Calculating alcohol in must by weight loss idea

[casebrew]

I brew fruit wines, on the peels, for maximum flavor and color. And efficiency too, pressing after all the enzymes have ripened the pulp has to allow for better extraction. Like mashing for beer.

But I've never had any confidence in checking sugar levels by specific gravity. What with the 'stuff' swirling around, and the sugar still bound up in pulp, I didn't think it worked. Refractometer neither, with much sugar still in pulp. And I want a guess at ABW, ever since I added too much sugar to a plum wine, and needed a chaser with every sip.

So, here's my idea- I weighed my vessel of must after all of the initial additions. Lets say 50 pounds. I'll weigh it before pressing, let's say 45 pounds. 5 pounds of CO2 lost, so being as yeast makes alcohol at the same rate as CO2, (49/51, equal is close enough for my calculations) , there ought to be 5# of alcohol. Press the wine, weigh again, calculate the ABW using the 5# of alcohol, convert to ABV. Then, using the 50% alcohol basis, add appropriate amount of sugar to hit target ABW.

At a later racking, I can figure ABV by refractometer and SG, for final adjustment.

It won't be within 1/10%, but it ought to be better than trying to guess at the sugar content of must.

Whaddya think?

PS, I have a doctor's office scale, marks in 1/4#. Excellent for so many uses in brewing. Perhaps this is a case of "If the only tool you have is a hammer, all of your problems look like nails"?

 

[Yooper]

I don't know- I've always been able to take a drop of juice out of the fruit and get a refractometer reading pretty easily. Then I just calculate the water/sugar additions to get the OG. Or even a reading of the must would be ok- it's not like more sugar comes out during fermentation. It's all there in the beginning.

I also ferment on skins/peels/pulp and I'm sure my OG readings are very close to the actual OG.

 

[casebrew]

... it's not like more sugar comes out during fermentation. It's all there in the beginning.

How can it be? There is still plenty of ripening to be done, that is why fruit turns brown, and gets sweeter. Or do the complex starches that later turn into sugar have the same SG as sugar? Or the same refractometer reading as sugar? I wouldn't think so.

But, when you calculate the amount of sugar to add, how do you allow for the weight of peels? I guess a guesstimation is close enough though.

Perhaps I am over analyzing things. I just realized that the root word of analyze is 'anal'...

 

[Yooper]

How can it be? There is still plenty of ripening to be done, that is why fruit turns brown, and gets sweeter. Or do the complex starches that later turn into sugar have the same SG as sugar? Or the same refractometer reading as sugar? I wouldn't think so.

But, when you calculate the amount of sugar to add, how do you allow for the weight of peels? I guess a guesstimation is close enough though.

Perhaps I am over analyzing things. I just realized that the root word of analyze is 'anal'...

The sugar is there- it's not like the fruit "ripens" during fermentation. Starches don't convert into sugar in the must- the sugars are already present and are fermented by the yeast. The refractometer reading in brix is basically measuring the sugar content.

When I make 6 gallons of wine, I make the calculations based on 6 gallons. The weight of the peels/pits/bag has nothing to do with the amount of volume.

 

[casebrew]

Now hang on. My fermenter has basically two active items in it. A fluid of juice, water, and added sugar. And chunks of fruit. You are saying that the chunks of fruit do NOT have any sugar to add to the fluid? Then what would be the point of pressing the must later?

I know I used chunks of fruit to make the must, and that in a week, the chunks will be pretty gone, so there is some enzyme/ripening/disolution action.

I guess what you are saying is that it is not enough to make a difference. We could tell fersure by checking brix with the refract before and after pressing.

No, wait, it has been fermenting for 5 days. Check the wine, and then check the juice by squashing a chunk, you say the chunk should not have a higher sugar level, correct?

I just did that, wine reads 15°, juice reads 16°.

So, pressing will make changes. The contents of the chunks are NOT reflected in OG or refract readings. Though they may be too small to matter, eh?

ETA, Lessee, I guess before brewing, I could check the fruit brix, caclulate the total sugar, and go from there. Like, 40# Loquats, 28# after pitting and chopping, 17% of 28# = 5# sugar, target 11% alcohol, 22# needed for a 7 gallon batch, so add 17# sugar. (adjust for abv vs abw) ETA, no, that won't allow for the weight of the peels etc that get discarded at pressing. So, go lighter on the sugar, weigh the junk at pressing, make another adjustment?

 

[mmadmikes1]

The fruit adds both sugars and water at the levels of original juice. That means your SG stays the same. If you add sugar to must , how much does it ntake to raise your SG .01? The fruit does not have any where that amount of sugar left in it to give up

 

[DrJerryrigger]

I have to agree that you'll get more accuracy with a hydrometer, as the fruit will change things only a little bit. Though if you have the equipment, try the weight thing, I'd be interested in your results.
I would guess that your results would be quite confusing as ripening fruit off gasses. It may be a better experiment for a simple wine first.

 

[casebrew]

... ripening fruit off gasses.

Thanks, that is my point- fruit changes in the fermenter.

Though the changes may be inconsequential to homebrew bathtub chemistry.

 

[mmadmikes1]

Of course it changes, other wise we would be making fruit juice

 

[DrJerryrigger]

So if you had a scale that could weigh a full carboy to 0.01 grams, you could see the fermentation's reduced weight due to CO2 off gassing. The dissolved CO2 will vary based on the temp and pressure. If you have fruit in there with it, the fruit will be breaking down in various ways, maybe giving off ethylene (and changing weight).
Anyway I think that it is too complicated a situation to accurately monitor by weight, even if you had really good equipment. A hydrometer is not a perfect solution for your situation either, but it's pretty good (about +or- 0.0015).

 

[DoctorCAD]

Wow,

I think you are reading way too much into this.

The yeast will make alcohol, period.

Why worry about it? The ABV will be somewhere between 10 - 15% if everything goes right.

 

[truckjohn]

Or... you could buy a refractometer and not have to worry about all the pulp messing up your sg readings with a hydrometer....

Thanks

 

[casebrew]

Jerryrigger, we are talking oh 10% in a 50 pound batch, or about 5# of alcohol. No need to weigh it to .o1grams.

Truckjohn, I do have a refractometer. I thought that would have been clear in my earlier mention of brix. Or not.

So far as ethylene gas goes, that is proof that not all of the sugar is in solution, as sugar. And the weight of ethylene is minuscule.

Well, my 54# batch lost 4# in a week, that is about 8% abw, x 1.2 = 10% ABV. So I added 4# sugar at pressing/racking. 12.5 refractometer brix. Total sugar added is 11#. The recipe, from Jack Keller, calls for 14#. An extra 3# would be an extra 3.6% ABV.

There is just no way to know sugar content of must. It is just too variable, especially among different species of fruit.

I'm not sure if I mentioned this batch is Loquat? This is my 8th batch of Loquat in three years. It sure is a light color, and the fruit is four weeks late this year. Tastes good though.

I sure like Loquats for wine. It usually ripens in March, brews fast, settles fast, drinkable in early May.