Storage of Fruit and Nut Crops

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Storage of Fruit and Nut Crops

• Post Harvest Physiology and Storage

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Fresh Fruit and Nuts are Alive!
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Fruits and Nuts are Living

• Consume
• O2
• Substrates
• Evolve
• CO2
• Heat
• Ethylene
• Lose H2O through epidermis

• Metabolically active
• Tissue softening
• Starch to sugars
• Sorbitol to fructose
• Organic acids decreasing
• Flavor volatiles increasing
• Color changes

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Objective of Storage

• Fresh fruit and nuts
• Minimize these changes
• Extend the life span of the fruit/nut

• Processed fruit/nuts
• Kill the fruit/nut
• Sterilize to avoid spoiling
• Extend time of edible state

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Types of Fruit

• Climacteric
• Apples
• Pears
• Apricot
• Peach
• Plum
• Fig
• Persimmon

• Non-climacteric
• Blueberries
• Grapes
• Cherries
• Strawberries
• Sweet oranges
• Lemons

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Types of FruitClimacteric vs. Non-climacteric

• Respiration increases during ripening

Fruit Growth
Respiration Climacteric
Respiration Non-climacteric
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Types of FruitClimacteric vs. Non-climacteric

• Ethylene content higher and increases more during
  ripening

Fruit Growth
Ethylene Climacteric
Ethylene Non-climacteric
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Fruit Respiration in Response to Ethylene
Rate dependent response to ethylene Amount of
ethylene dictates the ultimate level of response
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Fruit Respiration in Response to Ethylene
Non-rate dependent React to a threshold level to
give about same response
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• Non-climacteric fruit
• No increase in respiration
• Ripen slower
• Ethylene
• Produce less
• Lower internal levels
• No increase at ripening
• Applied Ethylene
• Rate dependent response

• Climacteric fruit
• Increased respiration at ripening
• Ripen faster
• Ethylene
• Produce more
• Higher internal level
• Level increases at ripening
• Applied Ethylene
• Respond to applied ethylene in non-rate dependent
  fashion

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Storage of Fresh Fruit - Crops

• Apples
• 3-10 months
• 40 stored
• Pears
• 2-7 months
• Grapes
• 2-3 months
• Nuts
• 1-4 years

• Stone fruit
• 2-8 weeks
• Berries
• 1-2 weeks
• Strawberry
• 1-5 days
• Fig
• 2-3 weeks

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Methods of StorageRefrigeration

• Temperature
• Lowers
• All enzymatic processes
• Respiration
• Reduce microbial growth
• Sensitivity to ethylene
• Optimal temperature
• Above tissue freezing point
• -2ºC to 0ºC
• Important to remove field heat quickly

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Methods of StorageRefrigeration

• Humidity
• 97 RH fruit does not lose moisture
• 95 RH microbial growth favored
• 90 RH poor microbial growth
• Loss of moisture
• Less product
• 5 shrivelling

• Fruit is water in an expensive package
• Prevention
• 90 RH
• Wax coatings
• Shrink wraps

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Methods of StorageModified Atmosphere Storage

• How does it work?
• Temperature
• Humidity
• Control of atmospheric gases
• CO2
• O2
• Ethylene

• Examples
• Burying apples
• Film wraps
• Chemical packages to absorb ethylene
• Not closely controlled

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Methods of StorageControlled Atmosphere Storage

• CA storage
• Control
• Temperature/humidity
• Oxygen
• Carbon dioxide
• Ethylene
• For long term storage

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Methods of StorageCA Storage of Apples

• Oxygen Level
• Lower to 3 from 21
• Reduce respiration
• Reduce ethylene production
• If too low
• Anaerobic metabolism
• Off flavors

• Carbon dioxide Level
• Increase to 5 from 0.03
• Reduce respiration
• Reduce ethylene production
• Inhibit the breakdown of pectic substances
• If too high
• Anaerobic metabolism
• Off flavors

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Methods of StorageCA Storage of Apples

• Ethylene Level
• One bad apple spoils the whole barrel
• Ripe/damaged fruit
• Release ethylene
• Induce other fruit to ripen

• Decrease sensitivity
• Lower temperatures
• Increase CO2
• Decrease O2
• Reduce levels
• Air ventilation
• Electric fork lifts
• Separate ripe from unripe fruit
• Remove ethylene via potassium permanganate

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Post Harvest DisordersSuperficial Scald

• Most important storage disorder in apples
• Dark brown, slightly depressed

• Caused by volatiles from the fruit
• Control
• Air circulation
• Antioxidants in post harvest dip
• Do not store susceptible varieties

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Post Harvest DisordersWater core

• Translucent areas in the flesh

• Can be induced by excessive heat
• More common in over mature fruit

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Post Harvest DisordersCalcium-related Disorders

• Bitter pit
• Sunburn
• Cork spot
• Cracking

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Post Harvest DisordersCalcium-related Disorders

• Bitter pit
• Sunburn
• Cork spot
• Cracking

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Post Harvest DisordersCalcium-related Disorders

• Bitter pit
• Sunburn
• Cork spot
• Cracking

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Post Harvest DisordersCalcium-related Disorders

• Bitter pit
• Sunburn
• Cork spot
• Cracking

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Post Harvest DisordersCalcium-related Disorders

• Not mobile in plant
• Moves slowly in soil
• Compete with Mg and K for uptake
• Worse under high temperature conditions
• Control Calcium applications to the fruit

• Role of calcium
• Functions in plant
• Regulate cell division
• Regulate nitrogen metabolism
• Important component of cell wall

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Post Harvest DisordersCalcium-related Disorders

• Sunburn
• Direct sun exposure
• Fruit tissue loses water
• Cell collapses
• Tissue under skin collapses

• Bitter pit
• Impairment of selective permeability of cell
  membranes
• Cell injury and necrosis
• Browning begins internally
• Develops external blemishes

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Post Harvest DisordersCalcium-related Disorders

• Cork spot
• After cell division cortical cells form
  additional cell walls within original cell
• Tissue hardens, ruptures, and browns

• Deep cracking
• Cell walls become thick and lose elasticity
• Fruit crack after rain or irrigation

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