Carbohydrates; gelatinisation and modified starch
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Carbohydrates; gelatinisation and modified starch

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GCSE food technology

GCSE food technology

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Carbohydrates; gelatinisation and modified starch Presentation Transcript

  • 1. Carbohydrates
    • Aims of today’s lesson:
    • To develop knowledge of carbohydrates, sources, functions and structure
  • 2. Carbohydrates
    • Carbohydrates are an important MACRO nutrient because they:
    • Carbohydrates are our primary source of energy. 
    • Supply energy for activity
    • Supply energy to maintain normal body temperature
    • Supply indigestible fibrous materials to aid digestion
  • 3. How are they broken down?
    • The two different types of carbohydrates affect the production of insulin differently.
    • Simple carbohydrates (sugar), are used up more quickly for energy.
    • Complex carbohydrates (starch) take longer to digest, resulting in longer lasting energy.
  • 4. What if we eat too many carbs?
    • When the body takes on carbohydrates, its stored in the liver and muscle cells as glycogen, to be used for when the body needs an extra burst of energy.
    • Any leftover, not used for energy, is stored as fat.
  • 5. Cellulose - Fibre
    • Fibre is a unique type of carbohydrate because it contains zero calories, zero vitamins and cannot be digested.  Therefore, it does not provide your body with any energy. 
    • Insoluble Fibre vs Soluble Fibre
    • Insoluble fibre absorbs water in your intestine to form a bulky mass which then helps clear waste materials from your digestive tract. 
    • Soluble fibre dissolves in the water in your intestine to form a thick gel which then holds food in your digestive tract for longer.
  • 6. Types of starch
    • Starch is obtained from cereals such as
    • wheat and maize.
      • Wheat flour contains a high percentage of starch
      • Cornflour and arrowroot are pure starch
  • 7. Gelatinisation Starch particles do not dissolve in liquid, instead they form something called a suspension. If liquid is not stirred the starch granules sink to the bottom, stick together and start to form lumps.
  • 8. Gelatinisation When heated at 60 o C, the starch granules begin to absorb the liquid and swell At 80 o C the particles will have absorbed about five times their volume of water until they burst open and release starch, thickening the liquid. This process is Gelatinisation
  • 9. Gelatinisation Gelatinisation is complete when the liquid reaches boiling point 100 o C When the sauce cools it goes even thicker, going into a Gel.
  • 10. Heat starch granules in liquid Starch granules become swollen Starch granules burst The liquid thickens and gelatinizes Starch gelatinizes when heated in a liquid, producing a thickened liquid
  • 11. Examples of Gelatinisation White Sauce for Lasagne Cheese Sauce Sweet & Sour Sauce
  • 12. Modified Starch This is starch that has been altered to perform additional functions to react to different processes. These are sometimes called SMART starches. Modified starch is used to thicken food when boiled water is added e.g. Cup a soup, dried custard or Pot Noodle.
  • 13. Food & Drink: Food for thought - What is modified starch? Roy Ballam, British Nutrition Foundation
    • The starch in some canned soups is bonded with phosphate, which allows it to absorb more water and so the soup from does not separate.
    • Fish batter contains an oxidised starch to make it "stickier" to adhere to the sides of the fish better.
    • Instant desserts, such as blancmange, use a pre-gelatinised starch which has been thickened by heat, then dried and added to the product.
    • Pizza, to stop the tomato sauce spilling off during baking, a starch treated with a chlorine solution is often added to the topping. This produces a gel that thickens during cooking, but goes runny when cooled.
  • 14. Task:
    • Design and make a macaroni cheese product suitable for children.
    • Specification;
    • Suitable for children – high in calcium
    • It must have a garnish
    • Increase the fibre content
    • Have a sauce – using the roux method
  • 15. What is a garnish
    • To enhance a dish before serving with an edible decoration or accompaniment, which is appealing to the eye and complements the flavours of the dish.
  • 16.  
  • 17. Roux Sauce
    • Milk is added to the roux and the sauce is cooked until thick and glossy.
    • BBC - Food - Techniques : Thickening a roux to make béchamel sauce