View Full Version : Calculating how fruit water content affects gravity

Hi everyone.

I've put together a recipe roughly based on Curt Stock's Super Berry Melomel scaled down for a 5L batch.

2.5kg honey

2.5kg blueberries

500ml red grape concentrate

2.5L water

Lalvin 71B

I measured the OG at 1.160 before I added the fruit (it might have actually been higher because this is about the limit for my hydrometer). A few weeks later and it's now down to 1.026 and still going. That would give me an ABV of over 17% which is higher than the yeast's tolerance.

So I'm assuming that the water from the fruit diluted and reduced the OG. My question is, how can I work out my actual OG to take into account the added water from the fruit? I've tried searching but not found a concrete answer.

caduseus

01-30-2017, 09:50 AM

Hi everyone.

I've put together a recipe roughly based on Curt Stock's Super Berry Melomel scaled down for a 5L batch.

2.5kg honey

2.5kg blueberries

500ml red grape concentrate

2.5L water

Lalvin 71B

I measured the OG at 1.160 before I added the fruit (it might have actually been higher because this is about the limit for my hydrometer). A few weeks later and it's now down to 1.026 and still going. That would give me an ABV of over 17% which is higher than the yeast's tolerance.

So I'm assuming that the water from the fruit diluted and reduced the OG. My question is, how can I work out my actual OG to take into account the added water from the fruit? I've tried searching but not found a concrete answer.

Mead calculator on this site or brewers friend recipe calculator

Unless I'm using it incorrectly, the calculator is telling me that adding the fruits increases the OG, rather than decreases it. Which is contrary to what I've read elsewhere.

djsxxx

01-30-2017, 04:12 PM

Yeah I don't understand how the calculator works with fruit... If said fruit has a gravity of 1.020 (just random figures here) and you add it to a must with gravity 1.100 then you're going to reduce the overall gravity.

The only way fruit could increase the gravity of your must is if the gravity of the fruit is higher than the must, which I doubt it ever will be.

Sent from my SM-G925F using Tapatalk

bernardsmith

01-30-2017, 04:23 PM

I don't use calculators (perhaps that's my problem?? ) but I would think that all you do is add the sugar content (in your example about 1/2 lb ) to the total sugar content (say 3 lbs) and add the volume of the juice - say 1 gallon to the total volume of the must say 1 gallon so you now have 3.5 lbs of sugar in 2 gallons (or approx 1.75 lbs in 1 gallon )- and 1.75 lbs * 040 (approx) = an SG of 1.070

Dadux

01-30-2017, 05:13 PM

The calculator calculates the SG from the volume. the volume is final, that is, if you add 2kg of honey to 4l of water you have around 5.5l, so for the SG to be calculated properly by the calculator you have to put in the "volume" field 5.5l (you must put the FINAL volume of the must once all the fruit juices and honey has been added). The OG rises because the fruit has sugars and the calculator asumes the volume is already provided by you in the "volume" field. Dont know if i express myself well. An easy way to see how much water you fruit will add is take its sugar % (given by the calculator, lets say its 10% for blueberries) and assume you have a juice of 1/2 the weight of the blueberries (aka 1.2l). You the add the 1.2l to the final volume and Voila! (the volume=1/2 of the weight is just my personal goto for some fruits. obviously some fruit have more than 50% water content (melon, pear, grape....) and some may have less (risins dont have nearly anything...). Im just guessing that for blueberries its 50% more or less but you can search for a more exact amount in the internet if you want.

With the concentrate is easier since its liquid (so you know the total volume it adds), and you should know how much sugar it has.

Hope this was of any help.

Edit: ah also, the ABV yeast tolerance means little. If good nutrient conditions are provided you can get a 14% ABV yeast to ferment to 18-19%. So you COULD be in the 17% ABV range.

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