NFS chapter 13 (food reactions only) and chapter 14

• Sense organs of the human body


  • Eyes - see
  • Nose - smell
  • Ears - hear
  • Tongue - taste
  • Skin - touch
• Reasons for conducting sensory evaluation


  • To describe the quality of the food
  • To determine how different the food products are
  • To measure how well liked a food is
• Qualitative evaluation


  Involves the use of our 5 human senses to identify the sensory attributes of food
• Qualitative data examples


  • Descriptive words
  • Photographs
• Descriptive words

  • Taste
  • Flavour
  • Temperature
  • Smell
  • Colour
  • Shape
  • Texture
• Quantitative evaluation


  An objective way of describing the attributes of a food product using numerical values derived from measurements
• Quantitative data collection steps


  1. Identify food attribute needed to be measured

  2. Choose appropriate measuring tools and scale

  3. Prepare the food samples

  4. Food products should be served in identical containers or dishes

  5. Collect data using measuring tools
• Measuring tools and scales


  • Measuring weight and height
  • Measuring volume
  • Measuring density
  • Measuring viscosity
  • Measuring tenderness
• Control the variables


  • Ensure the environment is conducive for the tasters
  • Ensure the testers are in good health
  • Ensure there is no strong odor in the room
  • Ensure food samples are labeled clearly using random codes
• Data presentation


  • Observation table
  • Bar chart
• Gelatinisation

  Starch granules absorb water and swell, eventually rupturing resulting in a thick consistency
• Dextrinisation


  Long chain starch molecules break down to smaller chain dextrains, resulting in a toasty and nutty flavour
• Caramelisation


  Browning reaction involving simple sugars, resulting in a sweet, bitter and nutty flavour
• Maillard browning


  Reactions between sugars and proteins at high temperatures, contributing to desirable brown colour and roasted flavour
• Denaturation


  Proteins uncoil and lose their original structure, changing the physical appearance and texture of the food
• Foaming


  Protein denaturation where air is trapped inside a solid or liquid, increasing the volume
• Coagulation


  Solidifying or curdling of protein rich food brought about by heat or acids, changing the physical appearance
• Gluten development


  Wheat proteins (gliadin and glutenin) join together to form a network of dough when mixed with water and kneaded
• Shortening


  Fats ability to shorten gluten strands when water is added to wheat flour, resulting in a crumbly texture
• Emulsion


  A mixture formed by combining two liquids that do not normally mix, stabilised by an emulsifier
• Types of emulsions


  • Oil in water emulsion
  • Water in oil emulsion
• Melting point


  The temperature at which a fat turns from solid state to liquid state
• Smoke point


  The temperature at which a fat begins to decompose, discolour, and produce toxic smoke
• Enzymatic browning


  A reaction that occurs on the surfaces of certain fruits and vegetables that are cut or bruised, causing brown discoloration
• Measures to reduce enzymatic browning


  • Immerse cut fruit pieces in lemon juice
  • Keep the cut fruits in the chiller, in cling wrap
  • Pack cut fruits in vacuum sealed packs
  • Coat cut fruits with sugar syrup and saltwater