Birallee Beer & Brewing: Raspberry Sour

Here's how our brew day for our Raspberry Sour went.

We started out with our usual water adjustments - fairly minimal for this particular beer as we're using the "Mild Ale" profile in Brewfather that has relatively low levels of sulfate and chloride.

We adjust our sparge water to get a pH in the 5.2 - 5.6 range, but we were thinking about this more and wondering if this is too low? As when the sparge water mixes with the grains it will lower the pH even further, so if we start at around 5.3, is this causing our pH to drop below the ideal 5.2-5.6 range after coming into contact with the grains? Or have the grains already released the majority of their enzymes in the actual mash so don't have much of an impact on the "secondary" sparge water?

Reading further into it and the generally accepted range is 5.6-5.8 - we might start aiming for 5.6 for our sparge water pH rather than getting it too low as we did here (5.34).

Doughing in with just over 4kg of grain and 20L of water was easy and left plenty of headroom.

Our latest toy is the mash stirrer drill attachment pictured above. Think of it like a giant kitchen mixer. After doughing in and wetting the grains with our regular mash paddle, we fired up the drill with this attachment and was pleased with how easy and painless it was - much faster and more efficient than manually having to stir it all through! Did it improve efficiency though?

After letting the mash bed settle for 10 minutes we took our first pH reading of the mash, 5.49. A little higher than we wanted, especially since we're souring this with Philly Sour so we'd prefer the starting pH to be a little lower.

Another 0.5mL of phosphoric acid to the mash and we got an updated pH of 5.29 - much better

We began recirculating the wort using our sergeant sparge head

Mash temp was 65°C which we managed to maintain fairly well throughout the mash.

The recirculation and sparge got pretty slow at times - although we only had a relatively small amount of oats (100g) it still certainly seemed to thicken everything up, but nothing a bit of stirring the grain bed couldn't fix.

An uneventful sparge, and our pre-boil volume of 25.5L was reached.

Pre-boil gravity of 1.042 - 1 point higher than expected in the recipe. Although not completely unexpected to get a slight improvement in efficiency, we've certainly never managed to do it when including oats in the grist, even with a small amount. Is this attributed to the drill mash paddle attachment? Quite possibly - but in any case using this certainly made stirring the grain bed quicker and easier for us, even throughout the 1 hour mash where we used it several times, so we'll be using this for all our brews moving forward.

Waiting for the boil, so time to measure out our first hop addition. A whopping 12g of Hallertau tradition.

We also took another pH reading out of curiosity to find a pre-boil pH of 5.43. Perhaps indicating that our relatively low pH for our mash water didn't have a negative impact on lowering the final mash pH too much.

Rolling boil underway

Only a 30 minute boil for this one, with a second hop addition added with 5 minutes remaining along with our yeast nutrient and whirlfloc

Post boil gravity (original gravity) reading of 1.044 - as per the pre-boil gravity, 1 point higher than expected.

Chilling time - now that the weather is getting colder, so is our ground water, so we were able to achieve pitching temperature in under 20 minutes using the standard stainless steel immersion chiller, something we've never been able to do before. Helps that Philly Sour yeast recommend a slightly higher ferment temp of ~23°C too so we don't have to get the actual pitching temperature super low.

Before transferring we turned off the whirlpool recirculation to let things settle - amazing how the whirlfloc works here to help everything drop down much faster.

We pitched our 2 packets of Philly Sour yeast at around 25°C and left it drop to around 23.5°C overnight to find slight fermentation activity the next morning. Lallemand state in one of their Philly Sour videos that pitching warm is fine to do.

After brewing late on Friday night, and having fermentation beginning on Saturday morning, we decided to add our 2.5kg of frozen raspberries on Sunday night - approx 36 hours into fermentation.

Not a particularly cost effective exercise having to buy 5 x 500g bags of frozen raspberries, but it ended up costing about the same as a few bags of hops that we wouldn't hesitate to spend to drop into an IPA. We initially planned to use 2kg, but decided to up it to 2.5kg after reading a few other stories from people who wish they had added more fruit. Haven't come across anyone who said they added too much fruit to a fruited sour.

We attempted to blend the frozen raspberries in an electric blender but soon discovered this just didn't work when they were frozen. They just gunked up the bottom around the blades and didn't mix well. We quickly gave up on this then tried mashing them with a potato masher which yielded some improvement, but still a bit difficult when they're frozen, We really wanted them squashed to help get as much juice and sugar out of them as possible.

Plan B was to add them to a large stock pot and gently heat on the stovetop to help defrost them, and get them to around fermentation temperature (23°C) to avoid disrupting the wort temperature when adding them in. This worked pretty well we think - the final product can be seen below - nice and saucy. The constant stirring whilst heating up broke them down well.

Full disclosure - we were pretty negligent with our sterilisation here - and although everything we used was clean, it wasn't sanitised. We didn't bother with this for a number of reasons. Firstly, we were lazy and it was late on Sunday night. Secondly, the fruit was frozen and hadn't been pasteurized anyway and we had no intention of doing this. Thirdly, we're hoping that by the time any infection could take place from adding the raspberries, the wort would be at a lower pH that wouldn't really allow any nasty bacteria to take hold, and there also shouldn't be any available oxygen in the fermenter either since it's sealed off with a spunding valve (only set to 1psi). Perhaps we're wrong, but hey, even if something unforeseen happens we'll let it ride out and see what we're left with!

Fermentation is tracking along nicely, though it is noticeable how much slower Philly Sour yeast works compared to other ale yeasts.

You can see the large dip in the red line (gravity) in the middle here is where the raspberries were added. We're guessing that some stuck to the Pill hydrometer that causes some funky readings for a brief period there.