The document discusses postharvest factors that affect the quality of fruits and vegetables. It focuses on the effects of humidity and temperature. Humidity affects water loss from produce through shriveling, wilting and loss of crispness. Temperature is the most important factor to control physiological and pathological deterioration. The rate of quality changes increases with higher temperatures, as shown by a temperature quotient (Q10) of over 2 for many produce items. Maintaining optimum humidity and temperature levels preserves quality and extends shelf life.

1. Week 4 – Postharvest Physiology of Fruits and Vegetables 2
Postharvest Technology
FT-310
Ali Ehsan
SFAS, UMT

2. Postharvest Physiology of Fruits and Vegetables
• CLO 2
• Describe the post-harvest physiological processes and factors
contributing to the post-harvest quality deterioration in various food
groups
• SLOs
• 2.1. Identify different stages in the lifespan of fruits and vegetables
• 2.2. Classify various physiological processes occurring in horticultural
commodities at different stages of development

3. Post-harvest factors
▪ Humidity
▪ Temperature
▪ Atmospheric gas composition
▪ Light
▪ Mechanical injury
▪ Post-harvest diseases or infections
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4. Post-harvest factors: Humidity
▪ Fresh fruits and vegetables contain sizable amounts of water, for example, watermelons
may contain water more than 95% of its fresh weight.
▪ Since most of the water is free water, the produce will continue to lose water to the
surrounding atmosphere.
▪ The loss in water manifests into symptoms of:
• Shriveling
• Wilting
• Loss of crispness
• Tough or mushy tissues
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6. Post-harvest factors: Humidity
▪ The reduction of saleable weight and loss of sensory characteristics lower the
marketing value.
▪ Weight loss by even 5% makes certain produces unsaleable.
▪ Factors affecting rate and the extent of water loss:
• Surface area/volume ratio
• Nature of surface
• Presence/Absence of cuticle
• Number of stomata (leaves), lenticels (fruits), periderm (tubers and roots)
• Injury to the plant tissues
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9. Post-harvest factors: Humidity
▪ Water loss can be prevented by maintaining:
• Optimum atmospheric relative humidity (RH)
▪ Optimum RH is 85%–90% for most fruits and 90%–98% for most vegetables except
dry onions and pumpkins (70%–75%).
▪ Maintaining high RH, in certain situations, may induce:
• Decay
• Surface mold development
• Physiological disorders, including impaired fruit ripening
• Surface condensation (sweating)
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10. Post-harvest factors: Temperature
▪ Temperature management is the most important tool in postharvest handling to control
both physiological and pathological deteriorations.
▪ Effect of temperature on the shelf life varies due to differences in physicochemical
properties of fruits and vegetables.
• For example, the most pronounced effect in increasing the shelf life by reducing
the temperature is expected for lettuce and green onion than for strawberry and
raspberry.
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11. Post-harvest factors: Temperature
▪ The effect of temperature on quality is expressed by a temperature quotient (Q10)
which is defined as:
• The temperature coefficient/quotient (Q10) is a measure of the rate of change of a
biological or chemical system as a consequence of increasing the temperature by
10°C.
▪ Where q2 and q1 are the rates of quality function at two temperatures, T2 and T1
respectively.
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12. Post-harvest factors: Temperature
▪ The Q10 values have been used to describe the effect of temperature on a
particular quality attribute, such as color, texture, flavor etc.
▪ For example, Q10 values for quality deterioration in asparagus when
expressed as appearance, sugar loss and fiber increase are 2.7, 5.8 and 10
respectively, in a temperature range of 0-10°C.
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13. Post-harvest factors: Temperature
▪ Proper temperature control will aid in:
• Lowering the risk of chilling and freezing injuries.
• Extending the shelf life.
• Reducing the loss of quality by lowering the metabolic processes such as
respiration and transpiration.
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14. Effect of temperature on shelf life of selected fruits and vegetables
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