Food prep

• Physical changes during food preparation


  1. Increase in size

  2. Tenderising

  3. Nutrient loss
• Physical change: Dried fruit and pulses soaked in water


  Absorb water and expand
• Physical change: Meat fibres

  Break up when meat is pounded with a hammer, minced or chopped, tenderising the meat
• Chemical changes during food preparation

  1. Yeast dough doubles in size during fermentation, as the yeast produces CO2 bubbles

  2. When meat is sprinkled with commercial tenderisers that contain proteolytic enzymes, e.g. papain, the meat fibres break down, which tenderises the meat

  3. The acid (vinegar) in a marinade has the same effect
• The most common proteolytic enzymes used to tenderise meat are bromelain (made from pineapples) and papain (made from papayas)
• Reasons why food is cooked: to destroy microorganisms (eg, salmonella in chicken), making food safer to eat and reducing the risk of food poisoning; to destroy enzymes in food (e.g. fish, lengthening the shelf life); to destroy toxins naturally present in food, eg. phytohoemagglutinin in kidney beans, which can be harmful if eaten without cooking; to make food (e.g. potatoes) easier to digest; to improve the appearance of food, eg, red meat becomes an appetising brown colour; to enhance the flavour of food, eg, meat, as fat melts and extractives are released from the fibres