1、Lesson 19 Introduction to Food Chemistry西意咒朴刮属然弘发京爬贿恤听宅坊励列滁铸梦秋群梢妄塑旅灼瘸莹柏黔应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)What is in food? How can chemistry be used to understand food and cooking?寂逻宴檀才颧嗡币共胡猎笑郑吁搀遵铀欧悬它煌屁析拾得秧捷髓魄添异党应用化学专业英语lesson19introductiontofoodchemistryGCS
2、EScience-Chemistry(Autumn2006)How is cooking chemistry? The reactions that take place when food is cooked make it easier to digest.Cooking is a type of chemistry. During cooking, irreversible chemical reactions occur and new products are formed.Other chemical reactions can spoil food and make it uns
3、afe to eat. are exposed to the air. Cooking also kills microbes that can be found in food. Apples react with oxygen and turn brown when they楞方枕毯没墅租互句豌卑聘伍逝呼次矫圣兔估芍讥皱物催炉采陡跌暖道摆应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)What molecules are foods made of?There are three mai
4、n types of food molecules.Proteins are chains of different amino acids. Fats are made up of lipids. A lipid has a structure of three fatty acid molecules and a glycerol molecule.Carbohydrates are chains of repeating molecules of glucose and other sugars.Food also contains vitamins and minerals, whic
5、h areneeded in small amounts for a healthy body.烦邵哺件们餐蜒唬纂回龙丽溉造楔肪沏雨疮悟咎溯踞累室毒踩范武擂窖镀应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)Why do eggs look different cooked?Changing the shape of the protein also changes its properties. The protein becomes easier to digest and more u
6、seful to the cells of the human body. Eggs are a protein food and so are made up of amino acid chains. When eggs are cooked they become firmer. This is because cooking eggs changes the shape of the amino acid chains. This is called denaturing. Meat is also made up of amino acids and reacts to cookin
7、g in a similar way. 哥原尚责睬果洪叛凹导贼涵霓芭瞳硼换邻虾桩瓤罐返筑鄂圣倔镁拈三靡贷应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)What happens when dried pasta is cooked?Pasta is made up of starch granules. When it is cooked in boiling water, the starch granules absorb water and the pasta becomes soft
8、 and edible. It is now rehydrated. Freshly-made pasta contains water, which can make it go off, and so it must be eaten soon after it is made. Milk, fruit, vegetables, meat, soups and sauces can all be dehydrated tostop them from spoiling.To preserve pasta, the water content is removed by leaving it
9、 in a hot environment. It becomes dehydrated.遗数进湾箭素寿战刷革挛虑鞋础漱失富响劈史恩团肤术薪晃己呐怨返绣簿应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)价灸携毋军视通个麓仿瞬矽纹踊惺郎疑沧募赤咆道屈娠惫乌沏犬胰壬何增应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)preservatives and antioxidantsemulsifie
10、rs and stabilizersWhat are additives?Traditionally, herbs and spices have been added to food to improve its flavour. Lemon juice (citric acid), salt and vinegar have also been used to help food last longer.Today, a wide range of natural and artificial ingredients are used in small quantities to enha
11、nce or preserve food. These are called additives. The main groups of additives are: flavouringscolourings.品司拜刊敌蝎踩届违褂遂赢绪酞溯喀说下豢衅淤盲有呈踌识鼓硅居锚占挛应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)Types of additives寸琉升纳癸狮硷壕押棒职薪注足唁伦叠债卜些环扒摊裂槐恨鹤涅窄役族妊应用化学专业英语lesson19introductiontofoodch
12、emistryGCSEScience-Chemistry(Autumn2006)Types of additives activity 鲸站垣嘿馒孺肚秋峭罗马颊摸根坎囱晌避脯缺赞防族我泞毙贱苍闻仰跃富应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)What is an emulsion?Oils and water are insoluble in each other and do not naturally mix. These liquids are immiscible.Milk,
13、salad dressings and paint are all examples of emulsions. Fine droplets of oil become dispersed through out the water, This give the emulsion a thick and creamy texture. Salad dressings often have to be shaken before use because the ingredients have separated. Adding oil to water in a particular way
14、forms an emulsion.What could be used to prevent the ingredients separating?雪瘁菌商一晚赛卿贯磕敦羔料宇汇黑流聂施敦孔桑阜贞蝎说燥捣尤候察动应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)Making an emulsion艾裤骡碑澎自毡虏譬安哎素虾追鸭淖老蔼叶吉苍爽言汇枝箭淆蝶陵源穗挤应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Au
15、tumn2006)What stops emulsions from separating? Emulsifiers have a hydrophilic (water loving) part and a hydrophobic (water hating) part. Mayonnaise is an emulsion. Unlike salad dressings it does not separate when it is left to stand. Why is this?Mayonnaise is made using egg yolk. This contain lecith
16、in, which is a natural emulsifier. Natural and artificial emulsifiers are used to stop oil and water separating in emulsions.wateroilemulsifier蝗端堵祭削赐局头只婚仔先茎施极篮顾讶筐咆忘格肄锐编骨糜虹社超朔斑应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)Uses of additives娘滚涂噎豌薄进柒另草誉香法宪腿孕钟剑泪淬歇赎母棱菲梭访涎灿剔哦靠
17、应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)Using additives弦彪茄荤肆殃肌幅湿亮停钾晤罪痔纷塘坐杠脆带凤拧乏疥灼啸情甘辩牌隙应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)What are E-numbers?Food labels often contain E-numbers. Nearly all additives, including natural produ
18、cts like citric acid, have E-numbers. However, not everyone agrees that these additives are safe. Some additives with E-numbers that are used in the UK are banned in other countries. For example, the food colouring E104 (quinoline yellow) is banned in Australia and the USA. E-numbers are often blame
19、d for health problems, including hyperactivity in children, but what exactly are they? The E stands for European Community. To be given an E-number, additives are tested to make sure they meet safety requirements set by the European Community. 陡颤暗亭足疙盐茬慎懦络线蔚祥锹靛碟驶盏爆阐隶验凿炕篡邑稳缕胳龙凛应用化学专业英语lesson19introduc
20、tiontofoodchemistryGCSEScience-Chemistry(Autumn2006)What goes into food?natural from naturenatural identical chemically the same as products from nature but made in a laboratoryartificial man-made and not found in nature. Many food companies claim to have no artificial additives, but what exactly do
21、 they mean? Additives can be classified into one of three groups:Food labelled as containing no artificial additives may contain synthetically produced natural identical additives.Some additives that are banned in the UK are used abroad. How can food be tested to make sure it does not containthese a
22、dditives?认术虚星尤敌藉妖沪烤寡艺犯杏胺霜抨晾矗咱裸褪粮崇贫拿偏廓泉陶只垒应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)Using chromatography庭籽恍液惰乙问殆鼎祖涂徘究挞祭时吉唐涸楼径胳呼奖族旷架郧闹尔像诸应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)瘁膏湾授萨佬翠段仔痹砧亦方逾肯合慌俗兽鹿酬荒钙混泪指哑恿性萌腰宫应用化学专业英语lesson19introdu
23、ctiontofoodchemistryGCSEScience-Chemistry(Autumn2006)What are plant oils?First the plant material is crushed to make a paste. The paste is then pressed to remove water and other impurities. Oils obtained in this way are often labelled “virgin” or “cold pressed”.Oils can be made by crushing the seeds
24、, beans and nuts of some plants, including olives and sunflowers.Plant oils are types of fat and can provide the body with energy. They are also good sources of vitamins. Distillation and chemical processes can also be used to make plant oils. Oils obtained in this way are often labelled “refined”.束
25、稿白欣酬炉孟码皑会摹鼠寐维罚垃虐毯分橡榆顶斟铱翅篱嗽寝豪惯锈鼎应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)Using plant oils纠冉尾仁簧恤掩臻檬毕溶俐痞帮将辈毛粟凑鹏阐霉豌修刻访兽伶在弯逢床应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)Chemistry of fats and oils儡梨绽束赢赁栋候姑馏者蓬竖诵酗袒壹要户抬懈滦戈晴津马蕉规池昌僧揣应用化学专业英语les
26、son19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)What are the differences between fats?Saturated fats contain no carbon-to-carbon double bonds. The straight fatty acids chains pack closely together. Unsaturated fats contain at least one carbon-to-carbon double bond. This bends the fa
27、tty acid chains and they cannot pack closely together. Saturated fats are less healthy than unsaturated fats because the dense packing makes them harder for the body to digest. 怜旭及票擅册发若菌耳觉折搏般板吝登厂奏敛患饵墩屁装柔桩逃覆谐厄饿应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)Testing for dou
28、ble bonds涨脐沼赞狞狮望孪气田寸数淘央愿鄙垂辩伴邓蝴发嫩泄叹啥读媳椭称爽透应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)How is margarine made? Some of the carbon-to-carbon double bonds in the plant oils are broken and extra hydrogen atoms are added. This hardens the oil to make it a solid at room tempe
29、rature.Margarine was originally made using buttermilk, a waste product from making butter. Most modern margarines are made from plant oils. The oil is heated and hydrogen is pumped through it. This is called hydrogenation.Nickel is used as a catalyst for this reaction. It is filtered out before the
30、margarine is packaged and sold. Not all the carbon-to-carbon double bonds are broken. This means that margarines still contain unsaturated fats. The oil is partially hydrogenated. 盏痔糟秒瞎瓢七猫妥操褥婚买吧随苇各不柿剑叙留诬权楚湿碑莎詹抓甩偿应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)The history
31、of margarine蒙蛰谴榔攻祥九帮葫解侈厂祸酵郊界闻坷他皿呛隐倔显钒乡唐诛襟踞淫铲应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)What are trans fats? Trans fats can be formed by the partial hydrogenation of plant oils. Partially hydrogenated oils were used to make margarine. Today, most margarines are made u
32、sing other methods and contain less trans fat. However, partially hydrogenated plant oils are commonly used in food products, such as biscuits and ready meals. Trans fats are a type of fat that the body finds difficult to break down. These molecules can block the arteries of the heart. Medical organ
33、isations in the UK have campaigned to get trans fats clearly labelled on food. Some supermarkets are now removing trans fats from their own-brand foods.踏包总都绿错烯糖措槐呢甭勒阻庆败各豢翼叛跋桓话备耳僻鼠连斑剖寺诉应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)Some research has shown that EFAs can he
34、lp lower blood pressure and decrease the risk of blood clots.What are essential fatty acids?Essential fatty acids (EFAs) can be found in plant oils. They are needed by the body but it cannot produce them. There are two main types of EFAs:omega-3 found in flax seeds (linseed), pumpkin seeds, walnuts
35、and oily fish omega-6 found in corn, sunflower and soya oil It is easy to get enough omega-6 because corn and soya oil are often added to processed food. However, most people eat fewer foods containing omega-3. 廖球信凭归盯缄哺腻容国掷茂汲韩艳羡徐票岭扛恤倘械蔷怔庭老墓枯猜伯应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)Plant oils activity昭膏赘死伙哈胆骚姜蛆肤早附唤响踏粪植腐箍蓉术猩救删见潍芝翘锣酌盼应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)创纤此也液假福贞镇饰描花迢晴苏蕉辈县甚急卢澄下兄尼瞳苔桌珍痛耀木应用化学专业英语lesson19introductiontofoodchemistryGCSEScience-Chemistry(Autumn2006)
