Harvest Does Not Stop Metabolism
Harvesting separates the plant organ from the mother plant.
But metabolism continues.
- Respiration continues
- Ethylene production may increase
- Sugars are consumed
- Pigments degrade or change
Postharvest loss is largely a biochemical process.
Respiration & Energy Depletion
Respiration breaks down stored carbohydrates to produce ATP.
- High respiration → rapid sugar loss
- Increased heat production
- Faster deterioration
Respiration rate increases with:
- High temperature
- Mechanical injury
- Ethylene exposure
Ripening & Ethylene Regulation
In climacteric fruits:
- Ethylene triggers ripening
- Sugar concentration changes
- Pigments accumulate or degrade
- Texture softens
In non-climacteric fruits:
- Ripening is less ethylene-dependent
Understanding hormonal and metabolic control is essential for storage management.
Biochemical Causes of Quality Loss
- Chlorophyll degradation → yellowing
- Cell wall breakdown → softening
- Oxidative reactions → browning
- Sugar depletion → reduced sweetness
- Water loss → shriveling
Temperature & Controlled Atmosphere
Lower temperature:
- Reduces respiration rate
- Slows enzymatic activity
- Extends shelf life
Controlled atmosphere storage:
- Modifies oxygen levels
- Reduces ethylene activity
- Slows metabolic processes
Postharvest technology is essentially metabolic rate management.
Economic Implications
In many developing systems:
- 30–50% losses occur after harvest
- Lack of cold chain increases deterioration
- Improper handling accelerates metabolic damage
Reducing biochemical deterioration increases:
- Farmer income
- Food security
- Export competitiveness
Career & Field Relevance
As a horticulture professional, you must:
- Determine optimal harvest maturity
- Control storage temperature
- Manage ethylene exposure
- Design cold-chain systems
- Reduce metabolic losses
Understanding postharvest biochemistry transforms loss reduction into a scientific strategy.
Reflective Questions
1. Why does high temperature accelerate fruit deterioration?
2. How does respiration influence sugar loss?
3. Why is ethylene control critical in storage systems?
4. How can biochemical understanding reduce postharvest losses?
What You Will Study in Detail Later
- Respiratory pathways in harvested tissues
- Ethylene biosynthesis mechanisms
- Cell wall degradation enzymes
- Oxidative stress during storage
- Controlled atmosphere technologies
Today you see how metabolism continues after harvest.
Later you will analyze the molecular mechanisms behind postharvest deterioration.