food spoilage

• high risk foods are ready to eat foods that if not stored correctly could grow harmful bacteria
• high risk foods have a short shelf life - you cant keep them for long, or the bacteria might multiply to dangerous levels
• often, pathogenic bacteria leave no signs - taste, colour, odour or texture arent affected
• you can check there are no visible signs of spoilage when buying food:

  • fresh meat should be brightly coloured, firm and have a fresh smell
  • fresh fish should have shiny skin, red gills, clear eyes and smell clean or slightly salty
• high risk foods include:

  • cooked meat, fish and poultry
  • dairy products
  • eggs
  • shellfish
  • cooked rice
• enzymes are biological catalysts that speed up chemical reactions
• enzymes in fruit cause them to ripen which affects the sweetness, colour and texture of the fruit
• when you slice fruits, the oxygen in the air will turn the fruit brown - oxidation - and enzymes inside the fruit will speed up this process
• you can slow or stop an enzyme from working by:

  • adding an acid - enzymes work best at a certain pH, so if you use lemon juice, the acidic conditions will stop enzymic browning
  • blanching - is used to prepare vegetables for freezing as it destroys the ripening enzymes, so the vegetables retain their colour and nutrients
  • freezing slows down the enzymes but does not stop them
• moulds and yeasts are both microorganisms - this means in the right conditions, they can grow and spread quickly
• moulds spoil bread, cheese and fruit - they can change the look, smell and taste of the food. you can easily spot mould
• waste products from moulds can cause food poisoning - even if you scrape it off, toxins will remain
• yeasts commonly grow on the surfaces of fruit and spoil fruit by fermenting the sugars into alcohol and carbon dioxide
• mould and yeast growth can be prevented by correctly storing food