Introduction to Post-Harvest Management of Vegetables
- Fresh vegetables are highly perishable due to active senescence processes.
- Post-harvest management includes all activities from harvest to consumption.
- Main goal: minimize losses and maintain quality and nutritional value.
- Key activities: harvesting, handling, storage, processing, packaging, transport, and marketing.
Objectives of Post-Harvest Management
- Understand techniques to reduce post-harvest losses in vegetables.
- Identify causes and control measures for post-harvest losses.
- Recognize marketing channels and associated losses.
- Learn various post-harvest management techniques.
Importance of Post-Harvest Management
- Maintains quality and extends shelf life of vegetables.
- Reduces food losses, poverty, and food insecurity.
- Improves market share and competitiveness for smallholders.
- Enhances human nutrition and health.
- Reducing losses is often easier than increasing yield.
Causes of Post-Harvest Losses
- Improper harvesting (immature, over-mature produce).
- Faulty post-harvest practices and poor handling.
- Inadequate sorting, grading, and storage conditions.
- Improper packaging and delayed transport.
- Biological (pests, diseases), chemical, mechanical, physical, and physiological factors.
Types of Post-Harvest Losses
- Biological: Pests, diseases, microbial spoilage.
- Chemical: Contamination, off-flavors from pathogens or chemicals.
- Mechanical: Injuries, bruises, cuts during handling.
- Physical: Water loss, temperature extremes.
- Physiological: Sprouting, rooting, senescence, respiration changes.
Vegetable Marketing Channels
- Farmers → Wholesalers → Retailers → Consumers
- Farmers → Cooperatives → Retailers/Consumers
- Farmers → Pre-harvest Contractors → Wholesalers → Retailers → Consumers
- Farmers → Local Collectors → Wholesalers → Retailers → Consumers
- Direct marketing: Farmers → Consumers
Post-Harvest Chain Overview
- Farm: Harvesting and field handling.
- Pack-house: Cleaning, sorting, sanitizing, packaging, cooling, storage.
- Transport: Loading, unloading, stacking, protection.
- Market: Re-sorting, re-packing, storage.
- Processing: Drying, sauce production, fermentation.
Key Post-Harvest Procedures
- Harvesting
- Reception
- Pre-cooling
- Selection, Cleaning & Disinfection
- Drying
- Grading
- Other Treatments
- Packing & Packaging
- Storage
- Transport
Harvesting and Maturity
- Quality cannot be improved after harvest; harvest at optimum maturity.
- Harvesting time depends on intended use and market requirements.
- Harvest during cooler parts of the day to reduce heat load.
- Avoid harvesting during rain; if unavoidable, wash and dry before packaging.
Maturity Indices for Vegetables
- Days from fruit set
- Visual indicators (color, shape, external appearance)
- Texture and firmness
- Specific gravity, starch content, soluble solids
- Sugar-acid ratio, oil content, odor
Curing of Vegetables
- Technique for reducing water loss in hardy vegetables (e.g., onion, garlic, sweet potato).
- Involves drying under shade to heal wounds and toughen outer layers.
- Prevents decay and moisture loss during storage.
Cleaning and Washing
- Removes dust, dirt, and pathogens from produce surface.
- Methods: dry dusting, wet washing with clean water and mild detergent (0.1%).
- Washing duration: 3–5 minutes at room temperature (~27°C).
Sorting and Grading
- Sorting: Removal of diseased, damaged, or deformed produce.
- Grading: Categorization by size, weight, color, maturity, and quality.
- Improves market value and reduces spread of infection.
Packaging of Vegetables
- Protects produce from physical damage and contamination.
- Should be cost-effective, easy to handle, and suitable for transport.
- Reduces losses during marketing and storage.
- Materials: cartons, crates, baskets, plastic containers, etc.
Storage of Vegetables
- Different vegetables require specific storage conditions.
- Starchy vegetables: store at 15.5–21.1°C in dry locations.
- Most others: store at refrigerator temperatures (0–5°C).
- Keep away from ethylene-producing fruits to prevent premature ripening.
Temperature Management in Storage
- Temperature is critical for extending shelf life and reducing spoilage.
- Improper temperature causes chilling or heat injuries.
- Optimal temperature inhibits pathogen growth and delays senescence.
Respiration Rate and Perishability
- Vegetables have varying respiration rates affecting shelf life.
- High respiration rate: shorter shelf life (e.g., asparagus, mushrooms).
- Low respiration rate: longer shelf life (e.g., onions, potatoes).
Transportation of Vegetables
- Transport is a major factor in post-harvest losses.
- Produce should be transported quickly and efficiently.
- Proper packaging and loading are essential to minimize damage.
- Use refrigerated vehicles for long distances when possible.
Transport Equipment
- Refrigerated and non-refrigerated vehicles for highways.
- Containers for air, rail, and sea transport.
- Pallets for bulk handling.
- Manual transport: carts, wheelbarrows, animal-drawn vehicles for short distances.
Summary and Recommendations
- Post-harvest losses in vegetables can reach 20–50% between harvest and retail.
- Losses increase with more intermediaries in the marketing chain.
- Proper post-harvest technologies and timely operations minimize losses.
- Focus on harvesting at optimum maturity, cleaning, sorting, grading, packaging, storage, and transport.