第二章 葡萄成熟与采收ppt课件.ppt
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1、College of Enology, NWSUAF,2 葡萄的成熟与采收,葡萄酒工艺学教学大纲规定:本章主要讲述葡萄浆果的各种成分及其在成熟过程中的变化以及与酒质的关系。要求学生建立“潜在质量”、“优良品种”以及“品种结构”、“品种适应性、特异性”、和“成熟系数”的概念,深刻理解葡萄是葡萄酒的物质基础,掌握确定最佳采收期的原则和方法。教学重点和难点:葡萄浆果与酒质的关系,最佳采收期的确定。,College of Enology, NWSUAF,2.1 葡萄浆果的成熟 (p20),葡萄酒只能是新鲜葡萄果实或葡萄汁经完全或部分酒精发酵后获得的饮料(P15)。葡萄浆果的质量(成熟度)决定着葡萄酒的
2、质量和种类,是影响葡萄酒生产的主要因素之一。好的产区是指能生产成熟度良好的葡萄,从而才能生产品质优良的葡萄酒的产区;好的年份也是指夏天的气候条件有利于葡萄果实充分成熟的年份。可通过控制葡萄的成熟度控制葡萄酒的质量和种类。如在气候较为炎热的地区,由于葡萄果实成熟很快,为了获得平衡、清爽的葡萄酒,应尽量避免葡萄过熟;在有的产区,根据采收时期的早迟,既可生产具有一定酸度、果香味浓的干白葡萄酒,也可生产酸度较低、醇厚饱满的红葡萄酒或具有一定残糖的葡萄酒。,College of Enology, NWSUAF,2.1 葡萄浆果的成熟 (p41),因此,了解葡萄果实的成熟和果实中的成分及其在成熟过程中的变
3、化,即葡萄浆果的生物化学,并根据需要进行控制,是保证葡萄酒质量的第一步。 2.1.1 葡萄浆果成熟的不同阶段2.1.2 葡萄浆果中的主要成分2.1.3 葡萄浆果主要成分的变化,College of Enology, NWSUAF,2.1.1 葡萄浆果成熟的不同阶段(p41),葡萄浆果从座果开始至完全成熟,需要经历幼果期、转色期、成熟期、过熟期等不同的阶段(图2-12)。,College of Enology, NWSUAF,葡萄酒工艺学主讲 王华,幼果期,幼果期的持续时间从座果开始,到转色期结束。在这一时期,幼果迅速膨大,并保持绿色,质地坚硬。糖开始在幼果中出现,但其含量不超过1020g/L。
4、酸的含量迅速增加,并在接近转色期时达到最大值,约24g(酒石酸)/L。 见图213(P43),College of Enology, NWSUAF,葡萄酒工艺学主讲 王华,转色期,转色期就是葡萄浆果着色的时期。在这一时期,浆果不再膨大。颜色:果皮叶绿素大量分解,白品种果色变浅,丧失绿色,呈微透明状;有色品种果皮开始积累色素,由绿色逐渐转为红色、深蓝色等。糖:浆果含糖量直线上升,由20g/L上升到100g/L。酸:含酸量开始下降。,College of Enology, NWSUAF,葡萄酒工艺学主讲 王华,成熟期,从转色期结束到浆果成熟,大约需3550天。在此期间,浆果再次膨大,逐渐达到品种固
5、有大小和色泽,果汁含酸量迅速降低,含糖量增高,其增加速度可达每天45g/L。浆果达到生理成熟。所谓生理成熟(P42),即浆果含糖量达到最大值,果粒也达到最大直径时的成熟度。,College of Enology, NWSUAF,过熟期,在浆果成熟以后,果实与植株其它部分的物质交换基本停止。果实的相对含糖量可以由于水分的蒸发而提高(果汁浓度增大),浆果进入过熟期。过熟作用可以提高果汁中糖的浓度,这对于酿造高酒度、高糖度的葡萄酒是必须的。,College of Enology, NWSUAF,2.1.1 葡萄浆果成熟的不同阶段Berry Development and Ripening,The w
6、inemaker is directly concerned with the ripening of the berries, particularly in the late stages. The period from berry set to veraison (onset of ripening) is less subject to problems such as overcropping, because the tiny berries, although numerous, are less total consumers of photosynthate than th
7、ey become as ripening and rapid sugar accumulation begins.,College of Enology, NWSUAF,2.1.1 葡萄浆果成熟的不同阶段Berry Development and Ripening,Nevertheless, considerable growth takes place during this early period. Berry size increases but pulp composition remains relatively constant especially in terms of h
8、igh acid and low sugar concentration. Initial berry size increase is mostly from cell multiplication followed soon by both cell enlargement and cell multiplication. In the final stages berry enlargement is exclusively from cell enlargement (Staudt et al.1986).,College of Enology, NWSUAF,葡萄酒工艺学主讲 王华,
9、Berry Development and Ripening Figure 2-2 p36,Figure 2-2 shows a typical example of this curve. These data are from Tokay, a larger-berry, lower-sugar, table grape, but are typical.,College of Enology, NWSUAF,葡萄酒工艺学主讲 王华,2.1.1 葡萄浆果成熟的不同阶段Berry Development and Ripening,Two periods of rapid volume inc
10、rease are separated by a short slower lag period. The first rapid enlargement prior to veraison involves growth from perhaps 50 mg to about 1 g for a typical wine grape giving a 20-fold increase. The second rapid growth period produced only another doubling or so, but the amount of increased fresh w
11、eight is equivalent to or greater than the whole previous period. Furthermore the moisture content is higher in the first stage with nearly all the sugar accumulation in the later one. Therefore dry weight increase is much greater late. Moisture stress can affect the first enlargement stage especial
12、ly strongly.,College of Enology, NWSUAF,The intermediate lag period _Veraison,The intermediate lag period marks the transition from growing to ripening (Figure2-2). Veraison, the onset of ripening, marks the resumption of rapid enlargement and coincides with the beginning of color changes (loss of c
13、hlorophyll and production of anthocyanins in red varieties) and sugar accumulation. Veraison is an abrupt change in a berry, but varies a little within a cluster and increasingly over the vine, the vineyard, and the area.,College of Enology, NWSUAF,The intermediate lag period _Veraison,Veraison is c
14、onsidered to follow the completion of development of viable seeds. With seed maturity presumably assured (but at a similar stage for seedless varieties), the vine is free to make the berry as attractive as possible for birds and other potential seed dispersers. Desirable ripeness is the culmination
15、of the production of more attractive odors and flavors begun at veraison. High sugar, lower acid, rich color, and full varietal fruitiness are criteria for harvesting the ripe fruit.,College of Enology, NWSUAF,Fruit maturity,At normal fruit maturity, enlargement ceases and physiological accumulation
16、 of sugar ceases at about 25 Brix (Singleton et al. 1966a) in wine grapes. Further increase in the Brix of the juice is the result of water loss which decreases berry volume and turgor, eventually leading to raisining. Shriveling of the berries is ordinarily undesirable especially for table wines, s
17、ince loss or modification of flavor and color are likely. In overcropped berries with inadequate sugar, concentration will occur, but this is a poor way to compensate for overcropping.,College of Enology, NWSUAF,Late-harvested table wines,A few specialty late-harvested table wines make use of shrive
18、ling to get must sugar content so high that the wines remain sweet after fermentation. In these cases, infection by the so called noble mold, Botrytis cinerea, is a required, desirable factor. An appropriate weather cycle of sufficient humidity for infection followed by drying conditions is needed.
19、The Botrytis infection makes the berry skin permeable to rapid water loss and dehydration concentrates the sugar to 30% or more. Owing to red color loss via oxidation by the molds enzyme laccase, the process is not suitable for red wines.,College of Enology, NWSUAF,2.1.2 葡萄浆果中的主要成分及其变化,一穗葡萄浆果包括果梗和果粒
20、两个部分(图2-1)。每颗果粒又由果皮、种子和果肉等部分组成。,葡萄果穗与浆果,College of Enology, NWSUAF,葡萄酒质量控制,葡萄果穗与浆果,在果穗总重量中:果梗占 3% (2 to 8%) 果皮占15% (5 to 20%) 种子占 4% (0 to 6%) 果肉占78% (74 to 90%)一穗葡萄:22%(梗皮子) 固体 关键78%(果肉) 液体 基本,College of Enology, NWSUAF,葡萄果穗与浆果,Ignoring the possibility of leaves or other contaminants in commerciall
21、y harvested grapes, the fresh weight of typical wine grape clusters are made up of about 3% (2 to 8%) stems, 15% (5 to 20%) skins, 4% (0 to 6%) seeds, with the flesh/pulp/juice accounting for the remaining 78% (74 to 90%). Small-berried varieties have proportionately less flesh and more skins.,Colle
22、ge of Enology, NWSUAF,葡萄酒工艺学主讲 王华,葡萄浆果中的主要成分,葡萄浆果,College of Enology, NWSUAF,葡萄浆果中的主要成分Berry Composition,The winemaker obviously is concerned with the composition of the berry at harvest and the variations near harvest that can affect the wines composition and, therefore, quality. Classes of grape b
23、erry components in roughly decreasing order are water and other inorganic substances, carbohydrates, acids, phenols of all types, nitrogen compounds, terpenoids, fats and lipoids, volatile odorants, or other flavorous compounds. In each of these categories and among others not so easily categorized,
24、 there usually are very many individual substances.,College of Enology, NWSUAF,葡萄浆果中的主要成分Berry Composition,New compounds in grapes continue to be reported and added to the several hundred already identified. Again, grapes often differ by variety and source. Therefore, it does not appear particularly
25、 useful to attempt to tabulate in detail all the known components of a typical grape or wine. Rough estimates of general analyses by classes are given in Table 2-7. Some possible components can be important in trace amounts for particular reasons or under peculiar circumstances (biotin as a yeast gr
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