Riwaka Peach Sour
05 Jun 2015

A slight throw back to summer with this one. There are few things I enjoy more than a low alcohol sour beer in summer. The addition of fresh fruit and hops is a great combo, you won't find many people that don't enjoy this style if its done well.

I must have guzzled at least 100L of Good George Kiwifruit Sour to my self over summer. It was my go to beer while out and about and it always seemed to fill either the beginning or the end of a pub session. Ive taken what I can from those many litres quaffed and made my own version that pays homage to the legends at Good George. The beauty of this style is its relatively fast and cheap to make at home! The low alcohol >4% means your grain bill is small and simple. The souring bugs abundant and easy to grow and the boil kills any bugs that might otherwise infect your equipment down the line

There are three main rules to consider for a light sour beer. Oxygen exposure, temperature and cell counts. The latter is an easy one and here's my method.

I use a handful of whole Gladfield Pilsner Malt kernels in 500ml of 1.030 starter wort. Keep this at 40 C for 24 hours. You should see a lot of bubbles and activity after this time. Then transfer the starter into 1L of fresh 1.30 wort (you can sieve out the grain at this point). After 12 hours transfer this into another 3L of wort. If you keep it at 40 C in 12 more hours you will have a raging lacto starter that will go to town on 20L of wort and it will work very quickly.

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This is the finished starter with an already thick pellicle and it smells strongly of lemons and stone fruit

By keeping the temperature high and stepping up the starter frequently you are selecting the most thermophilic and vigorous bacteria. There is a lot of wild yeast, pedio and all sorts of other bugs on the grain but none of them are capable of reproducing as fast as Lactobacillus. I find that when I finally pitch the 4.5L starter into my batch and hold it at 40 C, it sours to a PH of 3.6 in under 7 hours and its super clean!!!

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Mash and run off your wort into the boil kettle. The number one thing to avoid from here on out is oxygen. In a nut, all foul smelling things concerning bacteria are a product of oxygen exposure (acetobacter being the main culprit) so do everything in your power to remove oxygen from the wort. I like to do a  quick 15 minute boil to burn out some oxygen and sanitise the wort. Then chill and hold it as close to 40 C as you can, then pitch your starter.  If you have an oxygenation system (a sintered stone) you can run the wort into the kettle and blast CO2 into it at the same time stripping out oxygen, but Ive found that thoroughly purging the headspace of the kettle and then sealing the lid is sufficient to stop the foul aromas associated with aerobic bacteria. I let the PID's take control of the temperature and leave mine overnight then check the PH in the morning. 

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Once the PH is low enough (depends on your tastes but I like mine at or below 3.6) the wort should have a bright apple and lemon aroma and be a cloudy milky brown colour. From here you can proceed with the boil as normal. Some people like to merely pasteurise the wort. I know Good George do this, heating the beer to 75C and then pushing it straight to the fermenter. But I like to cover my bases and do a full boil so I can add some hops and make certain there is no DMS in the finished beer (although as I understand its the boil where its created so in theory a simple pasteurisation is enough).
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I then ferment the beer with a single packet of US-05 and add the fruit puree once its almost terminal. Try to find the freshest fruit you can and blend with a stick blender. Once fermentation subsides dry hop  and condition for a week, then rack it to a keg and force carb at 12psi. Don't try to bottle this beer as the fruit will bring some wild microbes which will eat any remaining sugars. You could leave the fermenter until gravity has been stable for a few months but I think the beer will be out of balance by that stage and we are shooting for a quick sour!

Riwaka Peach Sour

O.G. 1.035
ABV 3.5%


50% Gladfield Pilsner 
50% Gladfield Wheat

5.2  IBU Riwaka at 60 minutes

Yeast nutrients and Koppafloc at 10 minutes

Ferment with US-05. Just before its terminal add the fruit puree and let it ferment out. 

5KG of Peach Puree
3g/L Riwaka Dry Hop

Force carbonating at 15PSI for 7 days. 

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