玉米淀粉颗粒是什么 - 常见问题

湖北快3走开奖结果

欢迎光临安徽鑫科生物环保湖北快3开奖结果官方网站!

玉米淀粉颗粒是什么

玉米淀粉颗粒是什么

来源网址:http://www.rsoau.com 2019-03-23 16:15:29    

  淀粉颗粒是自然界绿色植物贮存能源的主 要形式。淀粉颗粒不溶于水,但参与植物能量的 新陈代谢。除少数几种淀粉如粘玉米淀粉和糯 米淀粉外,淀粉颗粒是由直链淀粉和支链淀粉 两种高分子有秩序集合而成。它是一种天然的 多晶体系,在淀粉的颗粒结构中包含着结晶区 和无定形区两大组成部分,由于支链淀粉分子 量较大,常常穿过淀粉颗粒的结晶区和无定形 区,故两部分的区分又不十分明显[1]。淀粉颗粒 的结构十分复杂,尽管人们多年来进行了大量 的研究工作,但目前仍未彻底搞清其真正的结 构。近年来科学家通过荧光显微镜和透射电镜 等现代研究手段发现:玉米、小麦和高粱淀粉颗 粒存在着从表面深入到脐点的空洞[2]。这是对 淀粉颗粒结构研究的又一大进步。
  Starch granules are the main form of energy storage for green plants in nature. Starch granules are insoluble in water, but participate in plant energy metabolism. Except for a few starches, such as glutinous corn starch and glutinous rice starch, starch granules are orderly aggregates of amylose and amylopectin. It is a natural polycrystalline system, which contains two parts of crystalline zone and amorphous zone in the granular structure of starch. Because amylopectin has a large molecular weight, it often passes through the crystalline zone and amorphous zone of starch granules, so the distinction between the two parts is not very obvious [1]. The structure of starch granules is very complex. Although a lot of research work has been done for many years, the real structure of starch granules has not yet been fully understood. In recent years, by means of fluorescence microscopy and transmission electron microscopy, scientists have found that there are holes in starch granules of maize, wheat and sorghum from the surface to the umbilical point [2]. This is another great progress in the study of starch granule structure.
  淀粉颗粒结构的研究是淀粉科学基础研究 领域的前沿课题。对其结构的揭示有助于人们 了解淀粉在化学改性过程中的反应机制,进而 对淀粉分子的取代部位和取代均匀度进行有效 的控制,实现定位改性,比较终达到变性淀粉质量 和附加值的提高,具有十分重要的理论意义和 实践价值。
  The study of starch granule structure is a frontier topic in the basic research field of starch science. Revealing the structure of starch is helpful to understand the reaction mechanism of starch in the process of chemical modification, and to effectively control the substitution position and homogeneity of starch molecule, so as to realize localized modification and ultimately improve the quality and added value of modified starch, which has very important theoretical significance and practical value.
  1淀粉颗粒的形状、大小
  1. Shape and size of starch granules
  淀粉颗粒由于品种的不同,其形状和大小 均各具特征。稻米淀粉颗粒是有菱角的不规则 形,颗粒较小,平均在5 pm,玉米淀粉大部分是 呈压碎的状的六角形,但它的角不象稻米淀粉 那样尖锐,而是稍带圆的,平均大小为15 pm。 小麦和大麦之类的淀粉是接近球状的椭球体, 颗粒有大的和小的两种,中等大小的很少。马铃 薯淀粉是近卵形的,颗粒较大,平均为33
  Starch granules have different shapes and sizes due to different varieties. Rice starch granules have irregular shape of rhombus horn. The granules are small, averaging 5 pm. Corn starch is mostly crushed hexagonal, but its horns are slightly rounded, with an average size of 15 pm, unlike rice starch. Starches such as wheat and barley are nearly spherical ellipsoids with large and small granules and few medium-sized ones. Potato starch is nearly oval with larger granules, averaging 33.
  2淀粉颗粒的结晶结构 2.1结晶结构的分类
  Crystalline Structure of 2 Starch Granules 2.1 Classification of Crystalline Structure
  淀粉颗粒具有结晶性结构,呈现一定的X 光衍射图样。淀粉颗粒的结晶结构随不同来源 的植物品种而异。Katz、van Italli按各种淀粉 的X射线衍射图形将它们分成A、B、C三种不 同的形态。各种植物淀粉颗粒的X射线衍射图 形可归纳成从A形到B形连续变化的系列,而 位于变化的中间状态称为C形,也可将C形评 价为A和B的混合物。谷物淀粉大多数属A 形,根茎和球根茎类的淀粉大多数属B形,而 根和豆类的淀粉则属C形者居多。通过物理或 化学的方法处理淀粉颗粒还可以得到具有V 型衍射图样的淀粉颗粒。
  Starch granules have crystalline structure, showing a certain X-ray diffraction pattern. The crystalline structure of starch granules varies with plant varieties from different sources. Katz and van Italli classify starches into three different forms: A, B and C according to their X-ray diffraction patterns. The X-ray diffraction patterns of various plant starch granules can be summarized as a series of continuous changes from A to B. The intermediate state of change is called C-shaped, and C-shaped can also be evaluated as a mixture of A and B. Most of the starch in cereals belongs to A-shaped, most of the starches in rhizomes and corms belong to B-shaped, while those in roots and legumes belong to C-shaped. Starch granules with V-shaped diffraction pattern can also be obtained by physical or chemical treatment of starch granules.
  2.2结晶区和无定形区
  2.2 Crystalline and amorphous regions
  一般淀粉颗粒是由直链淀粉和支链淀粉两 种成分组成,存在着结晶区和无定形区。而目前 人们一般认为淀粉颗粒的结晶区不是直链淀 粉,而是存在于支链淀粉之内。这主要是基于以 下理由:(1)用温水处理淀粉颗粒,将直链淀粉 浸出后仍未丧失其结晶性;(2)几乎不含直链淀 粉,只由支链淀粉的糯性品种淀粉粒,与含 20%?35%直链淀粉的梗性品种淀粉粒呈现出 了同样的X射线衍射图形;(3)含直链淀粉量 很高的高直链玉米淀粉和皱皮豌豆的淀粉颗 粒,它们的结晶性部分反而减少。直链淀粉分子 和支链淀粉分子的侧链都是直链,趋向平行排 列,相邻羟基间经氢键结合成散射状结晶性 “束”的结构,后来人们又将它看成双螺旋结构。
  Generally, starch granules are composed of amylose and amylopectin, and there are crystalline and amorphous regions. At present, it is generally believed that the crystallization zone of starch granules is not amylose, but exists in amylopectin. This is mainly based on the following reasons: (1) Starch granules are treated with warm water, and the crystallinity of amylose is still not lost after being leached; (2) Waxy starch granules containing almost no amylose, only amylopectin, show the same X-ray diffraction pattern as stalk starch granules containing 20%? 35% amylose; (3) High amylose starch with high amylose content. The crystallinity of starch granules of pea and crinkled pea decreased on the contrary. The side chains of amylose and amylopectin molecules are straight chains, which tend to be arranged in parallel. The adjacent hydroxyl groups are bonded by hydrogen bonds to form scattered crystalline "bundles" structure. Later, it is regarded as a double helix structure.
  2. 3淀粉颗粒的偏光十字
  2.3 Polarization Cross of Starch Granules
  用偏光显微镜来观察淀粉颗粒时,可以观 察到有双折射现象,又叫偏光十字。由于淀粉颗 粒内部存在着两种不同的结构即结晶结构和无 定形结构的缘故,在结晶区淀粉分子链是有序 排列的,而在无定形区淀粉分子链是无序排列 的,这两种结构在密度和折射率上存在差别,即 产生各向异性现象,从而在偏振光通过淀粉颗 粒时形成了偏光十字[7]。French用偏光显微镜 从各种方向对淀粉颗粒进行观察,研究了偏光 十字中心的位置,提出淀粉颗粒的葡萄糖链是 垂直于颗粒表面排列着的,也即淀粉颗粒的葡 萄糖链是以脐点为中心,向着淀粉颗粒的表面 呈放射状排列的[3]。
  When starch granules are observed by polarizing microscope, birefringence, also known as polarizing cross, can be observed. Because there are two different structures in starch granules, i.e. crystalline structure and amorphous structure, the molecular chains of starch are arranged orderly in the crystalline region, while the molecular chains of starch in the amorphous region are arranged disorderly. There are differences in density and refractive index between the two structures, i.e. anisotropic phenomena, resulting in polarized light passing through starch granules. Word [7]. French observed starch granules in various directions by polarizing microscope, studied the position of the cross center of polarizing light, and proposed that the glucose chains of starch granules were arranged perpendicular to the surface of granules, that is, the glucose chains of starch granules were arranged radially towards the surface of starch granules with the umbilical point as the center.
  2. 4淀粉颗粒中的水分与结晶
  2.4 Water and Crystallization in Starch Granules
  关于在淀粉颗粒中水分是否参与淀粉的结 晶一直存在着两种不同的观点:一种观点认为 淀粉在逐步加热干燥脱水的过程中,淀粉颗粒 由结晶结构转化为无定形结构的原因是颗粒中 含有的水分子参与了结晶,由于干燥使水分子 脱去,淀粉的结晶结构被破坏而比较后过渡为无 定形结构[1]。法国科学家Kainuma把浸透玉米 糖浆的淀粉糊精干燥至完全脱水状态时发现, 其仍然保持着结晶结构,因此,他指出水分子并 不参与结晶[3]。上述两个观点都不能对一定的 水分含量下,淀粉DSC曲线上出现的双峰融熔 现象作出很好的解释。
  There are two different opinions on whether water participates in starch crystallization in starch granules: one is that during the process of starch drying and dehydration, the crystalline structure of starch granules changes from crystalline structure to amorphous structure because the water molecule in the granules participates in crystallization, and the crystalline structure of starch is destroyed by drying. Transition to amorphous structure [1]. When Kainuma, a French scientist, dried the starch dextrin soaked in corn syrup to a completely dehydrated state, he found that it still maintained its crystalline structure. Therefore, he pointed out that water molecules were not involved in crystallization [3]. Neither of these two viewpoints can explain the phenomenon of double-peak melting on starch DSC curve at a certain moisture content.
                                                     玉米淀粉颗粒
  2.5淀粉颗粒的模型和分子结构
  MODEL AND MOLECULAR STRUCTURES OF 2.5 STARCH GRANULES
  早在1895年,A. Meyer在《淀粉颗粒的研 究》一书中提出了淀粉颗粒的结构模型,这是比较 早的淀粉颗粒模型。1969年Nikuni根据直链 淀粉分子是和支链淀粉结合而存在的设想提出 淀粉粒的单分子主张(Fig. 1,a)[1°]。1984年D. R. Lineback在此基础上稍稍改进(Fig. 1,b), 他主要是基于支链淀粉分子为“簇”的概念,而 直链淀粉则随机或呈螺旋结构而存在,这取决 于颗粒中的脂类物质,因为大多数谷类淀粉存 在着这类物质[11]。而Oostergetel和Van Bmggen认为:结晶区是由连续的超分子螺旋 结构的支链淀粉组成,螺旋结构中有许多空隙, 可以容纳直链淀粉分子[12]。一般认为,直链淀 粉单链也容易形成双螺旋结构,这些双螺旋又 通过氢键和范德华力得到稳定。比较后形成A型 或B型结构,它取决于键长和水分含量。尽管
  As early as 1895, A. Meyer put forward the structure model of starch granules in his book The Study of Starch Granules, which was the earliest model of starch granules. In 1969, Nikuni put forward the single-molecule proposition of starch granules (Fig. 1, a) [1 degree] according to the assumption that amylose molecules bind to amylopectin. In 1984, D. R. Lineback improved slightly on this basis (Fig. 1, b). He was mainly based on the concept that amylopectin molecule is "cluster", while amylose exists randomly or spirally, depending on the lipids in granules, because most cereal starches have such substances [11]. Oostergetel and Van Bmggen believe that the crystalline region is composed of amylopectin with continuous supramolecular helical structure, and there are many gaps in the helical structure, which can accommodate amylose molecules [12]. It is generally believed that amylose single chain is also easy to form double helix structure, which is stabilized by hydrogen bond and van der Waals force. Finally, a type A or B structure is formed, which depends on the bond length and water content. although
  支链淀粉的分支有时出现在无定形区,但支链之间极易形成双螺旋结构[13,14]。
  The branching of amylopectin sometimes occurs in amorphous region, but it is easy to form double helix structure between branching chains [13,14].
  3淀粉颗粒的层状结构和微孔结构
  Layered and microporous structure of starch granules
  用光学显微镜观察淀粉颗粒,大多情况下 可以看到层状结构,在它的中心有脐点。淀粉颗 粒是以脐点为中心由球晶按一定规则排列成放 射状而构成。而层状结构是由于淀粉颗粒内部 折射率之差,或是由于淀粉颗粒中淀粉分子的 装填方法、装填密度之差而产生的[3,24]。日本的 Ahinji tamaki等用糖化酶在常温下处理马铃 薯淀粉颗粒,然后用扫描电镜观察发现:淀粉颗 粒表面出现弹壳状残余,就像花蕾绽放式的膨 胀[25]。我国张本山通过三氯氧磷对木薯淀粉进 行交联也发现淀粉颗粒类似的膨胀历程[8]。
  When starch granules are observed by optical microscopy, the layered structure can be seen in most cases, and there are umbilical points in the center of starch granules. Starch granules are composed of spherulites arranged in radial shape with umbilical point as the center. The layered structure is due to the difference of refractive index in starch granules, or the difference of filling method and density of starch molecules in starch granules.  The potato starch granules were treated with glucoamylase at room temperature by Ahinji Tamaki et al. in Japan. Then the shell-like residues on the surface of the starch granules were observed by scanning electron microscopy, just like the blooming expansion of flower buds [25]. The cross-linking of cassava starch with phosphorus oxychloride in Zhangbenshan of China also found that the starch granules had similar expansion process [8].
  4展望
  4 outlook
  到目前为止,人们对淀粉颗粒的结构己经 有了一个基本的认识。淀粉的很多性质可以从 淀粉颗粒的结构中得到解释。但是还有许多重 要的问题没有解决。如淀粉颗粒结构中直链淀 粉分子所处的位置和作用以及怎样解释这些双 螺旋结构形成整个淀粉颗粒等。在应用领域,由 于化学变性所用化学试剂品种及取代度的限 制,目前的化学变性技术的发展方向只有进行 定位化学改性。也即控制取代基在淀粉颗粒的 位置,控制取代基对直链淀粉及支链淀粉的相 对分布及取代基在单个分子上的定位。如上所 述,由于淀粉颗粒的微孔性质,淀粉与化学试剂 接触表面积是相当大的,这也为定位取代提供 可能。但到目前还没有一种可以测定取代基位 置的仪器或方法,所以实现定位化学改性还有 很多工作有待于淀粉科学工作者共同努力。
  So far, people have a basic understanding of the structure of starch granules.  Many properties of starch can be explained by the structure of starch granules. But there are still many important problems unsolved. For example, the position and function of amylose molecules in starch granule structure and how to explain the formation of whole starch granules by these double helix structures. In the field of application, due to the limitation of chemical reagents used in chemical denaturation and their degree of substitution, the current development direction of chemical denaturation technology is only localized chemical modification. That is, to control the position of substituents in starch granules, the relative distribution of substituents to amylose and amylopectin, and the location of substituents in a single molecule. As mentioned above, due to the microporous nature of starch granules, the contact surface area between starch and chemical reagents is quite large, which also provides the possibility of localized substitution. However, up to now, there is no instrument or method to determine the position of substituents, so much work remains to be done for starch scientists to make joint efforts to achieve localized chemical modification.

安徽快3开奖结果 爱彩彩票APP下载 爱波彩票APP下载 湖北快3开奖结果 湖北快3走势图 湖北快三走势图 大星彩票APP下载 湖北快3开奖结果 博旺彩票APP下载 爱波彩票APP下载