I finally got around to brewing a 22 litre batch.
To be direct I don't think much of the recipe & my brew was based on several changes.
This I see is an old thread but it came up with a Google search so maybe others might benefit from my comments:
1) It's plain daft to call up a given number of lemons (12, 24 ??) because the lemon cultivars vary widely in acidity, size, & taste. The lemon tree in our garden is a Meyer, the fruit is a bit smaller than a tennis ball, thin skinned & with a milder almost sweet lemon flavour. Ordinarily they are easy to juice & yield good quantities of juice. So base your brew on a set quantity of juice from the lowest cost lemons available. In my case, due to a poor season the plentiful fruit yielded less juice than I expected. So fortunately, we had some frozen juice from last year, & so supplemented & we ended up with 3 litres which had been my target. BTW 3 litres was based on another recipe I found.
2) I strongly recommend against chopping up the lemons & using everything (skin, pulp, juice & pith).
Instead use the juice together with the zest from as many lemons as you can manage, zesting is time consuming & tedious. In my case my wife zested 12 lemons selecting those with the best skins.
3) You need to pasteurise the zest & juice to avoid a brew contamination. I brought my wort to 80 C for 15 minutes, that's more than sufficient.
4) If you use 5 litres as the recipe suggests you will have trouble getting your pitch temp down. I strongly suggest that the 3 litres of juice with the zest is just fine & when you make up to 22 litres with chilled water as I did (Gold Coast, Queensland !!) you will be able to reach an acceptable pitch temperature for your yeast.
5) So decisions on which yeast - I don't know sorry - I used US-05 & a sachet of Coopers ale yeast pitched with 2 sachets of yeast nutrient at 25 C. After 3 days no action whatever, & I was about to discard & go lick my wounds; but then on day 4 fermentation became discernable, this continued for a further 7 days. I have never before seen anything like this pattern & I was of the opinion that I would probably end up discarding this brew. When I eventually kegged the brew tasting revealed no infection & a lemon flavour that was quite strong but not too strong. The yeast seemed to have settled on the fermenter bottom but there was a much lower quantity than I am used to seeing when brewing beer.
If I ever do this again I will probably try a wine yeast, maybe in combination with an ale yeast.
6) I chose, with my wife's "advice," to back-sweeten in the keg with 4 litres of Aldi bought cloudy apple juice. The type that has no added sugar, colouring, or preservatives ..... At this point I should say the uncarbonated brew tasted OK, I suspect that after carbonation & served at the appropriate temp this will be a decent drop.
7) In summary, the only fermentable material was 2 Kg of dextrose, (no lactose !!!!).
Hope this long post will be of help, as always comment welcomed.