Thursday, July 12, 2012

Yeast - the Ubiquitous, Universal Fermenter.  In celebration of the  205th Anniversary of the Basi Revolt (September 29, 1806- 2012) 
Dr Abe V Rotor
Basi wine making, first day of fermentation. Note evolving gas - carbon dioxide. Wine is produced by anaerobic fermentation.

Bottled basi wine for tourists shops and for export. Basi was among the items carried between the Philippines and Europe via Acapulco, Mexico, during the Galleon Trade era (17th and 18th century) when the Philippines was a colony of Spain, so with Mexico. Old folks attribute the unique fine taste of basi to bubud (homemade yeast).

All kinds of alcoholic drink contain ethanol or ethyl alcohol - the only edible alcohol. Wine is as old as civilization. Serendipity must have led to early wine making techniques, the key being the domestication of  the first microorganism - Saccharomyces, the ubiquitous yeast.

Wine making is converting sugar into ethanol. Ethanol or ethyl alcohol (C2H5OH) is universal in all alcoholic drinks from beer to table wine to liquor, irrespective of generic or brand name. The strength of wine is indicated by proof, which is actually twice that of its percentage content.

Thus, 80 proof is 40 percent ethanol, which is the strength of Vodka, some Brandy, Cognac, Whiskey, and the like. The strength of beer normally ranges from 3 to 5 percent, unless fortified with distilled ethanol to raise it to say, 7 percent. Fortified wine is also common.

Natural table wine such as Basi of the Ilocos region, table wine from grapes and other fruits, normally contain 10 to 12 percent ethanol. Beyond this level, the fermenting yeasts simply die off from the accumulation of ethanol - a biological phenomenon called autotoxicity. It means that the yeasts are killed by their own product, often leaving behind the unfermented sugar. It is this residual sugar that makes a wine sweet - naturally, that is.


Closeup of bubud, homemade yeast complex.

Ripe leaves of samat or binuga (Cananga tenarius) is used in making basi. Yeast is found in ripening leaves. Here the leaves contain the highest level of sugar which the plant did not use or store. The yeast acts of the sugar and as the leaves fall to the ground, a myriad of microorganisms and animals (from fungi to earthworms and grazing animals) obtain their energy from them. Ultimately the organic matter left behind becomes part of the soil, releases the needed nutrients to the growing plants and those in the next generation.

Yeast is ubiquitous, it is found in flowers, ripening fruits, honeydew, ripening leaves. It comes in different species under the genus Saccharomyces, among them cerevisiae and ellipsoides. There are also other genera such as Brettanomyces and Debaryomyces. Not all yeasts make good wine. But one thing is universal to them. It is Nature's way of converting sugar molecules (C6H12O6) back to their elemental form.  Oxidation often accompanies such process, thus converting ethanol to acetic acid (CH3COOH), which is vinegar. Vinegar actually is a term, vin-egar, which means sour wine.

Natural vinegar is oxidized ethanol, usually with the aid of bacteria, principally Acetobacter and Leuconostoc. The latter forms gelatinous capsule that accumulates into a transparent to white layer we call nata. This is the principle involved in making Nata de coco and nata de piña.

So, even before sugar ferments to vinegar, nata bacteria and other contaminants can spoil wine and vinegar making. A host of organisms are soon attracted such as Drosophila flies, blue bottle flies, wasps, moths and butterflies that feed on the spoiled must. This is happening to unharvested fruits in the field, to remnants of pollination and fertilization, It is true in ponds and lakes where biomass of algae die of algal bloom. Ultimately the product is simply water, evaporating into the air or settling down into a pool or seeping into the ground, and all the organic compounds once part of the living world are back to their elemental components ready to be reassembled into the next living generation. Indeed this a great wonder on how Nature keeps a dynamic balance of the environment called homeostasis.

We can only imagine the ingenuity of wine makers far back during the Epyptian civilization, and in the Orient, the Chinese civilization. I had a chance to visit the ruins of an Assyrian fort outside Tel-Aviv. There, our guide pointing at broken tall jars, said, "The Assyrians were among the best wine makers in the ancient world." The Assyrians were powerful, not even Ramses could conquer them, They had a flourishing economy. Their vineyards can be glimpsed from the vineyards around the place Lakish today. Lakish wine is well-known all over the world, perhaps as famous as the Bordeaux in France.

Without yeast, our world would be a less happy one. Perhaps many organisms wouldn't be around in the first place, including us humans.

Here's a toast to the wonderful yeast. Cheers! KampaiMabuhay!~

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