Norton-Cythiana testing; pre-heat or not?

[runswithsizzers]

Is it necessary to pre-heat must from Norton/Cythiana grapes before acid testing to get accurate results? Do most wine makers consider this to be a commonly accepted practice?

I came across this suggestion in a paper called "Growing and Vinting Cynthiana/Norton Grapes" presented by Dr. Gary Main, University of Arkansas, at the 24th Annual Horticulture Industries Show in Fort Smith, Arkansas. You can read that paper here <http://www.hortla.okstate.edu/research-extension-youth/extension-and-youth/HIS/pdfs/2005-HIS.pdf/> and go to page 77.

 

[salcoco]

I have never heated the must for a acid check however try it both ways and see what you get. the biggest problem is the malic acid. use a yest that metabolizes malic acid such as 71B or Marvin B. cold stabilization is a must also. one winemaker suggested that acid measurement is not as good as ph measurement. make the ph in the proper range even if you have to add acid, then follow with MLF and cold stabilization to get numbers back in range.

 

[runswithsizzers]

I have never heated the must for a acid check however try it both ways and see what you get. the biggest problem is the malic acid. use a yest that metabolizes malic acid such as 71B or Marvin B. cold stabilization is a must also. one winemaker suggested that acid measurement is not as good as ph measurement. make the ph in the proper range even if you have to add acid, then follow with MLF and cold stabilization to get numbers back in range.

Today I did some testing on my Norton/Cynthiana must, both straight and pre-heated. My results:
---
Juice before heat treatment was pink, but not really red
SG (refractometer) 1.082; Brix: 19.6
pH by Accutest strips 3.8
pH by Hanna pH meter 3.5
TA by NaOH titration 6.0 g/L, tartaric (using phenolphthalein color change to show end point)
---
After heat treating to 165 F, juice was intensely red
SG (refractometer) 1.092; Brix: 22.0 (approximate; hard to read)
SG (hydrometer) 1.096; Brix: 23
pH by Accutest strips 3.8; (approximate; hard to read)
pH by Hanna pH meter 3.5
TA by NaOH titration 9.6 g/L (tartaric), using pH meter for endpoint. Using color change of phenolphthalein, I might have called it 8.8 g/L
---
Conclusion: After pre-heating the must my SG (by refractometer) was about 12% higher. Total acidity as measured by NaOH titration was about 60% higher. However, I judged the endpoint of the unheated juice by phenolphthalein color change, only - and I used my new pH meter to measure the endpoint of the pre-heated juice. Based on my perception of the color change and not the pH meter, the pre-heated result would have been about 47% higher. I wish I had used the pH meter on the unheated titration for a more direct comparison. I assume the pH meter gives more accurate results, and my unheated TA result may be too low..

Dr. Main's paper (link in post #1) says Norton/Cynthiana grapes contain 10-20% soluble solids compared to 5% in most musts, and pre-heating is necessary to extract skin components before testing to get accurate results. He says pre-heating can result an increase in TA of 40%. I got a bit more than that, but my methodology was not really consistent enough for comparison.

I was expecting to see the TA results go up in the pre-heated sample, but I was surprised by the increase in specific gravity/Brix. If pre-heating releases more soluble solids, it makes sense that SG will go up, but I was not expecting that much. As a rank beginner at grape growing I have been agonizing for over a week that my SG/Brix were not going as high as I had hoped. I was getting barely 20 Brix, but I kept hoping for 22, 23, or 24. Meanwhile, some berries were wrinkling up and falling off the stems. If I had been pre-heating my samples before measuring SG/Brix, I would have picked 7-10 days earlier and got a higher yield from better quality grapes.

Dr. Main says: "It is extremely important to monitor pH during fermentation and to keep the pH below 3.6 during both the alcoholic and malolactic fermentation." At a starting pH of 3.5, I am uncomfortably close to his ceiling, especially since my pH meter's accuracy is given as +/-0.2 pH. So I am thinking about adding some tartaric acid. As fermentation progresses, does pH tend to go up, down, or stay the same?

Finally, concerning yeast, Dr. Main's paper says: "Yeast strains that consume malic acid such as Lalvin 71B have not found favor due to flavors produced. Yeast strains that produce polysaccharides and improve structure should be used with Cynthiana. The Lalvin yeast strains ICV- D254, BM45, and BRL97 all work well for Cynthiana wines by contributing to mouthfeel and flavor." ... but he does not provide any references to support his recommendations.

 

[Stressbaby]

Dr. Main says: "It is extremely important to monitor pH during fermentation and to keep the pH below 3.6 during both the alcoholic and malolactic fermentation."

What would be the purpose of keeping the pH under 3.6?

 

[runswithsizzers]

In the article, which you can read at the link provided in post #1 (scroll down to page 77), Dr. Main says:
"Tartaric acid is used to keep the pH below 3.6. [...] it is a necessary procedure as off flavors can form, and color will be lost if the wine is fermented at high pH."

 

[salcoco]

ph of 3.6 is the tipping point additional acid can cause the ph to increase toward 4.00 or larger rather than going down due to buffering. Part of the problem si potassium retention in Norton can also be high giving high numbers. I didn't read the entire paper by Dr. Main but I believe the winemaker I discussed above was on the right track add tartaric now to get ph down to at least 3.4 ferment with a malic acid eating yeast, MLF and cold stabilize should be fine.
I donot understand how the numbers achieved by heating the must can be meaningful as the fermentation would not achieve that high a temp so the sugar or acid content would not be available to the yeast.

 

[stickman]

I believe the heating is to extract the components quickly for measuring purposes. The heating is not necessary for the yeast to have full access to those components during fermentation on the skins.

 

[runswithsizzers]

ph of 3.6 is the tipping point additional acid can cause the ph to increase toward 4.00 or larger rather than going down due to buffering. Part of the problem si potassium retention in Norton can also be high giving high numbers. I didn't read the entire paper by Dr. Main but I believe the winemaker I discussed above was on the right track add tartaric now to get ph down to at least 3.4 ferment with a malic acid eating yeast, MLF and cold stabilize should be fine.
I donot understand how the numbers achieved by heating the must can be meaningful as the fermentation would not achieve that high a temp so the sugar or acid content would not be available to the yeast.

Yes, treating with tartaric to reduce the pH is exactly what is recommended by Dr. Main, as well. I have decided to treat my must with tartaric to bring the pH down; so now I need to figure out how much to add.

Dr. Main gives an example in the paper, but does not go in much detail about what kind of calculations he used. My chemistry is not good enough to work out how to allow for buffering.

Does the winemaker you previously mentioned say how much tartaric acid is needed to change the pH by a given amount?

 

[salcoco]

no the best bet is take a liter of must for a bench trial. monitor with ph meter and add about a 1/2 tsp at a time to get ph down to at least 3.3-3.4. note result multiply by number of liters of must and add to basic batch.

 

[runswithsizzers]

no the best bet is take a liter of must for a bench trial. monitor with ph meter and add about a 1/2 tsp at a time to get ph down to at least 3.3-3.4. note result multiply by number of liters of must and add to basic batch.

RE: "multiply by number of liters"
When making these kinds of calculations, I know the volume of the must, including a considerable volume of skins and seeds - but, of course, I won't know the exact volume of liquid until after pressing. Is it better to use the known number of liters (including skins and seeds), or would it be better to estimate how many liters I may (or may not) have after pressing?

My total volume with skins and seeds is just under 5 gallons (44 lbs), but this is my first year making wine from Cynthiana, so I have no idea whether that will yield one gallon, two gallons, or three.

Edit: I just found this advice at https://morewinemaking.com/articles/testing_wine_must
"When making corrections, consider the varietal. Seed/skin to juice ratio varies for each grape. We will only be getting around 3 (Bordeaux) to 3.5 (Zin and Rhône)* gallons of finished wine from every 5 gallons of must! This comes out to 60-70% of the must volume. Don’t forget to take this into account when making corrections to the sugar levels or pH/Total Acidity (TA).

In addition, most products designed to go into the must should still use the entire must volume to calculate their dosage. This compensates for the portion of the additions that physically bind to the must itself and will not make it into the final wine volume. This includes SO2, enzymes, tannins, oak, Opti-Red, Booster-Rouge and Noblesse."

Has anyone got an approximate number for 'Seed/skin to juice ratio' for Norton/Cynthiana?

 

[Johnd]

RE: "multiply by number of liters"
When making these kinds of calculations, I know the volume of the must, including a considerable volume of skins and seeds - but, of course, I won't know the exact volume of liquid until after pressing. Is it better to use the known number of liters (including skins and seeds), or would it be better to estimate how many liters I may (or may not) have after pressing?

My total volume with skins and seeds is just under 5 gallons (44 lbs), but this is my first year making wine from Cynthiana, so I have no idea whether that will yield one gallon, two gallons, or three.

Most calculations should be made based upon the expected volume of finished wine. Rule of thumb is somewhere in the 65% - 70% range, so if you are starting with 5 gallons of must, you could expect to end up with 3.25 - 3.5 gallons of wine at bottling time. Of course, all grapes are different, big fat juicy grapes might yield more liquid than little tiny grapes, but you get the picture.

 

[runswithsizzers]

Most calculations should be made based upon the expected volume of finished wine. Rule of thumb is somewhere in the 65% - 70% range, so if you are starting with 5 gallons of must, you could expect to end up with 3.25 - 3.5 gallons of wine at bottling time. Of course, all grapes are different, big fat juicy grapes might yield more liquid than little tiny grapes, but you get the picture.

Thanks! I am guessing the rule of thumb is based on wine grapes in general? And from what I've read, this is another area where Norton/Cynthiana probably falls a bit outside the norm?

Sadly, many of my berries were quite small, full of seeds, and not-at-all juicy. I would be thrilled to get 3 gallons, but I am expecting less. That's just a guess, as I don't have any actual experience to base my expectations on. I am hoping someone with specific Norton/Cynthiana experiece will weigh in.

 

[Johnd]

Thanks! I am guessing the rule of thumb is based on wine grapes in general? And from what I've read, this is another area where Norton/Cynthiana probably falls a bit outside the norm?

Sadly, many of my berries were quite small, full of seeds, and not-at-all juicy. I would be thrilled to get 3 gallons, but I am expecting less. That's just a guess, as I don't have any actual experience to base my expectations on. I am hoping someone with specific Norton/Cynthiana experiece will weigh in.

Yes, a rule of thumb for wine grapes. I have no personal experience with Norton / Cynthiana to share, but suspect that some of our other members will chime in if they can shed some additional light on your specific varietal.

If you haven't already, you might consider using an enzyme like Lallzyme EX-V to aid in the breakdown of the fruit, it'll help release more of your juice, tannins, flavor compounds into the wine. It's particularly helpful on grapes as you have described that are small and seedy with less juice than expected.

 

[runswithsizzers]

Yes, a rule of thumb for wine grapes. I have no personal experience with Norton / Cynthiana to share, but suspect that some of our other members will chime in if they can shed some additional light on your specific varietal.

If you haven't already, you might consider using an enzyme like Lallzyme EX-V to aid in the breakdown of the fruit, it'll help release more of your juice, tannins, flavor compounds into the wine. It's particularly helpful on grapes as you have described that are small and seedy with less juice than expected.

Thanks again! Very helpful people on this forum!

I have added some generic "pectic enzymes" I got from my semi-local wine & beer making store. It's too late for me get the Scott Lallzyme brand this year (I will probably crush tomorrow), but I will keep in mind for next year.

 

[salcoco]

a conservative method is to calculate your finished wine at about 3 gallon or about 11 liters. calculate the amount of tartaric acid to add, then only add half as much to the must measure the ph, then add a quarter then the remainder if required. in this manner you won't overshoot the mark.

 

[cmason1957]

Ah Norton, small grapes, about half full of seeds, very little liquid, even in the best of grapes. I always assume that 100 lbs will end me up with just over 6 gallons of finished wine, after pressing and racking off the not inconsiderable lees that Norton can produce. I am going to guess that your 5 gallons of must will produce about 2.5-3 gallons finished.


Not my favorite Midwest grape by far, much prefer Chambourcin, but that's just me.

 

[user 36973]

Most calculations should be made based upon the expected volume of finished wine. Rule of thumb is somewhere in the 65% - 70% range, so if you are starting with 5 gallons of must, you could expect to end up with 3.25 - 3.5 gallons of wine at bottling time. Of course, all grapes are different, big fat juicy grapes might yield more liquid than little tiny grapes, but you get the picture.

If this helps, I ended up with about 225 gallons of Norton wine from 3000lbs of fruit. So, roughly 13.3lbs/gallon. This was from using a bladder press on the must after 4 days of fermentation.

 

[runswithsizzers]

If this helps, I ended up with about 225 gallons of Norton wine from 3000lbs of fruit. So, roughly 13.3lbs/gallon. This was from using a bladder press on the must after 4 days of fermentation.

Thanks, that does help - or it would if I was less careless. I pressed today, and put the juice in a glass carboy which does not have marks on it for gallons nor do I know how much the carboy weighs. So, bottom line, I don't really know how much juice I got. Just to eyeball it, I'm guessing my 5 gallons of must (44 pounds) made at least 3 gallons of juice, but probably less than 4. After 3 days of fermentation on the skins, I used an old fashioned screw press, the kind with an oak basket. If I got the same yield as you did, my 44 pounds would yield 3 and a third gallons.

My SG is down to 1.020 (about 4.5 Brix by my hydrometer). Should I go ahead and add the malolactic culture now, or wait until the yeast fermentation is closer to being complete?