FRUIT RIPENING SENSOR

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FRUIT RIPENING SENSOR

• Stephanie Pitcher
• Electrical Engineering Graduate Student
• University of Maine
• GK-12 Fellow

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THE NEED FOR AN ETHYLENE SENSOR

• Fruits emit ethylene while ripening
• If fruits are picked at the wrong time of the
  ripening process they taste bad
• An ethylene sensor is needed in the produce
  industry to allow harvesting for the most
  desirable product

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FRUITS

• The satisfaction of fresh fruits are not always
  available
• Too green and no flavor or over-ripe and too soft
• All the processes of fruits from picking to
  eating are subjects of studies/improvements
• The changes which occur (color, texture, aroma,
  flavor) are all known and common in the fruit
  ripening process
• Yet, there are differences that regulate and
  divide fruit into 2 categories

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CLIMACTERIC/NON-CLIMACTERIC

• Climacteric includes fruit whose ripening
  process depends on ethylene (a hormone emitted
  from plants)
• The fruits ripening process can be triggered off
  of and regulated by exposure to ethylene gas
• Fruits picked early can be ripened by confining
  them to an ethylene enriched atmosphere-storage
• Examples bananas, tomatoes, apples, melon, peach
• Non-Climacteric regulating the ripening process
  is unclear, and is currently being studied.
  Basically, they can not induce ripening process
  by ethylene gas exposure
• Examples grapes, strawberries, cherries

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ETHYLENE

• C2H4
• Simple gaseous hydrocarbon (plant hormone)
  synthesized by all plant tissues and some
  microorganisms
• hormone natural compound, which exists in
  small quantities that controls a physiological
  process
• Binds to a number of different protein receptors
• Has a direct relation to the ripening process of
  fruits
• Unripe fruits, low ethylene concentrations
  (0.05-0.1ppm)
• Increases 10 to 1000 times as fruit begins to
  ripen
• Ethylene levels increases to a maximum peak, then
  drops as fermentation occurs

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SENSOR TECHNOLOGY

• Semiconducting Metal Oxide (SMO) Sensors
• When a metal oxide film is exposed to a gas
  species (ethylene) the gas interacts with the
  film changing the films electrical properties
• By monitoring these properties in a gaseous
  environment one can detect if certain gasses are
  present

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TEST SETUP
Mass Flow Controllers
3-Way Valve
Computer
Gas Cylinders
Sensor in Sensor Chamber
Solartron
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BANANA OBSERVATION LAB

• Experiments
• 1) Control (need a basis to compare to)
• Banana unexposed
• 2) Variable 1
• Banana exposed to air
• 3) Variable 2
• Banana exposed to ethylene gas
• Observations
• 1) Record color changes
• 2) Record smells