Understanding Processed Foods: Benefits, Methods, and Preservation

2. What I Will Learn • To explain what a processed food is • To understand why food is processed or preserved • To state the aims of preserving foods • To outline the different methods of preserving foods • To develop a set of guidelines for home freezing

3. Processed Foods Most foods are prepared in some way before being put on the shelf. The degree of processing varies considerably. • Processing means foods are prepared in some way before being put on sale. • Preserving means treating foods to make them last longer. • Shelf life is the length of time a food remains nourishing and safe to eat.

4. Processed Foods (continued) • Minimal processing makes changes to basic foodstuffs, e.g. fruit and vegetables can be washed, peeled, sliced, juiced, frozen or dried. It can also be used to extend shelf life, e.g. milk is pasteurised. • Medium processing makes food saleable and ready for cooking and eating, e.g. milling wheat into flour or making vegetable oil from seeds and nuts. • High processing adds value to basic ingredients. It takes a basic processed food and uses it to produce a food product of a higher economic value, e.g. making margarine from vegetable oil; making bread, cakes and biscuits from flour; making dairy products from milk; producing convenience meals.

5. Class Activity Each group has a box of four to five food items. • Line up the foods from least processed (on the left) to most processed (on the right). • As a class, discuss: • Why did your group arrange its food the way it did? • What is the relationship between how processed a food is and how healthy it is? • What is the relationship between food processing and food safety? See Activity 17.1 in the TRB

6. Why is Food Processed? • To extend the shelf-life • To make them safe to eat • To save time and energy used in preparing and cooking food, e.g. cook chill foods • To cut down on waste • To add variety to the diet by creating new food products, e.g. cheese, ice-cream, yoghurt • For healthier food options, e.g. Benecol and Flora ProActive • To ensure a wider choice all year round, e.g. frozen and canned varieties of foods that are out of season • To add nutritional value and to fortify food, e.g. breakfast cereals and supermilk

7. Range of Processed Foods Milk, cheese, yoghurt, butter, margarine, spreads, flour, pasta, rice, bread, cakes, biscuits, breakfast cereals, prepared products and meals.

8. Food Preservation Food preservation is a form of food processing that slows down food spoilage (food going off). Food spoilage is caused by enzymes and micro-organisms (moulds, yeasts and bacteria).

9. Quick Recap Activity Fill out the sheet you have been given to recap food processing. See Activity 17.3 in the TRB

10. How is Food Preserved? Preservation works by: • Removing warmth: Refrigeration, freezing • Removing moisture: Drying (dehydration) • Removing oxygen: Canning, bottling • Changing the pH: Using vinegar as a preservative • Using sugar and salt as a preservative makes it difficult for micro-organisms to grow

11. How Does Food Preservation Work? Food preservation techniques aim to: • Kill or inactivate micro-organisms • Prevent any new micro-organisms from re-entering the food • Prevent enzyme activity which causes food to decay • Keep the original qualities of the food, i.e. flavour, texture and nutritive value

12. Methods of Preservation Freezing Removes warmth, at very low temperatures (–18⁰C to –30⁰C) the water is changed to ice and the food is wrapped or sealed.

13. Methods of Preservation (continued) Drying • Moisture is removed and the food is packed in airtight containers, e.g. pasta, raisins, rice, soups and breakfast cereals. • Freeze-drying (AFD accelerated freeze drying) can also be used: • Food is frozen, then moisture is removed and packaging is airtight • This ensures a better retention of flavour, colour and texture, e.g. coffee

14. Methods of Preservation (continued) Canning/bottling • Removes oxygen • Food is heated to a very high temperature and then sealed in airtight, sterilised bottles and cans, e.g. beans, jams, pickle and chutney

15. Methods of Preservation (continued) Using preservatives • Salt, sugar and vinegar change the pH of food and act as preservatives, e.g. salted fish, jam, pickles, chutneys and relishes • The chemicals in smoke preserve food, e.g. smoked fish, ham and bacon • In commercial products, chemical preservatives like antioxidants are used to prevent oxygen, which makes the food deteriorate

16. Methods of Preservation (continued) • Pasteurisation and sterilisation • Milk is heated and cooled and stored or sealed in sterile containers. • Irradiation • Energy waves are passed through the food to kill micro-organisms. • Discover more: Find out about irradiation in food and how it works and is regulated in the EU.

17. Class Activity Think-Pair-Share • Look at each of the methods of preservation and discuss what growth conditions have been removed in each. • Give two examples of foods that can be preserved by each method. • Compare your sheet with an another pair to see if you could add anything. See Activity 17.4 in the TRB

18. Case Study John is a keen home gardener. He has a lot of produce left over this year because he had a very high yield. He does not want anything to go to waste. Can you suggest ways he can preserve this produce? Fill out the table. See Activity 17.4 in the TRB

19. Advantages of Home Freezing • A simple, safe method of preserving • Foods are available out of season • Adds variety to the diet • Most foods can be frozen • Freezing leftovers avoids waste • Bulk cooking and freezing saves time and fuel • Useful in emergencies • Foods retain their colour, flavour, texture and nutritive value

20. Disadvantages of Home Freezing • Cost — and running cost — of freezer • Space needed for freezer • Rules for freezing and thawing must be followed for food safety • Defrosting freezer takes time and effort • Can cause some damage to texture of food

21. Guidelines for Home Freezing (continued) Preparation • Turn on fast-freeze button, 3–4 hours before the food goes in • Only freeze one-tenth of total freezer capacity at one time or over a 24-hour period • Choose good-quality fresh food • Cool foods well before freezing • Blanch vegetables first to destroy enzymes and prevent enzymatic spoilage of frozen foods • Open-freeze food that will stick together then pack, e.g. berries and prawns

22. Guidelines for Home Freezing (continued) Packaging • Pack in usable quantities. • Seal well in packaging, removing as much air as possible. • Use strong, vapour- and moisture-proof packaging, e.g. polythene freezer bags. • Allow expansion room in liquid foods. • Label food with name, quantity and date.

23. Guidelines for Home Freezing (continued) Freezing • Place in fast-freeze compartment, touching base or sides —don’t overpack compartment • Leave for recommended time — up to 24 hours — then remove frozen food and place in storage sections • Open-frozen foods can now be packed into the container • Turn off fast-freeze button

24. Guidelines for Home Freezing (continued) Storage • Store similar food together • Store for recommended time • Use in rotation • Keep freezer filled as it reduces running costs • Avoid opening the door unnecessarily

25. Packaging for Freezing Packaging must be airtight, waterproof and vapour-proof. Suitable materials for freezer packaging include: • Polythene boxes – strong, reusable but expensive • Polythene bags • Foil containers • Waxed cartons and tubs • Margarine/ice cream tubs

26. What Foods can be Frozen? • Raw and cooked meats, fish and poultry • Fresh fruit and vegetables • Reheated dishes, e.g. fishcakes and shepherd’s pie. • Uncooked dough and pastry • Sauces, soups, stews and savoury dishes • Find out how long you can store different foods in the freezer. • Breadcrumbs, stuffing, some sandwiches and packed lunches • Prepared baby foods • Advanced cooking for occasions, e.g. parties, Christmas, etc.

27. What Foods Cannot be Frozen? • Bananas, as they blacken • Lettuce, cucumber and salad greens go limp • Whole tomatoes; you can freeze purée • Whole melon or pears unless in a syrup • Milk, cream and plain yoghurt as they separate • Whole eggs but you can freeze the yolks and whites separately • Jelly and mayonnaise, as they separate • Whole potatoes; but you can freeze potato purée or partly cooked chips

28. Open Freezing • Suitable for items that could stick together, e.g. berries or sliced apple. • Prepare the food as for cooking — wash, peel, core trim, etc. • Lay the pieces individually on a tray, keeping them separate from each other, and freeze. • Once frozen, pack them in a box or bag and put back in the freezer to store for the recommended time.

29. Homework Activity Guidelines for freezing at home • Design a fact card that could be handed out to people to help them freeze food correctly. • Include all the information a person may require, and include illustrations and diagrams to make it eye-catching.

30. Quick Revision • What is a processed food? • Give three reasons why food is processed. • What are the aims of preserving foods. • Outline the different methods of preserving foods. • Compile a set of guidelines for home freezing.