Determine SG when mixing wort

[Bluelinebrewer]

Ok, so I'm not exactly mixing wort, but, I'm guessing there's a calculator somewhere for this, I just can't find one! Here's what I'm attempting. Trying to brew a grape ale, the fermentables are 75% pale malt and 25% grape juice. The OG needs to be at 1.040. (Trying to clone a beer here.) So, I need to figure out how much grape juice to add to what to figure out how to get to 1.040. Does that make any sense at all?? Maybe I'm going about this the wrong way, if anyone knows a simpler method, please feel free to enlighten me! Thanks!

 

[Hex23]

The answer as to how to go about it depends on what the 75/25 means. Is it 75/25 by weight or 75/25 by gravity contribution? If the latter, that's really easy to calculate. If the former, it's a little harder, but still pretty easy - would just require a little simple algebra.

 

[Bluelinebrewer]

The answer as to how to go about it depends on what the 75/25 means. Is it 75/25 by weight or 75/25 by gravity contribution? If the latter, that's really easy to calculate. If the former, it's a little harder, but still pretty easy - would just require a little simple algebra.

Well, the email from the brewmaster didn't exactly specify. I'm going to guess 75/25 gravity contribution. My initial thought was to just brew a 100% pale ale malt wort, at 4.125 gallons (I think that's 75% of 5.5 gallons) then add enough grape juice to make 5.5 gallons. But I'm afraid that'd really hike up the OG.

 

[Qhrumphf]

You're referring to actual fermentables, and not weight or volume of ingredients, correct? Want 75% wort sugar, and 25% grape juice sugar, and not 75% wort, 25% grape juice? Or 3 pounds grain to 1 pound grape juice?

Do you know the Brix of the grape juice? This is actual juice, not concentrate, correct?

According to this http://www.fruitsmart.com/PDFs/TechnicalForms/SSBrixChart.pdf, it may be 16 Brix, and a couple other locations seem to concur, one saying that 16 Brix is a federally regulated level. That would mean an SG of 1.065.

From there, work in Gravity Points. Say you're doing 5 gallons, and you want 1.040 OG. That's 200 gravity points, 25% of which is 50 gravity points. That 65 gravity points per gallon makes .77 gallons of grape juice to give you those 50 points. then you need 4.23 gallons of 1.035 wort. Should give you 5 gallons at 1.040, or close enough at least.

 

[Hex23]

First calculate total gravity points: 5.5 gallons * 40 pts = 220 pts

75% Pale => 165 pts from pale
25% Grape juice => 55 pts from grape juice

Assume 70% efficiency and 37PPG potential extract from the grain => 25.9 PPG

So, you need 6.4 lbs Pale malt to get 165 pts.

I read that grape juice is commonly around 1.090, but you might want to research that further.

To get 55 total points, you'd need 55/90 gallons => 0.6 gallons

So, the malt beer portion needs to comprise 4.9 gallons, which means you'll be making 4.9 gallons of a ~1.034 beer and adding about 0.6 gallons of grape juice

 

[Bluelinebrewer]

You're referring to actual fermentables, and not weight or volume of ingredients, correct? Want 75% wort sugar, and 25% grape juice sugar, and not 75% wort, 25% grape juice? Or 3 pounds grain to 1 pound grape juice?

Do you know the Brix of the grape juice? This is actual juice, not concentrate, correct?

According to this http://www.fruitsmart.com/PDFs/TechnicalForms/SSBrixChart.pdf, it may be 16 Brix, and a couple other locations seem to concur, one saying that 16 Brix is a federally regulated level. That would mean an SG of 1.065.

From there, work in Gravity Points. Say you're doing 5 gallons, and you want 1.040 OG. That's 200 gravity points, 25% of which is 50 gravity points. That 65 gravity points per gallon makes .77 gallons of grape juice to give you those 50 points. then you need 4.23 gallons of 1.035 wort. Should give you 5 gallons at 1.040, or close enough at least.

Yes!! Thank you!! That's exactly what I was looking for!

 

[Hex23]

Looks like grape juice gravity has a pretty wide spectrum. The 1.090 was what I read as a starting gravity for a common table wine. 1.065 might be closer for ordinary grape juice. You might be better off measuring it yourself.

 

[Bluelinebrewer]

Looks like grape juice gravity has a pretty wide spectrum. The 1.090 was what I read as a starting gravity for a common table wine. 1.065 might be closer for ordinary grape juice. You might be better off measuring it yourself.

The juice I was looking at was 18 brix, according to the website.

 

[Bluelinebrewer]

I did notice that it says it has sulfites added to the juice.. what kind of issues is that going to cause me?

 

[Hex23]

For grape juice, that should mean about 1.074.

 

[Hex23]

I did notice that it says it has sulfites added to the juice.. what kind of issues is that going to cause me?

It might depend on the amount, but it could impact the health of the fermentation. It's a preservative that can interfere with yeast reproduction.

 

[Bluelinebrewer]

It might depend on the amount, but it could impact the health of the fermentation. It's a preservative that can interfere with yeast reproduction.

Ok, thanks. Guess ill give it a shot and see what happens!

 

[Qhrumphf]

Looks like grape juice gravity has a pretty wide spectrum. The 1.090 was what I read as a starting gravity for a common table wine. 1.065 might be closer for ordinary grape juice. You might be better off measuring it yourself.

The juice I was looking at was 18 brix, according to the website.

http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=101.30

Source I was looking at was PARTIALLY correct. FDA regulations do list grape juice as 16 Brix, but that's a minimum. It can be more.

If it says it's 18 Brix, that's probably safe to go with. If you want to be thorough, I'd measure it yourself.

In any event, the math is the same, just plug in the relevant numbers.

And as far as sulfites, there I have no idea. Maybe the folks over the wine section could help?

 

[Bluelinebrewer]

http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=101.30

Source I was looking at was PARTIALLY correct. FDA regulations do list grape juice as 16 Brix, but that's a minimum. It can be more.

If it says it's 18 Brix, that's probably safe to go with. If you want to be thorough, I'd measure it yourself.

In any event, the math is the same, just plug in the relevant numbers.

And as far as sulfites, there I have no idea. Maybe the folks over the wine section could help?

Good idea, ill give them a shout and see what they have to say. Thanks again for the tips!