Improving food production
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Improving food production






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Improving food production Improving food production Presentation Transcript

  • Improving Food production
  • Objectives
    • Describe how the use of fertilisers and pesticides with plants and the use of antibiotics with animals can increase food production
    • Describe the advantages and disadvantages of using microorganisms to make food for human consumption
    • Outline methods used to prevent food spoilage by microbes
    • in many countries farming has become more intensive (since world war 2)
    • fertilisers/pesticides used
    • animals fed supplements and antibiotics
    • recent backlash
    • people prepared to pay more for organic food
  • fertilisers
    • ammonium nitrate
    • plants need ammonium ( NH 4 + ) and nitrate (NO 3 - ) ions
    • expensive
    • soil tested using GPS to see if needed – can be applied in exact quantities
    • too much fertiliser not only damages environment and is costly but actually reduces yield by reducing water potential in soil
    • precision not possible using manure
  • Classwork/Homework questions
    • saq 8, 9, 10 p158-159 cambridge
  • pesticides
    • insecticides/fungicides
    • DDT – accumulates in food chain. broad spectrum . banned. malaria
    • several applications a year needed
    • resistance can develop
    • traces left on food
  • antibiotics
    • intensively farmed animals
    • more susceptible to disease
    • treatment increases growth rates
    • may destroy bacteria in gut that would slow growth
    • widely used with pigs and chickens
    • risk of resistance to antibiotics evolving in bacteria if used too widely,
  • How can microbes spoil our food?
    • Visible growth on bread, cheese etc - Grows for a few days before it is noticible – Mucor – black, Penicillium - blue green
    • Sweet smell (bananas) – indicates enzymes are releasing sugars from carbohydrate – food will become mushy
    • Can cause infection – Salmonella , in chicken – also Clostridium botulinum and E.Coli
  • preventing food spoilage by microbes
    • Refrigeration – slows enzyme activity of microbes
    • Salting/sugaring/drying - dries the food by osmosis
    • Pickling - acid denatures microbe enzymes
    • freezing – lack of water prevents growth of microbes
    • pasteurisation/UHT - kills harmful microbes
    • Irradiation- disrupts DNA of microbes
    • vacuum sealing/canning- prevents air reaching food (needed for microbial aerobic respiration)
    • Name a different foodstuff that is preserved by each method
  • Using microbes to make food
    • Yogurt- milk turned sour by Lactobacillus bacteria- uses lactose sugar in milk to make lactic acid. This also thickens the milk proteins
    • Cheese - from curdled milk. Lactobacillus
    • Bread- uses yeast ( Saccharomyces ) to rise. The carbon dioxide produced provides the bubbles
    • Alcohol- a by product of anaerobic respiration- uses strain of yeast called Saccharomyces Carlsbergensis. This respires (ferments) on sugars in grapes( glucose /fructose) to make wine or malted barley ( maltose sugar) to make beer
  • mycoprotein (QUORN)
    • myco – fungus
    • Fusarium venenatum /graminearum
    • Single cell protein (SCP)
    • Advantages
      • Similar texture to meat
      • Faster growth than meat
      • All essential amino acids, lower in fat , no cholesterol
      • Production can easily be changed with demand
      • Can be grown all year round
    • Disadvantages
      • taste
      • Can be grown using waste as a substrate material such as paper and whey( curdled milk from which curds are removed)
      • Protein needs to be purified to avoid contamination
      • Care needs to be taken to avoid microbial infection of product
  • Homework Questions
    • Why should frozen food never be thawed and then refrozen?
    • Describe the effects of these temperatures on bacterial growth and activity (all degrees celsius): -12, 4, 25, 37, 50, 65, 100, 120
    • Explain how osmosis can help keep food fresh
    • What is the difference between milk that is pasteurised and UHT?