Lecture 2 - Part 2 Flashcards
refers to the deterioration or decay of harvested crops due to microbial growth, physical damage, environmental conditions, or inadequate storage and handling practices.
Crop Spoilage
A decline in the availability, utility and saleable weight.
Quantitative Loss
A decline in acceptability by the consumer. A change in chemical constituents, appearance, nutritive value can decrease edibility and acceptability
Qualitative Loss
Loss due to unintentional damage sustained by the commodity
Mechanical
Loss due to disease organism and insects
Biological
loss due to bacteria/fungi
Microbial
Loss due to change in color, flavor, texture and nutritional value due to chemical constituents naturally present in crops
Chemical
Loss due to faster rate of inherent processes in the produce or abnormalities
Physio-Chemical
loss due to environmental factors
Physical
loss due to human aversions
Psychological
What are the causes of pH losses?
- Physiological Deterioration
- mEchanical Damage ( Physical Injury)
- Disease andpests
- Type of produce
- Postharvest physiology
- Respiration
- Transpiration
- Ripening
- Extent of Postharvest Damage
During postharvest handling, metabolic processes such as enzymatic reactions may occur, leading to changes in pH due to the breakdown of organic acids and other compounds.
Physiological Deterioration
Physical injuries sustained during harvesting, handling, or transportation can disrupt cellular structures, accelerating enzymatic reactions and metabolic processes that contribute to pH changes.
Mechanical Damage
Infections by pathogens and infestations by pests can lead to microbial growth and metabolic activities, resulting in the production of organic acids and other compounds that alter pH levels.
Disease and pests
Different types of fruits and vegetables have varying pH levels, and factors such as cultivar, maturity stage, and environmental conditions can influence pH changes during postharvest handling.
Type of Produce
The physiological processes occurring in produce after harvest, such as respiration, transpiration, and ripening, can affect pH levels through the production or consumption of organic acids and other metabolites.
Postharvest physiology
The process of respiration in produce involves the breakdown of carbohydrates and release of carbon dioxide and organic acids, which can influence pH levels in tissues and surrounding environments.
Respiration
Loss of water vapor through transpiration can concentrate organic acids and other solutes in produce, leading to changes in pH, particularly in dehydrated or desiccated tissues.
Transpiration
fruits undergo biochemical changes, including the conversion of starches to sugars and the degradation of organic acids, which can affect pH levels and contribute to changes in flavor and texture.
Ripening
The severity of postharvest damage, such as bruising, cuts, or lesions, can increase the exposure of tissues to enzymatic reactions and microbial activity, leading to pH alterations as a result of tissue breakdown and metabolic processes.
Extent of postharvest damage
refers to the ongoing loss of water vapor from harvested crops, particularly perishable fruits and vegetables.
Transpiration
Harvested produce remains fresh only as long as
it retains water
rates can lead to dehydration, reduced quality and shorter shelf life of the produce
High transpiration
is quite common during noon due to transpiration being higher than the rate of water absorption. Wilting reduces photosynthesis and other metabolic activities.
Wilting or loss of turgidity
What are the negative effects of Transpiration?
- Wilting
- Reduced growth
- Reduced Yield
- Abscisic Acid
- Wastage of Energy
it prevents several plant processes and promotes abscission of leaves, flowers and fruits.
Abscisic acid
What are the positive effects of Transpiration
- It helps regulate leaf temperature, ensuring that the crops or plants remain cool and preventing heat stress during hot weather conditions.
- It also aids in the transport of essential nutrients from the roots to other parts of the plant, supporting growth and development.
- Transpiration helps prevent the growth of fungal pathogens, reducing the risk of diseases that can affect fruit and vegetable quality.
- It also contributes to the production of volatile compounds that enhance the flavor and aroma of ripe fruits.
What are the conditions causing high rates of transpiration
- Low Relative Humidity (RH)
- High Temperature
- High wind velocity during transport