School chemistry revision 14-16 GCSE level chemistry notes: Some aspects of 'domestic' chemistry - cooking

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15. Vitamins, drugs - analgesic medicines, food additives & some cooking chemistry!

Doc Brown's GCSE/IGCSE/O Level KS4 science-CHEMISTRY Revision Notes

What are vitamins? Drugs-medicines we regularly use! What are food additives used for? How safe are colourings, flavourings preservatives and sweeteners? What are E numbers? What is intelligent packaging and active packaging of food? Aspects of cooking chemistry.

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15a. Vitamins

15b. Drugs e.g. in analgesic medicines

15c. Food Additives, Intelligent Packaging and Active Packaging of Food

15d. A footnote on cooking chemistry !!

15. Vitamins, Drugs-analgesic medicines and Food Additives

15a. Vitamins

  • 15a Vitamins

  • What are vitamins?

  • Vitamins are particular essential molecules with particular roles in living systems which are NOT proteins, carbohydrates, fats or mineral salts.

    • If you have a good balanced diet, you shouldn't, in theory, require any extra dietary supplements.

    • However, to help avoid potential vitamin deficiency certain vitamins are added to particular foods such as bread, margarine, breakfast cereals, milk powder etc. to replace vitamins destroyed during food processing or to make good a natural deficiency.

  • One of the most important ones in any diet is Vitamin C or Ascorbic Acid. Its structure is related to 'simple' sugars but humans are one of the few mammals that are unable to synthesise vitamin C.

    • It is essential for healthy tissue and one of its functions is the removal of dangerously reactive chemical species called free radicals (see further on).

    • Vitamin C is present in fruit and vegetables but the amount is reduced by prolonged storage and cooking..

    • 250 years ago, as many as 2/3 of a ship's crew died from vitamin C deficiency causing scurvy. In 1747 it was decided to give sailors citrus fruits to recover from scurvy but wasn't until 200 years later that vitamin C was recognised.

    • In contrast to the other water-soluble vitamins, vitamin C has no clear cut role as a catalyst or part of an enzyme. It does, however, have a range of other important functions:

      • Collagen formation. Vitamin C in collagen formation which is found wherever tissues require strengthening, especially in tissues with a protective, connective, or structural function. Collagen is critical to the maintenance of bone and blood vessels and is essential in wound healing.

      • Antioxidant activity. Ascorbic acid can act as an antioxidant by donating electrons and hydrogen ions, and reacting with reactive oxygen species or free radicals.

      • Iron absorption. Vitamin C is important for the effective absorption of iron and reduces iron(III) Fe3+ to iron(II) Fe2+.

      • It helps in the synthesis of vital cell compounds. During times of physical and emotional stress, as well as during infection, there is increased production of oxygen radicals. Therefore there is increased reliance on vitamin C's activity as an antioxidant.

      • Vitamin C is vital for the function of the immune system, but the effectiveness of large doses of vitamin C in preventing and alleviating the symptoms of the common cold is still a matter of debate.

    • Two of the earliest signs of deficiency (prevention of collagen synthesis) relate to its roles in maintaining the integrity of blood vessels. The gums around the teeth bleed more easily, and the capillaries under the skin break spontaneously producing tiny haemorrhages. If you are short of vitamin C for say 20 days, scurvy can develop and is characterised by further haemorrhaging, muscles depletion, rough-brown-dry-scaly skin, deep bruising. Wounds fail to heal properly and bone fails to rebuild properly too and you are further likely to suffer from anaemia and infections.

    • Vitamin A1, A2 and the fat soluble vitamin D group are found in fish oils.

      • Lack of vitamin A can lead to eye disorders eg night blindness and corneal disease.

      • Vitamin D is required for the proper calcification of teeth and bones - still need the calcium too!

    • Vitamin E is found in some vegetable oils from seeds.

    • The B group of vitamins are mainly concerned with metabolism ie the utilization and release of energy from foods.

      • These vitamins are found in yeast and meat.

    • SO EAT your fruit and veg 'guys' (as well as a few crisps now and then!) AND keep your health and still pass those dreaded exams!!!!

    • For some examples read the section on food packaging labels further down the page in the food additives section.


15b Drugs e.g. in analgesic medicines

  • Drugs can be defined as an externally administered substances which modifies or affects chemical reactions in the body, usually for the bodies greater well-being. Poisons can be defined in the same way, but hopefully not intentionally and have undesired effects! A 'drug' is a specific molecule with a particular pharmacological or physiological action on an organism/animals chemistry and a medicine is the complete formulation of the means of administering the drug to a patient i.e. the method of delivery.

    • Analgesics are drugs used to reduce pain and are a type of anti-inflammatory agent.

    • The molecular structure of three well known analgesics are shown in the diagram below.

      • ASPIRIN formula C9H8O4

      • PARACETAMOL formula C8H9NO2

      • IBUPROFEN formula C13H18O2

    • All are used for 'headache' treatment, and hopefully using this website and others will help minimise their use!

The central hexagonal ring of 6 carbon atoms is called a 'benzene' or 'aromatic' ring. The 4th outer electron of carbon (group 4) is delocalised, so the expected 4th bond per C atom forms part of a 'communal' system (more on this at advanced level, but the covalence rule of 4 for carbon is not broken!, you have seen this situation before, check out graphite. You can show a benzene ring as a simple hexagon with a circle in it)

from + NaOH ==> + H2O

  • The modern pharmaceutical industry has its origins in herbal and other traditional medicine.

  • e.g. An extract of willow herb extract can be made from the leaves, bark and seeds of the willow tree. Amongst other ailments it was given to help curing feverish headaches and relief of pain in childbirth. When ingested the body hydrolyses and oxidises the naturally occurring 'precursor' molecule to form salicylic acid* which is the 'active' molecule in the body. in the 1890's the German chemist Hoffmann experimented with various chemical modifications of salicylic acid and found the best and chemically stable form was 'aspirin' (shown below). He tried the variations on his own father! who survived to provide valuable 'clinical trials' - hardly acceptable these days! * 'Oil of winter green' from certain plants is the methyl ester of salicylic acid and has similar 'medicinal effects'.

  • Aspirin (and the others shown) are not very soluble in water. Soluble aspirin is made by neutralising the carboxylic acid with the alkali sodium hydroxide to make the much more soluble sodium salt of the acid. The reaction, using skeletal formula, is shown in the diagram below the three analgesic drug structures.

  • New drugs and testing them:

  • It costs a lot of money to develop a new medicine so the price charged by the pharmaceutical company must cover the cost of research, production and marketing.

  • Patents are taken out to protect the company's commercial interests in the new medicine.

  • There can be a range of formulations of a particular medicine when you buy it over the counter e.g. tablet of 100% aspirin, soluble aspirin (via Na+ salt of the acid from neutralisation) and aspirin might form part of a mixture including substances that have other beneficial effects.

  • The main point here is that aspirin, like many drugs, can have multi-functional effects, hopefully all beneficial.

  • BUT this, sadly, is not always the case, because with any new drug there is always the danger of unknown side-effects.

  • Therefore there is a tremendous responsibility on pharmaceutical companies to ensure the development of safe and effective drugs.

  • Lots of time and money spent on discovering and developing new drugs and there are lots of factors to consider:

    • From the discovery of a potentially useful molecule, sometimes called the 'lead molecule', which can be from natural source or produced in some other project etc.

    • Is there room in the commercial market place for it?

    • Do research to see if its safe, otherwise further development is a waste of time and money or if not safe, can its molecular structure be modified?

    • Can the modification be safe? and more effective?

    • In what form, can it be/needs to be, administered in? for clinical trials.

    • Carefully clinical trials in various phases, noting particularly if any side-effects which may be harmful.

    • Do you test new drugs on animals? - an emotive issue, can non-animal testing always allow the safe development of new products?

    • Do you test new drugs on patients in a life threatening situation, give them a last chance at some risk?

    • Patient health and safety issues versus very big drug company commercial interests are a matter of public concern.

    • Any new drug must finally pass all the tests before legally licensed for patient consumption ...

      • sadly, the 'drug companies' and the 'powers to be' do not always get it right (e.g. thalidomide), but do not the benefits outweigh the occasional tragedy which we should do our best to avoid?


15c Food Additives, Intelligent Packaging and Active Packaging of Food

  • Food additives are chemicals added to food to give particular effects e.g. colourings, flavourings preservation and sweetening. All the improvements in flavour, colour and making them last longer (longer shelf-life), are all about improving the consumers eating experience. Personally I prefer natural flavours and freshly cooked food, salads and fruit as far as is possible, but I'm retired and don't have the same busy life-style as when I was teaching in the laboratory and classroom!

  • The addition of some of them is controversial i.e. health concerns like nitrates are carcinogenic, food colourings causing behavioural problems, but proving these 'cause and effect' claims are not easy.

    • Colourings to make food more attractive, more appetising, to fit in with the consumers perception of what it should look like.

    • Flavourings to make food more 'tasty', less 'bland', and to fit in with the consumers perception of what it should taste like.

      • Flavour enhancers improve the taste and smell of food without adding any taste of their own (salt ?)..

    • Preservatives are to increase the 'shelf-life' of packaged food, decrease risk of food poisoning by inhibiting bacteria/microbe growth (e.g. salt).

    • Antioxidants prevent oxidation of oils/fats by oxygen in the air, so helping preserve food, giving it a longer shelf-life. Oxygen from air reacts with food and the oxidation causes deterioration in quality and taste.

    • Sweeteners counter bitterness or pander to our taste!

    • Emulsifiers and stabilisers help keep a mixture of ingredients together i.e. prevent oily/fatty components separate out fro water/aqueous based components.

      • Emulsifiers oil and water based food components blend together e.g. like in mayonnaise and ice cream.

      • Processed foods that use emulsifiers include salad cream, biscuits, toffee, bread, extruded snacks, chewing gum, margarine / low fat spreads, breakfast cereals, frozen desserts, coffee whiteners, cakes, topping powders, desserts / mousses, dried potato, peanut butter, soft drinks, chocolate coatings, caramels etc. etc.

      • Emulsions provide better texture, coating ability and appearance, for example in salad dressings, ice creams, cosmetics and paints.

      • See Aqueous solution chemistry (section on emulsions)

      • and emulsifiers in margarine.

  • Food packaging has become more and more important as consumers demand a greater variety of products which are increasingly sold through super-markets.

    • A variety of food packing methods are used, variously described as e.g. intelligent packaging or active packaging etc.

    • If the packaging is air-tight no harmful bacteria can get in.

    • Excess water can be removed which inhibits the growth of mould or bacteria.

    • Air/oxygen can be removed or replaced with an unreactive gas like nitrogen/carbon dioxide, to stop oxidation of the food AND removes the need to use antioxidant chemicals.

  • E-numbers are reference numbers used by the European Union to help identification of food additives.

    • All food additives allowed and used in the European Union are identified by an E-number.

    • The "E" stands for "Europe" or "European Union".

    • Normally each food additive is assigned a unique number, though occasionally, related additives are given an extension (e.g. a,b,i or ii etc.) to another E-number.

    • The Commission of the European Union assigns E-numbers after the additive is cleared by the Scientific Committee on Food (SCF), the body responsible for the safety evaluation of food additives in the European Union. A summary is given below.

  • E100-199, food colours

    • E175 is edible gold, you may find it in expensive chocolates!

    • E200-299, preservatives
    • E300-399, anti-oxidants, phosphates, and complexing agents
    • E400-499, thickeners, gelling agents, phosphates, emulsifiers
    • E500-599, salts and related compounds
    • E600-699, flavourings
    • E700-899, not used for food additives (used for animal feed additives!)
    • E900-999, surface coating agents, gases, sweeteners
    • E1000-1399, miscellaneous additives
    • E1400-1499, starch derivatives
      • E-numbers are only used for substances added directly to food products, so contaminants, enzymes and processing aids, which may be classified as additives in the USA, are not included in the E-number system.
      • There is an EU directive on food labelling which requires food additives to be listed in the product ingredients whenever they are added for technological purposes.
      • This includes colouring, sweetening and flavour enhancement as well as for preservation, thickening, emulsifying and the like.
      • Ingredients must be listed in descending order of weight, which means that are generally found close to the end of the list of ingredients.
      • However, substances used in the protection of plants and plant products, flavourings and substances added as nutrients (e.g., minerals, trace elements or vitamins) do not need to be included in the ingredient list.
      • Because of this, some substances that are regulated as food additives in other countries may be exempt from the food additive definition in the EU.
  • Some examples of nutritional information on various foods
    • The Food Standards Agency (FSA) is an independent food safety watchdog that advises the government and the public about food safety and health and issues guidelines on the maximum amount of salt you should take in a day. This is known as the 'Guideline Daily Amount' (GDA). Two government departments, Department of Health and the Department for Environment, Food and Rural Affairs, are both involved with food safety issues and do risk assessments to check on the safety of chemicals used in food and advise the public on how food, and food additives may affect their health.

    • In terms of food labelling, the main nutritional guideline shown on food packaging is the GDA or RDA (recommended daily intake).

      • The GDA/RDA are the amounts of nutrients that an average adult should eat each day in a healthy balanced diet.

      • The amounts are quoted in grams micrograms per 100g or 'helping' and converted to %RDA or %GDA, see examples of nutritional labelling of food products below.

Spread 1 is made from vegetable fat and olive oil. Apart from the oil/fat composition you have all sorts of additives e.g. emulsifiers, salt, preservative, thickener, flavourings, colouring and vitamins.


The labelling on this fat spread 2 made from vegetable oil is packed with nutritional information. Again, apart from the oil/fat composition there added vitamins, salt, water, emulsifiers, flavourings etc. etc.


Baked beans mainly consists of water (by deducting all the g from a 100g). The rest is main carbohydrate from the beans, but there is some protein and a little added salt.


Cereal 1, like most cereals, is largely made up of carbohydrate from the original grain and a little added sugar (total 64%). All cereals have vitamins and minerals added (see Cereal 2 below)


Cereal 2 This cereal is designed for someone with a sweet tooth (children!), the carbohydrate content from the original grain is only 28.5% and the energy values increases a further 50% by adding sugar. However, there are lots of additives in the way of vitamins and minerals like iron and calcium for bone growth


Orange juice usually contains a good portion of vitamin C, either from the original fruit or added.


15d A footnote on cooking chemistry !!
  • Some more aspects of cooking chemistry!
  • Does cooking involve chemical changes?
    • The answer is yes! There are lots of ways to cook food e.g. baking, boiling, frying, grilling, steaming on cooking rings, heated ovens, microwaves etc.
    • All of these involve heating the food and all involve complex chemical changes and in effect produce new substances with a different molecular structure.
    • When the cooking is complete, you cannot go back to the original ingredients, cooking involves irreversible chemical changes.
  • Some examples of chemical changes in cooking
    • Cooking eggs or meat
      • Food is cooked for several reasons:

        • The high cooking temperature kills harmful microbes-bacteria, as long as cooked for the required time at a high enough temperature. Food poisoning is all too common from eating under cooked food. Some foods are actually poisonous when raw, but cooking renders them edible and safe to eat e.g. red kidney beans must be boiled for at least 10 minutes to destroy a poisonous substance and preferably cooked for a further two hours - safe and nutritious!

        • It may improve the texture, which is important in your appreciation of food, its not just about taste.

        • It may improve the flavour and taste (but remember some foods might taste better raw e.g. lettuce!)

        • It makes it easier for the body to digest the food because it begins the 'breaking-down' process, which your digestion system will complete.

      • Protein heat degradation

      • Most of meat from animals consists of protein together with smaller amounts of water and fat. Eggs and fish are also good sources of protein.

      • Protein molecules have a definite shape (diagram 1. above).

      • During the cooking of meat irreversible chemical changes take place.

      • The complex and specific structure of protein molecules is partly broken down in the cooking process (diagram 2.).

      • The high cooking temperature promotes particular chemical reactions to happen.

      • The structure changes and some of the chemical bonds are broken and new molecules can be formed that have a different taste-flavour and texture giving the food its own characteristic 'cooked' character.

      • The breaking down of protein complex protein molecules is called denaturing.

      • A similar process happens in the cooking of carbohydrate foods like potatoes which are broken down into far more readily digestible molecules - see below.

    • Cooking potatoes
      • Potatoes are a good source of carbohydrates, hence a good source of energy for the body.

      • BUT, potatoes are plants and potato cells are surrounded by a rigid cellulose wall which we can't digest, so we can't get to the starch that we can digest.

      • So, although raw potato is not easily digested, cooking partially breaks the structure of potato down so that we can digest it AND cooking also improves the texture and taste of the potato to make it more palatable to eat.

      • In the cooking process the plant cell walls of cellulose are softened and this allows hot water to penetrate the cells.

      • Further cooking causes the starch granules (starch grains) to swell and gelatinize as they absorb hot water.

      • This eventually causes the cells to separate producing the soft texture of well-cooked digestible potatoes!

      • Mash with milk, butter and salt to suit taste! Cheap and yummy!

    • Since fats and oils are important to our diet, there is the ever present danger of over-consumption (speaking as someone who loves chips and spicy crisps!).

      • So there are health and social, as well as 'molecular' issues to address!

      • Vegetable oils are an important source of energy and even vitamins like vitamin E in seed oils.

        • Vegetable oils are high calorie high energy food.

      • Vegetable oils contain essential fatty acids which are bodies need for certain metabolic processes.

      • So we need both oils and fats as sources of important essential fatty acids and energy.

      • Because vegetable oils have much higher boiling points than water, all the 'cooking chemistry' is speeded up, so, cooking time is reduced at this higher temperature when using vegetable oil compared to water.

        • However, there is a price with this high temperature faster cooking, 'sensitive' molecules like vitamin C and other nutrients can be destroyed.

        • On the other hand, we get food with a different flavour and we do seem to naturally like fried things!

        • Some of the flavours from the food get dissolved in the oil and contribute to the taste bud experience!

        • Cooking food in oil automatically increases the energy content of the meal - oils are high calorie foods!

      • We need both saturated and unsaturated fats or oils.

        • The main sources of saturated fats are from meat and dairy products e.g. 'dripping' and butter.

        • The main sources of unsaturated fats are plant oils e.g. olive oil.

      • It is recommended that we do not overdo the fat intake but we do need both saturated and unsaturated fats.

        • However, too much saturated fat raises cholesterol levels and is not too good for the heart.

      • See also the biofuels section in the alcohol notes

      • and Oils, fats and margarine notes

    • methods of gas preparation - apparatus, chemicals and equation (c) doc bRaising bread and cooking cakes etc.

      • Note on raising agents in cooking

      • An alternative to yeast (which produces carbon dioxide by fermenting sugar) is to use sodium hydrogencarbonate ('sodium bicarbonate' or 'baking soda') where you want a rising action in baking e.g. cakes.

      • When baking powder is heated it undergoes thermal decomposition.

      • The 'rising action' is due to the formation of carbon dioxide gas as the sodium hydrogencarbonate breaks down when heated.

      • sodium hydrogencarbonate ==> sodium carbonate + water + carbon dioxide

        • 2NaHCO3 ==> Na2CO3 + H2O + CO2

        • You can use the simple apparatus shown above-right to investigate the decomposition of sodium hydrogencarbonate and carry out the simple limewater test for carbon dioxide gas.

      • methods of gas preparation - apparatus, chemicals and equation (c) doc bIn using self-raising flour, the rising action is also due to carbon dioxide gas formed from its reaction with an acid (e.g. tartaric acid), and nothing to do with enzymes:

        • self-raising baking powder = sodium hydrogencarbonate + a solid harmless organic acid,

        • the reaction is ....

        • sodium hydrogencarbonate + acid ==> sodium salt of acid + water + carbon dioxide gas

        • This will be faster process because when water is added to the baking mixture it will facilitate the reaction between the harmless organic acid and the sodium hydrogen carbonate.

        • You can investigate mixing a self-raising flour with hot or cold water using the simple apparatus shown on the right, and again test for carbon dioxide gas (described below).

      • test for CO2Test for the carbon dioxide

        • If a sample of the evolved gas is carefully collected and bubbled into limewater a white precipitate is formed.

        • The formation of the carbon dioxide confirms the original compound was a carbonate. 

Multiple Choice Quizzes and Worksheets

KS4 Science GCSE/IGCSE m/c QUIZ on Oil Products (easier-foundation-level)

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KS4 Science GCSE/IGCSE m/c QUIZ on other aspects of Organic Chemistry

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... Ex AQA GCSE Science (c) doc b Useful products from crude oil AND (c) doc b Oil, Hydrocarbons & Cracking

... Ex OCR 21st C GCSE Science (c) doc b Worksheet gap-fill C1.1c Air pollutants etc ...

... Ex Edexcel GCSE Science Crude Oil and its Fractional distillation etc ...

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