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 Processed Foods ID: 1048304
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2. What I Will LearnTo explain what a processed food is To understand why food is processed or preservedTo state the aims of preserving foodsTo outline the different methods of preserving foods To develop a set of guidelines for home freezing
3. Processed FoodsMost 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 ActivityEach 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 foodsTo cut down on wasteTo 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 ProActiveTo ensure a wider choice all year round, e.g. frozen and canned varieties of foods that are out of seasonTo add nutritional value and to fortify food, e.g. breakfast cereals and supermilk
7. Range of Processed FoodsMilk, cheese, yoghurt, butter, margarine, spreads, flour, pasta, rice, bread, cakes, biscuits, breakfast cereals, prepared products and meals.
8. Food PreservationFood 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 ActivityFill 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, freezingRemoving moisture: Drying (dehydration)Removing oxygen: Canning, bottlingChanging the pH: Using vinegar as a preservativeUsing 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-organismsPrevent any new micro-organisms from re-entering the foodPrevent enzyme activity which causes food to decayKeep the original qualities of the food, i.e. flavour, texture and nutritive value
12. Methods of PreservationFreezingRemoves 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)DryingMoisture 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 airtightThis ensures a better retention of flavour, colour and texture, e.g. coffee
14. Methods of Preservation (continued)Canning/bottlingRemoves oxygenFood 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 preservativesSalt, sugar and vinegar change the pH of food and act as preservatives, e.g. salted fish, jam, pickles, chutneys and relishesThe chemicals in smoke preserve food, e.g. smoked fish, ham and baconIn commercial products, chemical preservatives like antioxidants are used to prevent oxygen, which makes the food deteriorate
16. Methods of Preservation (continued) IrradiationEnergy waves are passed through the food to kill micro-organisms.Pasteurisation and sterilisationMilk is heated and cooled and stored or sealed in sterile containers.Discover more: Find out about irradiation in food and how it works and is regulated in the EU.
17. Class ActivityThink-Pair-ShareLook 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 StudyJohn 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 freezerRules 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) PreparationTurn on fast-freeze button, 3–4 hours before the food goes inOnly freeze one-tenth of total freezer capacity at one time or over a 24-hour periodChoose good-quality fresh foodCool foods well before freezingBlanch vegetables first to destroy enzymes and prevent enzymatic spoilage of frozen foodsOpen-freeze food that will stick together then pack, e.g. berries and prawns
22. Guidelines for Home Freezing (continued) PackagingPack 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 compartmentLeave for recommended time — up to 24 hours — then remove frozen food and place in storage sectionsOpen-frozen foods can now be packed into the container Turn off fast-freeze button
24. Guidelines for Home Freezing (continued) Storage Store similar food togetherStore for recommended timeUse in rotationKeep freezer filled as it reduces running costsAvoid opening the door unnecessarily
25. Packaging for FreezingPackaging must be airtight, waterproof and vapour-proof.Suitable materials for freezer packaging include:Polythene boxes – strong, reusable but expensivePolythene bagsFoil containersWaxed cartons and tubsMargarine/ice cream tubs
26. Find out how long you can store different foods in the freezer.What Foods can be Frozen?Raw and cooked meats, fish and poultryFresh fruit and vegetablesReheated dishes, e.g. fishcakes and shepherd’s pie.Uncooked dough and pastrySauces, soups, stews and savoury dishesBreadcrumbs, stuffing, some sandwiches and packed lunchesPrepared baby foodsAdvanced cooking for occasions, e.g. parties, Christmas, etc.
27. What Foods Cannot be Frozen?Bananas, as they blackenLettuce, cucumber and salad greens go limpWhole tomatoes; you can freeze puréeWhole melon or pears unless in a syrupMilk, cream and plain yoghurt as they separateWhole eggs but you can freeze the yolks and whites separatelyJelly and mayonnaise, as they separateWhole potatoes; but you can freeze potato purée or partly cooked chips
28. Open FreezingSuitable 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 ActivityGuidelines for freezing at homeDesign 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 RevisionWhat 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.