12.第四章碳水化合物11.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,一、分类与食物来源,Classification and,food source,单糖,(monosaccharide),双糖,(disaccharide),寡糖,(oligosaccharide),多糖（,polysaccharide,）,第四章 碳水化合物,一、分类、来源,食品中重要的碳水化合物,CHO,也称为糖类，,能够准确测定的化合物,由碳、氢、氧三种元素构成,营养学上一般将其分为四类,多糖,双糖,可消化多糖,寡糖,单糖,非消化多糖,可消化寡糖,非消化寡糖,两分子单糖,（一）单糖,(monosaccharide),Glucose,:,D-and L-.A little in the natural foods.,葡萄糖主要由淀粉水解而来使机体唯一直接利用的形式，还可以以其为原料合成其他的糖类物质甜度74（蔗糖为,100,）,（一）单糖,(monosaccharide),2.Fructose,（果糖）,:,主要存在于水果和蜂蜜中，人工制造的玉米糖浆中含,40%-90%,It is found in fruits,honey(about half fructose and half glucose),and high-fructose corn syrup which is used in the production of soft drinks,frozen desserts,and confections(,糖果和蜜饯等,).,In most American diets,fructose accounts for about 8%-10%of total energy intake,.,机体的果糖主要有肠道的二糖酶将蔗糖水解成葡萄糖和果糖，吸收时部分果糖被肠道粘膜细胞转变成葡萄糖和乳酸；肝脏是实际利用果糖的唯一器官。

果糖代谢可不受胰岛素的制约果糖甜度很高（173）3.,Galactose,（,半乳糖）,：,以乳糖形式存在于天然食物（乳汁）中，是乳汁中碳水化合物的主要成分It is not usually found free in nature in large quantities,but rather combines with glucose to form lactose.,4.Others:,非己糖,ribose(,核糖,),，,deoxyribose,(,脱氧核糖,),、,arabinose,(,阿拉伯糖,),、,xylose,(,木糖,),、,单糖糖醇,(sugar alcohols),：,sorbitol,（山梨醇）、,mannitol,（甘露醇）、,dulcitol,（卫矛醇）、,inocitol,（肌醇）,(,二,),双糖（,disaccharide,）,1.Sucrose(,蔗糖,),：,葡萄糖果糖，,a-1.2糖苷键,，found in sugar cane,（甘蔗）,and sugar beets,（甜菜）,甜度,100,，,异构蔗糖,a-1.,6,糖苷键,2.,Maltose,（麦芽糖）：,葡萄糖葡萄糖，淀粉水解产物,3.,Lactose,（乳糖）：,葡萄糖半乳糖，乳及乳制品中,.,异构乳糖,：,由一分子半乳糖和一分子果糖组成,4.,Trehalose,(,海藻糖,),：,葡萄糖葡萄糖，真菌（,fungus,）及细菌中,(二)双糖,蔗糖,(,sucrose),1葡萄糖,1果 糖,麦芽糖,(,maltose),2葡萄糖,乳糖,(,lactose),1葡萄糖,1半乳糖,海藻糖,(,trehalose,),2葡萄糖,常见的双糖有蔗糖、麦芽糖、乳糖和海藻糖等,此外，还包括双糖醇,双糖 糖醇,糖醇为糖的衍生物，作为蔗糖替代剂,麦芽糖醇,由麦芽糖氢化而来，为,非能源物质,，不升高血糖，使心血管病人的甜味剂，还有,防龋,作用。

无羰氨反应,乳糖醇,乳糖催化加氢而成,(,三,),寡糖（,oligosaccharide,）,3-10,单糖组成有些具有重要的生理功能,大豆低聚糖,棉子糖、水苏糖和少量蔗糖,棉子糖由半乳糖、葡萄糖和果糖组成，水苏糖是在棉子糖的半乳糖基一侧再连接一个半乳糖由于人体缺乏,a-D-,半乳糖苷酶，前两者不能被水解，是“胀气因子”低聚异麦芽糖,2-5 个葡萄糖单位组成，且其中至少有一个糖苷键是,a(1-6),糖苷键，不引起龋齿；有利于双歧杆菌的增值，有利于后者合成,B,族维生素低聚果糖,蔗糖分子的果糖一侧连接1-3个果糖而成，作用与低聚异麦芽糖相同,低聚乳果糖,由半乳糖、葡萄糖和果糖连接构成的多糖，几乎不被人体吸收，甜度为蔗糖的30-50%,可供糖尿病人食用低聚木糖,由木糖、木二糖及少量木聚糖构成，几乎不被人体消化和吸收，但可被双歧杆菌利用四,),多糖（,polysaccharide,）,1.,糖原,(glycogen),：,动物淀粉,2.,淀粉（,starch,）：,直链淀粉,(,amylose,)-,支链淀粉,(,amylopectin,)-,3.,纤维（,fibre,）,Nonstarch,polysaccharides in plant foods that are not digested by human digestive enzymes,but some are digested by GI tract bacteria.Fiber in foods is also called,dietary fiber,.,definition:,淀粉,由,直链淀粉,(,-1,4,糖苷键)和,支链淀粉,(,-1,4,糖苷键和,-1,6,糖苷键)之分；,淀粉的,糊化,和,老化,。

人们通常食用淀粉后不会发生饮食性糖尿病淀粉是食品工业中重要的糖质原料如焙烤食品淀粉是植物的贮存物质动物淀粉糖原改性淀粉,是指利用化学、物理甚至基因工程的方法改变天然淀粉的理化性质，以满足食品加工所需功能特性的一类淀粉漂白淀粉、转化淀粉、,取代淀粉,、,交连淀粉,和稳定化淀粉,抗性淀粉,天然存在的，在健康人小肠中不被吸收的淀粉,生理受限淀粉,特殊淀粉颗粒,老化淀粉,非淀粉多糖,纤维素、半纤维素、果胶，以及植物胶、树胶、藻类多糖等,Cellulose,（纤维素）,:,It is the primary constituent of,plant cell walls,and therefore occurs in all vegetables,fruits and legumes,（豆类）,.,Hemicellulose,（半纤维素）,:,It is the main constituent of,cereal fiber,.The many backbones and side chains make the,hemicellulose,a diverse group;some are soluble,many of them are insoluble.,Lignin,（木质素）：,It is a,nonpolysaccharide,fiber,.It occurs in,the woody parts of vegetable such as carrots,or the small seeds of fruits such as strawberries.,lignin,hemicellulose,Insoluble fiber,(1),Pectins,（果胶）,：,It,is-1,4-D-galacturonic acid polymers,methylate,(,被甲酯化至一定程度的半乳糖醛酸多聚体,).Commonly found in,vegetables and fruits,(especially citrus,柑橘,and apples).,Pectins,may be isolated and used by the food industry to thicken jelly,because they readily form gels in water.,(2),Gums and,mucilages,（,树胶和粘胶）,：,Gums are composed of various,monosaccharides,and their derivatives.,Gums such as gum,arabic,(,阿拉伯胶,)are,used as,additives,by the food industry.,Mucilages,are similar to gums in structure.,They include guar,（瓜拉胶）,which are,added to food as,stabilizers,.,soluble fiber,Food source of dietary fiber,二、碳水化合物的功能,Function,1.Function of carbohydrate in body,1).Component of cells and tissues:,细胞与组织构成成分,glycoprotein,（糖蛋白）,and,glycolipid,（糖脂）,mucin,（粘蛋白）,and DNA,RNA.,2).,Storing glucose as glycogen and using it for energy,以糖原的形式储存能量,The,liver,stores one-third of the bodys total glycogen.When blood glucose falls,the liver cells dismantle(,拆除，释放,)the glycogen into single molecules of glucose and release them into the bloodstream to be used by,central nervous system,and other organs.,Muscle cells,can also store glucose as glycogen(the other two-thirds),but they use it just for themselves during exercise.,3).,Sparring protein from use as energy source,（,节约蛋白质作用,）,If,body can not consume enough carbohydrate to yield glucose,it is forced to make glucose from protein(this process is termed,glyconeogenesis,糖异生,),because,fats generally cannot be converted into glucose,.,So enough carbohydrates can spare body protein which can be used to make body tissues and to perform other vital processes.,(,即足够的碳水化物可以使体内蛋白质不被分解作为热能而消耗的作用,),sparing protein action?,4).Preventing ketosis,（抗生酮作用）,A,low carbohydrate intake,with the resulting decline in release of the insulin,leads to,incomplete break down,of fatty acids in the livers metabo。