Presentation on theme: "Terminology The sugar in wine is mainly glucose and fructose, with traces of arabinose, xylose and other sugars that are not fermentable by yeast,but can."— Presentation transcript:
Terminology The sugar in wine is mainly glucose and fructose, with traces of arabinose, xylose and other sugars that are not fermentable by yeast,but can be attacked by bacteria. Each country has its own system for measuring the sugar content or ripeness of grapes, known in English as the “must weight”.
Terminology Residual sugar is the sugar left after fermentation has finished or been stopped, measured in grams per litre. A dry wine has virtually none. Alcohol content (mainly ethyl alcohol) is expressed in per cent by volume ofthe total liquid. (Also known as “degrees”.) Table wines are usually between 11.5° and 13.5°, though up to 15° is increasingly seen.
Terminology Acidity is both fixed and volatile. Fixed acidity consists principally of tartaric, malic and citric acids, all found in the grape, and lactic and succinic acids,produced during fermentation. Volatile acidity consists mainly of acetic acid, which is rapidly formed by bacteria in the presence of oxygen. A small amount of volatile acidity is inevitable and even attractive. With a larger amount the wine becomes “pricked”– to use the Shakespearian term. It turns to vinegar. Acidity may be natural, in warm regions it may also be added. Total acidity is fixed and volatile acidity combined. As a rule of thumb, for a well-balanced wine it should be in the region of one gram per thousandfor each 10° Oechsle (see table on p.283).
Terminology Barriques Too much of the flavour of many modern wines is added in the form of oak; either from ageing and/or fermenting in barrels (the newer the barrel the stronger the influence) or from the addition of oak chips or – at worst – oak essence. Newcomers to wine can easily be beguiledby the vanilla-like scent and flavour into thinking they have bought something luxurious rather than something cosmetically flavoured. But barrels are expensive; real ones are only used for wines with the inherent quality to benefit long-term. French oak is classic and most expensive;
Terminology Malolactic fermentation is often referred to as a secondary fermentation, and can occur naturally or be induced. The process involves converting tart malic acid into softer lactic acid. Unrelated to alcoholic fermentation, “la malo” can add complexity and flavour to both red and white wines. In hotter climates where natural acidity may be low canny operators avoid it.
Terminology Micro-oxygenation is a widely used technique that allows the wine controlled contact with oxygen during maturation. This mimics the effect of barrelageing, reduces the need for racking, and helps to stabilize the wine. pH is a measure of the strength of the acidity: the lower the figure the more acid. Wine usually ranges from pH 2.8 to 3.8. High pH can be a problem in hot climates. Lower pH gives better colour, helps stop bacterial spoilage and allows more of the SO2 to be free and active as a preservative.
Terminology Sulphur dioxide (SO2) is added to prevent oxidation and other accidents in winemaking. Some of it combines with sugars etc and is “bound”. Onlythe “free” SO2 is effective as a preservative. Total SO2 is controlled by law according to the level of residual sugar: the more sugar, the moreSO2 is needed. Tannins are the focus of attention for red winemakers intent on producing softer, more approachable wines. Later picking, and picking by tannin ripeness rather than sugar levels gives riper, silkier tannins. Toast refers to the burning of the inside of the barrel. “High toast” givesthe wine caramel-like flavours.
Winemaking... nurturing the natural process... By definition, wine is a drink made by the partial or complete fermentation of the juice of fresh grapes. Grapes are the only fruit with a high enough level of sugar and with the proper balance of acid and nutrients to sustain a natural fermentation to dryness with stable results. Other fruits or berries may be fermented, but without additions of sugar, acid, or various yeast nutrients, they may readily spoil.
ANCIENT AND MYSTERIOUS Although the biochemistry of fermentation was a mystery until the late nineteenth century, the results of the process have been known to man for over 5000 years. Fermentation was thought to be a spontaneous act of Nature, merely set in motion by man. The grapes were crushed to release the juice (must) into a fermentation vessel. When the fermentation was complete, the wine was pressed by some mechanical means to separate the liquid from the stems, skins, pips and pulp. It was then stored to age and clarify until it was drunk. While modern technology and methods may have refined and enhanced it, this is still the basic process today.
Fermentation Fermentation is a natural process. Left alone, a grape would ripen until the skin broke and the juice fermented. The intervention of man is only necessary to increase the clarity and stability of the end product. "Making" wine is mostly a matter of the choices and decisions of the winemaker during each phase of production, from growing the raw material grapes to bottling the finished wine. These choices determine the wine's style, flavors, and aromas to a great extent.
Yeast Yeast is the microscopic, single-celled fungi which causes fermentation. Yeast populations are present in the air, especially in and around vineyards. This indigenous yeast population is known as "wild" or "ambient" yeast. Yeast cells instead are concentrated around the berry stem (peduncle) and much lower in concentration than thought, in the dozens rather than the thousands.
Fermentation contd. When yeast comes in contact with the grape juice, it begins to feed on it, grow and reproduce. There are approximately 6000 yeast cells per ounce of actively fermenting must. An enzyme (zymase) within the yeast converts sugar in the grape juice into roughly equal parts of alcohol and carbon dioxide and also releases energy in the form of heat.
Fermentation C6H12O6>ZYMASE>2C2H5OH + 2CO2 + HEAT Theoretically, this process could continue naturally until the sugar is used up, which is most often the case. Occasionally, fermentation continues only until the yeast cells are no longer able to tolerate the level of their waste products: alcohol, carbon dioxide and/or heat, thus leaving very small amounts of residual sugar.
Fermentation It is noteworthy there were no significant changes in the methods and practices of viticulture and enology from about 1000 BC until about 1860 AD. Other than small improvements such as using more metal and less wooden parts in presses and equipment, the French vignerons of 1850 knew little more of the scientific principals involved than did the ancient Romans.
Storage Certain events did occur, primarily regarding wine storage, which together marked the beginnings of serious wine collecting. An English print from 1778 is the first known evidence of a corkscrew. In 1797, it was first noticed at Chateau LaFite that wine that aged in bottles improved. A few years later, in 1815, came the first documented Declared Vintage of Port.
Neolithic period “Chateau Hajji Firuz If winemaking is best understood as an intentional human activity rather than a seasonal happenstance, then the Neolithic period (8500-4000 B.C.) is the first time in human prehistory when the necessary preconditions for this momentous innovation came together.
Archeologic evidence A major step forward in our understanding of Neolithic winemaking came from the analysis of a yellowish residue inside a jar excavated by Mary M. Voigt at the site of Hajji Firuz Tepe in the northern Zagros Mountains of Iran. The jar, with a volume of about 9 liters (2.5 gallons) was found together with five similar jars embedded in the earthen floor along one wall of a "kitchen" of a Neolithic mudbrick building, dated to ca. 5400-5000 B.C. The structure, consisting of a large living room that may have doubled as a bedroom, the "kitchen," and two storage rooms, might have accommodated an extended family. That the room in which the jars were found functioned as a kitchen was supported by the finding of numerous pottery vessels, which were probably used to prepare and cook foods, together with a fireplace.
Egypt Wine for the Afterlife The evidence for winemaking in the Delta during the preceding Early Dynastic Period (Dynasties 1 and 2) is more inferential. Rather than recording a large number of wine jars in an offering list, actual jars in large quantities were buried in the tombs of the pharoahs at Abydos and those of their families at Saqqara, the main religious centers. The jars are stoppered with a round pottery lid and a conical clay lump that was pressed over the lid and tightly around the rim. The clay stopper was generally impressed with multiple cylinder seal impressions giving the name of the pharoah....such seals have been interpreted as a primitive kind of wine label...
Mesopotamia Under the Grape Arbors... It has usually been argued that barley beer was the alcoholic beverage of choice in ancient Sumer, since the hot, dry climate of southern Iraq makes it difficult to grow grapevines, and the textual evidence for viniculture and winemaking in Mesopotamia is minimal before the 2nd millennium B.C. But based on chemical evidence for wine inside jars that could've been used to transport and serve it, wine was probably already being enjoyed by at least the upper classes in Late Uruk times (ca. 3500-3100 B.C.). Early Dynastic cylinder seals depict the royalty and their entourages drinking beer with tubes/straws from large jars and a second beverage—presumably wine—from hand-held cups
Mesopotamia contd. The wine imported into lowland Greater Mesopotamia could have been brought from the northern Zagros Mountains of Iran or other parts of the Near East, at least 600 kilometers away. The 5th century B.C. Greek historian Herodotus describes shipping wine down the Euphrates or Tigris from Armenia at a much later period: round skin boats were loaded with date-palm casks of wine and delivered to Babylon.
Mesopotamia contd. River transport was also an option in the Late Uruk Period. But if the demand for the beverage were great enough, transplantation of grapevines to closer locales in the central Zagros and possibly as far south as Susa would be anticipated. When the Late Uruk trade routes were suddenly cut off at the end of the period, the pressure to establish productive vineyards closer to the major urban centers would have intensified.
Mesopotamia Future excavation will be decisive in tracing the prehistory of viniculture and winemaking in this region of the ancient Near East; already there is a strong indication that the domesticated grape plant had already been transplanted there as early as the mid-3rd millennium B.C. Elamite cylinder seals, foreshadowing similiar scenes on Assyrian reliefs some two millennia later, depict males and females seated under grape arbors, drinking what is most likely wine.
The Evolution of modern wine By 17th century wine was in a unique position of being the one and only wholesome and up to a point storable beverage in Europe. Water was not safe to drink. Ale without hops went bad easily. There were no spirits. In the 17th century,chocolate came from central America. Then coffee came from Arabia.
Bottle and cork The early 17th century glass making technology advanced to make wine bottles stronger and cheaper to blow. Cork, bottle ande the corkskrew were also developed at the same time. It became clear that wine kept in a corked bottle kept longer than in a barrel.
Phylloxera A disease caused by a microorganism originated in America and reached Europe on steamships able to cross the Atlantic fast enough for it to survive on the botanical specimens. It caused the pulling up almost every vine in Europe and New World, and it seemed the end of wine production. American vines were resistant to it. Grafting European vines onto American roots is the only efective defence.
The Vine Wine is the fermented juice of a single fruit: the grape. Wine is made is made from rain (and in hotter regions irrigation of water) recovered from the ground by the mechanısm of the plant that bears grapes, the vine and in the presence of sunlight converted by photosythesis into fermentable sugar.
Vine The first two years of its life it creates roots and builds a strong woody stalk to bear and carry the grapes. Like most plants, vines will reproduce from seed but the seeds rarely turn out like their parents. Viticulturists propagate vines asexually instead so that they can be sure that the offspring are the same as the mother vine.
Vine For planting a new vineyard every vine originates as a cutting, either planted to take root on its own or grafted onto a rootstock, a rooted cutting of another species especially selected for the soil type or resistence to draught or nematodes. Only healthy cuttings are used. As a vine grows older its principal roots penetrate deeper in the ground. Yields decline after 25 to 30 years.
The vine stages Stage 1. As early as March, in Northern Europe and September in the Southern hemisphere, the buds left after winter pruning start to swell and the first signs of green can be seen emerging from the gnarled wood. The temperaure is important 10 C, although different grape varieties vary.
The vine stages Stage 2. Within 10 days of budbreak, leaves start to separate from the bud and embryonic taendrils begin to be visible and are too vulnerable to frost which can strike as loate as mid-May or mid-November. Late pruning can delay budbreak.
The vine stages Stage 3. Between six and 13 weeks after budbreak the crucial flowering of the vine begins with the emergence of tiny caps of fused petals. These look very like miniature versions of the grapes that will be formed here once the caps fall, exposing stamens to be fertilized by pollen to create the berries.
The vine stages Stage 4. The size of the eventual crop depends on the success of pollination. Poor weather during the ten-14 day flowering can result in having different sizes of grapes on the same bunch.
The vine stages Stage 5. The grapes swell during the summer and in August/February undergo veraison whereby they soften and turn reddish or yellow. The ripening process begins and sugars start to build rapidly inside the grape.
Wine and Weather After the vine the weather is the second most important factor. Without sufficient rainfall or warmth grapes wiil not ripen enough. An excess of either may decrease the quality of wine. Hail or frost can also influence the quantity rather than quality. Cool climate wines tend to be lower in alcohol and higher in acidity.
Wine and Weather The mean temperatures in the final month of ripening should be 15-21C to produce fine table wines and hotter temperatures can result in good fortified wines. Winters need to be sufficiently cool to allow the vine its revitalizing winter sleep. If temperatures regularly fall below -15 C in winter then the risk of freezing occur.
Wine and water The vine needs water as well as warmth An average rainfall of at least 500 mm is generally required. Growers take care of it if the rain fall is not enough by dripping method. If a vine runs short of water, it is said to suffer water stress and tends to produce smaller grapes with thicker skins.
Wine and Wind Winds can be beneficial by cooling hot vineyards and drying out damp ones. Continous wind stress can stop photosynthesis and delay the ripening process. Windbreakes can be built.
Terroir There is no exact translation for the French word, may be terrain. At its most restrictive the word means soil. The dirt, subsoil and rocks beneath it, its physical properties and how they relate to the local climate, the macroclimate of the region. For example: how quickly a patch of land drains whether it reflects the sunlight or absorbs the heatg.
International Grapes Cabernet Sauvignon: Blackcurrant, cedar, high tannin. Best travelled red wine variety, since it is relatively late ripener,it is viable to warm climates. Chardonnay: Broad, inoffensive unless over- oaked. The white burgundy grape, chardonnay can be grown and ripened without difficulty almost everywhere except at the extremes.
International grapes Merlot: plump and plummy. –Cabernet Sauvıgnon’s traditional slightly fleshier blending partner especially in Bordeaux where its earlier ripening makes Merlot a lot easier and it is the most planted grape there. Pinot Noir: Cherry, raspbery, violoets. –This is the most elusive grape. It is relatively early ripening and extremely sensitive to the terroir. Riesling: Aromatic, delicate, expressive –Riesling is to white wine what Cabernet Sauvignon is to red. It can make entirely different wines in different places and can age magnificently.
International grapes Syrah/Shiraz: Black pepper, dark chocolate, notable colour and tannin. Sauvignon Blanc: Grass, green fruits, razor sharp, rarely oaked. Gerwurtraminer: Lychees, roses, heady, high alsohol, deep coloured. Semillion: Figs, citrus fruits, full-bodied, rich