Basic Winemaking and Enology - 1 Winemaking predates recorded history. During the Cro-Magnon era, 45 thousand years ago, surely some family neglected some grapes they had collected. When they rediscovered the grapes, they found that the grapes had broken down and grape juice had escaped. They ate and drank the cracked grapes and drank the “juice”. An hour or so later, some family members got giggly and soon they all got sleepy and took a nap. The juice had naturally fermented into wine. They had been introduced to a new beverage. Winemaking has been known to be part of the diet of man since he settled in the Tigris- Euphrates basin several thousand years ago. It is widely accepted that Vitis vinifera grapes originated in Asia Minor in an area between and south of the Black and Caspian Seas. This area of the Caucasus and northern Mesopotamia (present day Syria) is where grapes were first cultivated. Men found these wild grapes growing into the treetops. They then took cuttings and planted vines and found certain varieties to their liking. As early human groups traveled, these domesticated grapes were carried with them for planting in their new homes. Over the past ten thousand years many different empires have dominated the lands in and around the Mediterranean. After they occupied new lands, the victors planted the grapes they were familiar with at home. When they found new grapes in the occupied territories, they brought them back for planting in their homelands. The oldest evidence of wine production is residues found in ancient Neolithic wine jars (amphora) found in the Iranian Z agros Mountains and dated to about 5,000 B.C. M ap of the ancient N ear E ast and E gypt, showing the distribution of the modern wild grapevine in purple shading. G rape remains (primarily pips) recovered from N eolithic and L ate U ruk sites are indicated by the grape cluster symbol. T he occurrences of wine jars, which have been chemically identified as such, are indicated by the jar symbol. 1 Later, the ancient Phoenicians settled on the rim of the Mediterranean and on Cyprus and Sicily and planted the vines they had used at home. The Greeks made their influence felt on the Island of Cyprus by 1,000 B.C. From about 350 B.C., the Dalmatian coast in present day Croatia was used as a Greek passage. The Greeks also settled in other parts of the Adriatic Sea and in Southern Italy. The Romans moved into these Greek territories around 165 B.C. and brought back for cultivation hosts of fruits and vegetables. From 830 AD until the 19th century, Croatia was dominated or controlled by the Franks, Byzantines, Hungarians, Venetians, Hapsburgs and finally the Austro-Hungarians. The Phoenicians, Greeks, and Romans, as did these newer infiltrators, always brought their grape vines with them to their new territories. They also brought newly discovered vines home with them. Since Cro-Magnon times, we’ve learned much about how to make wine. Winemaking has four basic phases: GRAPES> > > > > > > FERMENTATION > > > > > > STABILITY > > > > > > > AGING BIOLOGICAL MICROBILOGICAL PHYSICAL CHEMICAL 1. BIOLOGICAL. Grapes grow and ripen. At harvest, the potential quality of the wine is set. The winemaker can try to attain that potential, but not improve it. We do as little as possible, e.g., pumping, filtering, clarifying, etc., that can take from the quality potential. Winemaking is a negative craft. We need to minimize the damage we can cause. 2. MICROBIOLOGICAL/ ENZ YMATIC. Called fermentation. Microorganisms (yeast and bacteria) produce enzymes. Yeast enzymes convert grape sugar into alcohol, CO2 and hundreds of other compounds. Bacterial enzymes convert malic acid to lactic acid. 3. PHYSICAL OR CLARIFICATION. Stability is guided. Particles are settled with gravity or forced through screens. Tartaric acid combines with potassium and precipitates potassium bitartrate (KHT). Fining agents are added to make wine more pleasing to drink. 4. CHEMICAL or AGING. Ultimate quality is realized. Various components of wine combine with each other or oxygen and form new substances. When aging in wooden containers, the wood adds bouquet and flavor. The phases overlap. Some enzymatic action happens during grape ripening. Settling occurs during fermentation. Aging begins during clarification. Clarification continues during aging. Microbiological activity can continue into the bottle. Winemaking treatments include: varietal character, extraction from grapes, skins and microbes, aging effects and possibly wood extracts, residual sugar, CO2, extra alcohol, acid, oxidation products and flavorings. Some will be explained later. 2 When wines are aged, the grape aroma decreases and the bouquet increases. Wines aged in wood, pickup wood characters. Red wines, with more tannin than whites, take longer to become less harsh. With long aging, fruit diminishes and so does “varietal character”. Sugar increases the wine body, masks off flavors and gives sweet tastes most Americans prefer. Sparkling wines contain excess CO2 and young whites and reds can have a touch of spritz. During fermentation, most yeast stops working when the alcohol content exceeds 14%. Adding alcohol, with high proof, to raise alcohol to 16 to 20% will add resistance to yeast and bacterial activity. Flor yeast fermentation gives sherry bouquets and heating gives Madeira nutty characters. GRAPES The most important fruit crop grown in the world. Grapes are good for wine because: 1. High sugar content 2. Fruit acids 3. Minerals and other ideal substrates for yeast fermentation 4. Tannins from grape skins and seeds retard oxidation of wine 5. Grape flavors last longer than other fruit flavors 6. Grapes provide raw material for a wide range of wine types The botanical genus Vitis has two sub-genera. 1. Euvitis (true grape) or “bunch grapes”. They grow in bunches. 2. Muscadinia Grow as separate berries. Euvitis has about 60 species. Almost all are important in winemaking. They originated in the northern hemisphere. Most species is V. vinifera. It is native to the area of Asia Minor, south of the Black and Caspian seas (Turkey, Iraq and Iran). The most important species indigenous to America is V. labrusca, Concord being most widely known variety. Within V. vinifera are many varieties, like Chardonnay, Cabernet Sauvignon, etc. Grape growers found they can retain the quality of the parent grape vines by rooting cuttings taken from mature vine wood. Offspring produced in this way are “clones”. As identical to parents as possible. All Vitis vines are either male or female. Early cutting propagation attempts failed since the vines were invariably female. The presence of “unproductive” male vines was essential to a productive vineyard. Sometime in the history of grape culture, a spontaneous mutation of flower type occurred, resulting in vines with flowers that could 3 fertilize themselves. The mutation occurred long ago, causing “perfect flowers” to be had. (The North American native vines do not have “perfect flowers”.) During the last century, interest rose in producing new varieties by deliberately pollinating the flowers of on cultivar (varietal) with another. European botanists imported American grape cuttings to use. Unfortunately, American grapevine pests were inadvertently introduced into Europe. First, they imported powdery mildew. V. vinifera has no resistance. It swept through Europe. Next, the grape louse Phylloxera vastatrix. The eventual solutions were sprays and American rootstock. American rootstock was sent and Phylloxera was controlled. Some of the rootstock was infected with downy mildew and black rot, causing new problems. COMPOSITION OF WINE Compounds Grape Must % Dry wine % Water 70-85 85-93 Carbohydrates (sugars) 15-25 0.1-0.3 Alcohols 0.0 7-15 Organic Acids 0.3-1.5 0.3-1.1 Phenolic compounds 0.05-0.15 0.05-0.35 Nitrogen compounds 0.03-0.17 0.01-0.09 Carbonyl compounds 0.0 0.001-0.050 Inorganic compounds 0.3-0.5 0.15-0.40 Carbohydrates Approximately 90% to 94% of soluble solids are sugars. The non-sugar portion of soluble solids consists of acids, salts, tannin, coloring material, pectin, etc. The soluble solids in grapes and must can be estimated with refractometers or hydrometers. The units used in the U.S. is °Brix or °Balling. 1° Brix is 1 g sucrose per 100 g of solution. Refractometers measure refractive index, a mediums’ bending of light. The refractive index changes rapidly with temperature. Temperature corrections should be made. A 20g/ 100 ml reading at 68°F, would read about 20.45 at 56° F and 19.45 at 80° F. Since only 2 or so drops are used ion a “refract”, the sample error may be a problem. A hydrometer is a floating instrument which indicates the specific gravity of the liquid in which it floats. Temperature corrections must also be made with hydrometer readings. Most hydrometers are calibrated at 68°F. The approximate correction is + 0.03° Brix for each °F above the calibrated temperature and -0.03° Brix for each °F below the calibrated temperature. Make sure the hydrometers are clean and float freely. Generally, refractometers are used in the vineyards and hydrometers at the winery. Alcohol on must and wines affects readings of hydrometers and refractometers differently. A 12% alcohol in a water solution gives a -4° Brix reading with a hydrometer, but a + 4° Brix reading with a refractometer. Extracts (these are nonvolatile 4 materials in wine, which is basically everything but alcohol) contribute about + 2° Brix, so dry wines give about -2° Brix readings with a hydrometer and + 6° Brix reading with refractometer. If a fermenting wine has a reading of 19 ° Brix at 53°F, the temperature difference vs. hydrometer calibration would be -15°F. Multiplying 15 times -0.03° Brix, would give -0.45° Brix.