food production

• in making bread, the yeast first respires aerobically producing water and carbon dioxide. the carbon dioxide makes gas bubbles which causes the bread to rise and the bubbles leave hole in the bread. when the air runs out, the yeast respires anaerobically making ethanol and carbon dioxide. however the yeast cells are killed by baking, preventing further respiration, and the ethanol evaporates.
• yoghurt is made from milk that has been altered by lactobacillus which uses the lactose in milk as glucose for anaerobic respiration. this produces lactic acid which causes milk protein (caesin) to thicken and taste sour.
• 1. milk is pasteurized to 90 to kill unwanted bacteria so it doesnt slow production of yoghurt
  2. then cooled to 40 so lactobacillus isn't killed when added and it is the optimum temperature
  3. then lactobacillus added
  4. then cooled to 4.5 to halt action of lactobacillus but not denature it
• industrial fermenters are used to grow (culture) microorganisms in large amounts

  can be used for food production (beer, yoghurt) or other processes like producing genetically modified bacteria and fungi that produces antibiotics
• how/why are aseptic conditions controlled in a fermenter

  it is cleaned by steam

  to kill unwanted microorganisms and prevent chemical contamination
• how/ why are nutrients controlled in a fermenter

  nutrients are added to fermenter (like glucose) which is needed to respire and so the microorganisms can reproduce
• how/ why is temperature controlled in a fermenter

  monitored using probes and maintained using water jacket

  to maintain optimum temperature for enzymes to increase activity
• how/ why is pH controlled in a fermenter

  pH probes monitor pH which can be adjusted using acids or alkalis

  maintains optimum pH for enzymes to increase their activity
• how/ why is oxygenation controlled in a fermenter

  aeration system supplies oxygen when needed for aerobic respiration
• how/ why is agitation controlled in a fermenter

  stirring paddles hit contents so microorganisms, nutrients and oxygen are evenly distributed and the temperature and pH is consistent