clarity of the beer.
I’m definitely going to follow up on this experiment with another two experiment to see what cold temperature works best for dry hopping and also to see the effect of dry hopping cold vs dry hopping warm on the end clarity of beer. I’ll post back with the results.’ – Chris Neish
Have you experimented with dry hopping at different temperatures? What were your findings?

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