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< prev - next > Food processing Juices and drinks Grape wine (Printable PDF)
GRAPE WINE
Introduction
Grape wine is perhaps the most common fruit juice alcohol. Because of the commercialisation
of the product for industry, the process is well known and documented.
The production of grape wine is quite straight forward and can be carried out at the small-scale,
without the need for very expensive or specialised equipment. It does, however, require a basic
understanding of the processes involved, tightly controlled fermentation conditions to ensure a
high quality product and a strict adherence to cleanliness and hygiene to prevent contamination
of the wine by spoilage bacteria.
Essentially, wine production involves the following basic steps;
crushing the grapes to extract the juice
alcoholic fermentation
bulk storage and maturation of the wine in a cellar
clarification and packaging.
There are really two distinctive types of wine made from grapes red wine and white wine. The
main difference in the two types is the variety of grape used as raw material and the removal of
grape skins in the production of white wine. Grapes contain a number of chemical compounds
that all contribute to the flavour and colour of wine. Tannins are one group of compounds that
give the wine a bitterness and astringency. The tannins are found
in the grape skins, therefore red wines tend to be more astringent than white wines.
Ingredients
Grapes
Sugar
Wine yeast
Boiled water
Equipment needed
Large plastic bucket with a lid
Thermometer
Fermentation vessel that can be closed with an air lock
Funnel
Syphon tube
Sterilising solution (sodium metabisulphite)
Wine bottles and corks
Corking machine
Hydrometer (optional)
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 that 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
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