In commercial winemaking this is done with precision.
The home winemaker rarely makes the chemical test for total acidity but uses a rule of thumb. He corrects the assumed excess of acidity with a sugar solution consisting of 2 pounds of sugar to 1 gallon of water—adding 1 gallon of the sugar solution for every estimated 4 gallons of juice. This sugar solution is in addition to the sugar required to adjust sugar content of the juice itself.
In estimating the quantity of juice, another practical rule is that 1 full bushel of grapes will yield approximately 4 gallons. The winemaker therefore corrects with 1 gallon of sugar solution for each full bushel of crushed grapes.
The pigment of grapes is lodged almost entirely in the skins. It is during fermentation “on the skins” that the pigment is extracted and gives red wine its color.
How to proceed. Crush the grapes directly into your fermenter (a clean open barrel, plastic tub or large crock, never metal). Small hand crushers are available, but the grapes may be crushed as effectively by foot—wearing a clean rubber boot. Then remove a portion of the stems, which may otherwise give too much astringency to the wine.
Low-acid California grapes are quite vulnerable to bacterial spoilage during fermentation. To prevent spoilage and assure clean fermentation, dissolve a bit of potassium metabisulfite (known as “meta” and available at all winemakers’ shops) and mix it into the crushed mass. Use ¼ ounce (⅓ of a teaspoonful) per 100 pounds of grapes.
Kevin Hayes
A hand-crank grape crusher.
Also use a yeast “starter”. This comes as a 5 gram envelope of dehydrated wine yeast, also obtainable at winemakers’ shops. To prepare the starter, empty the granules of yeast into a shallow cup and add a few ounces of warm water. When all the water is taken up, bring it to the consistency of cream by adding a bit more water. Let stand for an hour, then mix it into the crushed grapes.
After the meta and yeast are added, cover the fermenter with cloth or plastic sheeting to keep out dust and fruit flies, and wait for fermentation.