I have a 2.5 gallon batch of watermelon berliner weisse fermenting right now (see previous thread). Based on aroma alone (I'll taste it tonight), the watermelon character doesn't seem to be quite as high as I was hoping. I'm thinking about priming with watermelon juice at bottling time next week, but I want to make sure I'm calculating the amount correctly. I'm shooting for 3.2 volumes of CO2, and I'm assuming that the sugars in the watermelon juice are 100% fermentable. An online calculator says I would need 3.4 oz of corn sugar (1.046 ppg) to prime this batch, which I calculate as about 10 gravity points total (3.4/16)*46 = ~9.8. Assuming the watermelon juice has a gravity of 1.030 (I'll take this reading when I collect the juice to be sure), this means I would add about 5.5 cups of watermelon juice to prime. (10/30 = .33) & (.33 * 16cups = ~5.3 - rounding up to 5.5) My volume will increase by that 5.5 cups, which would skew the original priming numbers a bit, but I'm thinking it'll be close enough given that I'm rounding up to 5.5 anyway. Am I wrong in my thinking here?
From the little I've done it looks like 2 tsp of table sugar would be the same as 9.8 oz of watermelon. I hope your reading of 1.030 is right on the watermelon gravity. The unknown answer that you need to account for is the FG of the watermelon. I hope, for your sake, it's around 1.000. https://www.google.com/webhp?source...&espv=2&ie=UTF-8#q=watermelon+sugar+content&* https://www.fatsecret.com/calories-nutrition/usda/granulated-sugar
I'll take a gravity reading of the juice once I collect it to confirm that gravity, but from what I've read 1.030 is typical for watermelon juice. My understanding is that fruit sugars are 100% fermentable, so I'm essentially treating them 1:1 with corn sugar. I just hope there isn't other "stuff" in the watermelon juice besides sugar which is accounting for its gravity. In case anyone brings it up, I've considered adding more watermelon juice to the primary fermenter, then priming with corn sugar as usual. However, I'm already pushing the capacity of my 3-gallon carboy, and I don't want to transfer all of this to one of my 6.5-gallon fermenters.
I'm not sure @CarolusP is assuming an FG of watermelon juice of 1.000. I think it would be more accurate to say that he's assuming the FG of watermelon juice is the same as the FG of an equivalent gravity of corn sugar. That might be right or it might be wrong, but it needn't be an FG of 1.000. I see that you've considered and rejected the suggestion I was going to make (adding watermelon now and then priming normally). If the issue is space in the fermenter, would it be feasible to add some kind of concentration or reduction of watermelon juice?
I could probably check my local grocery store to see if they have concentrated watermelon juice of some kind. I didn't want to attempt a reduction, since I had read that heating watermelon juice up to that point really destroys the flavor and aroma.
Hey Hey Hey: It sounds like if we up the ante any more we'll be sparging with warm watermelon juice when we try to make this.
