Micro-organisms and enzymes

• What is the definition of micro-organisms?

  Tiny forms of life, both plants and animals, only visible under a microscope
• What is the definition of food spoilage?

  Making food unfit and unsafe to eat
• What is the definition of contamination?

  Making a food unsafe to eat by allowing it to come into contact with micro-organisms that will grow and multiply in it
• What is the definition of pathogenic?

  Something that is capable of causing illness
• What is the definition of food poisoning?

  An illness caused by micro-organisms contaminating food
• What is the definition of high-risk foods?

  Foods that contain a lot of moisture and nutrients, especially protein (e.g. milk, cream, eggs, meat, fish), and easily support the growth of pathogenic micro-organisms, particularly bacteria. Also called perishable foods
• What is the definition of an enzyme?

  The name given to natural substances in living things that speed up chemical reactions
• What is the definition of a catalyst?

  A substance that speeds up the rate of a chemical reaction
• What are micro-organisms?

  Tiny forms of life, both plants and animals
• Why can micro-organisms only be seen under a microscope?

  Because they are too small for the naked eye
• What are micro-organisms sometimes called?

  Microbes
• Where can micro-organisms be found?

  • Water
  • Air
  • Dust
  • Dirt
  • Surfaces
  • Equipment
  • In and on people
  • In and on animals
  • In and on insects and birds
  • Rubbish
  • Clothing
  • Food
  • Food packaging
  • Soil
  • Sewage
• How do micro-organisms spoil food?

  By contaminating it with waste and toxins
• What are pathogens?

  Micro-organisms that make food unsafe to eat
• What types of micro-organisms can cause food poisoning?

  Pathogenic bacteria, moulds, and yeasts
• What are the ways micro-organisms make food unsafe to eat?

  • Contaminating food with waste products
  • Physical presence in the food
  • Producing toxins (poisons)
• Which micro-organisms can spoil food and make it unsafe to eat?

  . There are three groups of micro-organisms that you need to know about that spoil foods and cause food poisoning: bacteria, moulds and yeasts

  . Each of these groups has thousands of different types, but only some of them spoil food and make it unsafe to eat

  . Each type of micro-organism will be discussed in the following parts of this chapter
• What do micro-organisms need to live and multiply?

  Suitable conditions for growth
• How can the growth of micro-organisms be controlled?

  By changing or preventing suitable conditions
• What is the optimum temperature for most micro-organisms?

  Around 37°C
• What happens to micro-organisms in high temperatures?

  They can be destroyed
• What occurs to micro-organisms in low temperatures?

  Growth slows and they become dormant
• How can you prevent micro-organisms from growing in food?

  Cook food thoroughly at high temperatures
• What is the recommended refrigeration temperature for leftover food?

  Between 0°C and 5°C
• Why do micro-organisms need moisture?

  For biological processes
• What happens if there is not enough moisture in food?

  Micro-organisms cannot grow or multiply
• How can food be preserved to control moisture?

  By drying it or using sugar/salt
• What do micro-organisms need from food?

  Nutrients and energy
• How can you prevent contamination of food by micro-organisms?

  Keep food covered and away from sources
• Why is time important for micro-organisms?

  They need time to grow and multiply
• How often do most micro-organisms multiply?

  Every 10-20 minutes
• What should you do to avoid giving micro-organisms time to grow?

  Store, cook, and cool foods correctly
• What is the significance of pH for micro-organisms?

  It affects their growth and multiplication
• How can food be preserved to control pH?

  By using acid like vinegar
• What are the conditions required for micro-organisms to live and multiply?

  • Suitable temperature
  • Supply of moisture
  • Supply of food
  • Enough time
  • Right pH (acidity or alkalinity)
• What methods can be used to control the growth of micro-organisms?

  • Cook food thoroughly
  • Cool leftovers quickly
  • Preserve food by drying or using sugar/salt
  • Keep food covered and away from contamination
  • Store food correctly to limit time for growth
  • Use acid for preservation
• What conditions do micro-organisms need in order to live and multiply?

  Micro-organisms, particularly bacteria, will grow very easily in certain foods (e.g. meat, fish, seafood, poultry, milk, cream, cheese, cooked rice and eggs, and food products containing any of these) because they have lots of moisture and nutrients in them, especially protein. These foods are known as high-risk foods or perishable foods. Many of these foods are ready-to-eat and do not require any further heat treatment or cooking
• Enzymes

  . Enzymes are natural substances (mostly proteins) that are found in foods and all living things

  . They are called biological catalysts, which means they have the ability to speed up chemical reactions

  . Enzymes cause fruits and vegetables that have been harvested to ripen (e.g. bananas) and eventually break down the cells and tissues in them

  . Enzymes cause the tissues of meat and fish and other animal foods to break down once the animal has been killed

  . Enzymes are proteins, so their action can be controlled by causing them to denature (e.g. by heat or acids)