The food scientist has a many-sided interest in carbohydrates. He is concerned with their amounts in various foods, availability (nutritional and economic), methods of extraction and analysis, commercial forms and purity, nutritional valve, physiological effects, and functional properties in foods. Understanding their functional properties in processed foods requires not only knowledge of the physical and chemical properties of isolated carbohydrates, but also knowledge of the reactions and interactions that occur in situs between carbohydrates and other food constituents and the effects of these changes upon food quality and acceptance. This is a tall order for knowledge. Because processing affects both nutritional and esthetic values of food, knowledge of the changes that carbohydrates undergo during milling, cooking, dehydration, freezing, and storage is especially important.

   Students are advised to study the fundamental chemistry underlying useful carbohydrates properties Of service will be an understanding of the association of polar molecules through hydrogen bonding, ionic effects, substituent effects, chelation with inorganic ions, complexing with lipids and proteins, and decomposition reaction. This background will provide an understanding of properties that affect the texture and acceptance of processed foods (e.g., solubility, hygroscopicity, diffusion, osmosis, viscosity, plastity, and flavor production), properties that enable the formation or high quality pastries, gels, coatings, 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 forecasting requires either a wealth of experience with trial-and-error methods or a deep knowledge of carbohydrate properties as related to structure―perhaps both. However, scientific knowledge of cause and effect is highly respected when it shortens industrial development time 　

 

       Source, Types, and Terminology

 

  The layman’s conception of carbohydrates generally involves only the sugars and starches of foods―those that generate calories and fat. The food chemist knows many other types that are ingested.

      Because most people enjoy the sweetness of sugars and the mouth feel of cooked starches, they become familiar by association with table sugar (sucrose), invert sugar’s hydrolyzed sucrose, corn syrup sugars (D-glucose and maltose), milk sugar (lactose), and the more starchy foods. These carbohydrates are nutritionally available; i .e., they are digested (hydrolyzed to component monosaccharides) and utilized by the human body。Carbohydrates of dietary fiber (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 for human health.

  The carbohydrates of natural and processed foods are divided into available and unavailable types. The available carbohydrates vary in degrees of absorption and utilization depending upon quantities ingested, accompanying food types, and human differences in complements of defective enzymes and intestinal transport mechanisms. Malabsorption difficulties and adverse physiological effects 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 abundant polysaccharide cellulose is partially hydrolyzed to the same highly available sugar that starch provides upon digestion; i.e. D-glucose. Grazing animals do it through the celluloses generated by the microorganisms of their rumen. Cellulose is, therefore, a contributing source of voluble animal protein. Food chemists probably can improve upon the efficiency and economics of the ruminant’s conversion of cellulose to nutrients. Development of celluloses that are stable outside the cells of microorganisms enables the culturing of fungi and with yeasts on cellulose hydrolyzates. Fungi (e.g., mushrooms) can produce protein with the biological value of animal protein. The conversion of cellulose wastes to animal feed and human food is an intriguing prospect for limiting environmental pollution and for feeding the world’ expending population.

  Carbohydrates were first named according to their natural sources; e.g., beet sugar, cane sugar, grape sugar, malt sugar, milk sugar, cornstarch, liver glycogen, and sweet corn glycogen. Trivial names were then formed, in English terminology, often from a prefix related to the source followed by the suffix “-ose” to denote carbohydrate. Names arising in this way, for example, are fructose, maltose, lactose, xylose, and cellulose. These short, well-established names are still commonly used. They furnish no information on the chemical structures however, so a definitive carbohydrate nomenclature has been developed. From the definitive names, structural formulas can be written. Some of the terms involved in the definitive nomenclature are explained in the following paragraphs.

  The simple sugars (monosaccharides0 are basically aliphatic polyhydroxy aldehydes and ketones: HOCH2- (CHOH) n-CHO and HOCH2- (CHOOH) n-1-C-O-Ch2OH, called “aldoses” and “ketoses,” respectively. However, it must be understood that cyclic hemiacetals of those open-chain forms prevail I solids and at equilibrium in solutions. In the definitive nomenclature, the suffix “ose” is appended to prefixes denoting the number of carbon atoms in the nomosaccaride; e.g. trioses (n=1), tetroses (n=2), pentoses (n=3), hexoses (n=4) to distinguish aldoses from ketoses, ketoses are designated as”-uloses.” Thus, the simplest ketose, HOCH2-C:O-CH2OH, is a triulose; the most common ketose, D-fructose (levulose), is a hexlose. To designate the configurations of hydroxyl groups on the asymmetric carbon atoms of monosaccharides, the prefixes D and L are used together with prefixes derived from the trivial sugar names (e.g., D-glycero-, L-arabino-, D-xylo-) followed by pentose, hexose hexulose, etc.

  As open-chain hydroxy aldehydes and hydroxyl ketenes, the monosaccharides are very reactive. They readly enolize in alkaline soluions to reduce ions such as Cu²⁺ and Fe(CN)6^3-. Therefore, they are called “reducing sugars”. Plants protect the reactive monosaccharides for transport and storage by condensing them with loss of water, into less reactive sugars, e.g., D-glucose and D-fructose, are condensing in such a way that their reactive functions are lost to form the disaccharide no reducing sugar, sucrose. The less reactive sucrose is then transported to all parts of the plant for enzymin syntheses of oligo-and polysaccharides. From thousands or more D-glucose moieties of sucrose the glucans, starch and cellulose, are built. From the D-fructose moiety of sucrose, fructans such as inulin are assembled. Other polysaccharides are formed from other sugar, which rose by enzymic transformations of phosphorylated hexoes and sugar nucleotides.

The prefix “glyc,” is used in a generic sense to designate sugars and their derivatives; e.g., glycoses, glycosides, glycosans, glyconic glyceric, and glycuronic acids. The generic name for polysaccharides is “glycan”homoglycansare composed of single monosaccharide; for example, the D-glucans, cellulose and starch, release only D-glucose by hydrolysis. Other homoglycans (e.g., the hexcsans, 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 monosaccharides, are widely distributed than the homoglycans that are not glucans. Galactomnnans, glucomammans, arabinogalactans, and arabinoxylans are common diheteroglycans(composed of two sugars).the glycant vail over free glycoses in natural foods.

  The reducing sugars are readily oxidized. mild oxidation of aldoses yields aldonic acids, HOCH2-(CHOH)n-COOH; e.g., gluconic acid(n=4).oxidation of both ends of the aldose molecule yields aldaric acids, HOOC-(CHOH)n-COOH; e.g., tartaric acid(n=2). Oxidation of the terminal CH2OH group of hexoses without oxidation of the reducing function (protected) produces hexuronic acids, HOOC-(CHOH)-CHO. The hexuronic acids are common monosaccharide constituents of many heteroglycans .for example, they are found in acidic hemicelluloses, pectic substances, alginpl and exudate gumes, and the mucopolysaccharides of mammalian tissues. Penturonic acids have not been found in nature.

  Reduction of aldoses or ketoses yield sugar alcohols ,properly called ‘alditols,” HOCH2-(CHOH)n-CH2OH.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=1), is the alditol moiety of fats.Glycerol and D-glucitol(sorbitol) are acceptable and useful food addiaffinity 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 been isolated from avocados. Some aditols are nutritionally available; others are not.

  Other types of carbohydrates found in food are the condensed N-acetylated amino sugars of mucopolysaccharides, glycoproteins, and chitin; the condense deoxy sugars of gum, mucilages, and nucleotides; glcosides (sugars condensed with nonsugars); glucosinolates (toxic thioglycosides); cyclitols (myoinositol, phytic acid); and reductone, L-ascorbic acid.

  Complex carbohydrates, such as cellulose and hemicellulose, are largely indigestible, as are a number of origins

 

             Carbohydrate Composition of Foods

 

   Detains need more exact information on the carbohydrate compassion of foods. Food pressers also make practical use of carbohydrate composition data. For 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 nonenzymic browing that can expected during processing and storage. The possible hydrolysis of sucrose to reducing sugars during processing also is to be considered .the natural changes in carbohydrate composition that occur during maturation and post harvest ripening of plant foods is therefore of particular interest to food chemists.

  Citrus fruits, which normally ripen on the tree and contain no starch, undergo little change in carbohydrate composition following harvest. However, in 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 reducing sugar content of potatoes also increase during the sun drying of grapes and dates, sucrose is converted to D-glucose and D-fructose; accordingly, the color of the dried products is deepened by nonenzymic browning reactions.

  Green peas, green beans, and sweet corn are picked before maturity to obtain succulent textures and sweetness. Later the sugars would be converted to polysaccharides, water would be lost, and tough textures would develop. In soybean, which is allowed to mature completely before harvest, the starch reserve is depleted as sucrose and galactosy lsucroses (raffinose, stachyose, verbascose, etc.) are form in the malting of cereal grains, rapid conversions of reserve carbohydrate to sugars occur as enzymes are strongly activated.

  In foods of animal origin, postmortem activity of enzymes must be considered when carbohydrate composition data is obtained. The glycogen of animal tissues, especially liver is rapidly depolymerized to D-glucose after slaughter, and immediate deep freezing is required to preserve the glycogen. Mammalian internal 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 traces of available carbohydrate (D-glucose, D-fructose, and D-ribose) and these are extracted into bouillons and broths. Dairy products provide the main source of mammalian carbohydrate. Whole cow’s milk contains about 4.9% carbohydrates and dried skim milk contains over 50% lactose.

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

  Glycosides of many types are widely distributed in plants. Certain biologically active thioglucosides, properly called “glucosinolates”, are found in significant amount in crucifers. Mustard oils, nitriles, and goitrins are released by enzymic hydrolysis. Their suspected goitrogenic in humans have been investigated, but the amount of glucosnolates normally consumed in food such as fresh cabbage (300-1000ppm), cauliflower, Brussels sprouts, turning, rutabagas, and radishes are not now believed to cause adverse physiological effects. Cyan genetic glycosides, which release hydrogen cyanide by enzymic hydrolysis under certain condition of vegetable maceration, are known to be sources of acute toxicity in certain animal feeds; however they are not active in the customary foods of developed countries. Certain foreign varieties of lima beans and manic root (cassava) may yield up to 0.3% hydrogen cyanide by weight, but lima beans distributed in the United States yield less than 0.02%. Saponins, the surface-active glycosides of steroids and triterpenoids, are found in low concentrations in tealeaves, spinach, asparagus, beets sugar beet (0.3%), yams, soybeans (0.5%), alfalfa (2-3%), and peanuts and other legumes.

 

第二課  碳水化合物

    食品科學家對碳水化合物有著多方麵的興趣。他們關心碳水化合物在各種食品中的含量，關心它的可利用性（營養上和經濟上），它的提取方法和分析方法，它的商品形式和純度，它的營養價值
、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，不僅要有單離態碳水化合物的物理
、化(hua)學(xue)性(xing)質(zhi)的(de)知(zhi)識(shi)
，還(hai)要(yao)有(you)碳(tan)水(shui)化(hua)合(he)物(wu)與(yu)其(qi)它(ta)食(shi)物(wu)成(cheng)分(fen)之(zhi)間(jian)在(zai)加(jia)工(gong)食(shi)品(pin)中(zhong)就(jiu)地(di)所(suo)發(fa)生(sheng)的(de)反(fan)應(ying)和(he)相(xiang)互(hu)作(zuo)用(yong)的(de)知(zhi)識(shi)
，以(yi)及(ji)這(zhe)些(xie)反(fan)映(ying)變(bian)化(hua)對(dui)食(shi)品(pin)質(zhi)量(liang)和(he)食(shi)品(pin)可(ke)接(jie)受(shou)性(xing)的(de)影(ying)響(xiang)的(de)知(zhi)識(shi)。顯(xian)然(ran)要(yao)了(le)解(jie)這(zhe)些(xie)知(zhi)識(shi)是(shi)不(bu)容(rong)易(yi)的(de)。由(you)於(yu)食(shi)品(pin)加(jia)工(gong)過(guo)程(cheng)既(ji)影(ying)響(xiang)食(shi)品(pin)的(de)營(ying)養(yang)價(jia)值(zhi)，也(ye)影(ying)響(xiang)它(ta)的(de)美(mei)學(xue)價(jia)值(zhi)。所(suo)以(yi)了(le)解(jie)碳(tan)水(shui)化(hua)合(he)物(wu)在(zai)研(yan)磨(mo)、熱處理
、脫水
、冷凍和貯藏過程中所經受的變化就顯得特別重要。

    建議學員們學習基礎化學，這時認識碳水化合物有用性質的基礎。了解和認識極性分子通過氫鍵、離子效應、取代基效應
、與無機離子螯合、yuzhileihedanbaizhiluoheyijifenjiefanyingdengdedihezuoyongjiangjuyouzhongyaodeyiyi。zhexiejichuzhishijiangyouzhuyuwomenlejieyingxiangjiagongshipindezhigouhekejieshouxingdexingzhi（例如溶解度、吸濕性、擴散性、滲透性、粘度、可塑性
、風味形成）

，了解使優質糕點、凝膠食品
、糖衣
、糖果和可複原脫水食品、冷凍食品得以形成的性質。

    食shi品pin科ke學xue家jia實shi際ji工gong作zuo目mu標biao之zhi一yi是shi能neng夠gou預yu測ce在zai把ba各ge種zhong各ge樣yang碳tan水shui化hua合he物wu摻chan到dao加jia工gong食shi品pin中zhong之zhi後hou，可ke能neng會hui發fa生sheng什shen麼me樣yang的de功gong能neng性xing質zhi變bian化hua。作zuo這zhe樣yang的de預yu測ce要yao有you豐feng富fu的de用yong試shi探tan法fa摸mo索suo的de經jing驗yan，或huo者zhe要yao具ju備bei有you關guan結jie構gou的de碳tan水shui化hua合he物wu的de性xing質zhi的de深shen奧ao知zhi識shi，也ye可ke能neng上shang述shu兩liang者zhe都dou要yao具ju備bei。不bu過guo
，科ke學xue的de因yin果guo關guan係xi知zhi識shi隻zhi有you在zai它ta縮suo短duan了le工gong業ye產chan品pin試shi製zhi周zhou期qi之zhi時shi才cai受shou到dao高gao度du的de重zhong視shi。

碳水化合物的來源、種類和技術名稱   

    外行人的碳水化合物概念一般僅包括食物中能產生熱量和脂肪的糖和澱粉，而食品科學家還知道許多攝入的他種碳水化合物。

    由於大多數人喜歡糖的甜味和熟澱粉的口感，所以它們由於經常打交道而對食糖、（蔗糖）、轉化糖（蔗糖水解產物）、澱粉糖漿（D-葡萄糖和麥芽糖）、乳糖和含澱粉多的食品十分熟悉。這些碳水化合物都有很好的營養價值

，即它們可分為人體所消化（水解成單糖成分）和利用。相反，食用纖維類碳水化合物（纖維素、半纖維素、戊聚糖、果膠物質）因其大部分不能為人體所利用而往往被忽視。食用纖維類碳水化合物不能有效的被消化酶水解；盡管這樣，他對人體的健康可能相當重要。

    天然食物和加工食物中的碳水化合物被分成人體可利用和不可利用的兩類。可利用的碳水化合物在吸收、利用的程度上也有差別
，要看他的攝入量、伴ban隨sui食shi物wu的de種zhong類lei以yi及ji人ren體ti在zai消xiao化hua酶mei互hu補bu情qing況kuang上shang和he腸chang道dao輸shu送song機ji製zhi上shang的de差cha異yi而er定ding。大da家jia都dou知zhi道dao
，除chu了le糊hu化hua澱dian粉fen大da致zhi上shang沒mei有you問wen題ti以yi外wai，所suo有you可ke利li用yong碳tan水shui化hua合he物wu都dou有you吸xi收shou不bu良liang的de問wen題ti和he有you害hai的de生sheng理li影ying響xiang。

    zhongyaodeshiyaoyishidao，zaifanchudongwufangmian
，shuliangzuifengfuderenleibukeliyongdeduotangleixianweisushoudaolebufenshuijie
，bianchengledianfenxiaohuashisuoxingchengdegaodukeliyongtang，jiD-葡(pu)萄(tao)糖(tang)。食(shi)草(cao)動(dong)物(wu)利(li)用(yong)它(ta)們(men)瘤(liu)胃(wei)中(zhong)微(wei)生(sheng)物(wu)所(suo)產(chan)生(sheng)的(de)纖(xian)維(wei)素(su)酶(mei)來(lai)水(shui)解(jie)纖(xian)維(wei)素(su)。因(yin)此(ci)，纖(xian)維(wei)素(su)對(dui)有(you)價(jia)值(zhi)的(de)動(dong)物(wu)蛋(dan)白(bai)而(er)言(yan)是(shi)有(you)一(yi)定(ding)貢(gong)獻(xian)的(de)資(zi)源(yuan)。反(fan)芻(chu)動(dong)物(wu)將(jiang)纖(xian)維(wei)素(su)轉(zhuan)化(hua)為(wei)營(ying)養(yang)素(su)的(de)效(xiao)率(lv)和(he)經(jing)濟(ji)性(xing)有(you)可(ke)能(neng)經(jing)過(guo)食(shi)品(pin)化(hua)學(xue)家(jia)來(lai)改(gai)進(jin)。開(kai)發(fa)在(zai)微(wei)生(sheng)物(wu)細(xi)胞(bao)外(wai)部(bu)能(neng)穩(wen)定(ding)存(cun)在(zai)的(de)纖(xian)維(wei)素(su)酶(mei)使(shi)真(zhen)菌(jun)和(he)酵(jiao)母(mu)在(zai)纖(xian)維(wei)素(su)水(shui)解(jie)產(chan)物(wu)上(shang)培(pei)養(yang)有(you)了(le)可(ke)能(neng)。真(zhen)菌(jun)（如蘑菇）能(neng)產(chan)出(chu)具(ju)有(you)動(dong)物(wu)性(xing)蛋(dan)白(bai)質(zhi)生(sheng)理(li)效(xiao)價(jia)的(de)蛋(dan)白(bai)質(zhi)。對(dui)於(yu)控(kong)製(zhi)環(huan)境(jing)汙(wu)染(ran)和(he)供(gong)應(ying)增(zeng)長(chang)著(zhe)的(de)世(shi)界(jie)人(ren)口(kou)的(de)食(shi)品(pin)來(lai)說(shuo)
，將(jiang)纖(xian)維(wei)素(su)廢(fei)料(liao)轉(zhuan)化(hua)為(wei)動(dong)物(wu)飼(si)料(liao)和(he)人(ren)類(lei)食(shi)物(wu)有(you)著(zhe)誘(you)人(ren)的(de)前(qian)景(jing)。

    碳水化合物最初是按照它們的天然來源來命名的，例如甜菜糖、甘蔗糖
、葡萄糖、麥芽糖
、乳糖、玉米澱粉、肝糖原
、甜玉米糖原。以後的英語名稱中就形成了唱以前綴表示來源，加後綴“-ose”表示碳水化合物的俗名。由此法產生的名稱
，有如：fructose（果糖）、maltose（麥芽糖）、lactose（乳糖）、 xylose （木糖）
、cellulose（纖維素）等deng。這zhe些xie簡jian短duan而er明ming確que的de名ming稱cheng現xian在zai仍reng通tong用yong。可ke是shi
，這zhe些xie名ming稱cheng不bu反fan映ying其qi化hua學xue結jie構gou。於yu是shi就jiu產chan生sheng了le碳tan水shui化hua合he物wu的de定ding形xing命ming名ming法fa。國guo際ji定ding形xing名ming稱cheng
，可ke以yi寫xie出chu其qi結jie構gou式shi。下xia麵mian幾ji段duan將jiang對dui某mou些xie涉she及ji定ding形xing命ming名ming法fa的de專zhuan門men術shu語yu作zuo出chu解jie釋shi。

    單糖本質上是脂族的多羥基醛和酮，即HOCH₂-(CHOH)₂-CHO和HOCH2-(CHOH)n-1-C:O-CH2OH,fenbiechengweiquantanghetongtang。buguoyaozhidao，gutizhonghepinghengshirongyezhongdedantangshiyikailianxinghuanzhuangbansuoquanzhanduoshu。zaidingxingmingmingfazhong

，dantangmingyoubiaoshidantangtanyuanzishudeqianzhuijiahouzhui“-ose”構成。例如丙糖（trioses

，n=1）、丁糖（tetroses，n=2）、戊糖（pentoses，n=3）
，己糖（hexose，n=4）
，為區別醛糖和酮糖，就把酮糖後綴加成“-ulose”。這樣，最簡單的酮糖HOCH2-C：O-CH2OH即為triulose（丙酮糖）；最常見得酮糖D-果糖（左旋糖）即為hexulose（己酮糖）。為表明單糖不對稱碳原子上羥基的構型
，可將前綴D和L與取自俗名的前綴一起使用（例如D-甘油-、L-阿拉伯-、D-木-）

，後麵在接上戊糖、己糖
、己酮糖等等。

    以開鏈的羥基醛和羥基酮形式 存在的單糖非常活潑。它們在堿性溶液中易於烯醇化而使Cu²+、Fe（CN）₆³+之類的離子還原
，因此稱它們為“還原糖”。植物依靠脫水縮和方式將活潑的單糖變成不大活潑的糖類來保存單糖的還原活性，以便輸送和貯存。例如，D-葡萄糖和D-果糖縮合成無還原性雙糖――蔗(zhe)糖(tang)時(shi)
，變(bian)失(shi)去(qu)了(le)活(huo)潑(po)的(de)功(gong)能(neng)。不(bu)太(tai)活(huo)潑(po)的(de)蔗(zhe)糖(tang)然(ran)後(hou)被(bei)輸(shu)送(song)到(dao)植(zhi)物(wu)的(de)各(ge)個(ge)部(bu)位(wei)，由(you)酶(mei)合(he)成(cheng)低(di)聚(ju)糖(tang)和(he)多(duo)聚(ju)糖(tang)。由(you)數(shu)千(qian)或(huo)更(geng)多(duo)的(de)半(ban)個(ge)蔗(zhe)糖(tang)分(fen)子(zi)D-葡萄糖構成葡聚糖

、澱粉和纖維素；而由另半個蔗糖分子D-果糖聚合成為果聚糖
，如菊粉。其它多聚糖則是由磷酸化己糖和核苷酸糖通過酶作用生成的其它糖聚合形成的。

    前綴“glyc”（甘、糖）在一般意義上用來表示糖及其衍生物。例如：glycoses（單糖）
、glycosides（糖苷）、glycosans（聚糖）、glyconic acids (糖酸) 、glyconic acids（甘油酸）
、glycuronic acids（糖醛酸）。多聚糖的俗名是“聚糖”。均聚糖由一種單糖構成。例如D-葡聚糖、纖維素和澱粉，它們水解時隻產生D-葡萄糖。其它均聚糖（例如己聚糖D-半乳聚糖和D-甘露聚糖；戊聚糖有L-阿拉伯聚糖D-木聚糖）在自然界中很少見到。雜聚糖由兩種或多種單糖構成。它們在自然界的分布比均聚糖（除葡聚糖外）廣泛。半乳甘露聚糖、葡甘露聚糖、阿拉伯半乳聚糖、阿拉伯木聚糖時常見的雙雜聚糖（由兩種糖組成）。天然食物中的聚糖大大多餘遊離單糖。

    還原糖易於氧化。醛糖經輕度氧化可產生醛糖酸，HOCH2-（CHOH）n-COOH，如葡萄糖酸（n=4）。醛糖分子兩端氧化形成糖二酸，HOOC-（CHOH）n-COOH，例如酒產生的糖醛酸
，HOOC-（CHOH）4-CHO。己糖醛酸是組成多種雜聚糖的常見單糖成分
，例如在酸性半纖維素、果膠物質、藻酸
、植物滲出膠和哺乳動物組織中的粘多糖中就有己糖醛酸。戊糖醛酸還未在自然界中發現。

    醛糖或酮糖被還原後變產生糖醇
，確實的叫法為“多羥糖醇”（alditols），HOCH2-（CHOH）n-CH2OH。其後綴“-itol”（糖醇）接在俗名前綴之後表示不同的多羥糖醇，例如D-葡糖醇、D-甘露糖醇、木糖醇。丙糖醇，即甘油醇（常稱為甘油，n=1），是脂肪的多羥基糖醇部分。甘油和葡糖醇（山梨醇）成為受歡迎的有用的食品添加劑，因為它們能生成葡萄糖，並依靠其強烈的親水作用保持食品是濕潤。許多水果
、蔬菜和菇類中存在有少量的戊糖醇（n=3）和己糖醇（n=4）。庚糖醇、甘露庚糖醇（n=5）和某種辛糖醇已從鱷梨中分離出來。有些多羥糖醇是有營養的，有些則無營養。

    在食物中發現它種碳水化合物還有：粘多糖
、糖蛋白

、殼多糖之類的縮聚N-乙酰氨基糖；植物膠、粘漿、核苷酸之類的縮合脫氧糖；糖苷（糖與非糖縮合）；芥子油苷（毒性的硫代糖苷）

；環多糖（肌醇、植酸）
；L-抗壞血酸（一種還原酮）。

    複雜碳水化合物如纖維素、半纖維素基本上是不能消化的
，就象植物性食物中所找到的許多低聚糖、某些其它碳水化合物、樹膠和纖維質材料一樣。

                            食物中碳水化合物組成

    營ying養yang學xue家jia需xu要yao有you較jiao為wei嚴yan格ge的de有you關guan食shi物wu碳tan水shui化hua合he物wu組zu成cheng的de知zhi識shi。食shi品pin加jia工gong者zhe也ye把ba碳tan水shui化hua合he物wu組zu成cheng的de知zhi識shi用yong於yu實shi際ji工gong作zuo。例li如ru，欲yu待dai脫tuo水shui或huo熱re處chu理li的de水shui果guo和he蔬shu菜cai
，其qi還hai原yuan糖tang含han量liang常chang常chang時shi一yi項xiang預yu示shi加jia工gong和he貯zhu藏zang過guo程cheng中zhong非fei酶mei褐he變bian程cheng度du的de指zhi標biao。當dang然ran也ye要yao考kao慮lv加jia工gong過guo程cheng中zhong蔗zhe糖tang有you可ke能neng水shui解jie變bian成cheng還hai原yuan糖tang。因yin此ci，食shi品pin化hua學xue家jia對dui植zhi物wu性xing食shi物wu在zai成cheng熟shu和he後hou熟shu期qi間jian所suo發fa生sheng的de碳tan水shui化hua合he物wu組zu成cheng的de自zi然ran變bian化hua特te別bie感gan興xing趣qu。

    在果樹上正常成熟且不含澱粉的柑桔類水果，其碳水化合物組成在摘下後很少變化。可是，在許多完全成熟前摘下的水果（如蘋果、香蕉

、梨）zhong，zhucundedabufendianfenhuizaijixuchengshushizhuanhuaweitang。malingshuzailengzangjianhaiyuantanghanliangyehuizengjia。putaohehaizaozaishaiganqijian，suiqineiyuanzhetangmeihuoxingdebutong，huibutongchengdudishizhetangzhuanhuaD-葡萄糖和D-果糖。因此，其幹製品的顏色也會因非酶褐變而加深。

    豌豆、青qing刀dao豆dou和he甜tian玉yu米mi在zai成cheng熟shu前qian摘zhai下xia是shi為wei了le獲huo得de多duo汁zhi鮮xian嫩nen的de質zhi構gou和he甜tian味wei。遲chi了le，所suo含han的de糖tang就jiu會hui轉zhuan成cheng多duo聚ju糖tang，水shui分fen會hui失shi掉diao
，就jiu會hui產chan生sheng韌ren性xing的de質zhi構gou。熟shu透tou後hou在zai摘zhai收shou的de大da豆dou

，其qi澱dian粉fen儲chu量liang隨sui蔗zhe糖tang和he類lei半ban乳ru蔗zhe糖tang（棉籽糖
、水蘇糖、毛蕊花糖等）的形成而耗盡。用穀物加工麥芽糖使，由於酶被極度活化而使得貯存的碳水化合物迅速轉化成糖。

    在動物性食物方麵
，當獲得碳水化合物組成數據時，必須仔細估量動物宰後酶的活性。動物組織（尤其是肝髒）中的糖原在宰後會迅速解聚成D-葡萄糖，所以，要保存糖原
，就得立即進行深度冷凍。哺乳動物內部器官（如肝、腎
、腦和蛋類
、貝類所提供的D-葡萄糖隻占飲食中D-葡萄糖的一小部分。紅色的新鮮肉類僅含極少可利用的碳水化合物（D-葡萄糖

、D-果糖和D-核糖），而這些碳水化合物被溶出進入肉汁和肉湯。乳製品提供了哺乳動物碳水化合物的主要來源

，牛全乳含碳水化合物約4.9%，脫脂乳粉含乳糖量超過50%。

    查zha看kan一yi些xie食shi物wu成cheng分fen表biao便bian可ke知zhi道dao，通tong常chang穀gu類lei的de澱dian粉fen含han量liang最zui高gao而er糖tang含han量liang最zui低di。水shui果guo類lei遊you離li糖tang最zui多duo
，澱dian粉fen最zui少shao。以yi幹gan基ji計ji算suan

，水shui果guo的de可ke食shi部bu分fen通tong常chang含han80～90%的碳水化合物。豆類含澱粉不多不少
，但含有大量的不可利用的碳水化合物。

在植物界，廣泛分布著多種糖苷。在十字花科植物中大量存在著某些具有生理活性的硫葡糖苷（確切稱之為“芥子油柑”）。芥子油柑經酶水解產生芥子油、腈和甲狀腺腫素。人們已經研究了它在人體中可疑的甲狀腫病源性質。但目前還不認為食用新鮮卷心菜（其中芥子油柑量為300～1000ppm）、花椰菜
、抱子甘藍、蕪菁
、蕪菁甘藍
、小(xiao)蘿(luo)卜(bu)之(zhi)類(lei)食(shi)物(wu)中(zhong)的(de)芥(jie)子(zi)油(you)苷(gan)數(shu)量(liang)會(hui)引(yin)起(qi)有(you)害(hai)的(de)生(sheng)理(li)效(xiao)應(ying)。生(sheng)氰(qing)苷(gan)在(zai)一(yi)定(ding)蔬(shu)菜(cai)浸(jin)漬(zi)條(tiao)件(jian)下(xia)，通(tong)過(guo)酶(mei)水(shui)解(jie)能(neng)釋(shi)放(fang)出(chu)氰(qing)化(hua)氫(qing)。人(ren)們(men)都(dou)知(zhi)道(dao)生(sheng)氰(qing)苷(gan)是(shi)某(mou)些(xie)動(dong)物(wu)飼(si)料(liao)劇(ju)毒(du)性(xing)的(de)主(zhu)要(yao)來(lai)源(yuan)。可(ke)是(shi)在(zai)發(fa)達(da)國(guo)家(jia)的(de)平(ping)常(chang)食(shi)物(wu)中(zhong)，生(sheng)氰(qing)苷(gan)沒(mei)有(you)活(huo)性(xing)。某(mou)些(xie)外(wai)國(guo)品(pin)種(zhong)的(de)菜(cai)豆(dou)和(he)木(mu)薯(shu)可(ke)產(chan)生(sheng)高(gao)達(da)0.3%的氰化氫（按重量計），但遍布在美國的菜豆產氰化氫低於0.02%。皂角苷類（類固醇和三萜係化合物的表麵活性糖苷）會以低濃度出現在茶葉、菠菜、蘆筍、甜菜、糖用甜菜（0.3%）、甘薯、大豆（0.5%）
、苜蓿（2～3%）、花生及其它豆類。

 

Lesson 2 Carbohydrates

 

extraction 提取(法),萃取(法),抽提法

milling ①研磨,碾碎,磨碎,粉碎 ②磨(麵)粉

dehydration 脫水(作用),人工加熱幹燥(作用)

underlie vt.①位於…的下麵,放在…下麵 ②支承;構成 ③屈服於 ④(權利,素賠等)優先於

underlying  (理論,政策,行為等)的基礎

chelation  螯合

association n.①聯合;聯係,聯盟,合夥,交際,交往 ②聯想 ③協會,社團 ④[化]締合(作用)

hygroscopicity 吸濕性               diffusion 擴散性

osmosis 滲透性                     viscosity 粘度

pasticity可塑性

trial-and-error 反複試驗;不斷摸索

ingest 口服,口食

terminology n. 術語學;術語,專門名詞

corn ①玉米 ②穀物(泛指玉米,黑麥,燕麥,小麥等) ③穀粒 ④製成碎粒 ⑤用鹽醃製的

syrup  糖漿,糖水(罐)  

corn syrup 澱粉糖漿,葡萄糖漿      cornstarch玉米澱粉      corn sugar 葡萄糖

pentosan 戊聚糖

malabsorption n.[醫]吸收不良,養料吸收障礙 

 mal- ①表示“壞”,“惡”,“不良” ②表示 “不”,“非”,“不當”

adverse a.①(在位置或方向上)逆的,相反的,敵對的 ②不利的,有害的 ③[植](葉子等)朝著

        莖的,對生的

gelatinize ①膠(凝)化 ②(澱粉)糊化     gelatinized starches 糊化澱粉

ruminant 反芻動物

hydrolyzate 水解物

rumen 瘤胃(第一胃)

intriguing vt.①用詭計取得,[古]哄騙 ②(新聞用語)引起…的興趣(或好奇)

intrigue n.①陰謀,詭計 ②私通 vi.策劃陰謀,搗鬼,私通

expend vt.消費,花費(時間,精力,金錢等);用光,耗盡

glycogen 糖原,動物澱粉

trivial a.①瑣細的,輕微的;不重要的,價值不大的 ②平常人,平凡的;(名稱)通俗的 ③(人)

      淺薄的,輕浮的,無能的,缺德的

xylose 木糖

nomenclature n.①名詞,術詞 ②命名(過程),命名法 ③(某一學科的)術語表,術語集

aliphatic 脂肪族的,屬於開鏈碳化合物的

polyhydroxy 多羥基

aldehyde 醛                aldoses醛糖

ketone酮                   ketoses酮糖

hemiacetal半縮醛

prevail vi.①勝(過),優勝,成功,奏效 ②流行,盛行,普遍  ～ on 說服,勸說,誘導

cyclic環狀的

designate vt.①指明,指出,標示 ②指定,選派 ③把…叫做,稱呼

append vt.①附加②貼上,掛上

trioses丙糖                           tetroses丁糖

pentoses戊糖                         hexoses已糖

levulose左旋糖,果糖

hexulose已酮糖,

asymmetric不對稱

D-glycero- D-甘油

moiety n.①一半(尤用於法律方麵);約一半 ②組成部分;一份(尤指政府給告密者的一份報

       酬)  ③(部落的兩個基本分支中)一個分支

enolize使烯醇化        enolase烯醇化酶       enolization烯醇化作用

alkaline堿的,強堿的     alkali n.堿,強堿

monosaccharide單糖

disaccharide雙糖

condense冷凝,縮合,凝縮,濃縮

oligo-and-polysaccharides 低聚糖-多聚糖       oligo-  少,缺乏,[專]寡,低

glucan葡聚糖       (=glucosan)

fructan果聚糖

inulin菊粉         inulase菊粉酶

phosphorylate磷酸化    phosphorylase磷酸化酶

nucleotide核苷酸       nucleotidase 核苷酶

nucleoside核苷         nucleoprotein核蛋白

derivative衍生物

glycose單糖           glycosides糖苷,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雜聚糖               deheteroglycan雙雜聚糖

aldaric acid 糖二酸       

tartaric acid灑石酸

reducing function還原性功能團

alginpl藻酸

algin ①藻朊,海藻素[增稠劑] ②褐藻膠,藻酸,藻朊酸 alginic a. ～ acid 藻朊酸

 

 

 

 

 

exudate 滲出物(液),流出物(液)

mucopolysaccharide 粘多糖       mucosity n.粘(性)    mucus n.[生](由粘膜分泌的)粘液

alcohol ①醇,醇元 ②乙醇,酒精

alditol多羥糖醇,醛醇

triitol丙糖醇

glycerol甘油,丙三醇

sorbitol山梨醇

affinity ①親合性 ②親合勢 ③愛好飲料(一種飲料名稱)

heptitol庚糖醇

perseitol甘露庚糖醇

octitol辛糖醇

avocado鍔梨

condensed N-acetylated amino sugar 縮聚N-乙酰氨基糖

glycoprotein糖蛋白

chitin殼多糖,甲殼質,幾丁質

deoxy  deoxy- 脫氧

gum ①植物膠,(樹)膠 ②鬆脂 ③[複]膠質軟糖

mucilage ①粘漿,粘液 ②粘膠

glucosinolate芥子油苷

thioglycoside硫代糖苷    thiol (mercaptan) 硫醇    thioctic acid硫辛酸

cyclitols環多醇      

myoinositol肌醇         myogen n.肌漿蛋白      myology n. 肌學

phytic acid 植酸

reductone 還原酮

deplete vt.①(部分或全部地)弄空,使空虛,耗盡…的精力(或資源等)

         ②[醫]減少…的體液,放去…的血

date 海棗，棗椰子

green pea豌豆         green bean青刀豆

raffinose棉籽糖

stachyose水蘇糖

verbascose毛蕊花糖

postmortem宰後

depolymerize解聚

thioglucoside硫葡糖苷

bouillon湯,羹(用肉,雞等煮成)

broth肉湯(微生物的營養培養基)

skim撇去,撇出(浮在上麵的油脂,泡沫等)         skim milk 脫脂乳

legume ①莢(果);②豆科植物 ③豆莢,豆

cruciferae十字花科

malt ①麥芽；②麥芽酒
，啤酒

  nitrile腈

goitrin甲狀腺腫素

goitrigenic甲狀腺腫病源

cauliflower花柳菜

brussel sprouts  抱子甘藍,北京牙菜

turnip蕪菁

rutabagas蕪菁甘藍

radish小蘿卜

cyanogenetic生氰,能產生氰化物的     cyanide氰化合物      cyanidin氰定

glycoside苷

maceration 浸透,泡軟,浸漬(作用)

manioc木薯

cassava木薯

saponin皂角苷,皂素,皂綴糖

steroid甾族化合物,類固醇

triterpenoid三萜係化合物

asparagus石刁柏,蘆筍,龍須菜

yam薯蕷,山藥,甘薯,山芋

alfalfa紫花苜蓿[美],苜蓿