convertible sugar in watermelon juice?

I'm brewing up a watermelon wheat beer in a day or so. I'm trying to calculate the final abv and am wondering if there is much contribution from the sugars that are in the watermelon juice? I have about 5 liters.

Take the watermelon juice and throw a hydrometer in it. That'll get you the (approx) sugar content of that liquid.

Right, but will that tell me the difference between fermentable and unfermentable? Or is the sugar in juice all sucrose and easily digested? If so, then the hydrometer reading at the end of the boil / chilling process would work just fine.

theblaster said:

Right, but will that tell me the difference between fermentable and unfermentable? Or is the sugar in juice all sucrose and easily digested? If so, then the hydrometer reading at the end of the boil / chilling process would work just fine.

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Most, if not all the sugars in a watermelon are simple sugars that will be completely digested. That's how most fruit works.

theblaster said:

Right, but will that tell me the difference between fermentable and unfermentable? Or is the sugar in juice all sucrose and easily digested? If so, then the hydrometer reading at the end of the boil / chilling process would work just fine.

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Doesn't matter if you just want ABV calcs.

Are you adding this into the boil???

Watermelon juice is about 6%-10% sugar. Of the sugars, about 60% fructose, 35% glucose, 5% sucrose. Should be all fermentable. Give it a try, nothing to lose.

AmandaK said:

Doesn't matter if you just want ABV calcs.

Are you adding this into the boil???

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I would add it in secondary, watermelon just isn't the same when it is warmed up

Post boil for sure. Last time I did it at flame out (is there a better time?). About 2 liters of juice. It had some flavor, but less than what I had hoped. This time with 5 liters, I'm hoping to get there.

Doing some basic math based on the numbers in the site below, 5 liters of watermelon juice should provide about .4 lbs of sugar.

http://www.whfoods.com/genpage.php?tname=nutrientprofile&dbid=4

Thanks for the help and guidance.

5 liters? I assume this is for a 5 gallon batch? That should be a HUGE watermelon flavor. I've made two 5 gallon batches myself, with only 5 CUPS of watermelon juice in each, and both had a very prominent watermelon flavor (and tasted great, btw). I'm not sure if 5 liters would be overkill or not, but that is gonna be dependant on your preference. To me, 5 cups did the trick.

Also....I added my juice to the secondary and simply racked over top. Two week, primary, two week secondary, then bottle/keg.

I wouldn't be surprised if I lost a lot of flavor by adding it at flame out instead of in secondary. That may be why 2 liters didn't give me as much watermelon prominence as I wanted. 1 tweak at a time. If this doesn't work, maybe I'll drop it in secondary next time around.

I believe I used V2 on the link below. I think it's a good one

https://www.homebrewtalk.com/f75/watermelon-wheat-139086/

theblaster said:

I'm brewing up a watermelon wheat beer in a day or so. I'm trying to calculate the final abv and am wondering if there is much contribution from the sugars that are in the watermelon juice? I have about 5 liters.

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actual watermelon juice runs about 10-11% brix (1.020 or about). its mostly water.
commercial concentrate or juice can be much higher

theblaster said:

I wouldn't be surprised if I lost a lot of flavor by adding it at flame out instead of in secondary. That may be why 2 liters didn't give me as much watermelon prominence as I wanted. 1 tweak at a time. If this doesn't work, maybe I'll drop it in secondary next time around.

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I would really recommend doing secondary if you haven't already added it at flameout. In my experience it doesn't make the flavor less prominent, it completely ruins the watermelon flavor. I tried to make some watermelon wine a while back and it was hella trife because I used warm water to extract the flavor.