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I am making Blackberry wine.
I will be documenting the process from start to finnish.
Unravelling the Great Mystery
"The phenomenon of fermentation must surely have been
one of the longest-standing mysteries of civilization."
--Matt Kramer
| Step 1. Out in the Blackberry bramble. |
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| Click on photo for this album. |
| Step 2. Primary Fermentation under way. |
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| Click on photo for album. |
| Step 3. Secondary Fermentation |
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| Click on photo for album |
We really have no idea where the first serendipitous batch of wine was made or what the person who discovered it. We can
only imagine that someone left a container of grapes or grape juice sitting out and wild yeasts began to ferment it. In time,
the liquid was consumed, probably in small, experimental amounts, and the person didn't die. It was probably noted that the
resulting liquid would keep much longer than juice that had not been allowed to "spoil," and fermentation was then
sought as a preserving measure for the juice.
That yeast was involved was not known until several thousand years later. In 1680 Anton van Leeuwenhoek, Dutch naturalist
and inventor of the microscope, turned his attention to yeast cells and discovered that some kind of microscopic life existed.
His microscope was not powerful enough, however, to allow him to characterize the life or connect it to fermentation. In 1785
the French chemist Antoine Laurent Lavoisier postulated that alcohol fermentation was a chemical process. Sugar had already
been identified as the raw material of fermentation. Lavoisier noted that between the alcohol and carbon dioxide gas produced
during fermentation, all fermentable sugar was accounted for. Thus, he concluded that fermentation was caused by the sugar
molecule being chemically split, an imaginative and reasonable assumption for that particular period. It was not until 1835
that Charles Cagnaird de la Tour (France) and Schwann (Germany) independently turned their much improved microscopes to the
deposits left in beer vats. There they noted single-celled creatures multiplying before their very eyes by budding. Charles
Cagnaird de la Tour concluded that fermentation was the result of yeast growth rather than merely a chemical process as formerly
believed. He was, it turns out, only partially right.
In 1839, Justus Freiherr von Liebig, a German chemist who made significant contributions in understanding organic compounds,
turned his microscope to some fermenting beer. He wrote, "Beer yeast, when dispersed in water, breaks into an infinite
number of spheres. When these spheres are transferred to an aqueous solution of sugar, they develop into small animals. These
are endowed with a sort of suction trunk with which they gulp up sugar. Digestion is immediate and clearly recognizable because
of the discharge of excrements.
"These animals evacuate ethyl alcohol from their bowels and carbon dioxide from their urinary organs. Thus, one can
observe how a specially lighter fluid is exuded from the anus and rises vertically whereas a stream of carbon dioxide is ejected
at very short intervals from enormously long genitales." This humorous description, however anatomically and technically
flawed, is still too priceless to be forgotten. Whenever you wonder what your yeast are doing, think of von Liebig's description
and smile.
| Step 4. Racking the wine. |
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| The lees have settled to the bottom of the bottle.... That means it is time to RACK the wine! |
In 1846 the Swedish chemist Jons Berzelius coined the word "catalyst" to describe a process by which one substance
accelerates a change in another substance without being changed in the process. Berzelius reasoned that yeasts were actually
catalysts whose mere presence in a sugary liquid caused it to ferment. In other words, no biological activites were involved.
Justus von Leibig, a German chemist, supported Berzelius' theory, but with a refinement. He held that it was the process of
decay of the dead yeast cells which acted as the catalyst for fermentation and caused sugar to be converted into alcohol and
carbon dioxide. In combating supporters of the biological school of fermentation, von Leibig pointed to soured milk as proof
of a chemical cause, noting the absence of yeast in souring milk. In 1857, none other than the 34-year old Louis Pasteur entered
the fray. Through careful microscopic studies, he had found tiny cells reproducing in soured milk which he thought to be lactic
acid yeasts. They are, in fact, bacteria, but the important thing is that they were alive. Two years later, in 1857, Pasteur
presented his Note on Alcohol Fermentation, where he showed that the growth and reproduction of yeasts was the cause of fermentation.
The theory of "spontaneous generation" of alcohol and carbon dioxide through the catalytic presence of yeast was
laid to rest. We now know that Pasteur was partially correct and partially wrong, but that's getting ahead of the story.
Pasteur went on to discover something really amazing about yeast cells -- they can live without oxygen. From this he concluded,
"Fermentation is life without oxygen." This is not true, of course, because we now know that yeasts cause better
fermentation in the presence of oxygen than without it, but Pasteur at least recognized the extreme possibility when no one
else did. Pasteur died before two German brothers, Eduard and Hans Buchner, demonstrated in 1897 that yeasts, per se, do not
cause fermentation. While searching for an extract for a medicine, the Buchner brothers ground up yeast cells with sand and
silica and squeezed out the "extract" in a hydraulic press. Needing a way to preserve the "extract," they
recalled how well high-sugar content solutions such as jam and syrup were preserved and decided to use pure sugar. However,
when the "extract" was applied to sugar, the sugar fermented. Eduard Buchner would receive the Nobel Prize for his
discovery of "cell-less fermentation," although another German had already postulated and named the process.
Wilhelm Kuhne, in 1878, recognized that a catalyst was indeed at work in yeast to cause fermentation. Although unable
to isolate the catalyst as the Buchners later did, he had at least named it. The catalyst, he said, was contained in the yeast,
and thus he coined the word enzyme to describe it from the Greek en (in) and zume (yeast). He was, indeed, entirely correct.
It is the enzymes secreted by yeast cells that act upon sugar molecules and create the process known as fermentation. The
enzymes, plural because we now know that over two dozen enzymes are involved in creating some 30 chemical reactions, are the
catalysts that transform sugar molecules into alcohol and carbon dioxide gas. These reactions are ordered, one dependent upon
the preceeding one to succeed. Protease works only on proteins; invertase breaks down sucrose; and so on until zymase creates
alcohol itself. And so the process is chemical after all, but it is also vitalistic since yeast is required to manufacture
the enzymes.
As it was in the beginning, winemaking is still dependent upon this tiny organism. One drop of fermenting juice can contain
five million yeast cells capable of doubling their number every two hours in absolutely perfect conditions.
taken from: http://winemaking.jackkeller.net/yeast.asp
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