What Is Post-Harvest Technology?
Post-harvest technology encompasses harvesting, handling, storage, and transport to minimize losses and maintain freshness from field to consumer. It's critical because increased production doesn't guarantee quality supply—post-harvest losses can reach 28–42% annually (under Philippine conditions) due to inadequate facilities and technology.
Causes of Post-Harvest Losses
1. Technological (Biological) Causes
- Decay/Rotting: Especially in leafy vegetables and fruits.
- Yellowing: Common in leafy veggies; indicates ripening then decay in fruits.
- Wilting: Leafy vegetables.
- Softening: Fruits and some leafy crops.
- Sprouting: Root vegetables (carrots, potatoes, onions, garlic) during long storage.
2. Non-Technological (Infrastructure) Causes
- Transportation: Lack of vehicles delays produce movement.
- Storage: Inadequate facilities; a top priority for success.
- Adverse Weather: Affects cropping patterns; choose suitable crops.
- Inefficient Distribution: Poor channels cause severe crop damage.
- Lack of Market Demand: Unsold produce leads to losses.
3. Physiological Damage
Changes in texture, flavor, and aroma.
4. Mechanical Damage
Rough handling during picking, packing, loading/unloading causing cuts, punctures, cracks, or shape changes.
5. Insect Damage
Occurs in storage or field pre-harvest. Control insects early; disinfect storage areas.
Basis of Post-Harvest Technology
1. Vegetables Are Living, Perishable Organs
- After harvest, respiration continues but photosynthesis stops; reserves deplete.
- Faster respiration = faster rotting; high stored food delays decay.
- High water content (80–95%) lost via transpiration, especially in hot, dry months.
2. Morphological, Structural, and Chemical Differences
- Leafy vegetables: Wilting, yellowing; many stomata → high respiration/transpiration.
- Fruit vegetables: Ripen to over-ripeness.
- Flower vegetables: Flowers open.
- Modified stems (tubers, bulbs): Produce new buds/sprouts; low surface area, few stomata, some lenticels.
3. Environmental Response
- Temperature: Most critical factor. Lower temps reduce respiration, transpiration, microbial and insect activity.
- Relative Humidity: Affects water loss.
- Atmospheric Gases: Ideal: 78% N₂, 21% O₂, 0.03% CO₂.
- Microorganisms/Insects: Vegetables serve as food; exclusion extends shelf life.
Strategies to Reduce Vegetable Losses
1. Start with Quality Seeds and Cultural Practices
- Select seeds for size, shape, color, texture, weight, nutrients.
- Environmental conditions (temp, light, rain) affect quality.
- Proper field prep: seedbed, water management, weeding, fertilization, pest/disease control.
2. Avoid Physical Damage
From harvest through sorting, cleaning, transport, and storage. Follow correct handling methods.
3. Control Environmental Factors
- Temperature Management: Refrigeration is most effective. Without it: harvest early/late, avoid direct sun, ensure ventilation, use white covers, travel at night.
- Relative Humidity Management: Maintain ~85%. Methods: wet floors, mist/steam in ventilation, open water containers, evaporative cooling.
- Gas Control: Lower O₂, raise CO₂ via perforated polyethylene bags. Avoid ethylene except for fruit ripening.
How to Avoid Ethylene Effects
- Ensure ventilation to dilute ethylene.
- Separate ripening fruits from leafy vegetables.
- Practice proper handling during transport/storage.
- Sort and remove diseased/injured produce.
- Avoid enclosed, smoky areas.
Reduce Microorganism Multiplication
- Clean containers, vehicles, rooms before use.
- Handle gently to avoid injury (entry points for pathogens).
- Avoid hot, moist conditions; ensure dry, airy storage.
- Sort and separate diseased produce.
- Disinfect with alum or lime (especially leafy veggies).
- Cure root/bulb crops at 20–35°C before storage/transport to extend shelf life.
