食品專業(yè)英語 LESSON 3 Lipids And Their Uses In Food

1、食品專業(yè)英語 LESSON 3 Lipids And Their Uses In FoodThe chemistry of food lipids is complicated because they are diverse types of compounds that undergo many interactions with other components of a food. Many important and well-understood chemical changes that occur in an isolated lipid may be modified by

2、such factors as location of the lipid in a tissue system, the presence or absence of water, and the imposition of such stresses as heat or radiation. Metals, both in the free state as irons and as components of organ metallic compounds, affect the chemistry of lipids, especially in oxidation reactio

3、ns. Non-lipid components of a food may interact with lipids and this can produce change in food quality.DEFINITION AND CLASSIFICATION OF LIPIDSThe consumer and the processor of foods utilize substances from the nutrients group known as fats and oils. Fats and oils represent the most prevalent single

4、 category of a series of compounds known as lipids.The word lipid is defined in Websters unabridged dictionary as any of a group substance that sparingly soluble in ether; chloroform, or other solvents for fats but are only sparingly soluble in water, that with proteins and carbohydrates constitute

5、the and principal structural components of living cells, and related and derived compounds, and sometimes steroids and carotenoids, This definition describes a broad group of substances that have some properties in common and have some compositional similarities.A classification of lipids proposed b

6、y Bloor contains the following elements, which are useful in第三課 脂類化合物及其在食品中的用途食用脂類的組成和化學性質是復雜的，因為食用脂類包括了多種類型的化合物，這些化合物 受到了與食物中其它成份的多種相互作用。單離類脂中所發(fā)生的重要而確定的化學反響可能 會由于某些因素而使之改變，例如該類脂在細胞組織體系中所處的位置，水分的存在或不存 在，類脂經受過度熱或輻射方面的處理。金屬，不管象離子那樣呈游離態(tài)的，還是作為有機 金屬化合物結構成分的，都會影響脂類的化學行為，尤其是氧化作用。食物的非脂成分也可 能與脂類互相作用，導致食品品質的變

7、化。脂類化合物的定義和分類食品消費者和食品加工者利用了來自稱為“油脂”的營養(yǎng)素族中的多種物質。油脂是一 系列稱為脂類化合物中的最普遍的一類?！爸悺?一詞在未刪略的韋氏詞典中的定義是“任 何一族通常溶于乙醴、氯仿和其它油脂溶劑而僅微容與水且與蛋白質、碳水化合物一起構成 活細胞重要結構成分的物質及其有關的衍生化合物，有時還包括類固醇和類胡蘿卜素?！边@ 一定義描述了很廣的一大類具有某些共同性質和某些共同結構的物質。布盧爾提出的脂類分類法包括的以下便于區(qū)分許多脂類物質的主要方面：L簡單脂類（中間脂類）一一脂肪酸和醇類形成的脂。a,油脂：脂肪酸和甘油形成的脂。b.蠟：脂肪酸與非甘油的其它醇類所形成的脂

8、。2.復合脂類一一除脂肪酸與醇形成的脂外，還含有其它基團的化合物。a.磷脂：含有脂肪酸、磷酸和通常含氮的其它基團的脂。b.腦甘脂：含有假設干個脂肪酸、一個碳水化合物和一個含氮局部，但不含磷酸的化合物。c.其它復合脂：神經鞘類脂和腦硫脂。3用亍生脂類一一由中性脂類或復合脂類衍生出來具有脂類一般性質的物質。a.脂肪酸。b.醇類：通常為直鏈高級醇和固醇。c.燃類。食物中可能含有任何一種或全部上述的脂類物質，但最主要的是油脂（即甘油脂）和磷 脂。“油脂” 一詞適用一切甘油三酸脂，而不管它們在常溫下是固態(tài)或液態(tài)。液態(tài)油脂通常 稱為油類。豆油、棉籽油、橄欖油等都是來自植物的油。豬油和牛、羊脂是典型來自動物

9、的 固態(tài)油脂。不過，來源于馬的油脂在室溫下是液態(tài)的，故稱之為馬油。油脂也可以根據它們的屬性來分類。五個公認的油脂族為：乳脂屬、月桂酸屬、油酸- 亞油酸屬、亞麻酸屬、動物儲藏脂肪屬。乳脂屬主要由反芻動物乳汁中的油脂構成，尤以乳牛乳為多，不過在某些地區(qū)，可能以 水牛、綿羊和山羊乳為多。乳脂的特征是含有3040%油酸、2532%棕桐酸和1015%硬 脂酸。一般還含有相當多的C4-C12酸，而且是唯一含有丁酸的常用油脂，丁酸含量因油 脂來源不同而異，范圍約在315%之間。乳脂組成特別容易因動物食料所引起的變化而受 到影響。月桂酸屬油脂的特征是含有高比例(4050%)的月桂酸(C12)和C8、CIO、C

10、14、C16 和C18酸。它的不飽和酸的含量非常低，這是它貯藏限期很常的原因。由于這類油脂的碳鏈 短，所以其熔點往往較低。應用最廣泛的這一類油脂來源于椰子、油棕子和巴巴蘇棕桐果。油酸-亞麻酸屬油脂是數(shù)量豐富、品種最多、僅來源植物的油脂。這些油脂含飽和脂肪 酸通常低于20%,且以油酸和亞油酸為主。這類油脂一般從棉籽、玉米胚芽、芝麻、花生米、 葵花籽、紅花籽以及橄欖和油棕的種皮(即果肉)中取得的。亞麻酸屬油脂中含有大量亞麻酸，不過也可能含有較多的油酸和亞油酸。此屬中最主要 的食用油是大豆油其它還有麥胚油、大麻籽油、紫蘇子油、亞麻子油等。亞麻酸含量最高是 產生干性油特性的原因，尤其是亞麻酸含量高達5

11、0%的亞麻子油。動物脂肪屬主要由豬油、牛脂和羊脂組成。它們以含3040%的C16和C18飽和脂肪酸和 高達60%的油脂、亞油酸為特征動物脂肪的熔點比擬高，局部原因是它們的飽和脂肪酸含量 和甘油脂類型所致。就后一點而論，飽和脂肪酸含量高達60%的植物種子油脂中通常幾乎不 含三飽和脂肪酸甘油脂，而飽和脂肪酸含量為55%的牛羊脂，卻含有高達26%的甘油飽和三 酸脂。甘油三酸脂組成上的不同影響到油脂的物理性質，進而對所給油脂的使用方法產生很 大的影響。脂類在食物中的作用和用途油脂是最集中的食物能量源。每克油脂可提供9kal熱量，這約為同量蛋白質或碳水化 合物提供熱能的一倍。油脂是脂溶性維生素的載體，它

12、賦予食物以風味和可口性，并給人飯 后以飽感。以甘油三酸脂、磷脂、膽固醇和膽固醇脂形式存在的脂類對生物膜和細胞壁的結構、組 成和滲透性起著重要的作用。它們還有在植物果實、種子中和動物體內貯藏能量的效用。脂 類是脂肪組織的主要成分。脂肪組織是機體的保溫層，對內臟器官油防震作用，是機體體形 的構建物。油脂作為炸用脂或冷卻用油使用時，它起著可控的熱交換介質的作用，同時也油色、香、 味的貢獻。作為起酥油，它通過潤滑作用和某種能力（改變其它組分見的相互作用）的結合 賦予焙烤食品以疏松柔軟的品質。作為色拉油，它的風味物質的載體，賦予食物以口感，當 與其它組分一起乳化形成粘性可倒出的調味品或多脂半固態(tài)的所謂蛋

13、黃醬或色品。糖果種常 用專門挑選或制作的油脂，特別是涂層、涂膜劑使用。這類專用脂肪必須在溫度為體溫附近 時有狹窄融化區(qū)。其它脂類物質，如甘油單酸酯和甘油二酸酯以及某些磷脂（如卵磷脂），用作乳化劑有 很好的效果。甘油單酸和甘油二酸在焙烤制品中賦予制品以松脆的性能，并起著抗老化劑的 作用。卵磷脂可以用著糖果的脫模劑，可用來控制巧克力涂衣糖果的外表出油反霜，也可作 人造奶油加熱時的防濺劑使用。我們可以獲得多種形式的油脂。奶油、烹飪油、人造奶油、色拉油和起酥油基本上是全 脂的形式。色拉調味品和蛋黃醬是由高比例的油脂構成的。我們攝入的油脂不僅包括明顯的 油脂資源，也包括來自那些不顯眼的油脂資源，如谷類、

14、干酪、蛋黃、魚類、水果類、豆類、 肉類、乳類、堅果類、蔬菜類等等。后一組約占攝入油脂重量的60%左右。色拉油和烹飪油由棉籽油、大豆油、玉米油、花生油、紅花油、橄欖油或葵花籽油制成。 這些油通常要經精煉、脫色、脫臭處理。有些油經輕度氫化處理可獲得特殊的性質，并且增 強風味的穩(wěn)定性。人造奶油主要用作餐用涂抹油，也有一定數(shù)量用作烹飪油.人造奶油由精制的油脂和其 他配料如乳固體、鹽香料和維生素A、D等經適當調配而制成。起脂肪含量至少要有80%o制造人造奶油主要是用植物油，不過也用一點動物脂肪。制造人造奶油的油脂可以是單一的 氫化脂或氫化脂的混合物，也可以是氫化脂和未氫化油的混合物。增加多不飽和脂的用量

15、可 制成專用的人造奶油。這類專用的人造奶油已經根據醫(yī)學研究的要求生產出來了。醫(yī)學研究 說明，這種特殊形式的人造奶油可能有好處，尤其對于動脈粥樣硬化病傾向的人更有益。商品起酥油是半固體的可塑性脂肪，制造時可加乳化劑或不加乳化劑?？伤苄裕唇浭?壓練的性能）是商品起酥油區(qū)別與其他油脂的主要特征。早先起酥油的成份是豬油或牛羊脂, 而現(xiàn)在那么用各種植物油和各種混合油脂，以形成烘烤所要求的特殊性質。棉籽油、大豆油、 豬油、牛羊脂是用作起酥油的主要油脂?？墒?，沒有哪種天然的油脂具備所有我們所要求的 特性。奶油經稀奶油經攪制得到，是一種含8081%乳糖（以可塑狀態(tài)出現(xiàn)）的油包水型乳膠。 奶油中其它成分的數(shù)量

16、都較少，包括酪蛋白、乳糖、磷脂、膽固醇和鈣鹽，通常還有13% 的氯化鈉。奶油中含量少而不定的維生素A、E和D,此外還有由丁二酮、內酯、丁酸和乳 酸組成的風味物質。從可可豆來的可可脂是糖果制造業(yè)上比擬適用的脂肪。但可可脂常常供不應求，而且價格昂 貴，因此人們?yōu)閷ふ液线m的增補料以替代可可脂作出了許多的努力。食用脂類的命名法脂類命名法中包括來的術語范圍較廣，這是由于商業(yè)上使用的是俗名、科技文獻中使用的是系統(tǒng)命名法，而為了表示一些帶有復雜科學名稱的物質又用合適的速記名稱的緣故。國際純粹化學和應用化學聯(lián)合會-國際生物化學聯(lián)合會（IUPAC-IUB）的生物化學命名法 委員會已經提出了一種適合于描述甘油衍生

17、物立體化學的命名法。這一命名法采取了費舍爾 垂直碳鏈投影法，在垂直碳鏈上仲碳羥基列在左邊，頂端碳原子即為C-1?？s寫術語為“sn” （按立體定向編號）將該編號系統(tǒng)與不反映立體信息的傳統(tǒng)命名系統(tǒng)區(qū)分開來。此速寫術語 直接插在表示甘油之詞的前面，并用連綴號與之分開。甘油三酸酯按甘油的衍生物命名，其取代基確實定位置可按立體定向編號（sn）系統(tǒng)表 出。這樣，含有棕柳酸（C-1）、油酸（C-2）和硬脂酸（C-3）的甘油三酸脂的命名便是：sn- 甘油基2油酸酯3硬脂酸酯。通常略去甘油基一詞，而稱該甘油三酸酯為棕檀酰-油酰硬脂 酰甘油酯。含有二分子棕桐酸和一分子硬脂酸的二酸式甘油三酸脂可命名為二棕桐酰硬脂酰

18、 甘油酯或硬脂酰二棕桐酰甘油酯。食品中最重要的磷脂是那些含有一分子（在甘油分子上某一位置上酯化的）磷酸的磷脂。 此磷酸本身又與另一局部如膽堿、乙醇胺或肌醇分子酯化結合。磷酸甘油酯的命名法和甘油 三酸酯的命名法相同。譬如，商業(yè)上稱為“卵磷脂”的物質應寫成1, 2.二?；?sn-甘油基3 磷酸膽堿。卵磷脂是膽堿磷酸甘油酯，也稱為磷脂酰膽堿或最好稱為3-sn.磷脂酰膽堿。磷 脂酰一詞用來表示除膽堿以外的那一局部卵磷脂分子。類似這樣的名稱有磷脂酰乙醇胺（腦 磷脂）、磷脂酰肌醇和其它物質。脂類中的脂肪酸通常是飽和的或不飽和的脂族化合物，少數(shù)情況下還可能有支鏈。脂肪酸的命名需要系統(tǒng)命名法和常遇俗名兩方面的

19、知識。根據日內瓦會議所采納的系統(tǒng)，脂肪酸是按照它的母體煌來命名的。當提到飽和脂肪酸時, 便將煌類名稱的最后字母“e”用“oic”代替。這樣，hexadecanoic acid十六烷燒（通常稱 為棕稠酸）即是與16c的煌hexadecane （十六烷）相應的脂肪酸。后綴“ene”用來表示含 雙鍵的煌類。據此，有一個雙鍵的16c酸即為hexadecanenoic acid十六稀酸，俗名稱為棕樞I 油酸。脂肪酸分子內有多于一個雙鍵時，其后綴為“-dienoic”（雙?。?、“trienoic（三?。?或其它恰當表示雙鍵數(shù)目的后綴。Lesson 3 Lipids and Their Uses in Fo

20、odimposition n.征稅;稅,稅款;負擔增加，強迫接受，過分的要求欺詐stress n.vt.壓力，重壓，緊迫，緊張重要，重點,強調應力unabridged未刪節(jié)的，未節(jié)略的,完整的ether醒乙醛 chloroform氯仿，三氯甲烷sparing a.節(jié)約的，吝惜的,愛惜的貧乏的,少量的 fat脂肪，肥肉多脂肪的，肥的 carotenoid類胡蘿卜素，類葉紅素 alcohol醇,醇元乙醇，酒精 glycerol甘油,丙三醇 phospholipid 磷脂cerebrosides 腦昔酯類cerebellum 小腦sphingolipid （神經）鞘類脂物sphingomyelin

21、（神經）鞘髓磷脂sulfolipid 硫脂glyceride甘油酯 ambient a.周圍的，包圍著的lard熟豬油用肥肉餡填滿脂肪的tallow （煉制牛，羊）油脂tallow oil （動物）脂油tallowy脂肪的，油脂的，油哈味,哈敗的（指油脂） lauric acid月桂酸，十二（烷）酸 oleic油酸的 oleic-linoleic acid 油酸-亞油酸linoleic acid(=linolic acid)亞油酸，十八(碳)二烯9,12.酸，罌酸 linolein亞油精，甘油三亞油酸酯 linolenic acid亞麻酸，十八（碳）三烯-9,12,15-酸 depot倉庫，堆

22、?；胤ň浦谐恋韉epot-fat儲存脂肪 buffalo 水牛 distinguishing the many lipid substances:1.Simple lipids (neutral lipids)-esters of fatty acids with alcohols.Fats: esters of fatty acids with glycerol.Waxes; esters of fatty acids with alcohols other than glycerol.Compound lipids-compounds containing other groups in

23、 addition ester of a fatty acid with an alcohol.a.Phospholipids (phosphatides): esters containing fatty acids, phosphoric acid and other groups usually containing nitrogen.b.Cerebrosides (phosphatides); compounds containing fatty acids, a carbohydrate and a nitrogen moiety, but no phosphoric acidc.O

24、ther compound lipids: sphingolipids: sphingolipids and sulfolipids.Derived lipids-substances derived from neutral lipids or compound lipids and having general properties of lipids.palmitic acid棕桐酸，十六（烷）酸,軟脂酸 stearic acid硬脂酸，十八（碳）（烷）酸 butyric丁酸的，酪酸的丁酸（發(fā)酵）菌coconut 椰子coco椰子樹才耶子babassu nut （巴西）巴巴蘇棕桐（堅）果

25、coquilla nut 棕桐果sesame芝麻 sunflower向日葵 safflower 紅花pulp漿,果漿打漿 germ n.微生物，細菌，病菌生呦芽,胚原基萌牙，起源vi.（喻）萌芽，發(fā)生hempseed oil大麻籽油 perilla oil紫蘇子油 linseed oil亞麻子油 bovine牛，牛的 ovine綿羊的，似綿羊的palatability可口性，味道，味道質量test 口味質量評定palatable可口的，味美的,好吃的.喻雁意的，合趣味的satiety n.飽足，過飽,厭膩satiete vt,使充分滿足,使飽享,使過飽生厭,使厭膩 triglyceride甘油

26、三酸酯 cholesterol膽雷醇,膽固醇 permeability滲透性，穿透性adipose a.脂肪質的，脂肪多的，肥胖的n.動物脂肪,脂細胞，脂肪 fry油炸食品油炸,油煎，油炒 魚苗，小魚shortening起酥油 油酥 縮短 shorten油酥面團 impart vt.把分給給予,傳遞告訴，透露 emulsify 乳化viscous粘的，有粘性的,粘滯的 pourable dressing可倒出的調味品 dressing（畜，禽，魚）剝皮（或去毛、鱗）,去內臟及分割加工 烤禽前腹內填餡（面粉）過篩加上調味品（液），佐料修整,包裝margarine人造奶油 mayonnaise蛋黃

27、醬蛋黃醬拌的涼菜 enrobe （糖果冰淇淋等慢掛巧克力漿或其他涂漿.melting溶化熔煉，煉出（脂油）.溶解，融化.細致的，軟的，柔和的/炎的（口味，風味） short短的.酥的,松脆的.（飲料等）濃的,強的復次貨，次粉，細糠,二級麥皮 diglyceride甘油二酸酯 lecithin卵磷脂 stale干硬的，不新鮮的,發(fā)霉的，走了氣的,走味的（煙，酒等）,陳腐的 spatter vt.濺，濺污，灑污蔑，中傷vi.滴下，飛濺n.濺，灑，滴落，飛濺（雨等的）淅瀝聲,飛濺聲潑濺的污跡少量，點滴antispatter 防濺antispattering agent 防濺齊Ucereal禾谷類，五

28、谷，糧谷，谷物的，谷類作物的，谷類制成的.谷類食物.谷物制的食品肉餡中面粉或米粉的加料bleach漂白齊小漂白度，脫色 deodorize vt.除去臭味,防止的臭味deodorizer除臭劑，解臭劑,防臭劑hydrogenated fat氫化脂,硬化油hydrogenate氫化，還原atherosclerotic動脈粥樣硬化的atherosclerosis動脈粥樣硬化 emulsifier乳化劑乳化器 emulsion乳濁液，乳膠，乳劑香腸的細斬拌肉餡 churning奶油攪拌，攪乳 一次生產奶油的批量，一次提制的奶油cream稀奶油,（鮮）奶油，稀奶油做的,乳漿，利口酒 casein酪蛋白

29、，干酪素 diacetyl雙乙酰，丁二酮lactone 內酯extender補充劑，增補劑 shorthand 速記stereochemistry 立體化學vertical垂直的 precede vt.先于,位于之前;比優(yōu)先,（地位等）高于在前加上，為加上引言.Vi.在前面，居前，領先signify vt.表示，說明，意味預示vi.要緊，有重要性 美俚冒充內行hyphen n.連字號（即-）vt.用連字號連接 palmito-oleo-stearin棕桐酰-油酰-硬脂酰（甘油酯） palmitate棕桐酸酯 dipalmitostearin二棕桐酰硬脂酰（甘油酯） stearodipalmit

30、in硬脂酰二棕桐酰（甘油酯） choline 膽堿ethanolamine乙醇胺;氨基乙醇 inositol肌醇，環(huán)己六醇 phosphatidyl 磷脂酰aliphatic脂肪族的，屬于開鏈碳化合物hexadecanoic acid 十六(烷)酸(=palmitic acid) hexadecane 十六烷hexadecenoic acid 十六烯酸palmitoleic acid 棕桐油酸convention n.（政治，宗教，政黨等的）會議，大會，全國性大會.召集,集會，公約，協(xié)定慣例，習俗，常規(guī).Presence or absenceExistence and inexistenceF

31、: many important and well-understood chemical changes that occur in an isolated lipid may be modified by such factors as location of the lipid in a tissue system, the presence or absence of water, and the imposition of such stresses as heat or radiation.In turn依此地（兩者常用于，實驗試劑加 入、作用方式。Respectively :各自

32、地F： Differences in triglyceride composition affect physical properties, and this Differences in triglyceride composition affect physical properties, and this in turn greatly influences the use to which a given fat is put.F： The simple sugars (monosaccharidesO are basically aliphatic polyhydroxy alde

33、hydes andketones: HOCH2- (CHOH) n-CHO and HOCH2- (CHOOH) n-l-C-OCh2OH, called “aldoses” and “ ketoses, “ respectively.Concentrate: 富集Condense in: 濃集于F: Fats and oils the most concentrated source or food energy.F: D-glucose and D-fructose, are condensing in such a way that their reactive functions ar

34、e lost to form the disaccharide no reducing sugar, sucrose.代替Substitute for:Instead of:ReplaceF: Cocoa butter, derived from the cocoa bean, is a fat preferred for confectionary uses it is usually in insufficient supply and is costly, so that many efforts have been made to substitute for it or to fin

35、d suitable extenders.F: The final in the name of a hydrocarbon is replaced by ”-oicEnglish experienceSOME GOOD SENTENCES：linseed oil contains up to 50% linolenic acid, （up to 意為到達）They perform a function of energy storage in seeds, fruits of plants and animals.（起的功能）This definition describes a broad

36、 group of substances that have some properties incommon and have some compositional similarities, （group 作名詞時,常作“基團、族”解）What we eat as well as how much we eat determine our nutrition status to animportant extent, and influenced by a diversity of external and internal factors.（彳艮大程度上）Margarines, used

37、 mostly as table spreads and to some extent as cooking fats, are prepared by blending suitably prepared fats and oils with othe門ngredients.（某種程度上）a.Fatty acidsb.Alcohols: usually normal chain higher alcohols and sterolsc.HydrocarbonsFoods may contain any or all of these substances but those of great

38、est concern are the fats or glycosides and the phosphatides. The term fatis applicable to all triglycerides regardless of whether they are normally nonliquid or liquid at ambient temperatures. Liquid fats are commonly referred to as oils. Such oils as soybean oil, cottonseed oil, and olive oil are o

39、f plant origin, lard and tallow are examples of nonliquid fats from animals, yet fat from the horse is liquid at ambient temperatures and is referred to as horse oil.Fats and oils also can be classed according to group characteristics/ Five well-recognized groups are the milkfat group, the lauric ac

40、id group, the oleiclinoleic acid group, the linolenic acid group, and the animal depot-fats group.The milkfat group pertains essentially to the milk of ruminants and especially to that of the cow, although in certain areas milk of the water buffalo of sheep and goats may be prominent. , Milk fats ar

41、e characterized by 30-40% oleic, 25-32% palmitic, and 10-15% stearic acids. They generally have substantial amounts of c4-cl2 acids and are the only commonly used fats to contain butyric acid, which composition is particularly susceptible to variation as a consequence of the animals本句中，defineas意為給 下

42、定義”或“將 定義為“。That in general are soluble in ether-* in water 是定語從句,彳修飾 a group of substances; that with proteins and carbohydrates constitute the principal structural components of living cells 也是定語從句， 也修 飾 a group of substanceso 作為 as 的賓語，any of a group of substances, related and derived compounds,

43、steroids and carotenoids 三者是并歹!的。fats and oil為主句主語,as frying fats or cooling oils的as短語做主語的補語, where引導的狀語從句修飾謂語are used,此從句中有兩個并列的不定式動詞to provide as 和 to contribute.as shortenings為目的的狀語，主語they指上文中的fats and oils, through帶出的 介詞短語（至句末）修飾謂語important的方式狀語。Lubrication和ability為介詞of的并 列賓語，構成的介詞短語修飾a combinat

44、ion; To alterother constituents為不定式短語，作 an ability 的定語；among other constituents 是介詞短語，作定語，修飾 interaction.diet.The lauric acid group is characterized by a high proportion (40-50%)of lauric acid (cl2) and lesser amounts of c8, clO, cl4, cl6, and cl8 acids. the unsaturated acid content is very low and

45、this contributes to extremely good shelf life. These fats generally melt at low temperatures because of the short carbon chains present. The most widely used fats of this group are from the coconut, seeds of the oil palm, and the babassu or the coquilla nut.The oleic-linole9oc acid group, the larges

46、t and most varied group, contains only fats and oils of vegetable origin. These fats usually contain less than 20% saturated fatty acids, with oleic and linoleic acids being dominant. Such fats are commonly derived from seeds of cotton, corn, sesame, peanut, sunflower, and safflower and the seed coa

47、t or fruit pulp of the olive and the oil palm.Fats of the linolenic acid group contain high levels oleic and linoleic acid. The most although they also may contain high levels of oleic and linoleic acid. The most important food oil of this group is that from the soybean. Other is wheat germ oil, hem

48、pseed oil. Perilla oil, and linseed oil. The high linolenic acid content contributes to the during oil characteristic, especially of linseed oil which contains up to 50% linolenic acid.The animal fat group consists mainly of lard from the pig and tallows from bovine and ovine sources; these are char

49、acterized by 30-40% cl6 and CIS-saturated fatty acids and up to 60% oleic and linoleic acids. The melting points of these fats are types of glycerides present, with respect to the latter point, seed fats with as much as 60%saturated fatty acids often contain negligible may contain up to 26%trisatura

50、ted glycerides. Differences in triglyceride composition affect physical properties, and this in turn greatly influences the use to which a given fat is put.ROLE AND USE OF LIPIDS IN FOODSFats and oils the most concentrated source or food energy. Provide 9 kcal of energy per gram, which is approximat

51、ely, double the energy provided they contribute to food flavor and palatability as well as to the feeling satiety after eating.Lipids, cholesterol, and cholesterol esters are important to the structure, composition, and permeable membranes and cell walls. They perform a function of energy storage in

52、 seeds, fruits of plants and animals. Lipids are major component of adipose tissue internal organs, and as a contributor to body shape.Fats and oils are used as frying fats or cooling oils where their role is to provide a controlled heat-exchange medium as well as to contribute to color and flavor.A

53、s shortenings, they impart as: “short or tender quality to baked goods through a combination of lubrication and an ability to alter interaction among other constituents.As salad oils, they contribute to mouth feel and as carrier for flavors, and when emulsified with other ingredients they perform th

54、e same functions in the form of viscous pour able dressing or semisolid fatty foods know as mayonnaise or salad dressing. Margarines are used both for baking and cooking and as table spreads. Specially selected or manufactured fats are useful in confections, especially as enrobing or coating agents.

55、 These fats must have a short melting rang at body temperature.Other fatty materials, such as the mono-and diglycerides, and certain phosphlipids, such as lecithin, have useful roles as emulsifiers. Mono-and diglycerides contribute to shortening performance and act as staling inhibitors in bakery pr

56、oduces. Lecithin is used as a mold release agent in confections, to control fat bloom in chocolate candied, and as an antispattering agent in cooking margarines.Fats and oils are available in variety of forms. Butter; cooking oils margarines, salad oils, and shortenings are essentially all-lipid for

57、ms. Salad dressings and mayonnaise are composed of high proportions of fats or oils. Ingested and mayonnaise are composed of high proportions of fats or oils. Ingested fats and oils include not only those from obvious source but also those from invisible fat sources, such as cereals, cheese eggs, fi

58、sh, fruits, legumes, meat, milk nuts and vegetables. This latter group constitutes approximately 60% of the dietary fat.Salad and cooking oils are prepared from cottonseed oil, soybean oil. Corn oil peanut oil, safflower oil, olive m, or sunflower seed oil. These oils are usually refined, bleached,

59、and deodorized. Some oils may be lightly hydrogenated to provide special properties and to enhance flavor stability.Margarines, used mostly as table spreads and to some extent as cooking fats, are prepared by blending suitably prepared fats and oils with other ingredients, such as milk skids, salt,

60、flavoring materials, and vitamins a and d. The fat content must be at least 80%. Vegetable oils are used predominantly for manufacture of marine although some animal fats are used. The fats may be single hydrogenated fats, mixtures of hydrogenated fats, or blends of hydrogenated fats and unhydrogena