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In viticulture, ripeness is the completion of the ripening process of wine grapes on the vine which signals the beginning of harvest. What exactly constitutes ripeness will vary depending on what style of wine is being produced (sparkling, still, fortified, ''rosé'', dessert wine, etc.) and what the winemaker and viticulturist personally believe constitutes ripeness. Once the grapes are harvested, the physical and chemical components of the grape which will influence a wine's quality are essentially set so determining the optimal moment of ripeness may be considered the most crucial decision in winemaking.〔J. Cox ''"From Vines to Wines"'' Fourth Edition, pg 97-106 Storey Publishing 1999 ISBN 1-58017-105-2〕 There are several factors that contribute to the ripeness of the grape. As the grapes go through ''veraison'', sugars in the grapes will continue to rise as acid levels fall. The balance between sugar (as well as the potential alcohol level) and acids is considered one of the most critical aspects of producing quality wine so both the must weight and "total acidity", as well as the pH of the grapes, are evaluated to determine ripeness. Towards the end of the 20th century, winemakers and viticulturists began focusing on the concept of achieving "physiological" ripeness in the grapes-described as a more complete ripeness of tannins and other phenolic compounds in the grapes that contribute to the color, flavor and aroma of wine.〔J. Robinson (ed) ''"The Oxford Companion to Wine"'' Third Edition pg 255-274, 317-324, 397, 523-524, 582-581 Oxford University Press 2006 ISBN 0-19-860990-6〕 ==What happens to a grape as it ripens== If ripening is broadly defined as the development of wine grapes, then it could be said that ripening is happening throughout the continuous annual cycle of the grapevine. More narrowly defined, ripening begins at the inception of ''veraison''. At this point (which is normally 40–60 days after fruit set though it may be longer in cooler climates), the grapes are hard and green with low sugar levels and very high levels of mostly malic acids. During ''veraison'', which may last from 30–70 days depending on the climate and other factors, the grapes go through several changes which impact their sugar, acid, tannin and mineral composition. The concentration of phenolic compounds in the skin, most notably anthocyanins for red wine grapes, replace the green color of chlorophyll as the grape berries themselves change color.〔〔D. K. Salunkhe, S. S. Kadam ''"(Handbook of fruit science and technology )"'' pg 13 CRC Press, 1995〕 The increase of sugars in the grapes comes from the storage of carbohydrates in the roots and trunk of the grapevines as well as through the process of photosynthesis. Sucrose produced by photosynthesis is transferred from the leaves to the berries as it is broken down into glucose and fructose molecules. The rate of this build up will depend on several factors including the climate (such as a string of cloudy weather which prohibits sunlight from reaching the vine) as well as the potential yield size of grape clusters and young vine shoot tips which compete for the resources of the mother grapevine. As the concentration of sugars build up, the concentration of acids decrease due, in part, to simple dilution but also to the consumption of acids in the process of plant respiration. The decrease in free acids, as well as the buildup of potassium, triggers a rise in the pH level of the grape juice.〔 In addition to the change in sugar, acids and pH levels other components of the grapes are building up during the ripening process. The mineral components of potassium, calcium, magnesium and sodium increase in concentration as they are disseminated among the skin of the grapes and its fleshy pulp. The color of the grape berries begin to change due to the building up of phenolic compounds such as anthocyanin in the skins. Flavonoids and volatile compounds known as "flavor precursors" which contribute to the eventual flavor and aroma of the wine also begin to build up in the skins and pulp. Additionally the concentration of tannins in the grape increases in several areas of the grape including the skin, seeds and stem.〔 Early in the ripening process these tannins are very bitter and "green". Exposure to the warmth and sunlight during the ripening period ushers in chemical changes to the tannins that when processed into wine makes the tannins feel softer in the mouth.〔D. Bird ''"Understanding Wine Technology"'' pg 18-27 DBQA Publishing 2005 ISBN 1-891267-91-4〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「ripeness in viticulture」の詳細全文を読む スポンサード リンク
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