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
Excessive transpiration leads to:
- Loss in saleable weight
- Wilting and shriveling
- Toughening
- Discoloration
- Flavor changes
- Loss in nutrients
- Accelerated senescence
Colorless and odorless gaseous compound, a plant hormone produced by all plant tissues more in some parts and when organs are wounded or stressed.
Ethylene
it produces a high amount of ethylene
climacteric fruits
Ethylene causes:
Ripening of fruits
Abscission of leaves and petals of cutflowers
Yellowing of leaves and fading of flower colors
Epinasty of leaves and flowers
Sprouting of root, tuber and bulb crops
Toughening
Development of bitter flavor such as in carrots and cabbage
Induction of some physiological disorders (russet spotting in lettuce)
What are the classification of produce according to ethylene production and commodity response
- Stage of maturity
- Physiological State
- Environmental conditions
- Stress and Mechanical Damage
Immature commodities produce higher amounts of ethylene
Stage of maturity
Ripening commodities produce more ethylene than unripe ones. More mature organs are more sensitive to ethylene,
Physiological state
High temperature and the presence of external ethylene gas hasten production of ethylene in mature fruits.
Environmental conditions
Any stress (water loss, insect or physical injury and rots) can increase ethylene production
Stress and Mechanical Damage
refers to the metabolic process by which harvested crops continue to respire or undergo biochemical reactions, leading to the consumption of stored nutrients and the release of carbon dioxide, water vapor, and heat energy.
Post-harvest respiration
the process of releasing water vapor containing oxygen in exchange for carbon dioxide.
Transpiration
the exact opposite of photosynthesis and transpiration
Respiration
process of using oxygen and producing carbon dioxide
Respiration
it is used to breakdown and use food resulting in the release of carbon dioxide,
oxygen
during respiration, fruits and vegetables consume oxygen and release carbon dioxide and water vapor. This process generates heat and can lead to the
loss of moisture content
There is an inverse relationship between respiration rates and the postharvest life of fresh vegetables
The higher the respiration rate, the more perishable (shorter postharvest life) the commodity
Respiration plays a major role in the postharvest life of fresh vegetables for the reasons:
- Loss of substrate
- Oxygen Requirements
- Carbon dioxide Production
- Release of Heat Energy
Use of various substrates in respiration can result in loss of food reserves in the tissue and loss of taste quality (especially sweetness) and food value to the consumer.
Loss of Substrate
An adequate O2 concentration must be available to maintain aerobic respiration. This should be considered in selecting the various postharvest handling procedures, such as waxing and other surface coatings, film wrapping, and packaging.
Oxygen Requirements
Accumulation of CO2 produced by the commodity in its ambient atmosphere can 1 e beneficial or harmful, depending upon each commodity’s tolerance to elevated CO2 Ievels
Carbon dioxide Production
The heat produced by respiration (vital heat), which is about 673 kcal for each mole of sugar (180 g) utilized, can be a major factor in establishing the refrigeration requirements during transport and storage.
Release of Heat Energy
fruits ripen after being harvested
Climacteric fruits
fruits do not ripen after harvesting
Non-climacteric fruits
have an increased respiration rate
Climacteric fruits
do not display any increase in the rate of resporation
Non-climacteric fruits
Signs or indicators of the readiness of the plant to harvest
The basis for determining harvest date
It involves assessment of some characteristics that changes as the crop matures
It is compromise between indices that ensure the best eating quality and those that provide the needed flexibility in marketing
It is the sign of minimum acceptability for majority of consumers
Maturity indices
The characteristics of the commodity at different stages of maturity using a particular type of index
Maturity Standards
What are the techniques of maturity determination
- Use of Subjective Indices
- Use of Objective Indices
- Predicting when to harvest based on units
Uses senses – can be visual of physical means
Easy and inexpensive to apply
Disadvantages:
Not accurate enough to set standards
Inconvenient for large scale enterprise
It influenced by growing conditions
Use of Subjective Indices
These are measurable indices
Includes measurement of time, chemical constituents, rate of physiological characteristics
More difficult to determine and sometimes time consuming but provides accurate measure of readiness of the commodity to be harvested.
Use of Objective Indices
Best to predict when to harvest based on the growing temperature
Recently developed techniques of determining maturity. New objective and non-destructive methods of determining maturity but requires expensive equipment and are usually used for research studies
Predicting when to harvest based on heat units
drying of leaves, fullness of fingers, for export market, calibration size for the indication of fullness of fingers (by caliper measurements), number of days from the appearance of the falsehand
Banana
Polygon on the rind become larger and spaces widen
Breadfruit (Rimas)
Change from green to yellow or colour break stage or when predominantly yellowish green.
Carambola (Balimbing)
In Philippines, Malaysia and Inddonesia, it is considered mature when it falls on the ground and ripe if it gives off distinctive odor; change in peel color (green to tinge of yellow); increase in spine stiffness; sap from stem becomes clear and not thick enough to stick on the fruit.
Durian
Curd is compact and bright green; florets not yet open
Broccoli
Tender when pierced with the thumb nail
Gourd
Harvest when 50 – 75% of the plant leaves fall down and neck is small
Onion
Harvest when 1/3 or ½ of the flowers opened
Baby Aster
Flowers are fully open
Birds of Paradise ( Sterilizia)
Harvest when the flower is half open
Calla Lily
For immediate usage: ½ of the petals are open or when first two petals begin to unfold
- For Storage: first two florets show color
Roses
A good index should be
- quick and easy to determine
- reliable
- Independent of ripeness for fruits
- Show a significant relationship with consumer acceptance
WHY IS MEASURING LOSSES IMPORTANT?
- To implement strategies to minimize wastage and improve profitability.
- identify areas where improvements in handling, storage, threshing, shelling, milling, drying, packaging, or transportation are needed to maintain product quality.
