FOOD SPOILAGE AND CONTAMINATION

• • Micro-organisms are tiny forms in life, both plants and animals, only visible under a microscope
• • Food spoilage - making food unfit and unsafe to eat
• • Contaminate - making food unsafe to eat by allowing contact with micro-organisms that will grow and multiply in it
• • Pathogenic - something that is capable of causing illness
• • Food poisoning - an illness caused by micro-organisms contaminating food
• • High risk foods - foods that contain a lot of moisture and nutrients that can easily support the growth of pathogenic micro-organisms especially bacteria
• • Enzyme - natural substances in living things that speeds up chemical reactions
• • Catalyst - substance that speeds up the rate of a chemical reaction
• • Micro-organisms found in: water, people, animals, air, clothing, food etc
• • Micro-organisms spoil food and make it unsafe to eat as they contaminate it with their waste products, physical presence and toxins (poisons) they produce
• • 3 groups of micro-organisms that spoil food and cause food poisoning: bacteria, moulds and yeasts
  • Each of these groups have different types but only some of them spoil food
• • Suitable conditions needed by micro-organisms: suitable temperature, supply of moisture, supply of food, enough time, right pH (acidity or alkalinity)
• • Ripening - process of a fruit or vegetable maturing so that it is ready to eat
• • Enzymes cause fruits or vegetables that have been harvested to ripen 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 (eg by heat or acids)
• • Enzymes change texture, flavour an aroma of fruits and vegetables
• • Enzymic browning - discolouration of a fruit or vegetable due to the reaction of enzymes with plant cell substances and oxygen from the air
  • When you open certain fruits and vegetables, they develop a brown/black/grey discolouration: these fruits/vegertables include apples, potatoes, avocados, mushrooms, aubergines and bananas
• How do some types of mould contaminate foods?

  By growing and multiplying or producing waste products or toxins
• What effects do moulds have on food?

  They spoil appearance, smell, texture, and flavour of foods and can cause food poisoning
• What is a visible sign of mould growth on food?

  A furry appearance on the surface
• What conditions do moulds need to grow?

  Right temperature, moisture, food, time, and pH
• How do moulds multiply?

  By sending out tiny airborne spores that land on food and germinate if conditions are right
• What happens when spores germinate on food?

  They send down roots into the food, forming mycelium
• What is mycelium?

  The roots sent down into the food by germinated spores
• How can you see mould growth on food?

  By observing the thousands of shoots with fruiting bodies on top
• What is the process of mould growth on food?

  • Moulds contaminate food by growing or producing toxins
  • Visible signs include a furry appearance
  • Conditions needed: temperature, moisture, food, time, pH
  • Moulds multiply via airborne spores
  • Germinated spores form mycelium and shoots with fruiting bodies
• How yeasts affect foods

  • Wild yeast can spoil foods especially those that contain sugar such as fresh and dried fruits (eg grapes, apples, strawberries)
  • Yeast settle on food and start to grow then ferment sugar to produce carbon dioxide gas and alcohol
  • Yeast spoilage appears as pale brown, spotted growth on skin of fruit which becomes brown and mushy as yeast continues to grow