Need help adjusting acid level in black currant wine

[swhitsit]

I've been making some Black Currant wine using Vintner's Harvest "Fruit Base" and its been quite excellent. So, I decided to step it up and acquire 5 gallons of Black Currant concentrate and make an approx 35 gallon batch of black currant wine. My question, and it's rather urgent, has to do with the dilution level and Total Acidity of this new monster batch.

As background, I measured the BRIX and acid levels on Vintner's Harvest and it appears to be a diluted form of black current ... not at all a concentrate. The standard BRIX for black currant juice is 11, but the BRIX from the VH fruit base out of the can (before dilution) is only 6. Using two 96oz cans (1.5 Gal) in a 6 gallons with 10 lb of sugar typically gets me to about a BRIX of 22 or SG of 1.09. But at that dilution level it would seem that the black currant is actually quite diluted. I'm assuming that I am missing something here because the resulting wine is not thin at all.

Fast forward to the concentrate I have, and it is delivered as a true concentrate with a BRIX of 65 (I have no way to measure than on my refractometer) . My calculations showed that I would dilute it at a factor of 5 (1 gal of conctrate and 5 gal of water) to get to a normal brix of 11. My plan was then to Chaptalize the resulting must back to something around an SG of 1.090.

Because the juice is so concentrated, the acid level is way high. I took 4 gallons of the concentrate into a 44 gallon primary, diluted with about 32-33 gallons of water to get the juice itself close to 7 Brix. I then used 40 pounds of sugar and got my must to an SG of 1.090, which was my goal. However, the total acid was still way to high (25 g/L or 2.5%).

I was hoping some of the acid would ferment out, but on day 3 the SG is now 1.065 and the acid level has not changed. I need to do something quickly to adjust, and my thought is that my original juice was way too concentrated ... even though it was diluted below where a standard black currant juice would be by just looking at the Brix level.

My thought is as follow:
Prepare a spring water, sugar, and yeast nutrient mix with a matching SG of 1.090.
Rack from the primary into my 32 Gal secondary fermenter with a blend of this water and let it continue to ferment. I'm thinking that if the yeast can keep going the resulting wine will still be in the 12% range. But to get my acid from 2.5% down to 0.7- 0.8% I will need to dilute by more than half.

It seems drastic, but if the Vintner's Harvest black currant startes at a brix of 6 and is diluted 3 to 1, maybe I should have diluted this batch significantly more to begin with?

Help me obi won kenobi ... you are my only hope

 

[Bob_wv]

If it falls to me, all hope is lost

That's alot of acid. How did you measure that acidity? I never made black currant, but I looked around and most recipes and more citric acid (1 tsp/gal or so). Are you sure it's not .25%?

 

[swhitsit]

These are the details from the vendor.

Product of Poland
65 brix
14.24% approx. acid

I measured the concentrate, and it was about 14% before dilution so I think the testing and their number is pretty close. I am using the standard TA test with Sodium Hydroxide 0.1N and a pH meter to estimate completion. I measured the must yesterday, and it took 19 ml of the 0.1N solution to get to pH 8.2, which would calculate out to about 28 g/L or 2.8%.

So, last night I mixed up 5 gallons of 1.090 sugar water and added 1 tsp of Fermaid K nutrient. I did bench trials with a variety of mixes (1/4, 1/3, 1/2, 2/3 water to must) and then tested pH and TA. Apparently the pH doesn't change much when you dilute must as even after mixing the pH was still around 3.05 per my Hannah Checker pH meter.

The 1/2 water to 1/2 must mix tested out to 18 g/L, or 1.8%, which is still too high for me. But, it has an SG of 1.07 now and should ferment for several days so I'm hoping it will continue to come down. The 1/2 mix is still relative strong flavored and a VERY dark purple, so I'm coming to the conclusion that I way under diluted the juice.

I think this is probably a common issue for people that try to work with large quantities of fruit concentrate, because the acid is quite high to help preserve the juice. Kit juices like Vintner's Harvest seem to be quite diluted to begin with (ingredients are black currant juice and water), and I've had to add acid back to those juices to get my must into the .6 - .7% target range.

I guess one of my big questions for the community regarding acid is where I might find a table that shows average TA for various fruit juices. The average brix is easy to find (black currant is 11) but I have no idea what the average TA should be for the juice itself. I'm also curious about whether people dilute the black currant juice to something like a brix of 2 before sugar. From what I can tell, the Vintner's Harvest fruit base ends up with juice of about 2brix when mixed 3-1 with water as per standard recipes.

 

[bernardsmith]

Is the dominant acid in black currents tartaric? If it is tartaric then measuring TA makes sense but if the dominant acid is different then I guess I don't understand why you are treating those berries as if they are grapes.

 

[swhitsit]

Is the dominant acid in black currents tartaric? If it is tartaric then measuring TA makes sense but if the dominant acid is different then I guess I don't understand why you are treating those berries as if they are grapes.

Bernard - the dominant acid in black currant is Citric Acid. I am not using berries, but a black currant juice concentrate.

As I understand it, the TA test using Sodium Hydroxide measures total acids, not just tartaric. Is that not correct? I don't have any testing equipment to just measure the citric or malic acid, but in the end I don't think it matters. On the other hand, if I tried to use calcium carbonate or potassium bicarbonate to reduce the acid, I think that would only reduce the tartaric acid? That point has always been a little confusing for me as I don't make many grape wines.

BTW - I found a document that has some very good acid details for fruit. http://llufb.llu.lv/conference/foodbalt/2014/FoodBalt_Proceedings_2014-184-187.pdf

In their tests they found the TA of black currant to be 2.22 mmol L-1. I'm not sure if this is the same as g/L (see figure 4). Does anyone know?

 

[bernardsmith]

I am no expert but I think conventional measures of TA (total acidity) use tartaric acid as the base line (because tartaric is the dominant acid in grapes). Other acids can be compared to tartaric and I don't know how citric compares to tartaric. I know that Claude Jolicoeur talks about this in his book on cider making (because apples are mainly malic and not tartaric). Certainly , the base (calcium carbonate or K-bicarbonate) will neutralize any acid BUT pH does not refer to the same thing as TA -pH refers to how strong the acid is and TA refers to its concentration. You can have a very strong concentration of a very weak acid (and that might give you a higher pH (close to 7) or a very weak concentration of a very strong acid (and that might give you a low pH say 3.0), TA (total acidity) affects flavor (malic acids taste different than lactic and lactic tastes different than citric) but pH will have an impact not on flavor or taste but on spoilage and stability

 

[swhitsit]

Well, I think I've resolved this question and it boils down to some basic math regarding the dilution of the concentrate. Based on the Vintner's Harvest juice that I've tested and the resulting excellent tasting wine, the brix I need to be starting with is only 3 or 3.5. This is because black currant juice is way too acidic in its natural form, similar to some grapes like Mustang.

When I made my original must, I diluted the concentrate using a 7:1 ratio to get to a brix of 11 thinking I would start with pure currant juice. The 40 gallons of must therefore should have the high acid level that I've seen.

Instead, I needed to dilute the concentrate with more like 115 gallons of water to make 120 gallons of must (instead of 40). This would result in the TA level as follows:

Total Acid in the 5 Gallons of Concentrate:
14.2% = 142 g/L = 537.5 g/Gallon x 5 Gallons = 2687 g in the 5 gallons concentrate

TA in 120 gallons of diluted concentrate:
120 gallons = 454 L

2687 g / 454 L = 6 g/L or the desired 0.6% of TA

Also, the brix numbers make sense at this level as well when compared to the VH fruit bases as follows.

I used the Vinoelogy.com water dilution calculator (http://vinoenology.com/calculators/chaptalization-and-water-dilution/) and starting with 5 gallons of 65 brix must with a target brix of 3.5 requires the addition of 116 gallons of water.

This makes good sense to me, and I wish I would have pulled out Excel before my original batch. But luckily I still have time to make some adjustments ... I just need more gear to manage this monster!

 

[Bob_wv]

Bernard - the dominant acid in black currant is Citric Acid. I am not using berries, but a black currant juice concentrate.

As I understand it, the TA test using Sodium Hydroxide measures total acids, not just tartaric. Is that not correct? I don't have any testing equipment to just measure the citric or malic acid, but in the end I don't think it matters. On the other hand, if I tried to use calcium carbonate or potassium bicarbonate to reduce the acid, I think that would only reduce the tartaric acid? That point has always been a little confusing for me as I don't make many grape wines.

BTW - I found a document that has some very good acid details for fruit. http://llufb.llu.lv/conference/foodbalt/2014/FoodBalt_Proceedings_2014-184-187.pdf

In their tests they found the TA of black currant to be 2.22 mmol L-1. I'm not sure if this is the same as g/L (see figure 4). Does anyone know?

I believe TA means , "titratable acidity" which is simply the amount of acid obtained by titration. Yes, it measures all titratable acids, and a base like NaOH will neutralize all of them

I believe 2.2 mmol/l converts to about 0.3 g/l tartaric, but it is not entirely clear from the paper. In any case it is FAR less than what you are measuring. Someone added quite a lot of acid. to that concentrate.


Glad it worked out, keep us posted with your progress.

 

[swhitsit]

Thanks Bob.

I feel pretty confident now in the level of dilution, because I've more or less matched the concentration of the Vintner's Harvest fruit base and the numbers are all relatively close between the two at this level (brix and acid). Although it was a pain making these adjustments after I already pitched the yeast, I'm ending up with considerably more wine ... so no reason to complain

I did several small batches, ranging from 1 to 3 gallons, with different levels of concentration. If I can remember, I'll come back and post some of the findings as the wine progresses with each batch. This was a bit of an experiment for me working with highly concentrated currant and I've already learned quite a bit.

 

[PatrickSweetman]

2.2 mM citric acid is 0.42 g/Litre. As Bob said, either a lot extra has been added or the juice is more concentrated than advertised.

 

[swhitsit]

Thanks Patrick. I did a little digging, and found this calculator for converting moles to grames for Citric Acid (the dominant acid in black currant).

http://www.convertunits.com/from/moles+Citric+Acid/to/grams

(I used this to doubled check converting mmol to moles - http://www.convertunits.com/from/mmol/to/moles)

It does indeed show that 2.2 millimoles/L equates to only .42 grams/L, which would be only 0.042% acid.

It's been too many years since college, so I'm going to pose the next question here

The chart in that document expresses the TA as mmol/L^-1. If the value of L is 1, then the negative power is also 1. But if anything else it would be considerably less than 1 making the standard acid level much higher. Is anyone familiar with the L^-1 designation?

I'm pretty sure the total acid level in black currant, and even apple, is higher than 0.04%. So I have to wonder if we are misinterpreting the document or they are measuring something unrelated.

 

[Bob_wv]

Thanks Patrick. I did a little digging, and found this calculator for converting moles to grames for Citric Acid (the dominant acid in black currant).

http://www.convertunits.com/from/moles+Citric+Acid/to/grams

(I used this to doubled check converting mmol to moles - http://www.convertunits.com/from/mmol/to/moles)

It does indeed show that 2.2 millimoles/L equates to only .42 grams/L, which would be only 0.042% acid.

It's been too many years since college, so I'm going to pose the next question here

The chart in that document expresses the TA as mmol/L^-1. If the value of L is 1, then the negative power is also 1. But if anything else it would be considerably less than 1 making the standard acid level much higher. Is anyone familiar with the L^-1 designation?

I'm pretty sure the total acid level in black currant, and even apple, is higher than 0.04%. So I have to wonder if we are misinterpreting the document or they are measuring something unrelated.

oh goody lets do some chemistry.

The standard acid in winemaking is tartaric. That is what you measure with your test kit. If you look at the units for the percentage, it probable says, "% tartaric" For the purposes of comparison, it doesn't matter that the actual acid is citric.

Moles per liter, M, moles/L and moles*L-1 all mean the same thing the '-1' in the moles*L-1 just means that the liter is in the denominator. Mathematically it means, take the moles, and multiply by the inverse of the liters. It is the number of moles in a liter of solution. you can get the grams using the molar mass.

so as Patrick calculated, 2.2mmol/L * 192.12 g/mol * mol/1000 mmol = 0.42 g CITRIC acid/L


2.2mmol/l citric = 2.2mmol of tartaric *150.087 g/mol * mol/1000 mmol = .330 g Tartaric acid/L

But there is one other annoyance.


Citric acid provides 3 protons/mole; tartaric provides only 2. So citric acid should take only 2/3 as much per mole; not per gram) to achieve the the same acidity as the same number of moles of tartaric.

So
0.42 g/L citric is equivalent to :

.33 * 1.5 = .63 g/l tartaric. therefore it takes .21 g/l more tartaric to achieve the same acidity.

This has implications with one rule of thumb.

To raise the acidity of 6 gal of must .1% (tartaric) you add 18 gram of acid blend/gal. You would need less citric, as the blend is a mixture of tartaric citric and malic, and citric is a stronger acid.

It's late I hope this makes sense.

Bob