Fruit and Veg - Food Technology

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Climacteric and Non- Climacteric

  • Climacteric - rapid rise in respiration rates after harvesting leading to rapid ripening, rapid ripening leads to spoilage, fleshy, banana, mango
  • Non-climacteric - gradual change in respiration, long keeping qualities, citrus group, pineapple
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Controlled Atmospheric Storage

  • Lower oxygen levels
  • Higer CO2 levels
  • Correctly blended gases fed into chamber
  • Slows rate of respiration
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Hypobaric Storage

  • Lowers oxygen
  • Diffuses ethylene
  • Delays respiration
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Ethylene

  • Stimulates ripening process
  • Produced at climacteric peak
  • Comes from amino acids
  • Can be applied externally
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Drying

  • AFD
  • Sun drying
  • Spray drying
  • Diced
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Juicing

  • Low viscosity e.g. Apples - macerated to form pulp, rack + cloth press to release juice, pasteurised, canned
  • High viscosity e.g. Tomatoes - macerated then heated at 80c to inactive pectolytic enzymes
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Pickling

  • Wooden vat filled 1/3 full with 10% brine
  • Vegetables added
  • Dry salt added
  • Lactic acid produced
  • Cumcumbers 
  • Onions
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Preserves

  • Jam - sugar added to equal weight of fruit
  • Candied fruit - strong sugar solution added to slices so they become dehyrated
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Factors influence ripening

  • High temperature = rapid ripening 
  • Oxygen must be sufficient or fruit ferments
  • Ethylene stimulates ripening
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Changes during ripening

  • Starch broken down
  • Pectin broken down
  • Sweetens due to breakdown of starch 
  • Cell wall polysaccharides degraded
  • Fruit softens
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