大多数植物的果实包含一个以上的种子

1、The wheat grain AnatomyThe fruits of most plants contain one or more seeds which, at ripeness, can be easily separated from the rest of the fruit tissue. For Gramineae this is different: a fertilized egg cell in the ovary develops into a single seed, comprising the whole fruit. Fruit wall (pericarp)

2、 and seed coat are united (Figure 2.1), as a result the seed and fruit cannot be separated. This type of fruit, which is characteristic for all grasses, including cereals, is given the botanical term of caryopsis. 大多數植物的果實包含一個以上的種子，成熟時可以容易地與其他的組織分開。禾本科植物則有所不同：一個雌雄的種子結合後，發育成一個單一的種子，形成整個果實。果實外表（果皮）和種皮

3、是連結在一起的（圖2.1 ），以致種子和果實不能分開。這種類型的果實，即草本植物的特性，包括穀物，亦即植物學上所稱為caryatid。Figure 2.2a shows a whole wheat grain of a length of about 5 mm. The kernel has a somewhat vaulted shape with the germ or embryo (the future plantlet) at one end, and a bundle of hairs, which is referred to as the beard or brush at t

4、he other end. Figure 2.2b shows a cross-section of the grain, in which the endosperm is clearly visible. The endosperm is rich in starch and contains the proteins that will form the gluten at dough making. The ventral, at side of the grain has a rather deep crease. The endosperm is surrounded by the

5、 fused pericarp and seed coat. The endosperm mainly contains food reserves, which are needed for the growth of the seedling. 由圖2.2a可發現整個小麥籽粒的長度約5毫米。核心一端有著略微有圓頂的形狀為菌體或胚胎 （未來將形成植物），另一端有著鬚毛，圖 2.2b 為穀粒的一個剖面圖，其中胚乳可清晰可見。胚乳富含澱粉，且富有製造生麵團時所需的麩質蛋白質。腹部部份，在穀粒的邊有一條相當深的摺痕。胚乳被果皮和種子包住，胚乳主要功能為保存食物，這是對植物的生長是必要的。Figur

6、e 2.2c shows an enlarged view of part of the endosperm. The section consists for the greater part of prismatic cells, lled with starch granules embedded in protein. In the centre of the grain (not shown in this picture) these cells are round. Only the outer endosperm, the aleurone layer,has a differ

7、ent structure: it consists of a single layer of cells of cubic shape. The inner endosperm, i.e. the endosperm without the aleurone layer, is referred to as mealy or starchy endosperm. The aleurone layer is rich in proteins and enzymes, which play a vital role in the germination process. 圖 2.2c 表為胚乳的

8、部份放大圖。此部分為較佳的分光細胞的組成，裝滿在富含蛋白質的澱粉粒中。在穀粒 （不在此圖中）細胞的中心是圓形的。只有外部的胚乳，糊狀層，有不同的結構：它有立方體形狀的細胞層。內部的胚乳,也就是沒有糊狀層的胚乳，被稱為粉狀的或澱粉的胚乳。糊狀層富含蛋白質和酵素，扮演發芽程序的重要角色。During the rst stage of milling, the outer layers of the wheat grain, i.e. the bran, are separated from the mealy endosperm. The fracture is located right und

9、er the aleurone layer. This means that bran is made up of the fused pericarp, plus the seed coat, plus the aleurone layer. Wheat grains have either a dark, orange-brown appearance (red wheats or red-seeded wheats) or a light, yellowish colour (white wheats or white-seeded wheats). There was a time w

10、hen many countries preferred white-seeded wheats. In Europe this preference has gradually disappeared and mainly red-coloured varieties are grown nowadays. 在製粉時的第一個階段時，小麥穀粒外層(也就是麩)與粉狀的胚乳分離。碎塊被放置在糊狀層的下方。這意謂麩由融合的果皮組成，加上種子外衣及糊狀層。小麥穀粒有深橘色褐色外表 ，（紅小麥或色種子的小麥）偶而為淡微黃的色澤 （白小麥或白色種子小麥）。有許多國家曾相當偏愛了白色種子小麥。在歐洲這種喜好

11、已經逐漸地消失，而且主要紅小麥的多樣性正在發展中。1 For more information see Evers (1988); Hoseney (1986); Kingswood (1975). The main reason for this change is that white wheats are more susceptible to pre-harvest sprouting than the majority of the red wheats. White wheat varieties are grown particularly in Australia, and t

12、o a lesser extent in Canada and the USA. 這一個改變的主要理由是由於白小麥較多數的紅小麥的易發芽。白小麥的發展在加拿大和美國中較少的發掘，但在澳洲則受到特別地喜好及栽種。In brief, the wheat grain is constituted by three distinct parts: the germ (embryo), the bran and the mealy endosperm. Wheat grains contain 23% germ, 1317% bran and 8085% mealy endosperm (all con

13、stituents conver-ted to a dry matter basis). 簡而言之，小麥穀粒被三個部份所構成：菌體 （胚胎）, 麩和粉狀的胚乳。小麥穀粒包含 2% 3% 菌體， 13 17% 麩和 80 85% 粉狀的胚乳。2.2. Chemical composition化學成分 2 The moisture content of commercial lots of wheat may vary between 12 and 18%, depending on the weather during harvest. 小麥的溼度在 12% 和 18% 之間,主要受收穫期間的天

14、氣所影響。Until recently, the composition in percentages of wheat bres were based on analysis of crude bre material according to a method developed by Ween-de. The values resulting from this analysis tend to be rather low. A more accurate method was inroduced later by Van Soest: the Neutral Detergent Fib

15、re (NDF) method. It measures the dietary bres and results in higher values that correspond more closely to reality. The bre contents mentioned in Table 2.1 have been measured using the NDF method. As a consequence, the values for carbohydrates are lower than those for the method of Weende. 直到最近，小麥纖維

16、的組成可依天然纖維組成的方式分來析，此一分析法乃由Ween-de所研發。評估的數據顯示出不高的數據。一個較為正確的方法是由Van Soest所研發：亦即NDF法。此法測量飲食纖維，測出高含量且較接近於實際成份。在表 2.1 提到的纖維內容是由NDF法所測出。對於碳水化合物的含量較 Weende 的方法更低。Table 2.1. Chemical composition of the whole wheat grain and its various parts (converted to percentages on a dry matter basis) Whole Mealy Bran G

17、erm grain endosperm Proteins 16 13 16 22 Fats 2 1.5 57 Carbohydrates 68 82 16 40 Dietary bers 11 1.5 53 25 Minerals (ash) 1.8 0.5 7.2 4.5 Other components 1.2 1.5 2.8 1.5 Total 100 100 100 100 Most of the mealy endosperm consists of food reserves: 82% carbohydrates (mainly starch), 13% proteins and

18、1.5% fats. The contents of minerals (ash) and of dietary bres are low, 0.5% and 1.5%, respectively. 大部份的粉狀乳胚具有食物保留的功能：82% 碳水化合物 （主要為澱粉）， 13% 蛋白質和 1.5% 脂肪。礦物和飲食纖維的成份較低，分別為0.5%和1.5%。More than half the bran consists of bre components (53%). Proteins and carbohydrates each represent 16% of total dry mat

19、ter. The mineral content is rather high (7.2%). The two external layers of the grain (pericarp and seed coat) are made up of empty cells and are dead. The cells of the inner bran layer, i.e. the aleurone layer, are lled with living protoplasts. This explains the rather high levels of protein and car

20、bohydrate in the bran. 超過一半的麩含有纖維成份 （53%) 。蛋白質和碳水化合物分別含有16%的乾性成份。礦物的成份相對較高(7.2%) 。外部二層(果皮和種子外套)的穀粒由空的細胞組成並且己非細胞。內部麩層的細胞，也就是糊狀層，充滿了原生物。Finally, the germ is rich in proteins, fats, carbohydrates and dietary bres. The mineral level is also rather high (4.5%). 最後，胚芽含有豐富的蛋白質，脂肪，碳水化合物和膳食纖維。礦產水平也相當高（ 4.5 ）

21、。2 For more information see Pomeranz (1988). 2.3. Grain hardness Note that the terms hard wheat and soft wheat, used in ofcial EU reg-ulations, do not have the same meaning as described in this section. EU ofcials use the term hard wheat exclusively for durum or macaroni wheats, and the term soft wh

22、eat for aestivum or bread wheats, irrespective of the hardness of their grains. 關於硬小麥和軟小麥的差異，在官方的歐盟法規中，並無類似的說明內容。歐盟官員使用硬小麥或通心粉小麥，特別是要指出硬小麥為durum及macaroni，軟小麥為aestivum及麵包用的小麥，而與穀粒的堅硬無關。Wheat varieties vary widely in grain hardness. Two categories are distin-guished: varieties with hard and varieties

23、with soft grains. The kernels of hard wheats often, but not always, have a dark, shiny aspect and they look vitreous. Soft grains have a more opaque, oury appearance. 小麥的種類在穀粒的硬度上有很大的差異。其中二個類別是不相同的：硬性與軟性，小麥的核心常有一個深色又有光澤一面，而且看起來像玻璃。軟性的穀粒有一個不透明面及粉狀的表面。Grain hardness is a character of particular intere

24、st to the milling and bak-ing industries. Hard grains exhibit more resistance to grinding than soft wheat grains; the several methods for determining grain hardness are based on this property (see Section 8). In general, hard wheat grains have a higher protein content than soft ones. Growing conditi

25、ons also play a role. 穀粒堅度對於麵粉製造業及烘培業是個重要的議題。硬穀粒表現出超越過軟麥穀粒更高的耐磨力；決定穀粒堅硬的屬性乃是由以上的這些方法為基礎。大體上，硬小麥穀粒較軟穀粒有較高的蛋白質成份。成長的環境也扮演了重要的角色。Hard wheats result in more damaged starch than soft wheats in the milling process. In bread, this damage largely contributes to the soft texture and the gentle, pleasant mout

26、hfeel of the crumb; moreover starch damage has a retarding effect on the bread going stale. Soft wheat ours, on the other hand, have less damaged starch. They are more suited for the production of biscuits, cakes, crackers, wafers, etc. The lower protein content and the ner granulation of a soft whe

27、at our undoubtedly contributes to its suitability for these products. 硬小麥相較於軟小麥在製粉過程中易受較多破壞。在麵包中，這樣的損害大幅的影響了，麵包的鬆軟性、溫和性、愉快性等的口感因素；而且澱粉成份的損害，在不新鮮的麵包上，有更嚴重的影響。軟小麥麵粉，則較不受到損壞。且更適合用作為餅乾，蛋糕，餅乾，簿餅等。軟小麥麵粉中含較低含量的蛋白質及較小的顆粒，細微的顆粒無疑地使這些產品更為適合的因素。The inheritance of grain hardness has been documented by Symes (19

28、65, 1969), who in crosses between soft and hard wheat cultivars demonstrated that in most cases one single gene is responsible for grain hardness. However, in some cases grain hardness is caused by more than one gene. For a wheat breeder, these are important conclusions, since the conversion of a so

29、ft wheat variety into a hard one, and vice versa, should be relatively easy by means of crossing and back-crossing. Photographs taken with a SEM (Figure 2.3) clearly show that differences in hardness can be related to differences in the interior structure of the endo-sperm cells (Belderok, 1973). 穀粒

30、堅硬的遺傳在 Symes（1965,1969)所提出,他在軟小麥和硬小麥栽培品種間的交集中，顯示出大部份的情形下，單一變數常為主要影響硬度的變數。然而，穀粒堅硬的影響變數常超過一個變數所引起。對於一個小麥培育者，這是重要的結論，因為軟性小麥轉變為硬性，反之亦然，由SEM（圖 2.3)可清楚的顯示硬度受到內部結構的不同，而受到重大的影響。（Belderok， 1973)Figure 2.3a shows a European wheat variety with soft grains that are low in protein content (10.9% on dry matter ba

31、sis). Elliptical starch granules are clearly visible. The surface of these granules is generally smooth but dents can be seen on a few spots. Probably these dents have been caused by neigh-bouring starch granules that were in the way during the growing process. Between the starch granules, one can s

32、ee a small number of round, angular particles of smaller size and lighter shade. The light-coloured particles are what are known as protein bodies. The image suggests that, inside the cell, starch granules and protein bodies exist as discrete particles without much coherence. Furthermore, one can di

33、scern small voids, which are actually lled with air. Such a loose structure scatters light falling in many directions and causes the mealy, oury appearance of soft wheat grains. 圖 2.3 中，軟性穀料的低蛋白質的含量為歐洲小麥的特性. （乾性成份的 10.9%基礎）橢圓的澱粉顆粒可清楚的由圖中看見。這些顆粒的表面平滑，但是一些地方可發現凹痕。這些凹痕可能已經在成長期間由neigh-bouring 澱粉顆粒所引起。在澱

34、粉顆粒間，一般人能見到一些顆粒較小，較輕的圓形有陵角的粒子。淺色的顆粒是蛋白質體。影像中，細胞裡澱粉顆粒和蛋白質體呈現出的規律的不連續的粒子。此外，亦能辨別出小的空隙，實際上是空氣。一個如此寬鬆的結構散佈向著多個方向，且形成粉狀，軟小麥穀粒的料狀外表。Figure 2.3b shows the inside of an endosperm cell of a US spring wheat variety, with a medium-hard grain structure and a protein content of 16.5% of total dry matter. In spit

35、e of a relatively high protein level, cell elements are more or less the same as in Figure 2.3a. However, the distribution of the protein is both in the form of protein bodies and a paste spread between the starch granules. This causes a higher degree of consistency of cell content. 圖 2.3b 中顯示出美國春天小

36、麥的一個內胚乳細胞的內部，包含中硬度的穀粒結構，其中包含16.5%的蛋白質成份。儘管相對地較含量的蛋白質，細胞元素或多或少是與圖2.3中相同。然而，蛋白質的分佈是在澱粉顆粒間以蛋白質本體的形式和糊狀分佈。這引起細胞內部的一致性的更高。Figure 2.3c shows an extremely hard, vitreous Australian Prime-Hard wheat with a protein content of 17.8% (dry matter basis). The protein bodies do not appear as separate particles, b

37、ut as a paste that is spread between the starch granules, covering them completely. Obviously the content of this cell is much more coherent than that of the cells shown in Figures 2.3a and 2.3b. The compact structure and the absence of voids between the starch granules explain the vitreous appearance of Prime-Hard wheat, since most light passes right through the grains and is not ree