food safety

• what are microbes?

  tiny organisms surrounding us that are too small to be seen with our eyes
• example of microbes

  bacteria and mould
• microscope are required to see the individual cells of microbes
• bacteria can cause milk to turn sour due to microbial activity
• mould can grow on bread
• microbial activity is affected by

  pH, oxygen supply , water content, temperature
• methods of prevention

  lowering pH, reduce oxygen supply, reducing water content, using high temperature and low temperature
• pickling is a method of preserving food in an acidic solution. when environment too acidic , microbial activity is reduced.
• most microbes cannot survive without oxygen. Vacuum packaging and bottling remove most of the oxygen that is in contact with the food.
• microbes need water to survive. reduce water content by freeze drying, dehydration and using chemical preservatives
• freeze drying : food is frozen rapidly, most of the water content is removed
• dehydration : the water content in foods is removed by using heat , removing moisture
• chemical preservatives : dehydration agents are used to keep the air in food packaging dry. Salt and sugar are also used to reduced water content in food
• high temperature include sterilisation, pasteurisation and canning
• sterilisation involves heating food to high temperature to stop microbial activity and preserves food for a long period of time
• pasteurisation involves heating food to a high temperature to reduce microbial activity ,and then cooling the food rapidly, preserves food for a short time
• canning involves heating food to a very high temperature under pressure to stop microbial activity, preserves food for a long time
• low temperature involve freezing food to reduce microbial activity
• preservatives: salt, sugar, sulfur dioxide, vinegar
• nutritional supplements: minerals, vitamins
• texture and appearance modifiers: food coloring, starch