Comment Flashcards
To define and describe.
Comment on the function of prompt buds.
Prompt buds form and break open in the same growing season. They form on the primary shoot (that has just grown from a compound bud) and produce lateral shoots. Lateral shoots are smaller and thinner than the primary shoots. Lateral shoots have a stem, leaves, buds, tendrils and sometimes inflorescences. Their main function is to allow the plant to carry on growing if the tip of the primary shoot has been damaged or eaten. Lateral shoots can provide an additional source of leaves for photosynthesis, which can be useful if the laterals are near the ends of the primary shoots and able to benefit from sunlight. Growth of laterals nearer the base of the primary shoot can be undesirable as they impede air flow and can shade the fruit too much. They may be removed in summer pruning. Lateral shoots often produce inflorescences, which can be known as a ‘second crop’. However, this can depend on the grape variety and canopy management techniques. Pinot Noir is a grape variety that often forms inflorescences on lateral shoots. These inflorescences become bunches of grapes later than those on the main stem and hence ripen later. If harvested at the same time as the main crop, the bunches in the second crop will be higher in acidity, lower in sugar and may have unripe tannins and aromas/flavours and, in black grapes, less colour development. The second crop may be removed during the growing season by green harvesting; this technique is thought to enhance the ripening process and improve the uniformity of ripeness of the remaining bunches. Alternatively, if fruit is hand-harvested, the ability to be selective means the second crop need not be picked or can be separated. However, this is not possible when fruit is machine harvested, and the second crop may therefore have an impact on the must (the substance that is fermented to make wine) and finished wine.
Comment on the benefits of slope and aspect for high quality wine production.
Vineyards planted on slopes will face a particular direction. This is called aspect. Vineyards that face the sun throughout most of the day (south-facing in the northern hemisphere and north-facing in the southern hemisphere) will receive more solar radiation than those facing the opposite direction. The importance of aspect and the steepness of the slope increases at high latitudes because solar radiation hits the Earth at a low angle at high latitudes. The slope increases the angle (nearer to perpendicular) at which the solar radiation hits the Earth’s surface, hence increasing the intensity of heat and light. The amount of warmth is also often a limiting factor in high latitude areas, so a slope can make a marked difference on the viability of a vineyard, the grape varieties that can be grown there and the ripeness of those grapes. Extra warmth and light during spring and autumn extend the viable growing season for vines grown on slopes that face towards the sun. As evidence of this, in the cool climate regions of Burgundy and Alsace, the Grand Cru sites that give wines with greater ripeness and concentration are usually positioned on south-east facing slopes, while the vineyards of the generic appellation are found on the flat. In warm climates, it may be desirable to limit the amount of heat and light. Planting on slopes that face away from the sun throughout most of the day can help achieve this. This may allow the grape grower to grow earlier-ripening grape varieties or produce wines with less alcohol and more acidity than would otherwise be the case at that latitude. For example, in Stellenbosch, white grape varieties are sometimes planted on south-facing slopes so that the grapes retain refreshing acidity. Slopes facing east benefit from morning sunshine that can heat up the atmosphere when air and soil temperatures are at their lowest. This can extend the hours of vine growth and grape ripening each day, especially in cool climates. The grape canopy, which can be covered with dew in the morning, also dries out earlier in east-facing vineyards, reducing the spread of fungal disease, which is beneficial for grape quality and yields. Slopes can provide additional benefits, including shallower, poorer soils and better drainage. Slopes can also provide shelter from winds and rain, and protection from frosts (air movement down the slope prevents frosts.
Comment on the benefits and choices of cover crops in the vineyard.
Cover crops are plants that are specifically planted, or allowed to grow, that have a beneficial effect on the vineyard. Cover crops may be grown to suppress weeds. They may also be planted to improve soil structure,
compete with the vine for nutrient and water availability in fertile sites, manage soil erosion, enhance biodiversity and provide a surface to drive on. Cover crops that are quick to establish and are adapted to the soil and climatic conditions are best.
Examples of cover crops include legumes (such as beans and clover) and various cereals (such as ryegrass and oats). Cover crops are widely used around the world but have to be matched to the needs of the vineyard. For example, Wine
Australia provides an online cover crop finder for particular conditions for its grape growers. It is also possible to leave natural vegetation to grow in the vineyard to achieve any of the above aims. Although this is cheap, and can permit greater diversity, specific cover crops with known characteristics allow more control. The cover crop must be managed so that it does not compete too much with the vine for water and nutrients at key times in the vine cycle. If ploughed into the soil, the cover crop or natural vegetation can provide organic matter and, in this way, fertilise the soil (this is called green manure).
Advantages include:
* This method does not use any chemicals and increases soil biological activity and biodiversity in the vineyard, so is commonly used in organic and biodynamic viticulture.
* The ability to influence the vigour of the vine by introducing competition for water and nutrients.
* The provision of a good surface for machinery, particularly in climates with high annual rainfall.
Comment on the effects of a vegetative cycle in the vineyard.
If the yield of fruit is too low (termed under-cropping) for the vigour of the vine, shoot growth continues through the vine cycle because there is not much fruit to ripen. The growing shoots and leaves compete with the grapes for sugar and other compounds needed for growth and can negatively affect grape formation and ripening. This also leads to a dense, shady canopy, and hence lower quality fruit due to lack of sunlight interception. This may also result in low yields the next year due to reduced bud fruitfulness. Low yields in the next season may lead to under-cropping in that year and hence the vine enters what is known as ‘a vegetative cycle’. (P.77 diagram)
Comment on a producer’s decision to green harvest.
This is the removal of bunches of grapes to increase ripeness of those grapes left on the vine. If this process is timed near véraison, it can enhance ripening. In cases where fruit ripening is uneven (e.g. because of uneven budburst or fruit set, frost or the presence of bunches on lateral shoots), the least ripe bunches of grapes may be removed to improve uniformity of ripening, and hence enhance quality. In large-volume, inexpensive wine producing regions such as Central Valley, California, green harvesting, which requires dropping fruit, is unlikely, as this would reduce yields.
Comment on the formation of Acetaldehyde in wines.
Acetaldehyde occurs in wines due to the oxidation of ethanol. It is also known as ethanal. It masks fresh fruit aromas and has a stale smell that is regarded as a fault in most wines. However, it is an important component of the distinctive smell of Fino sherry. For example, acetaldehyde can give a nutty, bruised apple aroma.
Comment on the component of Glycerol in wines.
Glycerol is the third most abundant part of wine after water and alcohol (in dry wines) and is derived from the sugar in grapes. It occurs in higher levels in wines made from botrytis-affected grapes (e.g. Tokaji) and wines made by carbonic maceration (e.g. basic Beaujolais) although to a lesser extent than those made from botrytis-affected grapes.
Glycerol contributes smoothness to the texture of wine and the perception of the fullness of the body. It has a slightly sweet taste. Glycerol levels increase, which can add texture, and a range of distinctive aromas is created inside the grape, commonly including kirsch, banana, bubble gum and cinnamon. In terms of no- or low-alcohol winemaking, once the alcohol is removed, further additions or adjustments can be made to correct flavour or textural elements that were lost during the dealcoholization process. Thanks to its viscous texture, glycerol is commonly used to boost body and texture.
Comment on the most effective points during winemaking for the addition of sulfur dioxide.
Sulfur dioxide is a preservative that is almost universally used in winemaking, where it has the following properties:
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Anti-oxidant – SO2 only reacts with oxygen itself very slowly; it reduces the effects of oxidation by reacting with the products of oxidation reactions, so they cannot oxidise further compounds in the wine. It also inhibits oxidative enzymes.
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Anti-microbial – It inhibits the development of microbes such as yeast and bacteria. Different species of yeast and bacteria can vary in their tolerance to SO2.
SO2 is generally added soon after the grapes are picked and/or reach the winery. It may then be added at various points during the winemaking process and usually at bottling. When SO2 is added to must or wine, it dissolves and some of it reacts with compounds in the liquid. This proportion is called ‘bound SO2’ and it is ineffective against oxidation and microbes. The proportion that is not bound is called ‘free SO2’. The vast majority of the free SO2 exists in a relatively inactive form and a small proportion exists as molecular SO2, which is the most effective against oxidation and microbes.
The pH level of the must or wine has a key effect on the efficacy of SO2 in that a greater proportion of free SO2 is in the molecular form at lower pH levels. This means that a greater amount of SO2 needs to be added to musts and wines with relatively high pH to protect them from oxidation and microbes.
The timing and size of SO2 additions also influences the effectiveness of the added SO2. Adding a larger amount when the grapes are crushed, at the end of malolactic conversion and at bottling is considered as more effective than adding smaller amounts throughout the winemaking process.
Judicious additions of SO2 are beneficial and often necessary to produce unfaulty wines that remain unfaulty once packaged. However, where possible, quality-conscious winemakers will aim to limit additions of SO2 both because of the legal restrictions listed above and also because high levels of SO2 can dull wine aromas/flavours and sometimes cause the wine to taste harsh.
Good winery hygiene and effective grape sorting can limit the amount of harmful microbes in the wine and the winery. Limiting oxygen exposure and keeping grapes, must or wine at cool temperatures can also reduce the amount of SO2 needed to protect from oxidation and spoilage organisms.
Comment on the oxidation of wine as a fault.
This is the result of excessive exposure to oxygen either in the winemaking process or once in bottle or other container. The latter can be due to faulty bottling, poor quality corks or plastic closures, or simply keeping wine for too long if it is not of a quality to age. The effect is that the wine becomes prematurely brown in colour with a loss of primary fruit and then a vinegary smell. Oxygen is generally threatening for the production of fresh, fruity wines. Many of the aroma compounds that give these wines their fruity style, for example the thiols found in Sauvignon Blanc, break down in the presence of oxygen, and this can lead to a loss of fruitiness. Furthermore, the products of oxidation reactions may contribute unwanted aromas to the wine; for example, acetaldehyde (from the oxidation of ethanol) can give a nutty, apple aroma. The colour of white wines can also turn darker, becoming gold and then brown with increased oxidation, and therefore white wines tend to need greater protection.
Comment on the importance of traceability as a control and quality measure for wine making.
A formal system for traceability is necessary if a wine company is to:
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respond to and investigate complaints about its wine. Complaints can come from any point of the supply chain, including the final consumer
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improve its practice so that similar problems do not occur in the future.
Each consignment of wine is given a lot number, which appears on the bottle. This is a requirement in the EU and many other markets. The lot number enables a company to trace back where the grapes came from, what additives have been used and what processes the wine went through. The winery must keep records of its activities at every point of its production, from the vineyard, through the winery and then in the transportation of the wine. Larger firms and those concerned about traceability will keep samples of every batch so that they can investigate what has gone wrong and compare returned bottles with their library of samples. Common problems include cork taint, tartrate crystals and faulty or missing labels. (P.176 diagram)