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Starter. Put about 1cm depth of water in a test tube. Add about 1cm depth of oil into your test tube and put a bung on the top. Shake the tube well. What do you think will happen?. Objectives. To know what an emulsion is. To understand how an emulsifier works. Emulsions.

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Starter

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  1. Starter • Put about 1cm depth of water in a test tube. • Add about 1cm depth of oil into your test tube and put a bung on the top. • Shake the tube well. • What do you think will happen?

  2. Objectives • To know what an emulsion is. • To understand how an emulsifier works.

  3. Emulsions • An emulsifier sticks its head into the oil and tail into the water. This means that the oil and water will now mix.

  4. Making an emulsion

  5. What stops emulsions from separating? 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 lecithin, which is a natural emulsifier. emulsifier Emulsifiers have a hydrophilic (‘water loving’) part and a hydrophobic (‘water hating’) part. water Natural and artificial emulsifiers are used to stop oil and water separating in emulsions. oil

  6. In your notes . . . • Explain what an emulsion is. • Explain the structure and role of an emulsifier.

  7. What 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 enhance or preserve food. These are called additives. The main groups of additives are: • flavourings • emulsifiers and stabilizers • preservatives and antioxidants • colourings.

  8. Types of additives

  9. Types of additives – activity

  10. What are E-numbers? Food labels often contain E-numbers. Nearly all additives, including natural products like citric acid, have E-numbers. E-numbers are often blamed 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. 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.

  11. Plenary • Return to your test tube of oil and water. • Add some washing up liquid. • Shake. • What happens now?

  12. How can you keep food fresh? Starter

  13. Objectives • To know what causes food to become unsuitable to eat. • Ways in which packaging can stop food from going off. • Ways in which packaging is becoming intelligent.

  14. What makes food go off? • Bacteria and fungus feed off the food releasing enzymes. These break down the food. • Fats oxidise.

  15. How can we minimise the effect of the microbes • How could we stop the microbes from respiring? • Remove the oxygen • Use packets of iron to react with oxygen. • Package in an atmosphere without oxygen (N2 or CO2). • Remove the water. • Silica gel can absorb the water.

  16. Microchips on the packaging • Microchips on the packaging to give details on the supply chain. • Microchips can check that the product is being stored in the correct conditions.

  17. Intelligent packaging – the future? Microchips that could talk to appliances? Will the microwave just know how long to cook for?

  18. What is smart packaging? Almost all products are packaged in some way for protection during transportation, handling or storage. New types of ‘smart’ packaging are able to mechanically, chemically and electronically respond to their contents. For example, a sensor fitted into fruit packaging detects chemicals released by the fruit as it ripens, and changes colour. This allows the customer to choose when to eat the fruit according to their preference.

  19. What is active packaging? Active packaging maintains the quality of products without the use of food additives. The packaging contains substances that absorb oxygen or moisture, or prevent the growth of microbes. In normal (passive) packaging, oxygen molecules can pass through the wrapping, encouraging food spoilage and the growth of bacteria. Sachets, bottle cap inserts and high-tech labels containing iron oxide or ascorbic acid bind to free oxygen molecules and trap them away from the package contents.

  20. Plenary – mobile phone • Lst da 3 key pts frm der len as txt spk

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