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15 Cards in this Set
- Front
- Back
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Water content of commodities
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Most fruits and vegetables contain from 80-95% water
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All commodities lose moisture during storage
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This is primarily through transpiration, not respiration
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What is transpiration
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The evaporation of water from the surface of leaves, stems, fruit, etc.
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Moisture loss
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A 3-5 percent moisture loss may cause wilting and textural changes A 5% loss causes apples to shrivel and sweet corn kernels to dent
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Reduced moisture
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less weight --> less $$
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water loss
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Stomata -- in leaves -- closed stomata still lose a little water.
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Natural water loss sites
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Stem scars (tomato) Lenticels (apples, potato)
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Created water loss
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Cracks and injuries -- major source of water loss
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Sprouting in storage
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loss of water from sprouts --quickly shrivel and lose marketability.
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The amount of water air can hold and temperature
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rises as the temperature rises.
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The relative humidity of intercellular spaces can be assumed to be
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≈ 100%. If the air surrounding produce has < 100% RH, water vapor moves out of the tissue into the air.
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It is essential to cool produce to the temperature of the surrounding air.
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Water will be lost more rapidly from a warm than a cool vegetable at a given RH [it has a higher vapor pressure difference relative to the storage air than does a cool vegetable].
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It is usually essential to maintain _____RH values between a commodity and the atmosphere at a given temperature.
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Similar That is, at any given temperature, the RH of the storage air should be high (an exception to this is onions and garlic)
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Most water loss occurs during
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the initial cooling down period [due to the large VPD] -- > another reason we need fast cooling!
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Increased air dryness and increased rate of air movement (unless 100% RH) cause
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increased water loss. Air velocity should be just sufficient to remove respiratory heat
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