Grapes into Wine by Philip M. Wagner

Author:Philip M. Wagner [Wagner, Philip M.]
Language: eng
Format: epub
ISBN: 978-0-307-78428-5
Publisher: Knopf Doubleday Publishing Group
Published: 2011-04-13T00:00:00+00:00

The sugar may be added in several ways. The simplest is to sprinkle it in and dissolve it by stirring. The best is to take out some of the juice, dissolve the sugar in that, and return it. A third is to dissolve it in a minimum quantity of warm water: this requires an increase of sugar to account for the volume of water used (1.7 lb. per gallon). Whatever the method, the correction should be evenly distributed by stirring. As the amount of correction is based on an estimate of the amount of wine the batch is going to yield, the sugar should be tested again following the correction. The estimated volume should also be checked when the still-fermenting wine is pressed: a small deficiency can be made up even then.

If sugar content proves to be too high, as may sometimes happen when California grapes are used, there are three choices. The first possibility is to adjust by mixing in some low-sugar grapes, if they are available. Or you could try your hand at making a natural sweet wine (see Chapter 15). The third choice is to bring the sugar content down to normal by diluting with water. But since excessively sweet grapes also have excessively low acidity the acidity must be corrected too.

TOTAL ACIDITY TEST. California grapes often have an acidity rather lower than the ideal, and Eastern grapes an acidity rather higher. Home winemakers tend to skip the test for acidity and count on luck. But this test is so simple that once the idea is grasped, it can be done quickly and easily without any background in chemistry; then one knows what one is working with.

For this purpose the several acids (mainly tartaric and malic) and their salts are simply lumped together as total acidity and expressed in terms of an acid of known strength, usually tartaric acid. Thus one says that a given must has a total acidity of 0.9 gm. per 100 milliliters expressed as tartaric (or 9.0 gm. per liter, which is the same thing with the decimal point moved over one digit). This is of course an arbitrary unit of measure. What it means to the chemist is that the total acidity of the must is such that the quantity of basic, or alkaline, substance required to neutralize it is the same as would be necessary if all the acid in the must were tartaric acid. The known strength of any other acid would do as well for a measuring unit, but tartaric is the commonly accepted standard in the United States. (In France it is sulfuric acid. To convert to sulfuric, multiply the tartaric acid reading by 0.653.)

The total acidity is determined by titration. A simple titrating set that can be either assembled or bought as a kit consists of:

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