Agriculture Reference
In-Depth Information
To give you some idea of how much sugar would need to be
added to the juices of various fruits, I have included a table
listing some fruits and the range of specific gravities I
obtained when testing different varieties. Keep in mind that
this is just a guideline. Don't substitute use of this table for
testing the specific gravity yourself because the particular
fruits you use will be of different varieties, grown in other
places, and harvested at different times.
Tannins
Tannins are complex polyphenols
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produced by plants. In
foods, they are bitter and astringent, and it is theorized that
they serve to deter herbivores, though it is likely that they
serve other purposes as well. Chemically, they can be divided
into several categories, but they all have in common the
characteristic that they are able to bind to proteins and
precipitate them out of solutions.
Tannins are more present in the skins, seeds, and woody
portions of plants. Hence, when red wine is made by
fermenting the seeds and skins of the grapes, tannin is
dissolved into the wine. The solubility of tannin is affected by
the pH of the solution. Tannins are more soluble in neutral
solutions than in acidic ones, and they are more soluble in
alcohol than in water. So when a fermentation first starts, very
little color and tannin is extracted but once some alcohol is
produced, the extraction proceeds more rapidly. In addition,
tannins are imparted to wines through aging processes that
utilize oak barrels or the addition of oak cubes to the
fermenter.
