Carbohydrates

• What is gelatinisation?

  The swelling of starch granules when they are cooked with a liquid to the point where they burst and release starch molecules
• What is dextrinisation?

  The breaking up of starch molecules into smaller groups of glucose molecules when they are exposed to dry heat
• What is caramelisation?

  The breaking up of sucrose (sugar) molecules when they are heated, which changes the colour, flavour and texture of the sugar as it turns into caramel
• What happens when starch is heated in a liquid?

  It gelatinises
• What are starch molecules made of?

  Thousands of glucose molecules joined together
• How are starch molecules structured?

  In long straight chains or short branched chains
• Where is starch stored in plants?

  In tiny packets called starch granules
• How do starch granules behave in cold water?

  They sink to the bottom of the pan
• What happens to starch granules when heated in water at about 60°C?

  They start to absorb water and swell up
• Why does the sauce start to thicken when starch granules swell?

  There is less room for swollen granules to move
• Why is it important to stir the sauce regularly while heating?

  To prevent granules from sticking together and lumping
• What occurs at about 80°C with starch granules?

  They burst and release starch molecules
• What do the released starch molecules form in the liquid?

  A 3-dimensional network that traps water
• What happens to the sauce at boiling point (100°C)?

  It completely thickens
• How long should the sauce be heated to ensure all starch is cooked?

  A few minutes
• What is the entire process of thickening a sauce with starch called?

  Gelatinisation
• What happens to starch molecules as a cooked sauce cools down?

  They form longer chains trapping water molecules
• What is gelatinisation?

  The process of starch forming a gel when cooked
• When does gelatinisation occur in cooking?

  When foods containing starch are cooked
• What can happen if rice or pasta is boiled for too long?

  Starch granules burst, causing stickiness
• What is a consequence of starch bursting in rice or pasta?

  Grains stick together, making them hard to serve
• Why are some types of rice naturally sticky?

  Due to their composition and amount of starch
• Name two types of sticky rice mentioned in the material.

  Thai sticky rice and sushi rice
• What is the process of gelatinisation in cooking?

  • Starch molecules form longer chains
  • Water molecules are trapped inside
  • Sauce gradually becomes a solid gel
• What are the effects of overcooking rice or pasta?

  • Starch granules burst
  • Released starch causes stickiness
  • Makes serving and eating difficult
• What factors contribute to the stickiness of certain rice types?

  • Composition of starch
  • Amount of starch present
  • Examples: Thai sticky rice, sushi rice
• What is the process called when starches are cooked by dry heat?

  Dextrinisation
• What happens to starch molecules when foods are cooked by dry heat?

  They break into smaller groups called dextrin
• What contributes to the flavor of the crust or toast?

  The formation of dextrin
• What types of foods undergo dextrinisation when cooked by dry heat?

  Bread, cakes, scones, biscuits, pastries
• What are the visual effects of toasting bread for different lengths of time?

  • Bread develops a brown color
  • Color intensity increases with longer toasting
  • Over-toasting leads to a very dark color
• What happens to the bread when it is toasted until very dark?

  Oxygen and hydrogen are driven off as water
• What elements make up carbohydrates?

  Carbon, hydrogen, and oxygen
• What is left behind in the bread after excessive toasting?

  Carbon
• What is sucrose made from?

  Glucose and fructose
• What happens to sugar when it is heated?

  It melts, forms syrup, and boils
• What occurs to sucrose molecules during heating?

  They start to break up
• What do hydrogen and oxygen atoms in sugar form when heated?

  Water, which evaporates
• How does the color of sugar change during caramelisation?

  From clear to golden brown to black
• How does the flavor of sugar change during caramelisation?

  From sweet to toffee to bitter