4 Figure 34.2 All the foods and drinks shown here have been processed. 34.1 INTRODUCING FOOD ADDITIVES
5 In food processing, small amounts of certain chemicals are often added these are called food additives. A FOOD ADDITIVE is a chemical added to food to improve it or to preserve it. The main reasons for using food additives are to colour food to flavour food to change the texture (sponginess) of food to add nutrients to preserve food 34.1 INTRODUCING FOOD ADDITIVES
6 Figure 34.3 A fruit juice with the additive vitamin C. 34.1 INTRODUCING FOOD ADDITIVES
7 Figure 34.4 Would you like this soft drink if no artificial flavouring and colouring had been added to it? (a)The normal look of the soft drink. (b)What the soft drink would look like if no artificial colouring had been added. (a)(b) 34.1 INTRODUCING FOOD ADDITIVES
8 CONTROL OF FOOD ADDITIVES The EU (European Union) countries have drawn a list of 314 safe food additives. Each of them is given an E number. Figure 34.5 The E number identifies an additive. 34.1 INTRODUCING FOOD ADDITIVES
9 TYPES OF FOOD ADDITIVES 34.1 INTRODUCING FOOD ADDITIVES
10 Table 34.1 Different types of food additives. 34.1 INTRODUCING FOOD ADDITIVES
11 Figure 34.6 Can you list the basic foodstuff and food additives in this food? 34.1 INTRODUCING FOOD ADDITIVES INSPECTING FOOD LABELS FOR ADDITIVES
12 Figure 34.7 Can you list the food additives in these chocolate beans? 34.1 INTRODUCING FOOD ADDITIVES
13 A34.1 E110 is used as an artificial colouring. E201 is used as a preservative. E320 is used as an anti-oxidant. E322 is used as an emulsifier and stabilizer. A34.2 Colouring, preservative and flavouring. 34.1 INTRODUCING FOOD ADDITIVES
14 34.2 FOOD COLOURINGS WHY USE FOOD COLOURINGS? Food colourings are dyes. They are added to food for the following purposes: To give food an attractive colour, so as to make it more appetizing and more saleable. To restore the original colour which may be changed or lost during food processing or storage. To ensure colour consistency.
15 Figure 34.8 When fruits are processed, their colours change. Artificial colourings are added to make them look like fresh fruits. 34.2 FOOD COLOURINGS
16 ARE FOOD COLOURINGS ESSENTIAL? There is no definite conclusion to this. But one thing is certain most processed foods on market nowadays contain colourings. NATURAL AND SYNTHETIC COLOURINGS Synthetic colourings are more commonly used. USE OF COLOURINGS WORLDWIDE In most places nowadays, the use of food colourings is under strict control by the government. ANALYSING COLOURINGS BY CHROMATOGRAPHY Food colourings can be analysed by chromatography. 34.2 FOOD COLOURINGS
17 34.2 FOOD COLOURINGS Paper chromatography of black ink..
18 Figure 34.10 Colourful chocolate beans. 34.2 FOOD COLOURINGS Figure 34.11 Chocolate beans become white when the colourings are removed.
19 Figure 34.12 A simple set-up for paper chromatography of colouring on chocolate beans. chromatography paper strip stopper spot of colouring starting line water 34.2 FOOD COLOURINGS
20 34.2 FOOD COLOURINGS To separate dyes in the colouring of a Smarties chocolate bean.
21 34.3 FOOD FLAVOURINGS WHY USE FOOD FLAVOURINGS? Flavourings are added to food for the following purposes: To enhance flavour of food To restore the original flavour which may be lost during food processing To add flavour to foods which are tasteless themselves (e.g. ice cream, jelly)
22 Figure 34.14 The flavour of an ice cream is due to the flavourings added. 34.3 FOOD FLAVOURINGS
23 COMMON FLAVOURINGS Flavourings make up the largest class of food additives. Both natural and artificial flavourings are used. 34.3 FOOD FLAVOURINGS
24 Figure 34.15 Common flavourings. 34.3 FOOD FLAVOURINGS
25 A34.3 Synthetic esters are widely used as fruit flavours in drinks, ice creams and sweets. Monosodium glutamate Monosodium glutamate is a white solid. It possesses little flavour of its own, but it can bring out the flavour of foods. It is therefore actually a flavour enhancer. 34.3 FOOD FLAVOURINGS
26 Figure 34.16 Monosodium glutamate is a widely-used flavour enhancer. 34.3 FOOD FLAVOURINGS
27 Figure 34.17 Instant noodle supplied with the packet of flavouring (mainly MSG). 34.3 FOOD FLAVOURINGS
28 34.4 FOOD PRESERVATIVES TO PRESERVE FOOD Food spoilage is mainly due to micro-organisms (microbes). Thus there are two ways to preserve food: Kill the microbes in food Keep food in conditions where the microbes cannot multiply
29 (a)(b)(c) Figure 34.19 Three main types of micro-organisms: (a) Bacteria (b) Mould (c) Yeast 34.4 FOOD PRESERVATIVES
30 Common methods to preserve food Common methods to preserve food include: Canning Cook food and then seal it in tin cans under sterile conditions. Drying Dry food in the sun or in special ovens. Drying takes away the water needed by microbes. Freezing and refrigeration Freeze food quickly. Freezing turns liquid water into ice, thus controlling the growth of microbes. Refrigeration slows down biochemical changes of microbes. 34.4 FOOD PRESERVATIVES
31 Irradiation Expose food to gamma rays from certain radioactive isotopes for a short time. The microbes are killed at once. Using preservatives 34.4 FOOD PRESERVATIVES
32 (a) (d) (b) Figure 34.20 Foods preserved by different methods: (a)Canned foods. (b)Dried fruits. (c)Frozen foods. (d)Irradiated strawberries (compared with non-irradiated ones) (c) 34.4 FOOD PRESERVATIVES
33 A34.4 (a)Drying (b)Canning PRESERVATIVES AND THEIR FUNCTIONS We add preservatives to food to kill microbes or inhibit their growth, so that the food spoils less quickly. Common food preservatives are common salt, sugar, vinegar, sulphur dioxide, benzoic acid and sodium nitrite. 34.4 FOOD PRESERVATIVES
34 Common salt and sugar Salting and sugaring are two of the oldest methods of preserving food. Figure 34.21 Using salt to preserve fish. 34.4 FOOD PRESERVATIVES
36 A34.5 (a)Osmosis. (b)Salting and sugaring. Vinegar Pickling in vinegar is a common method of preserving onions, cucumbers and beetroot. 34.4 FOOD PRESERVATIVES
37 Figure 34.23 Onion is pickled in vinegar. 34.4 FOOD PRESERVATIVES
38 Sulphur dioxide Sulphur dioxide has been used in wine-making for hundreds of years to control the growth of unwanted microbes. A wide range of other foods, such as fruit juices and dried fruits, also have sulphur dioxide added as a preservative. 34.4 FOOD PRESERVATIVES
39 Figure 34.24 Sulphur dioxide is a common preservative for dried fruits. 34.4 FOOD PRESERVATIVES
40 Benzoic acid Benzoic acid (or sodium benzoate) is a preservative commonly used in fruit juices and other drinks. It is able to stop the growth of bacteria and yeasts. 34.4 FOOD PRESERVATIVES
41 Figure 34.25 Fruit juices usually contain small amounts of benzoic acid (or sodium benzoate) as preservative. 34.4 FOOD PRESERVATIVES
42 Sodium nitrite In the process of manufacturing ham, bacon and sausages, the meats are soaked in a solution containing sodium chloride, sodium nitrate and sodium nitrite. This is called curing. 34.4 FOOD PRESERVATIVES
43 Figure 34.26 Luncheon meat and ham contain sodium nitrite as preservative. 34.4 FOOD PRESERVATIVES
44 Table 34.2 Main functions of food preservatives. 34.4 FOOD PRESERVATIVES
45 A34.6 (b) B, C(c) B (d) A, D (e) A, C(f) D 34.4 FOOD PRESERVATIVES
46 34.5 ARE FOOD ADDITIVES REALLY SAFE? DIFFERENT OPINIONS ON SAFETY OF FOOD ADDITIVES It is hard to draw general rules to control food additives which would apply to all people.
47 34.5 ARE FOOD ADDITIVES REALLY SAFE? Activity 4 Some guiding questions for this discussion are: Selecting one or two food items, try to decide what the food would be like without the additives. For example, what would vanilla-flavoured ice cream be like without colouring? Without flavouring? Without emulsifiers and stabilizers? For the same food items, would you still buy them without the additives? Or would you buy another different food instead? Are some types of additives more useful than others? If so, which ones? Could we do without any additives?
48 Should we worry about the possible effect of food additives on health? Without food additives, the variety of food available in shops would be much smaller (just imagine potato crisps with no flavour). Would this have a great impact on sales? A list of ingredients is not found in some foods, e.g. fresh fruit, vegetables and alcoholic drinks. Why do you think this is so? Should all foods have ingredient lists? 34.5 ARE FOOD ADDITIVES REALLY SAFE?
49 POSSIBLE HAZARDS OF FOOD ADDITIVES Possible hazards of some food additives to our health are: Hazards of colourings Food colourings permitted by law may not be really safe. Hazards of MSG Some people are allergic to MSG. 34.5 ARE FOOD ADDITIVES REALLY SAFE?
50 Figure 34.27 All these contain much MSG. 34.5 ARE FOOD ADDITIVES REALLY SAFE?
51 Hazards of preservatives Sulphur dioxide would cause breathing difficulties and stomach upset in some asthma patients. Besides, sodium nitrite is suspected of causing cancer. 34.5 ARE FOOD ADDITIVES REALLY SAFE?
52 SUMMARY 1.A food additive is a chemical added to food to improve it or to preserve it. 2.The main reasons for using food additives are: To colour food (by colourings) To flavour food (by flavourings) To keep oils and water mixed in food (by emulsifiers and stabilizers) To add nutrients To preserve food (by preservatives) SUMMARY
53 SUMMARY 3.Food additives approved by the EU countries often have an E number. (See Table 34.1 on p. 305.) 4.Paper chromatography can be used to separate the dyes in food colourings. 5.Common food flavourings include common salt, sugar, vinegar and synthetic esters. MSG is a flavour enhancer. 6.Food spoilage is mainly due to micro-organisms (bacteria, fungi, yeast). 7.Food preservatives include common salt, sugar, vinegar, sulphur dioxide, benzoic acid and sodium nitrite. 8.Food preservatives can function as such because they either kill microbes or inhibit their growth.
54 SUMMARY 9.Some food additives such as tartrazine (E102) and sodium nitrite are hazardous to health.