I got into brewing seltzer during the spring of 2021, and these are my notes. They're in descending order, so the most-recent are at the top. The notes got progressively less-detailed as time went by, so those looking to actually learn things (e.g. "How much yeast nutrient should I use in a seltzer that's 100% dextrose") should read the highlights and then read from bottom-up. :)

Highlights:

• Kveik Voss is fast-fermenting and relatively transparent flavour. Excellent for seltzer
• It does take a couple days post-fining for the yeast scent to diminish
• Recycling yeast is tricky with seltzer due to all the fruit sediment
• With only sugars and fruit flesh, yeast nutrient is essential - about 15 grams seems to do the trick
• One kg of dextrose in 19 litres will raise the ABV by approximately 2.65%
• Don't boil the fruit or you'll get pectin haze; raise it to about 75°C to sterilise it, though
• Table sugar is a perfectly passable sugar; make invert sugar by boiling it with a little citric acid, 20-60 minutes
• Citric acid is amazing

Fruit notes:

• Mashing the fruit a little bit is a significant factor in releasing the fruit flavours
• Lychee have quite a prominent character, good to pair with something that can compete
• Mandarins will impart very little flavour unless you mash them really good pre-ferment
• Jackfruit is almost undetectable, even with two cans; will try blending next time
• Pineapple seems to digest(?) other fruits. The other fruit becomes quickly less-noticable while the pineapple becomes more prominent
• Raspberries create a visually beautiful brew, as do plums
• Passionfruit pulp is pretty disappointing; in brew #7 I used THREE cans, and it was nearly undetectable
• Mango is pretty awful, really - lots of fruit mush, lots of haze, some weird aged-fruit flavour... avoid imho

Yeast Awakener

To reawaken the yeast from the fridge, I make a mix of:

• A tablespoon of sugar (any variety, often dextrose)
• 10 grams chopped raisins OR 2tsp lemon juice
• 6 grams Marmite
• Pinch of yeast nutrient

Once those are dissolved together, I pour in collected yeast from the previous batch.

Other thoughts:

• 2022-01-04 - my brews are still coming out very sweet - I'm yearning for something with a dryer character. Hard seltzer was featured in an exBEERiment on Brulosophy on the difference between dextrose and sucrose (it seems table sugar will be fine!), where Phil mentions using the W04 Paramount wine yeast(!), along with 32g of yeast nutrient(!!). Perhaps this will solve my sweet brews? Might also get my water acidity tested to make sure it's at a good pH for the fermentation.
• 2022-01-21 - the increased yest nutrient is working out very well; much cleaner and dryer - 25g seems good. Ordered some Fermaid AT today as well to see if a slower release of yeast-available nitrogen (YAN) will support the yeast better

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Recipes and notes

Brew #11, 2022-03-12 - brewing: Blueberry and Mandarin Seltzer - large edition

Recipe:

• 3kg invert table sugar
• 10g Citric acid
• 15g+15g Fermaid-AT
• Kveik Voss
• 310g tinned mandarins
• 1275g tinned blueberries

Notes:

• Decided it was high time to brew a larger batch - this is a 25 litre brew
• The citric acid has been amazing - boosted the quantity in this one to compensate for the larger proportion of fruit
• Dosed 15g of Fermaid-AT at inital brew; will dose another 15g at 3 days
• Looking to try some amylase enzyme to see if I can really dry out the seltzer

Brew #10, 2022-02-20 - 2022-02-28: Blueberry and Mandarin Seltzer

Recipe:

• 2kg white table sugar (see notes)
• 5g Citric acid
• 10g+10g yeast nutrient (Fermaid-AT)
• A fresh Kveik Voss
• 310g tinned mandarins
• 850g tinned blueberries

Notes:

• My Fermaid-AT has arrived! It's used at a rate up to 1g/l in low-YAN environments, so used 10g and will add another 10g in 2 days
• Two batches of 10g FermaidAT was pretty good, the Kveik chews that stuff up super-quick, literally over 36 hours
• I really liked this combination so revisiting the double-blueberry and mandarin with a couple tweaks
• The invert sugar experiment seemed to be a success, so 2kg table sugar + 5g citric acid; boil for 20mins
• Easily one of my favourites - possibly THE favourite - so far. 4/5, only minor improvements
• Update, citric acid is amazing, absolutely brings the zing that I was craving. Still getting sweet brews but much more balanced now
• Next brew will try 15g+10g nutrient

Brew #9, 2022-01-26 - 2022-02-01: Apple, Mango, and Guava Seltzer

Recipe:

• 2kg white table sugar (see notes)
• 4g Citric acid
• 23g yeast nutrient
• My weird hybrid yeast now (see notes)
• 1kg diced apple
• 410g tinned guava
• 850g mango pulp

Notes:

• I ran out of yeast nutrient so only 23g this time
• Overshot water, but had lots more fruit than normal so this is a 24l batch
• Decided to attempt invert sugar instead of dextrose! 2kg table sugar + 4g citric acid; boil for 20mins
• The Kveik Voss + Mangrove Jack's Seltzer yeast is doing the job very nicely
• Initial flavour suggests this might be a goodie.
• Final flavour - meh. 2/5, I wouldn't brew this again. The citric acid seemed to be a good call though.

Brew #8, 2022-01-16 - 2022-01-21: Blueberry and Mandarin Seltzer

Recipe:

• 1.7kg Dextrose, 300g white sugar
• Kveik Voss plus Mangrove Jacks' Seltzer yeast
• 25g yeast nutrient
• 310g tinned mandarins
• 850g tinned blueberries

Notes:

• Previous run went very well (much drier result), so bumped nutrient to 25g!
• Recycled the Kveik Voss + MJ's Seltzer yeast from last batch; seemed pretty okay
• Result - an absolute banger! Really delicious; next time I'll replace the mandarin with something more acidic though

Brew #7, 2022-01-05 - 2022-01-10: Pineapple Passion Seltzer

Recipe:

• 2kg Dextrose
• Kveik Voss plus Mangrove Jacks' Seltzer yeast
• 20g yeast nutrient
• 420g tinned crushed pineapple
• 510g tinned passionfruit pulp

Notes:

• Increased yeast nutrient to 20g this time, will see if it makes a difference. (Update - huge difference!)
• Probably made a mistake with my yeast. I'd started up some Mangrove Jacks' seltzer yeast to try... but then remembered how slow it is, so I pitched some fresh Kviek on top of it. Eek... I expect the Seltzer yeast to create some off flavours at 36°
• Also made a mistake with the yeast nutrient - I completely forgot it until the fermenter was already in the fridge! Boiled some up and added it in, hopefully it doesn't really need much boiling.
• Result - this one wasn't a winner for me. It was dry like I wanted, but the passionfruit was a big disappointment

Brew #6, 2021-12-28 - 2022-01-02: Plum, Pineapple, and Mandarin Seltzer

Recipe:

• 2kg Dextrose
• Kveik Voss yeast
• 14g yeast nutrient
• 850g tinned Black Doris plums
• 420g tinned crushed pineapple
• 310g tinned mandarins

Notes:

• Thoroughly crushed the plums and mandarins with the back of a fork this time
• Had real trouble reinvigorating the yeast from the previous brew; might need to order a spare yeast for backup
• 10% Brix at start; finished just under 8% Brix... if this refractometer is accurate, these are very low ABV
• Result - this was absolutely one of my favourites. Great outcome!

Brew #5, 2021-12-21 - 2021-12-25: Pineapple and Double Raspberry Seltzer

Recipe:

• 2kg Dextrose
• Kveik Voss yeast
• 16g yeast nutrient
• 850g tinned Raspberries
• 420g tinned crushed pineapple

Notes:

• Visually beautiful, great nose, and quite refreshingly delightful to drink.
• The acidity of the raspberry and pineapple combined made this taste much like a kombucha. Weird.
• Failed to take any gravity readings.

Brew #4, 2021-12-12 - 2021-12-17: Black Doris Plum and Pineapple Seltzer

Recipe:

• 2kg Dextrose
• Kveik Voss yeast
• 12g yeast nutrient
• 850g tinned Black Doris plums
• 850g tinned pineapple (half crushed; half chunks)

Notes:

• Initial tasting is very much drier than the others - not sure if this was the acids in the pineapple cutting the sugar, or if the sugar syrup in the cans was way thinner? Either way, this may end up a low percentage.
• Original brix reading looked to be about 7%, suggesting an expected ABV of only 3.6%
• (later): turns out I have no idea how refractometers work. Never mind.
• This recipe came out amazing, absolutely delicious. Started out with a fairly subtle plum flavour, with the pineapple just becoming perceptible at the end.
• However, during the week the plum flavour diminished and the pineapple flourished. This continued to the point where it was actually really unbalanced; I suspect it was caused by enzymes in the pineapple... to combat this, next time I'll use only one tin.

Brew #3, 2021-12-04 - 2021-12-10: Lychee and Jackfruit Seltzer

Recipe:

• 1.2kg Dextrose, plus other assorted sugars to 2kg (approx 5.3%)
• Kveik Voss yeast
• 16g yeast nutrient
• 850g tinned jackfruit
• 560g tinned lychee

Notes:

• Brewing out much quicker now with the increased nutrient
• Lychee is very prominent in finished product. Not overwhelming but definitely star of the show
• Jackfruit brings very little flavour. Next time I might blend it up but worried about post-brew yeast collection

Brew #3, 2021-11-26 - 2021-12-03: Double Raspberry and Mandarin Seltzer

Recipe:

• 2kg Dextrose (for approx 5.3%)
• Kveik Voss yeast
• 16g yeast nutrient
• 820g tinned raspberries
• 310g tinned mandarins

Notes:

• Doubled the raspberry; reduced the dextrose; tripled the yeast nutrient
• Raspberry far more prominent and yum. Zero impact from mandarin
• Yeast nutrient really helped. Still a bit sweet but far better; probably no need to change
• Adding the dextrose, plus approximate sugar syrup and fruit sugars, suggests a 6% ABV

Brew #2, 2021-11-17 to 2021-11-24: Raspberry and Mandarin Seltzer

Recipe:

• 2.5kg Dextrose (for approx 6%)
• Kveik Voss yeast
• 5g yeast nutrient
• 410g tinned raspberries
• 310g tinned mandarins

Method:

• Filled keg to 12l line with tap water
• 2.5kg Dextrose + 6g nutrient into 3 litres of water. Heated to 80°C
• Took off heat, added tin of raspberries and tin of mandarins, including syrup; mashed up a bit
• Brought temp back up to 75°C, and poured it into 16 litres of room temp water
• Pitched Kveik yeast at 29°C. Total 20 litres ish, fermenting at 32°C

Notes:

• Brew finished on 2021-11-24, exactly a week later
• Kveik ferments much quicker, and very clean; happy
• Mandarin very subtle, raspberry present but light. Still delicious
• Didn't add enough yeast nutrient!! Extremely sweet, but yeast has gone mostly dormant
• Forgot to account for sugars from fruits; happy the yeast went to sleep before I got rocket fuel

Brew #1, 2021-10-25 to 2021-11-12: Mangrove Jack's Pineapple Sunset Hard Seltzer

Brewed as per instructions, but added 12g of Mangrove Jack's Passionfruit Beer flavour boost. Fermented a little slow; took a bit over two weeks to finish

Tasting notes:

• Came out with the same acrid/chemical flavour that many others complain about
• Brewing process super simple, though. Think I can do this myself without a kit