The signs of food spoilage

• What is the definition of ripening?

  The process of a fruit or vegetable maturing so that it is ready to eat
• How enzymes affect foods

  Ripening:

  . Enzymes cause foods such as fruits to ripen

  . The enzymes in the fruits or vegetables cause it to change colour

  . What you cannot see is that other enzymes have also changed the texture, flavour and aroma of the fruits

  . In the tomatoes, they will gradually become sweeter, juicier and softer and have a typical tomato aroma

  . Green bananas have very little flavour; they will be hard and will contain a lot of starch. As the enzymes start to ripen them, they will become sweeter, because the enzymes gradually break down the starch molecules into glucose molecules. They will become softer in texture and will develop a typical banana flavour and texture

  . Eventually bananas will turn a dark brown colour. They will be very soft and syrupy inside and very sweet. They will still be edible, but may not look on nice to eat. They would be perfect, however, to make a banana bread, so would not need to be wasted
• What happens to certain fruits and vegetables when they are cut or bruised?

  They develop a brown/black/grey discoloration
• Which fruits and vegetables are known to undergo enzymic browning?

  Apples, potatoes, avocados, mushrooms
• What do plant cells contain that contributes to enzymic browning?

  Storage vacuoles with natural substances
• What is the role of enzymes in the process of enzymic browning?

  They mix with oxygen and substances in vacuoles
• What is oxidation in the context of enzymic browning?

  Combining substances with oxygen
• How does enzymic browning affect the appearance of food?

  It makes the food less appetizing to eat
• What methods can delay or prevent enzymic browning?

  • Adding an acid (e.g., lemon juice)
  • Cooking the food
  • Putting food in cold water
  • Blanching vegetables before freezing
• How does adding an acid like lemon juice prevent enzymic browning?

  It denatures the enzyme protein
• What happens to enzymes when food is cooked?

  Heat denatures the enzyme protein
• Why does putting food into cold water help prevent enzymic browning?

  It prevents oxygen from mixing with enzymes
• What is the process of blanching vegetables?

  1. Plunge vegetables into boiling water briefly
  2. Drain through a colander or sieve
  3. Plunge into iced or very cold water
  4. Drain again and freeze
• What is the purpose of plunging vegetables into iced water after blanching?

  To stop the heating process
• What is the final step after blanching vegetables before freezing?

  Drain them again and freeze
• What is the definition of enzymic browning?

  The discolouration of a fruit or vegetable due to the reaction of enzymes with plant cell substances and oxygen from the air
• What is the definition of oxidation?

  When substances combine with (pick up) oxygen
• What is the definition of germinate?

  This is the process that happens when a spore from a mould starts to grow on a food
• What are moulds classified as?

  A type of micro-organism
• How do some types of mould affect food?

  They produce toxins that spoil food
• What is necessary to prevent moulds from multiplying in food?

  Understanding how they grow and multiply
• How can moulds be visually identified on food?

  They have a furry appearance on the surface
• What conditions do moulds need to grow and multiply?

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

  By sending out tiny airborne spores
• What happens when spores land on food under suitable conditions?

  They germinate and start to grow
• What is mycelium in relation to mould?

  Roots sent down into the food by germinated spores
• What do the shoots of mould produce?

  A fruiting body on the top
• What happens when the fruiting bodies of mould burst?

  They send out a shower of spores
• How does the life cycle of mould repeat?

  Spores travel through the air to other foods
• What can happen to foods that have gone mouldy during storage?

  They may look fine inside if cut
• What is a risk of eating mouldy food even if cut?

  Harmful waste substances may spread inside
• Why might harmful substances from mould not be detectable?

  They cannot be tasted or smelled
• How yeast affect foods

  . There are many species of wild yeasts and they can spoil foods, especially those that contain sugars, such as fresh and dried fruits (e.g. grapes, apples, strawberries)

  . Like moulds, they will settle on the food and start to grow, and then ferment the sugar to produce CO2 gas and alcohol

  . Yeast spoilage appears as a pale brown. spotted growth on the skin of the fruit, which becomes brown and mushy as the yeast continues to grow