Austin Community College Introduction To Foods

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Austin Community CollegeIntroduction To Foods 

• Introduction to Fruits

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What are Fruits?

•     Produced from flowers
• - the ripened ovaries and adjacent tissue

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Three classes of fruits 

• 1) Simple     Ovary of one pistil (grapes,
  stone fruit and pomes)2) Aggregate     Single
  flower with several pistils (raspberry and
  strawberry)3) Multiple    Formed from many
  flowers that remain together (pineapple)

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Problem with Fruit Classification

• Examples are tomato, squash, cucumbers, peppers
  are fruits    Based upon a legal case in 1893
  involving tariffs on vegetables

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Problem with Fruit Classification

•     Importer argued that tomatoes should be
  exempt from the tariff since they are botanically
  classified as a fruit    Justice Horace Gray
  argued that tomatoes were a vegetable since they
  were served with the main part of a meal (fruits
  used as desserts)    Established precedent
  which stands today

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Fruit Composition

• Remember that fruits contain both edible and
  inedible product (waste up to 40 in some cases)

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Major Components

• 1)       Water (75-93)2)       Carbohydrates
  (sugars, cellulose)3)       Pectin
  substances4)       Aromatic compounds, organic
  acids and essential oils5)       Vitamins,
  minerals, pigments

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Flavor Components

•     Sugars    Aromatic compounds    Esters,
  aldehydes, alcohols    Acids (citric, acetic,
  tartaric)    Essential oils

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Ripening Changes 

•     Four major changes1)       Color changes
  (green to red, yellow, orange or
  combination)2)       Softening of flesh
  (pectin)3)       Development of flavors4)      
  Changes in sugar and acid levels

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Enzymes

•     Organic catalyst produced by cells that
  change the rate of reactions without being used

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 Complete Ripening Reaction

• 1)       Hormonal changes in plant trigger
  ripening(Example the weather warming, sun
  position) 2)       Increase in enzymatic
  activity to catalyze reactions3)       Increased
  respiration (ethylene gas is produced)   
  Ethylene gas aids in starting process (storage
  ripening)

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Complete Ripening Reaction

• 4)       Reduction in organic acids5)      
  Reduction in the quantity of chlorophyll6)      
  Increased production of other pigments7)      
  Reduction of starch levels8)       Increased
  sugar levels

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Complete Ripening Reaction 

• 9)       Pectic substances allow for softening of
  texture and development of flavor substances   
  Prospecting inside cell converts to pectinic acid
  (gel like substance)    Increased ripening
  changes this to pectin (broken down)

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Selection Characteristics for Fruits

•     Understand what is the proper color for the
  fruit    Examine the surface characteristics of
  the fruit    Purchase the heaviest fruit
  possible due to the high percentage of water
      Smell the product    Check by squeezing
  to see if theres a slight yield to pressure   
  Examine the entry point of the stem for mold

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Storage Concerns

•     Fruits should only be washed just before
  usage unless theres visual evidence of soil or
  insects    Should the fruit be refrigerated and
  at what temperature

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 Preparation Osmosis

•     Selective permeability
•     Movement of water and or solutions through
  a cell membrane to either form equilibrium or
  create a balance desired by the cell
•     Cell membrane is normally living

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 Diffusion

•     Movement of a solution or water from an area
  of higher concentration to an area of lower
  concentration
•     Cell membrane is normally dead   
  Therefore, the cell membrane does not control
  movement

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Example

•     In raw products    Water moves to form
  equalized water solutions dependant upon the
  cells needs     Upon cooking    Cell
  membrane dies (no more selective
  permeability)    Substances are free to move to
  form equalized solutions

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Dried Fruit Products

•     Low water concentrations    Water absorbed
  to equalize (diffusion)    Check sweetness
  level when cooking

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Oxidative Enzymatic Browning

•     Only conditions that this occurs
  in1)  Fruit that contains low levels of acid
  (not pH related)2)  Fruit that is damaged or cut
  in some aspect3)  Light colored

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 Oxidative Enzymatic Browning  

•     Polyphenolic compounds (found in cells)
  oxidized by enzymatic activity (found outside the
  cell wall)    Produces melanin compounds (gray
  to black)

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Oxidative Enzymatic Browning

•     Prevent discoloration with 1)       
  Refrigeration slows down reaction2)        Cover
  product in water3)        Any type of cooking
  (destroys enzyme)4)        Addition of an acid
  to the surface (citrus) 5)        Addition of
  antioxidants or ascorbic acid (fruit fresh)
  6)        Addition of a salt solution to the
  surface7)        Cooking in a sugar syrupTreat
  the surface with sulfur dioxide