食品专业英语 LESSON 2 Carbohydrates

1、The food scientist has a many-sided interest in carbohydrates. He is conce rned with their amounts in various foods, availability (nutritional and economi c), methods of extraction and analysis, commercial forms and purity, nutritiona 1 valve, physiological effects, and functional properties in food

2、s. Understand! ng their functional properties in processed foods requires not only knowledge o f the physical and chemical properties of isolated carbohydrates, but also know ledge of the reactions and interactions that occur in situs between carbohydrat es and other food constituents and the effect

3、s of these changes upon food quali ty and acceptance. This is a tall order for knowledge. Because processing affec ts both nutritional and esthetic values of food, knowledge of the changes that carbohydrates undergo during milling, cooking, dehydration, freezing, and stora ge is especially important

4、.Students are advised to study the fundamental chemistry underlying u seful carbohydrates properties Of service will be an understanding of the assoc iation of polar molecules through hydrogen bonding, ionic effects, substituent effects, chelation with inorganic ions, complexing with lipids and prot

5、eins, an d decomposition reaction. This background will provide an understanding of prop erties that affect the texture and acceptance of processed foods (e.g., solubil ity, hygroscopicity, diffusion, osmosis, viscosity, plastity, and flavor produc tion), properties that enable the formation or high

6、 quality pastries, gels, coa tings, confections, and reconstitutable dehydrated and frozen foods.Ability to predict what changes in functional properties are likely to ensue from incorporating various types of carbohydrates into processed foods is a practical goal of the food scientist.Such forecast

7、ing requires either a weal th of experience with trial-and-error methods or a deep knowledge of carbohydra te properties as related to structure一perhaps both. However, scientific knowle dge of cause and effect is highly respected when it shortens industrial develop ment timeSource, Types, and Termin

8、ology 随其内源蔗糖酶活性的不同，会不同程度地使蔗糖转化D-葡萄糖和1）-果糖。因此，其干制 品的颜色也会因非酶褐变而加深。豌豆、青刀豆和甜玉米在成熟前摘下是为了获得多汁鲜嫩的质构和甜味。迟 了，所含的糖就会转成多聚糖，水分会失掉，就会产生韧性的质构。熟透后在摘收的大豆, 其淀粉储量随蔗糖和类半乳蔗糖（棉籽糖、水苏糖、毛蕊花糖等）的形成而耗尽。用谷物加 工麦芽糖使，由于酶被极度活化而使得贮存的碳水化合物迅速转化成糖。在动物性食物方面，当获得碳水化合物组成数据时，必须仔细估量动物宰后 酶的活性。动物组织（尤其是肝脏）中的糖原在宰后会迅速解聚成D-葡萄糖，所以，要保 存糖原，就得立即进行深度冷

9、冻。哺乳动物内部器官（如肝、肾、脑和蛋类、贝类所提供的 D-葡萄糖只占饮食中D-葡萄糖的一小局部。红色的新鲜肉类仅含极少可利用的碳水化合物 （D-葡萄糖、D-果糖和D-核糖），而这些碳水化合物被溶出进入肉汁和肉汤。乳制品提供 了哺乳动物碳水化合物的主要来源，牛全乳含碳水化合物约4.9%,脱脂乳粉含乳糖量超过5 0%o查看一些食物成分表便可知道，通常谷类的淀粉含量最高而糖含量最低。水 果类游离糖最多，淀粉最少。以干基计算，水果的可食局部通常含8090%的碳水化合物。 豆类含淀粉不多不少，但含有大量的不可利用的碳水化合物。在植物界，广泛分布着多种糖苔。在十字花科植物中大量存在着某些具有生理活性的

10、硫葡糖普（确切称之为“芥子油柑” ）o芥子油柑经酶水解产生芥子油、胞和甲状腺肿素。 人们已经研究了它在人体中可疑的甲状肿病源性质。但目前还不认为食用新鲜卷心菜（其中 芥子油柑量为300lOOOppm）、花椰菜、抱子甘蓝、芜菁、芜菁甘蓝、小萝卜之类食物 中的芥子油昔数量会引起有害的生理效应。生象菩在一定蔬菜浸渍条件下，通过酶水解能释 放出氨化氢。人们都知道生鼠普是某些动物饲料刷毒性的主要来源。可是在兴旺国家的平常 食物中,生氟普没有活性。某些外国品种的菜豆和木薯可产生高达03%的氯化氢（按重量 计），但遍布在美国的菜豆产氯化氢低于002%。皂角菩类（类固醇和三施系化合物的表 面活性糖普）会以低浓

11、度出现在茶叶、菠菜、芦笋、甜菜、糖用甜菜（0.3%）.甘薯、大 豆（0.5%）.苜蓿（2-3%）.花生及其它豆类。Lesson 2 Carbohydratesextraction提取（法），萃取（法），抽提法milling研磨，碾碎，磨碎，粉碎 磨（面）粉dehydration脱水（作用）,人工加热干燥（作用）underlie vt.位于的下面，放在下面支承;构成 屈服于（权利，素赔等）优先于underlying （理论，政策，行为等）的基础chelation 螯合association n.联合;联系，联盟，合伙，交际，交往 联想 协会，社团化缔合（作用）hygroscopicity 吸湿性

12、diffusion 扩散性osmosis 渗透性viscosity 粘度pasticity可塑性trial-and-error反复试验;不断摸索ingest 口服，口食terminology n.术语学;术语，专门名词corn玉米谷物（泛指玉米，黑麦，燕麦，小麦等）谷粒制成碎粒用盐腌制的syrup糖浆，糖水（罐）corn syrup淀粉糖浆，葡萄糖浆cornstarch玉米淀粉corn sugar葡萄糖pentosan戊聚糖malabsorption n.医吸收不良,养料吸收障碍mal-表示坏恶，不良 表示 不，非，不当adverse a.（在位置或方向上）逆的，相反的，敌对的不利的，有害的植

13、（叶子等）朝着茎的,对生的gelatinize胶（凝）化 （淀粉）糊化gelatinized starches糊化淀粉ruminant反刍动物hydrolyzate 水解物rumen瘤胃（第一胃）intriguing vt.用诡计取得，古哄骗 （新闻用语）引起的兴趣（或好奇）intrigue n.阴谋，诡计 私通vi.筹划阴谋，捣鬼，私通expend vt.消费，花费（时间，精力，金钱等）;用光，耗尽glycogen糖原，动物淀粉trivial a.琐细的，轻微的;不重要的，价值不大的平常人，平凡的；（名称）通俗的（人）浅薄的,轻浮的,无能的,缺德的xylose木糖nomenclature n

14、.名词，术词 命名（过程），命名法 （某一学科的）术语表，术语集aliphatic脂肪族的,属于开链碳化合物的polyhydroxy 多羟基aldehyde 醛aldoses 醛糖ketone 酮ketoses 酮糖hemiacetal 半缩醛prevail vi.胜（过），优胜,成功,奏效流行,盛行,普遍on说服劝说,诱导cyclic环状的designate vt.指明，指此标示 指定，选派把叫做，称呼append vt.附力贴上，挂上trioses 丙糖tetroses 丁糖pentoses 戊糖hexoses 已糖levulose左旋糖，果糖hexulose己酮糖，asymmetric

15、不对称D-glycero- D-甘油moiety n.一半（尤用于法律方面）；约一半 组成局部;一份（尤指政府给告密者的一份报酬） （部落的两个基本分支中）一个分支enolize使烯醇化enolase烯醇化酶enolization烯醇化作用alkaline碱的,强碱的alkali n.碱，强碱monosaccharide 单糖disaccharide 双糖condense冷凝，缩合，凝缩，浓缩oligo-and-polysaccharides 低聚糖-多聚糖 oligo-少,缺乏,专寡/氐glucan 葡聚糖 （=glucosan）fructan果聚糖inulin菊粉 inulase菊粉酶ph

16、osphorylate 磷酸化 phosphorylase 磷酸化酶nucleotide 核甘酸 nucleotidase 核音酶nucleoside 核昔nucleoside 核昔nucleoprotein 核蛋白derivative 衍生物derivative 衍生物glycose 单糖glycosides糖甘，配糖物glycosan聚糖glyconic acids 糖酸glyceric acids 甘油酸glycuronic acid 糖醛酸homoglycan 均聚糖hexosan已聚糖galactan半乳聚糖mannan甘露聚糖pentosan戊聚糖heteroglycan 杂聚糖d

17、eheteroglycan 双杂聚糖aldaric acid 糖二酸tartaric acid 洒石酸reducing function还原性功能团alginpl 藻酸algin藻肮，海藻素增稠剂褐藻胶，藻酸，藻阮酸alginic a.acid藻肮酸exudate渗出物（液），流出物（液）mucopolysaccharide 粘多糖 mucosity n.粘（性）mucus生（由粘膜分泌的）粘液alcohol醇,醇元 乙醇,酒精alditol多羟糖醇，醛醇triitol丙糖醇glycerol甘油,丙三醇sorbitol山梨醇affinity亲合性亲合势爱好饮料（一种饮料名称）heptitol庚

18、糖醇perseitol甘露庚糖醇octitol辛糖醇avocado 铐梨condensed N-acetylated amino sugar 缩聚 N-乙酰氨基糖glycoprotein 糖蛋白chitin壳多糖，甲壳质,几丁质deoxy deoxy-脱氧gum植物胶，（树）胶松脂复胶质软糖mucilage粘浆，粘液粘胶glucosinolate 芥子油昔thioglycoside 硫代糖昔 thiol （mercaptan）硫醇 thioctic acid 硫辛酸cyclitols环多醇myoinositol 肌醇 myogen n.肌浆蛋白myology n.肌学phytic acid 植

19、酸reductone还原酮deplete vt.（局部或全部地）弄空，使空虚,耗尽的精力（或资源等）医减少的体液,放去的血date海枣，枣椰子green pea 豌豆 green bean 青刀豆raffinose棉籽糖stachyose水苏糖verbascose毛蕊花糖postmortem 宰后depolymerize 解聚thioglucoside 硫葡糖昔bouillon汤，羹（用肉，鸡等煮成）broth肉汤（微生物的营养培养基）skim撇去，撇出（浮在上面的油脂，泡沫等）skim milk脱脂乳legume荚（果）；豆科植物 豆荚，豆cruciferae十字花科malt麦芽；麦芽酒，啤

20、酒nitrile 月青goitrin甲状腺肿素goitrigenic甲状腺肿病源cauliflower 花柳菜brussel sprouts抱子甘蓝，北京牙菜 turnip芜菁rutabagas芜菁甘蓝radish小萝卜cyanidin 裁定cyanogenetic生鼠能产生氟化物的 cyanide氟化合物glycoside 昔maceration浸透，泡软，浸渍（作用）manioc木薯cassava 木薯saponin皂角甘，皂素，皂缀糖steroid留族化合物,类固醇triterpenoid三菇系化合物asparagus石刁柏，芦笋，龙须菜yam薯茄，山药，甘薯，山芋alfalfa紫花苜蓿

21、美，苜蓿The layman s conception of carbohydrates generally involves only the s ugars and starches of foods一those that generate calories and fat. The food che mist knows many other types that are ingested.Because most people enjoy the sweetness of sugars and the mout h feel of cooked starches, they becom

22、e familiar by association with table sugar (sucrose), invert sugar? s hydrolyzed sucrose, corn syrup sugars (D-glucose an d maltose), milk sugar (lactose), and the more starchy foods. These carbohydrat es are nutritionally available; i . e. , they are digested (hydrolyzed to compone nt monosaccharid

23、es) and utilized by the human body。 Carbohydrates of dietary fi ber (cellulose, hemicelluse, pentosans, and pectic substances), in contrast, tend to be overlooked because they are largely unavailable. Digestive enzymes do not hydrolyze them significantly; nevertheless, they may be quite important fo

24、r human health.The carbohydrates of natural and processed foods are divided into avail able and unavailable types. The available carbohydrates vary in degrees of abso rption and utilization depending upon quantities ingested, accompanying food ty pes, and human differences in complements of defectiv

25、e enzymes and intestinal t ransport mechanisms. Malabsorption difficulties and adverse physiological effec ts are known for all the available carbohydrates but gelatinized starches give little or no trouble.It is important to realize that in ruminants the unavailable and most a bundant polysaccharid

26、e cellulose is partially hydrolyzed to the same highly ava ilable sugar that starch provides upon digestion; i. e. D-glucose. Grazing anima Is do it through the celluloses generated by the microorganisms of their rumen. Cellulose is, therefore, a contributing source of voluble animal protein. Food c

27、hemists probably can improve upon the efficiency and economics of the ruminan t s conversion of cellulose to nutrients. Development of celluloses that are s table outside the cells of microorganisms enables the culturing of fungi and wi Lh yeasts on cellulose hydrolyzates. Fungi (e. g., niushroums)

28、can produce prolei n with the biological value of animal protein. The conversion of cellulose wast es to animal feed and human food is an intriguing prospect for limiting environ mental pollution and for feeding the world, expending population.Carbohydrates were first named according to their natura

29、l sources; e. g., beet sugar, cane sugar, grape sugar, malt sugar, milk sugar, cornstarch, li ver glycogen, and sweet corn glycogen. Trivial names were then formed, in Engli sh terminology, often from a prefix related to the source followed by the suffi x “-ose” to denote carbohydrate. Names arising

30、 in this way, for example, are fructose, maltose, lactose, xylose, and cellulose. These short, well-establishe d names are still commonly used. They furnish no information on the chemical st ructures however, so a definitive carbohydrate nomenclature has been developed. From the definitive names, st

31、ructural formulas can be written. Some of the ter ms involved in the definitive nomenclature are explained in the following parag raphs.The simple sugars (monosaccharidesO are basically aliphatic polyhydroxy aldehydes and ketones: H0CH2- (CHOH) n-CH0 and HOCH2- (CHOOH) n-l-C-0-Ch20H, c ailed “aldose

32、s” and uketoses, “ respectively. However, it must be understood that cyclic hemiacetals of those open-chain forms prevail I solids and at equil ibrium in solutions. In the definitive nomenclature, the suffix “ose” is appe nded to prefixes denoting the number of carbon atoms in the nomosaccaride; e.g

33、. trioses (n=1), tetroses (n=2), pentoses (n=3), hexoses (n=4) to distinguish al doses from ketoses, ketoses are designated as” -uloses. Thus, the simplest ke tose, H0CH2-C:0-Cl 12011, is a triulose; the most common ketose, D-fructose (levul ose), is a hexlose. To designate the configurations of hyd

34、roxyl groups on the a symmetric carbon atoms of monosaccharides, the prefixes D and L are used togeth er with prefixes derived from the trivial sugar names (e.g. , D-glycero-, L-arab ino-, D-xylo-) followed by pentose, hexose hexulose, etc.As open-chain hydroxy aldehydes and hydroxyl ketenes, the mo

35、nosaccharid es are very reactive. They readly enolize in alkaline soluions to reduce ions s uch as Cu2+ and Fe(CN)63. Therefore, they are called “reducing sugarsv . Plant s protect the reactive monosaccharides for transport and storage by condensing them with loss of water, into less reactive sugars

36、, e. g. , D-glucose and Dfrucl ose, are condensing in such a way that their reactive functions are lost to for m the disaccharide no reducing sugar, sucrose. The less reactive sucrose is the n transported to all parts of the plant for enzymin syntheses of oligo-and poly saccharides. From thousands o

37、r more D-glucose moieties of sucrose the glucans, starch and cellulose, are built. From the D-fructose moiety of sucrose, fructan s such as inulin are assembled. Other polysaccharides are formed from other sug ar, which rose by enzymic transformations of phosphorylated hexoes and sugar nu cleotides.

38、The prefix uglyc, is used in a generic sense to designate sugars and the ir derivatives; e.g., glycoses, glycosides, glycosans, glyconic glyceric, and g lycuronic acids. The generic name for polysaccharides is “glycan” homoglycansa re composed of single monosaccharide; for example, the D-glucans, ce

39、llulose and starch, release only D-glucose by hydrolysis. Other homoglycans (e.g., the hex csans, D-galactan and D-manan, and the pentosans, L-arabinan and D-xy-lan) are uncommon in nature. Heteroglycans, composed of two or more different monosaccha rides, are widely distributed than the homoglycans

40、 that are not glucans. Galact omnnans, glucomammans, arabinogalactans, and arabinoxylans are common diheterog lycans(composed of two sugars). the glycant vail over free glycoses in natural f oods.The reducing sugars are readily oxidized, mild oxidation of aldoses yie Ids aldonic acids, IIOCH2- (CHOH

41、)n-COOH; e.g., gluconic acid(n=4). oxidation of bo th ends of the aldose molecule yields aldaric acids, HOOC-(CHOH)n-COOH; e. g. , t artaric acid(n=2). Oxidation of the terminal CH20H group of hexoses without oxi dation of the reducing function (protected) produces hexuronic acids, HOOC-(CHO H)CHO.

42、The hexuronic acids are common monosaccharide constituents of many hete roglycans . for example, they are found in acidic hemicelluloses, pectic substan ces, alginpl and exudate gumes, and the mucopolysaccharides of mammalian tissue s. Penturonic acids have not been found in nature.Reduction of aldo

43、ses or ketoses yield sugar alcohols , properly called a Iditols, H0CH2-(CHOH)n-CH20H. the suffix “-itol is applied to the trivial prefixes to denote different alditols; e.g. , D-glucitol, D-manniitol, xylitol. The triitol, gllyceritol (by common usage, glycerol, n=l), is the alditol moiet y of fats.

44、 Glycerol and Dglucitol (sorbitol) are acceptable and useful food addi affinity for water. Pentitols(n=3) and hexutols(n=4) are found in small amount in many fruits, vegetables and hexitol, perseitol (n=5), and an octitol have be en isolated from avocados. Some aditols are nutritionally available; o

45、thers arenot.Other types of carbohydrates found in food are the condensed N-acetylated amino sugars of mucopolysaccharides, glycoproteins, and chitin; the condense d eoxy sugars of gum, mucilages, and nucleotides; glcosides (sugars condensed wit h nonsugars); glucosinolates (toxic thioglycosides); c

46、yclitols (myoinositol, ph ytic acid); and reductone, L-ascorbic acid.Complex carbohydrates, such as cellulose and hemicellulose, are largely indigestible, as are a number of originsCarbohydrate Composition of FoodsDetains need more exact information on the carbohydrate compassion of f oods. Food pre

47、ssers also make practical use of carbohydrate composition data. F or example, the reducing sugar content of fruits and vegetables that are to be dehydrated or processed with heat is frequently an indicator of the extent of n onenzymic browing that can expected during processing and storage. The poss

48、ible hydrolysis of sucrose to reducing sugars during processing also is to be consi dered . the natural changes in carbohydrate composition that occur during matura tion and post harvest ripening of plant foods is therefore of particular intere st to food chemists.Citrus fruits, which normally ripen

49、 on the tree and contain no starch, undergo little change in carbohydrate composition following harvest. However, i n fruit that are picked before complete ripening (e.g., apples, bananas, pears), much of the stored starch is converted to sugars as ripening process. The redu cing sugar content of po

50、tatoes also increase during the sun drying of grapes an d dates, sucrose is converted to D-glucose and D-fructose; accordingly, the col or of the dried products is deepened by nonenzymic browning reactions.Green peas, green beans, and sweet corn are picked before maturity to o btain succulent textur

51、es and sweetness. Later the sugars would be converted to polysaccharides, water would be lost, and tough textures would develop. In suyb ean, which is allowed to mature completely before harvest, the starch reserve i s depleted as sucrose and galactosy Isucroses (raffinose, stachyose, verbascose, et

52、c.) are form in the malting of cereal grains, rapid conversions of reserve c arbohydrate to sugars occur as enzymes are strongly activated.In foods of animal origin, postmortem activity of enzymes must be conside red when carbohydrate composition data is obtained. The glycogen of animal tiss ues, es

53、pecially liver is rapidly depolymerized to D-glucose after slaughter, an d immediate deep freezing is required to preserve the glycogen. Mammalian inter nal organs, such as liver, kidney, and brains also eggs and shellfish, provide small amount of D-glucose in the diet . Red fresh meats contain only

54、 traces of a vailable carbohydrate (D-glucose, D-fructose, and D-ribose) and these are extra cted into bouillons and broths. Dairy products provide the main source of mamma lian carbohydrate. Whole cow s milk contains about 4.9% carbohydrates and drie d skim milk contains over 50% lactose.Examinatio

55、n of food composition tables shows that in general, cereals a re highest in starch content and lowest in sugars. Fruit are highest in free su gars and lowest in starch . on a dry basis, the edible portions of fruit usually contain 80-90% carbohydrate. Legumes occupy intermediate portion with regard

56、t o starch and are high in unavailable carbohydrate.Glycosides of many types are widely distributed in plants. Certain biol ogically active thioglucosides, properly called Uglucosinolatesv , are found i n significant amount in crucifers. Mustard oils, nitriles, and goitrins are rel eased by enzymic

57、hydrolysis. Their suspected goitrogenic in humans have been in vestigated, but the amount of glucosnolates normally consumed in food such as f resh cabbage (300-1000ppm), cauliflower, Brussels sprouts, turning, rutabagas, and radishes are not now believed to cause adverse physiological effects. Cyan

58、 genetic glycosides, which release hydrogen cyanide by enzymic hydrolysis under certain condition of vegetable maceration, are known to be sources of acute tox icity in certain animal feeds; however they are not active in the customary foo ds of developed countries. Certain foreign varieties of lima

59、 beans and manic ro ot (cassava) may yield up to 0. 3% hydrogen cyanide by weight, but lima beans di stributed in the United States yield less than 0. 02%. Saponins, the surface-act ive glycosides of steroids and tri terpenoids, are found in low concentrations in tealeaves, spinach, asparagus, beets

60、 sugar beet (0.3%), yams, soybeans (0.5%), alfalfa (2-3%), and peanuts and other legumes.第二课 碳水化合物食品科学家对碳水化合物有着多方面的兴趣。他们关心碳水化合物在各种食 品中的含量，关心它的可利用性（营养上和经济上），它的提取方法和分析方法，它的商品 形式和纯度，它的营养价值、生理效用以及在食品中的功能特性。要了解碳水化合物在加工 食品中的功能特性，不仅要有单离态碳水化合物的物理、化学性质的知识，还要有碳水化合 物与其它食物成分之间在加工食品中就地所发生的反响和相互作用的知识，以及这些反映变 化对食品