1. Temperature Effects on DeteriorationTemperature Effects on Deterioration
There are six direct temperature effects onThere are six direct temperature effects on
deteriorationdeterioration
 The rate of respiration is determined by theThe rate of respiration is determined by the
temperature of the producttemperature of the product
 The rate of water loss from harvested produce isThe rate of water loss from harvested produce is
directly influenced by the temperature of thedirectly influenced by the temperature of the
environment that the product is held in.environment that the product is held in.
 The temperature of the product influences allThe temperature of the product influences all
metabolic activity in the tissue including the synthesismetabolic activity in the tissue including the synthesis
of ethylene, its activity and its sensitivity if exposed toof ethylene, its activity and its sensitivity if exposed to
an external source of ethylene.an external source of ethylene.

2. Lower temperature will offer some controlLower temperature will offer some control
over a lot the disease organisms that causeover a lot the disease organisms that cause
decay.decay.
Lower temperature will slow down the activityLower temperature will slow down the activity
of insects and over prolonged periods, mayof insects and over prolonged periods, may
kill the pest.kill the pest.
The temperature of the environment and theThe temperature of the environment and the
product will determine the amount of growthproduct will determine the amount of growth
and development that occurs after harvestand development that occurs after harvest

3. Gaseous Environment Effects onGaseous Environment Effects on
DeteriorationDeterioration
 There are four gases of importance in theThere are four gases of importance in the
postharvest phase, they are oxygen, carbonpostharvest phase, they are oxygen, carbon
dioxide, ethylene, and water vapor.dioxide, ethylene, and water vapor.
 The movement of gases into and out of aThe movement of gases into and out of a
product is one of simple gas diffusion.product is one of simple gas diffusion.
 There will be a greater overall movement ofThere will be a greater overall movement of
water vapor molecules out of the product towater vapor molecules out of the product to
external environment than there will be form theexternal environment than there will be form the
external environment to the product. This willexternal environment to the product. This will
continue until there is an equilibrium (or balance)continue until there is an equilibrium (or balance)
achieved between the two concentrations ofachieved between the two concentrations of
water vapor.water vapor.

4. The rate of gas diffusion is governed by :The rate of gas diffusion is governed by :
The concentrations gradient between theThe concentrations gradient between the
internal environment (in the product) and theinternal environment (in the product) and the
external environment (in the package orexternal environment (in the package or
coolroom for example). The greater thecoolroom for example). The greater the
difference in concentration, then the greaterdifference in concentration, then the greater
the rate of diffusion of the gas from highthe rate of diffusion of the gas from high
concentration to the low concentration.concentration to the low concentration.

5. Air movement will alter concentration of all ofAir movement will alter concentration of all of
these gases adjacent to the surface of thethese gases adjacent to the surface of the
product which may influence the direction ofproduct which may influence the direction of
the diffusion.the diffusion.
Air pressure influences the rate of diffusion.Air pressure influences the rate of diffusion.
As air pressure decreases, then the rate ofAs air pressure decreases, then the rate of
diffusion increase.diffusion increase.

6. Respiration EffectsRespiration Effects
 An oxygen supply must be maintained to theAn oxygen supply must be maintained to the
product in the postharvest phase at all times soproduct in the postharvest phase at all times so
as to sustain the living processes.as to sustain the living processes.
 As respiration is a reversible reaction, it isAs respiration is a reversible reaction, it is
possible to adjust the level of oxygen topossible to adjust the level of oxygen to
manipulate the rate of diffusion andmanipulate the rate of diffusion and
consequently, respiration.consequently, respiration.
 The amount of carbon dioxide in theThe amount of carbon dioxide in the
environment around the product can beenvironment around the product can be
increased to reduce the rate of diffusion out andincreased to reduce the rate of diffusion out and
promote the backward direction of thepromote the backward direction of the
respiration process.respiration process.

7. Ethylene EffectsEthylene Effects
Ethylene is a natural plant hormone whichEthylene is a natural plant hormone which
is important in both senescence of freshis important in both senescence of fresh
produce and the ripening of climactericproduce and the ripening of climacteric
fruit.fruit.
Ethylene is involved in the ripening ofEthylene is involved in the ripening of
many important commercial fruit that havemany important commercial fruit that have
a climacteric pattern of respiration.a climacteric pattern of respiration.

8.  Ethylene has both beneficial and detrimentalEthylene has both beneficial and detrimental
effects in the post harvest horticulture. The twoeffects in the post harvest horticulture. The two
most common benefits seen are controlledmost common benefits seen are controlled
ripening (bananas, tomatoes, avocados, andripening (bananas, tomatoes, avocados, and
mangos) and the de-greening of citrus. Ethylenemangos) and the de-greening of citrus. Ethylene
treatments promote a faster, more uniform fruittreatments promote a faster, more uniform fruit
ripening.ripening.
 The detrimental effects are increased rate ofThe detrimental effects are increased rate of
senescence, loss of chlorophyll, thesenescence, loss of chlorophyll, the
development of abscission zones and prematuredevelopment of abscission zones and premature
wilting of flowers.wilting of flowers.

9. Water LossWater Loss
 Most horticultural products have a very highMost horticultural products have a very high
water content. They are susceptible to waterwater content. They are susceptible to water
loss after harvesting as they are removed fromloss after harvesting as they are removed from
their source of water.their source of water.
 Water loss result in both qualitative andWater loss result in both qualitative and
quantitative losses in the product.quantitative losses in the product.
 Reduced appearance through wilting andReduced appearance through wilting and
shriveling, and reduced succulence signified byshriveling, and reduced succulence signified by
lack of turgidity, lack of crispness and loss oflack of turgidity, lack of crispness and loss of
juiciness, are qualitative losses. For thosejuiciness, are qualitative losses. For those
products that are sold by weight, water loss is aproducts that are sold by weight, water loss is a
quantitative loss of saleable weight.quantitative loss of saleable weight.

10. The rate of water loss depends on :The rate of water loss depends on :
The nature and condition of the surface of theThe nature and condition of the surface of the
productproduct
The surface area to volume ratioThe surface area to volume ratio
The environmentThe environment

11. The environment around the productThe environment around the product
 Temperature, relative humidity, air movementTemperature, relative humidity, air movement
and air pressure are the four components of theand air pressure are the four components of the
environment that will influence the rate of waterenvironment that will influence the rate of water
loss from harvested produce.loss from harvested produce.
 High temperatures, low relative humidity, rapidHigh temperatures, low relative humidity, rapid
air movement and/or a reduction in air pressureair movement and/or a reduction in air pressure
will all increase the rate of evaporation of waterwill all increase the rate of evaporation of water
vapor from the product.vapor from the product.

12. Temperature and Relative HumidityTemperature and Relative Humidity
 Relative humidity (RH) is the commonly usedRelative humidity (RH) is the commonly used
term describing the amount of water vapor heldterm describing the amount of water vapor held
in the air.in the air.
 The amount that can be held in the air dependsThe amount that can be held in the air depends
on the temperature.on the temperature.
 Warmer air can hold more water vapor. ForWarmer air can hold more water vapor. For
example, air at 30example, air at 30oo
C and 905 RH is more dryingC and 905 RH is more drying
than air at 20than air at 20oo
C and 90% RH simply because itC and 90% RH simply because it
can hold more water vapor.can hold more water vapor.