Principles of wine making
Wine making uses the following basic principles:
• The sugars present in the fruit (and any sugar that is added to the fruit) are fermented by yeast
(Saccharomyces cerevisiae var. ellipsoedins) is added to the mixture. There are natural yeasts
present on the skins of fruits, but these are usually not sufficient to carry out the fermentation
on their own.
• When sugar is fermented by yeast, it is converted into alcohol (ethanol) and carbon dioxide gas
is released. You will see bubbles of carbon dioxide gas in the air lock while the fermentation is
active. You know the fermentation is over when no more gas is produced.
• The fermentation has to take place without oxygen (it is an anaerobic fermentation). If oxygen
gets into the system during the fermentation, the alcohol will be converted into acid (this is
what happens when you make vinegar, which is acetic acid). Wine that has spoiled because it
has been exposed to the air may taste very acidic.
• There are lots of bacteria and yeasts around in the air and on the surface of the fruits. They all
have the potential to spoil the wine. It is extremely important that these bacteria do not start to
grow in the fermenting grape juice. Particular care must be taken with the cleanliness of the
equipment and personal hygiene.
• All equipment must be sterilized with a solution of sodium or potassium metabisulphite before
it is used.
Production of red grape wine
• Red grape wine is an alcoholic fruit drink of between 10 and 14% alcoholic strength that is made
from the fruit of the grape plant (Vitis vinifera). The color ranges from a light red to a deep dark
red depending on the grape variety and the length of fermentation and maturation. There are
many varieties of grape used including Cabernet Sauvignon, Grenache, Nebbiolo, Pinot Noir, and
Torrontes. The skins of the grape are included in the production of red wine, to allow for the
extraction of color and tannins, which contribute to the flavor.
• For the production of dry red wine (10-14 %v/v), the must(liquid) should have Brix (TSS) of 22 to
27 degree and the acidity of must(liquid) must be between 0.6 to 0.7 % and pH below 3.3.
• For the production of Sweet red wine (10-14 %v/v), the must(liquid) should have Brix (TSS) of 28
to 33 degree and the residual sugar (3–5-degree Brix) is maintained in the final wine. The acidity
of must(liquid) must be between 0.6 to 0.7 % and pH below 3.3.
Production of white grape wine
• White grape wine is an alcoholic fruit drink of red winbetween 10 and 14% alcoholic strength
that is made from the fruit of the grape plant (Vitis vifera). grape varieties used for making
white wine include the following: Airen, Chardonnay, Palomino, Sauvignon Blanc and Ugni Blanc.
White wine has a pale-yellow color. The skins are from the grapes before fermentation begins.
• For the production of Dry White wine (10-14 %v/v), the must(liquid) should have Brix (TSS) of 22
to 27 degree and the acidity of must(liquid) must be between 0.65 to 0.75 % and pH below 3.5.
• For the production of Sweet White wine (10-14 %v/v), the must(liquid) should have Brix (TSS) of
28 to 33 degree and the residual sugar (3–5-degree Brix) is maintained in the final wine. The
acidity of wine must(liquid) must be between 0.65 to 0.75 % and pH below 3.5.
The fermentation process is very similar for both types of wine:
Raw material preparation
Select healthy, ripe, undamaged grapes. The fruit should taste sweet, ripe and slightly tart. Make sure
they are ripe by squashing two handfuls, straining the juice and measuring the sugar level with a
refractometer if you have one available. The total soluble sugars should be about 22° Brix, which is
equivalent to a specific gravity of 1.0982 or 11% potential alcohol. Remove the grapes from the stems
(stems make the wine taste bitter). Discard any that are rotten or unripe. Wash them well in clean water
to remove dust. Crush the grapes to yield the juice plus skins, which is known as must. Traditionally
grapes are crushed in large open vessels by people walking on them with bare feet. This really is not very
hygienic and is not recommended. It is preferable to use a sterilized potato masher or very clean hands.
Sterilize the equipment
It is essential to sterilize all the equipment before use. Wash the equipment in boiling water. Use a
solution of sodium or potassium metabisulphite to clean the fermentation vessel and the bottles for
storage. Add 3 tablespoons of potassium metabisulphite to 4.5 liters of water and mix well. Rinse the
bottles well with boiled water afterwards to get rid of any residual sulphite.
Processing
Red wine
Transfer the crushed grapes plus skins to a large fermentation vessel, such as a plastic bucket with a lid.
Seal the lid, place in a warm room (21-24°C) and leave to ferment for between 24 hours and three
weeks. The ethanol produced during this initial fermentation helps with the extraction of pigment from
the skins. The longer the fermentation, the darker the wine.
Remove the skins and transfer the partially fermented wine to a separate tank to complete the
fermentation. Add yeast to the fermenting grape must, close the top of the fermentation vessel with an
airlock that contains water, place in a warm place (21-24°C) and leave to ferment until all the sugar has
been converted to alcohol or the alcohol content of the wine has reached a high enough level. You know
this has happened when the bubbles stop appearing in the water in the air lock. You can measure the
specific gravity of the wine with a hydrometer. This gives an indication of the amount of alcohol that is
present.
White wine
Strain the extracted grape juice into a fermentation bucket. Add the wine yeast, seal the fermentation
vessel and leave in a warm place (12-18°C) for 7 to 14 days to ferment. The low temperature and slow
fermentation encourage the retention of volatile compounds which give the wine flavor.
Adjusting the Juice
Controlling the acidity, sugar content and temperature of the juice (must) are all critical to producing
good quality wine. The acid content can be measured using a titration. The ideal acid content is 6 to 7
grams per liter for dry reds (0.6 to0.7 %) and 6.5 to 7.5 grams per litre for dry whites. If the acidity is too
low, add tartaric acid (in very small amounts) until the acidity reaches the desired level.
The sugar level should be about 22° Brix for both red and white wines. If it is lower than this, increase it
by adding a sugar to the juice. Make the sugar syrup by dissolving one cup sugar into one-third cup of
water. Bring it to a boil in a saucepan and immediately remove from the heat. Cool before adding in
small amounts, one tablespoon at a time, until the desired degrees Brix is reached. To lower the sugar
level, simply dilute the must or juice with water.
The temperature of the must should be adjusted to provide optimum conditions for the yeast to grow.
The optimum temperature of the juice is about 22-24°C for red wines and 12-18°C for white wines. If the
juice is colder than this, warm it by gentle heating, but do not boil as this affects the flavor of the wine.
Racking the Wine
"Racking" means transferring the fermenting wine away from the sediment at the bottom of the bucket.
Use a clear plastic tube to siphon off the wine into a sterilized fermentation jug. Do not disturb the
sediment at the base of the bucket – it is important to have a clear wine without cloudiness or debris.
Seal the top of the fermentation jug with a sterilized bung and a fermentation airlock. Leave to ferment
until no more carbon dioxide gas can be seen escaping via the air lock (this means that all the available
sugar has been converted into alcohol, or the yeast has died and the fermentation is complete).
Bottling the Batch
After fermentation, the wine is bottled by siphoning it off into clean, sterilized bottles. Do not fill the
bottles to the top (leave about 5cm of head space) to allow room for fermentation in the bottle if it
happens. Insert a cork into the bottle using a hand corking machine.
Some wines can be drunk immediately, however most develop distinctive flavors and aromas by leaving
them to age for a while. The bottles should be laid on their sides during ageing to keep the cork wet. If
the cork dries out, it may allow air into the wine, which causes it to oxidize and spoil.
Flow diagram:
Dry Red Table Wine
Ingredients (for 4.5l of wine) 9kg ripe red grapes, potassium metabisulphite powder, Tartaric acid, if
necessary Granulated sugar, 1 packet wine yeast
1. Harvest the grapes once they have reached 22-24 percent sugar (22- 24° Brix). Wash well to
remove dust. Remove stalks.
2. Sanitize all equipment by washing well with a solution of potassium metabisulphite (0.4 to 0.6
per 4.5 liters of water). Place the grapes bunch into a nylon Cloth (or muslin cloth). Using very
clean hands or a sterilized tool such as a potato masher, juice press firmly crush/press the
grapes inside the food-grade bucket. Sprinkle 0.5g potassium metabisulphite over the
must/cleared juice in the bucket containing must. This is to control the growth of natural yeasts
and bacteria that may be present on the skins of the grapes. Cover the bucket with cheesecloth
and let it sit for one hour.
3. Measure the temperature of the must. It should be between 22-24°C. Take a sample of the juice
in the bucket and measure the level of acid with a titration. If it's not between 6- 7 grams per
liter (0.6% to 0.7%) then adjust with tartaric acid.
4. Check the level of total sugars (° Brix or specific gravity) of the must. If should be about 22° Brix
(1.0982 SG). If it is lower than this, add a little bit of sugar dissolved in water.
5. Transfer the must (approx. 4.5 liters) in the air tight container/closed vessel/fermenter
containing air lock system containing water will be best.
6. Dissolve 1.8 to 2g active dry wine yeast in 10-25 ml warm (30-35°C) water and let it stand until
bubbly (it should take no more than10 minutes). When it is bubbling, pour the yeast solution
directly onto the must. Shake the container containing yeast mix the yeast. Closed the container
with, set in a warm place (20-25°C) and check that fermentation has begun (bubbling of
Carbondioxide gas starts) in at least 24 hours. Monitor the temperature and the progression of
the fermentation regularly. It may be necessary to wrap a blanket or cool around the fermenting
vessel to maintain the optimum temperature (21-24°C) for fermentation.
7. Keep the red skins of red grape for color extraction under the fermentation juice(must) at all
times and mix twice daily.
8. After 15 days, the must has reached "dryness" (at least 0.5° Brix or 0.998 SG) and bubbling
process will cease or slow or has been stopped.
9. Remove the skin from the fermentation vessel and pour the wine into another sanitized 4.5litre
jug/closed vessel for another 10-15 days in a cool and dry place (around 15°C) for racking
(separation of yeast and sediments from the wine).
10. After 10-15 days, decant/siphon the wine into clean, sanitized bottles siphon the clarified,
settled wine. Cork with the hand-corker. This process can be repeated 2-3 times until cleared
wine is obtained.
11. After racking, flavoring may add in the wine as tannin (Dose :0.07 to 0.1 g per liter of wine).
12. Before filtration, the wine is stored at –1 to 2°C for 24 hours and can be filtered in the laboratory
with the help of Buchner funnel filtration set using 5-to-10-micron Whatman filter paper or
sintered filtration system
13. Store bottles in cool, dark place and wait at least 1-2 months before drinking for better results.
14. Red wine is fermented with the pulp and skins. This "Sealed cap" will rise to the top, so you need
to "punch it down" frequently.
Flow diagram
Dry White Table Wine
Ingredients (for 4.5l of wine) 9kg ripe White grapes, potassium metabisulphite powder, Tartaric acid, if
necessary Granulated sugar, 1 packet wine yeast
1. Harvest the grapes once they have reached 22-24 percent sugar (22- 24° Brix). Wash well to remove
dust. Remove stalks.
2. Sanitize all equipment by washing well with a solution of potassium metabisulphite (0.4 to 0.6 per 4.5
liters of water). Place the grapes bunch into a nylon Cloth (or muslin cloth). Using very clean hands or a
sterilized tool such as a potato masher, juice press firmly crush/press the grapes inside the food-grade
bucket. Sprinkle 0.5g potassium metabisulphite over the must/cleared juice in the bucket containing
must. This is to control the growth of natural yeasts and bacteria that may be present on the skins of the
grapes. Cover the bucket with cheesecloth and let it sit for one hour.
3. Measure the temperature of the must. It should be between 22-24°C. Take a sample of the juice in
the bucket and measure the level of acid with a titration. If it's not between 6.5- 7.5 grams per liter
(0.65% to 0.75%) then adjust with tartaric acid.
4. Check the level of total sugars (° Brix or specific gravity) of the must. If should be about 22° Brix
(1.0982 SG). If it is lower than this, add a little bit of sugar dissolved in water.
5. Transfer the must (approx. 4.5 liters) in the air tight container/closed vessel/fermenter containing air
lock system containing water will be best.
6. Dissolve 1.8 to 2g active dry wine yeast in 10-25 ml warm (30-35°C) water and let it stand until bubbly
(it should take no more than10 minutes). When it is bubbling, pour the yeast solution directly onto the
must. Shake the container containing yeast mix the yeast. Closed the container with, set in a cool place
(12-18°C) and check that fermentation has begun (bubbling of Carbondioxide gas starts) in at least 24
hours. Monitor the temperature and the progression of the fermentation regularly. It may be necessary
to cool around the fermenting vessel to maintain the optimum temperature (12-18°C) for fermentation.
7. After 15 days, the must has reached "dryness" (at least 0.5° Brix or 0.998 SG) and bubbling process
will cease or slow or has been stopped.
8. After 15 days, pour the wine into another sanitized 4.5litre jug/closed vessel for another 10-15 days in
a cool and dry place (around 15°C) for racking (separation of yeast and sediments from the wine).
9. After 10-15 days, decant/siphon the wine into clean, sanitized bottles siphon the clarified, settled
wine. Cork with the hand-corker. This process can be repeated 2-3 times until cleared wine is obtained.
10. After racking, flavoring may add in the wine as tannin (Dose :0.07 to 0.1 g per liter of wine)and
others.
11. Before filtration, the wine is stored at –1 to 8°C for 24 hours and can be filtered in the laboratory
with the help of Buchner funnel filtration set using 5-to-10-micron Whatman filter paper or sintered
filtration system
12. Store bottles in cool, dark place and wait at least 1-2 months before drinking for better result.
13. White wine is fermented with the pulp. This "Sealed cap" will rise to the top, so you need to "punch
it down" frequently.
1.DETERMINING TOTAL ACIDITY
The ideal total acidity of a finished wine ranges from about 0.6% to 0.8%, expressed as tartaric acid.
EQUIPMENT NEEDED: Burette with stand and clamp, 5 mL volumetric pipette, N/10 sodium hydroxide,
distilled or boiled tap water and beaker or glass.
PROCEDURE FOR WHITE WINES OR JUICES
a.) Fill burette with sodium hydroxide. Run enough through the burette so that no air bubbles remain
below the pinchcock or stopcock.
b.) Using the pipette, add a 5 mL sample of wine or juice to be tested to the beaker or water glass.
c.) Add about 100 mL of distilled water to the wine or juice sample.
d.) Add about 5 drops of phenolphthalein indicator to the sample.
e.) Place the wine sample container under the burette. Record the sodium hydroxide (NaOH) level in the
burette before starting. Begin running NaOH into the sample; this will cause it to turn pink. Upon stirring
or swirling the sample the pink color will disappear quickly. As you approach the end point the pink
takes longer to fade. The end point is the first faint pink blush what will not fade within 20 seconds.
f.) Upon reaching the end point, record the level the NaOH in the burette. Subtract your first reading
from this to determine the mL of NaOH used. Millimeters of NaOH x 0.15 equals percent acidity
expressed as tartaric acid. (Example: 4.8 mL x 0.15 = 0.72%)
PROCEDURE FOR RED WINES OR JUICES
a.) Do not immediately add the phenolphthalein indicator as you would with a white wine or must. The
red pigments make it difficult to see the end point unless you first titrate without phenolphthalein until
the color turns the red to a blue or green. Only then will you add the indicator and then continue to the
first pink that persists.
b.) Determine how many mL of NaOH were used and multiply by 0.15 to determine the percent acidity
expressed as tartaric acid.
c.) If the sample is deeply pigmented you can dilute it with more distilled water which does not affect
the result. A bright light under the sample (or behind it) makes it easier to see the color changes.
2.How to Determine the Alcohol Content of Wine by Hydrometer
Simple subtraction. Take a hydrometer reading right before you pitch the wine yeast into your must (see
“How to Take a Hydrometer Reading” ).
Make a note of this reading, which should be in the range between 1.060 and 1.120, depending on the
recipe and style you are making.
After the fermentation is complete, take another hydrometer reading right before you bottle. This
reading will usually fall between 0.090 and 1.010, again depending on the style of wine made.
Then you simply subtract the second reading from the first, and multiply by 131 and this will give you a
very close approximation of your alcohol by volume. For example- your starting gravity reading is 1.0982
and your final gravity reading is 0.998 the math would look like this:
(1.0982 - 0.998) X 131= 13.1, your alcohol by volume would be approximately 13.1%.
(Note: Alcohol Content of wine can also be determined by distillation and use of pycnometer with
corresponding chart Similar to that of molasses and grain fermented wash).
3.How to Determine the Brix of Juice/Must/Wine by Brix Refractometer
For determination of brix or TSS of Juice/Must/Wine, select the proper range of Hand-held Brix
refractometer, place the pinch of sample(juice/wine) into the surface of refractometer and take the
reading which will give the corresponding brix measurement.
