Weight
-
1 tsp = 5 gm
-
1 tbsp = 15 gm
-
1 oz = 2 tbsp = 30 gm
-
1 cup = 8 oz = 240 gm
-
1 oz = 30 gm
-
1 pt = 480 gm
-
1 fifth = 750 gm
-
1 qt = 960 gm
-
1 gal = 3750 gm
SO2 Additions
for Wine
Method
Which Corrects for pH of the Wine
The level of free sulfur dioxide (SO2) in wine is measured in terms
of parts per million (ppm). The portion of the measured concentration
that is active is greatly affected by the pH of the wine. The active
portion is referred to as molecular SO2. There are two common target
values, one at 0.8 ppm molecular which will inhibit Malo-lactic bacteria
and the other at 0.5 ppm molecular which allows Malo-lactic fermentation
to proceed. The pH of the wine or must has a great effect on the portion
of free SO2 which is in molecular form. Since the portion of molecular
SO2 decreases as the pH of the must or wine increases, accurate additions
will require that you can also measure the pH of your must or wine.
Use the following steps and tables to guide you in additions of bisulfite
to your wine.
-
Measure the existing SO2 in the wine. The method I am quoting refers
to using the vacuum aspiration method.
-
Prepare a bisulfate stock solution by mixing 4 ounces of potassium
metabisulfite into 1 gallon of cold water. Please note that this
solution concentration is 3.2% which is different than the UCD table
which is based on a solution of 10% strength. Shake and stir well
but do not sniff-it's bad on the nasal passages. Keep this solution
fresh so don't store over 2 months and use fresh potassium metabisulfite
not over 6 months because it also deteriorates.
-
Accurately measure the pH of your wine.
-
From Table A below, determine the ppm free SO2 required for the pH
measured in the wine. For example, if I want 0.8 ppm molecular SO2
and the pH of my wine was 3.2 I would need add 21 ppm free SO2. If
the wine were of higher pH say at 3.4 then I would need to add 40
ppm free SO2 to attain 0.8 ppm molecular SO2. If you measured the
amount of SO2 in your wine as indicated in step1, subtract this value
from the amount of free SO2 you will need to add which was determined
from Table A. The difference is the amount you will need to add to
your wine.
-
Armed with the knowledge of the ppm free SO2 that you will need to
add to your wine, go to Table B to find out how much stock bisulfite
solution to add to your wine. Note that the amount to add has been
adjusted upward because some of the added SO2 will combine with components
in the wine and should not be considered free. These calculations
assumed that 2/3 of the addition will remain in a free state. Stir
well!
-
For the hyperactive winemakers, measure the new SO2 level in 3 or
4 days and adjust again, if necessary. Measure and adjust, if necessary,
after every cellar operation and before bottling.
-
Add the smallest amount of SO2 to prevent deterioration of the wine.
It has been recommended that the pH of the wine be lowered to at least
3.50 to keep total additions of SO2 to a minimum: 100 pm SO2 has been
suggested as a target value. To lower the pH of the must or wine,
refer to additions of Tartaric acid.
TABLE A
|
|
Table Contains Free ppm SO2 for Target Molecular Values of:
|
|
pH of Wine
|
>0.5 ppm Molecular
|
0.8 ppm Molecular
|
|
2.90
|
7 ppm
|
11 ppm
|
|
2.95
|
7 ppm
|
12 ppm
|
|
3.00
|
8 ppm
|
13 ppm
|
|
3.05
|
9 ppm
|
15 ppm
|
|
3.10
|
10 ppm
|
16 ppm
|
|
3.15
|
12 ppm
|
19 ppm
|
|
3.20
|
13 ppm
|
21 ppm
|
|
3.25
|
15 ppm
|
23 ppm
|
|
3.30
|
16 ppm
|
26 ppm
|
|
3.35
|
18 ppm
|
29 ppm
|
|
3.40
|
20 ppm
|
32 ppm
|
|
3.45
|
23 ppm
|
37 ppm
|
|
3.50
|
25 ppm
|
40 ppm
|
|
3.55
|
29 ppm
|
46 ppm
|
|
3.60
|
31 ppm
|
50 ppm
|
|
3.65
|
36 ppm
|
57 ppm
|
|
3.70
|
39 ppm
|
63 ppm
|
|
3.75
|
45 ppm
|
72 ppm
|
|
3.80
|
49 ppm
|
79 ppm
|
|
3.85
|
57 ppm
|
91 ppm
|
|
3.90
|
62 ppm
|
99 ppm
|
|
3.95
|
71 ppm
|
114 ppm
|
|
4.00
|
78 ppm
|
125 ppm
|
TABLE B
|
|
|
Amount of Bisulfate Stock Solution (step 2) to Add to:
|
|
Desired Free SO2
|
Adjusted SO2
|
5 Gallons
|
10 Gallons
|
15 Gallons
|
|
5 ppm
|
7.5 ppm
|
5/8 tablespoon
|
1-1/4 tablespoons
|
2 tablespoons
|
|
10 ppm
|
15 ppm
|
1-1/4 tablespoons
|
2-1/2 tablespoons
|
3-3/4 tablespoons
|
|
15 ppm
|
23 ppm
|
1-7/8 tablespoons
|
3-3/4 tablespoons
|
5-3/8 tablespoons
|
|
20 ppm
|
30 ppm
|
2-1/2 tablespoons
|
5 tablespoons
|
1/2 cup
|
|
25 ppm
|
38 ppm
|
3-1/8 tablespoons
|
6-1/4 tablespoons
|
5/8 cup
|
|
30 ppm
|
45 ppm
|
3-3/4 tablespoons
|
7-1/2 tablespoons
|
3/4 cup
|
|
40 ppm
|
60 ppm
|
5 tablespoons
|
5/8 cup
|
1 cup
|
|
50 ppm
|
75 ppm
|
5-1/4 tablespoons
|
3/4 cup
|
1-1/4 cups
|
|
60 ppm
|
90 ppm
|
7-1/2 tablespoons
|
1 cup
|
1-1/2 cups
|
|
70 ppm
|
105 ppm
|
8-3/4 tablespoons
|
1-1/8 cups
|
1-3/4 cups
|
|
80 ppm
|
120 ppm
|
5/8 cup
|
1-1/4 cups
|
2 cups
|
|
90 ppm
|
135 ppm
|
3/4 cup
|
1-1/2 cups
|
2-1/4 cups
|
|
100 ppm
|
150 ppm
|
7/8 cup
|
1-3/4 cups
|
2-1/2 cups
|
SO2 Additions
for Wine
UCD Table
for Additions of Potassium Metabisulfite
The following table has been reprinted from the UC publication on making
table wine. It does not refer to pH adjustments but it can be used as
a quick reference. Please note that this table is based on a 10%
solution which is different than the solution used for the tables that
take pH into account.
---- Desired final SO2 concentration (ppm)* ----
---- of Must or Wine ----
------------------------------------------------
10 20 25 30 40 50 75 100
----------------------------------------------------------
(gal) (Add ml of 10% SO2 stock solution)
1/10 0.07 0.13 0.16 0.20 0.26 0.33 0.49 0.65
1/5 0.13 0.26 0.33 0.39 0.53 0.66 0.99 1.3
1/2 0.33 0.66 0.82 0.99 1.3 1.6 2.5 3.3
1 0.66 1.3 1.6 2.0 2.6 3.3 4.9 6.6
2 1.3 2.6 3.3 3.9 5.3 6.6 9.9 13.1
3 2.0 3.9 4.9 5.9 7.9 9.9 14.8 19.7
4 2.6 5.3 6.6 7.9 10.5 13.1 19.7 26.3
5 3.3 6.6 8.2 9.9 13.1 16.4 24.6 32.9
10 6.6 13.1 16.4 19.7 26.3 32.9 49.3 65.7
25 16.4 32.9 41.1 49.3 65.7 82.1 123.2 164.3
50 32.9 65.7 82.1 98.6 131.4 164.3 264.4 328.6
----------------------------------------------------------
* The volumes indicated assume 100 percent purity of the
potassium metabisulfite (K2S2O5) and full strength of the
stock solution.
For a 10% SO2 stock solution:
Make 2 ounces of bisulfate powder up to 591 ml. Use room temperature
water, agitate until dissolved, then refrigerate.
Note: It is more convenient to mix up 750 ml of stock solution
rather than 591 ml because you can use a wine bottle in which to both
mix and store the stock solution. To use a wine bottle, add 72 grams
(or 4 Tablespoons and 1 teaspoon) of Potassium metabisulfite to an empty
wine bottle. Fill the wine bottle with water, then agitate until the
powder is dissolved. This will provide you with the 10% SO2 stock solution
with which to make additions as per the table above.
Citric
Acid and SO2 Method for Cleaning Barrels
Household
Measurements
Follow these steps using the amounts listed in the Table below.
-
Rinse the barrel with cold water several times with the barrel about
1/4 full of water rolling both sideways and end for end.
-
Fill half-way with water.
-
Add sodium bisulphate solution from the table below. Normally, sodium
metabisulfite is used for cleaning barrels while potassium metabisulfite
is used for addition to musts or wine.
-
Add citric acid solution from the table below.
-
Mix by rolling, fill completely with cold water, replace bung and
place into storage. If sterilizing for wine use, let stand for 48
hours and then rinse several times with cold water before using.
-
If storing the barrel, check the
level in the barrel every month and add cold water to keep barrel
full. For an active and fresh solution, change the water and refill
the citric acid and sulfite solution every 2-3 months.
|
|
Household Measurements
|
|
Gallons of Wine
|
Sodium Bisulfate
|
Citric Acid
|
|
1
|
2 teaspoons in
|
1 teaspoon in
|
|
|
1/2 cup water
|
1/2 cup water
|
|
2
|
4 teaspoons in
|
2 teaspoons in
|
|
|
1/2 cup water
|
1/2 cup water
|
|
5
|
3 tablespoons in
|
1-1/2 tablespoons in
|
|
|
1 pint water
|
1 pint water
|
|
10
|
1/3 cup in
|
3 tablespoons in
|
|
|
1 pint water
|
1 pint water
|
|
15
|
1/2 cup in
|
5 tablespoons in
|
|
|
1 pint water
|
1 pint water
|
|
25
|
3/4 cup in
|
1/2 cup in
|
|
|
1 quart water
|
1 quart water
|
|
50
|
1-1/2 cup in
|
1 cup in
|
|
|
1 gallon water
|
1 gallon water
|
Citric
Acid and SO2 Method for Cleaning Barrels
Metric
Equivalents
Follow these steps using the amounts listed in the Table below.
-
Rinse the barrel with cold water several times with the barrel about
1/4 full of water rolling both sideways and end for end.
-
Fill half-way with water.
-
Add sodium bisulfite solution from the table below. Normally, sodium
metabisulfite is used for cleaning barrels while potassium metabisulfite
is used for addition to musts or wine.
-
Add citric acid solution from the table below.
-
Mix by rolling, fill completely with cold water, replace bung and
place into storage. If sterilizing for wine use, let stand for 48
hours and then rinse several times with cold water before using.
-
If storing the barrel, check the
level in the barrel every month and add cold water to keep barrel
full. For an active and fresh solution, change the water and refill
the citric acid and sulfite solution every 2-3 months.
|
|
Metric Equivalents
|
|
Gallons of Wine
|
Sodium Bisulfite
|
Citric Acid
|
|
1
|
9 grams in
|
5 grams1 in
|
|
|
240 ml water
|
240 ml water
|
|
2
|
18 grams in
|
9 grams in
|
|
|
240 ml water
|
240 ml water
|
|
5
|
46 grams in
|
23 grams1 in
|
|
|
480 ml water
|
480 ml water
|
|
10
|
92 grams1 in
|
46 grams in
|
|
|
480 ml water
|
480 ml water
|
|
15
|
140 grams in
|
70 grams in
|
|
|
480 ml water
|
480 ml water
|
|
25
|
230 grams in
|
115 grams in
|
|
|
950 ml water
|
950 ml water
|
|
50
|
460 grams in
|
230 grams in
|
|
|
3.8 liters water
|
3.8 liters water
|
Determining
Titratable Acidity with Sodium Hydroxide
Using
Phenolphthalen Indicator Solution
Follow these steps to determine the Titratable Acidity (often just
refered to as TA) in your must or wine.
-
Add a known amount of grape juice to a beaker (usually 10 or 15 milliters).
-
Add additional water if the juice is rather dark. The amount of water
you add is not critical, adding water does not change total amount
of acid in your sample. Do not, however, add more water than 5 times
the amount of juice.
-
Add about 5 drops of phenolphthalen. Phenolphthalen is an indicator
that is clear when it is in a solution that is acidic, but will change
to a purplish color when that solution becomes neutral to basic.
-
Add 0.1N NaOH (1/10 Normal Sodium Hydroxide) until the solution starts
to turn pinkish and stay pinkish then note the amount of NaOH used
for the titration. Make NaOH addition using a pipet graduated in milliters.
A 10 ml pipet works well.
-
Use the following formula to determine the TA of your wine or must.
TA = (Number or milliters of NaOH / Number of milliters of juice)
X 0.75 The units for the TA in this calculation are: Number of grams
of tartaric acid per 100 milliters of juice.
Determining
Titratable Acidity with Sodium Hydroxide
Using
a pH Meter
A pH meter substitutes for the color endpoint. When sodium hydroxide
is added to wine, it increases the pH. Standard solution, usually at
0.1 N, is added until the pH meter reads 8.2. Follow these steps to
determine the Titratable Acidity (often just refered to as TA) in your
must or wine.
-
Calibrate the pH meter using a
two point calibration. The most common buffer solutions used for calibration
are pH 7 and pH 4 but pH 10 is also available. Our pH meter has two
set screws with one marked pH 7 and the other pH 4 or 10. Fresh pH
buffer solutions are important to assure accuracy in the calibration
of the meter.
-
First, calibrate with pH 7 buffer because this is a weaker solution.
If the meter does not read pH 7 with the pH 7 buffer, we turn set
screw marked pH 7.0 to attain 7.0.
-
Then calibrate with the pH 4 buffer solution turning the set screw
marked pH 4, or whatever method used for your meter.
-
Add a known amount of grape juice or wine into a beaker (usually 10
milliters).
-
Place the pH meter into the solution. At this point you can take a
reading of the pH of the must or wine.
-
Add 0.1N NaOH (1/10 Normal Sodium Hydroxide) to the solution until
the pH meter reads 8.2. In our set-up, we have a stand that supports
a 10 ml buret with a stopcock on the bottom of the buret. The buret
is calibrated in 0.1 increments. When the stopcock is opened, the
solution is allowed to flow into the beaker. Closing the stopcock
stops the flow of solution and allows a reading from the buret of
how much solution has been dispensed. As the solution pH rises to
around a pH of 6.0, changes occur faster so be careful as you pass
pH 7.0 on your way to pH 8.2.
-
Use the following formula to determine
the TA of your wine or must. TA = (Number or milliters of NaOH / Number
of milliters of juice) X 0.75 The units for the TA in this calculation
are: Number of grams of tartaric acid per 100 milliters of juice.
Tables
for Addition of Tartaric Acid
Household
Measurements
Since
California grapes can be low in acid content at harvest,
measurement and addition of acid to musts or wine have
become common among many home winemakers. Acid measurements
are usually expressed as grams of acid per 100 ml
of must or wine and in the USA it is expressed in
terms of tartaric acid. To use the following tables,
lets suppose that we measured acid content and found
that our wine contained 0.6 g/100 ml. We want to raise
this value to 0.7 so we need to add 0.1 g/100 ml. The
wine is in a strange looking 26 gallon barrel so how
much tartaric acid do I need to add? In the table, I
look at the column for my target addition of 0.1 g/100
ml and scroll down to the 26 gallon size of the container
(I've put in the most frequently used sizes, it
just so happens that we have 26 gallon French barrels).
I note that I will need to add 3.5 ounces in household
measurements or 98.8 grams in metric equivalents of
tartaric acid. I will dissolve this in as small amount
of water as possible and then add it to the wine.
Tartaric Acid Additions
|
|
Ounces of Tartaric Acid for Additions of
|
|
Gallons of Wine
|
0.1 g/100 ml
|
0.2 g/100 ml
|
0.3 g/100 ml
|
0.4 g/100 ml
|
0.5 g/100 ml
|
|
1.0
|
0.14
|
0.3
|
0.4
|
0.6
|
0.7
|
|
2.0
|
0.3
|
0.6
|
0.8
|
1.1
|
1.4
|
|
3.0
|
0.4
|
0.8
|
1.2
|
1.6
|
2.0
|
|
5.0
|
0.7
|
1.4
|
2.0
|
2.7
|
3.4
|
|
6.5
|
0.9
|
1.8
|
2.6
|
3.5
|
4.4
|
|
13.2
|
1.8
|
3.6
|
5.4
|
7.2
|
9.0
|
|
15.5
|
1.4
|
4.2
|
6.3
|
8.4
|
10.5
|
|
26.0
|
3.5
|
7.0
|
10.6
|
14.1
|
17.6
|
|
30.0
|
4.1
|
8.1
|
12.2
|
16.3
|
20.4
|
|
55.0
|
7.5
|
14.9
|
22.4
|
29.9
|
37.3
|
Table
for Addition of Tartaric Acid
Metric Equivalents
Since
California grapes can be low in acid content at harvest,
measurement and addition of acid to musts or wine have
become common among many home winemakers. Acid measurements
are usually expressed as grams of acid per 100 ml
of must or wine and in the USA it is expressed in
terms of tartaric acid. To use the following tables,
lets suppose that we measured acid content and found
that our wine contained 0.6 g/100 ml. We want to raise
this value to 0.7 so we need to add 0.1 g/100 ml. The
wine is in a strange looking 26 gallon barrel so how
much tartaric acid do I need to add? In the table, I
look at the column for my target addition of 0.1 g/100
ml and scroll down to the 26 gallon size of the container
(I've put in the most frequently used sizes, it
just so happens that we have 26 gallon French barrels).
I note that I will need to add 3.5 ounces in household
measurements or 98.8 grams in metric equivalents of
tartaric acid. I will dissolve this in as small amount
of water as possible and then add it to the wine.
Tartaric Acid Additions
|
|
Grams of Tartaric Acid for Additions of
|
|
Gallons of Wine
|
0.1 g/100 ml
|
0.2 g/100 ml
|
0.3 g/100 ml
|
0.4 g/100 ml
|
0.5 g/100 ml
|
|
1.0
|
3.8
|
7.7
|
11.4
|
15.5
|
19.0
|
|
2.0
|
7.7
|
15.4
|
23.1
|
30.8
|
38.5
|
|
3.0
|
11.4
|
22.8
|
34.2
|
45.6
|
57.0
|
|
5.0
|
19.0
|
38.5
|
57.0
|
76.0
|
95.0
|
|
6.5
|
24.7
|
49.4
|
74.1
|
98.8
|
123.5
|
|
13.2
|
50.2
|
100.4
|
150.5
|
200.6
|
250.8
|
|
15.5
|
58.9
|
117.8
|
176.7
|
235.6
|
294.5
|
|
26.0
|
98.8
|
197.6
|
296.4
|
395.2
|
494.0
|
|
30.0
|
114.0
|
228.0
|
342.0
|
456.0
|
570.0
|
|
55.0
|
209.0
|
418.0
|
627.0
|
836.0
|
1045.0
|
Please note that the above calculations were based on 3.8g/gallon=0.1g/100
ml increase
For the scientist types some notes on L Tartaric acid:
-
mw = 150.09 g
-
pH of 0.1N = 2.2
-
1 g dissolves in 0.75 ml H2O at room temperature or 0.5 ml boiling
-
1g dissolves in 3 ml ethanol
-
maximum solubility @ 10 C = 126g/100ml; @ 20 C=139 g; @ 30 C=156 g
-
pKa1 = 2.93; pKa2 = 4.23 @ 25 C
