Post-Harvest Handling – SS1 Horticulture and Crop Production Lesson Note (Second Term)

Post-harvest handling is everything done to a crop from the moment it is cut until it reaches the final consumer.

Behavioural objectives

By the end of the lesson, students should be able to:

1. State why post-harvest handling is important.
2. Explain the difference between cleaning, sorting and grading.
3. Describe how horticultural crops are graded.
4. Name common packaging materials and give the rules for packaging.
5. Describe the types of storage used for horticultural crops.

What are the steps in post-harvest handling?

Post-harvest handling has six stages: harvesting, cleaning, sorting, grading, packaging and storage.

1. Harvest: the crop is cut or picked at the right stage of maturity.
2. Clean: soil, dust and insects are removed.
3. Sort: damaged and rotten items are thrown out.
4. Grade: good items are grouped by quality.
5. Package: items are packed in suitable containers.
6. Store: items are kept safe until sold or eaten.

Why is post-harvest handling important?

Post-harvest handling is important because horticultural crops such as tomatoes, mangoes and spinach are mostly water and spoil quickly.

• Reduces waste: it stops fruits from rotting before they can be eaten.
• Adds value: clean, well-packaged vegetables sell for a higher price than dirty ones.
• Protects health: proper handling prevents germs and mould from growing on food.
• Lengthens market life: crops stay fresh-looking for a longer time.
• Increases income: less waste and better quality mean more money for the farmer.

What causes post-harvest losses?

Post-harvest losses are the parts of a harvest that spoil or become unfit to sell before they are used.

• Bruising: rough handling, overloaded baskets and bumpy roads damage the skin.
• Heat: high temperatures make crops ripen and rot faster.
• Water loss: crops wilt and shrivel when left in the sun.
• Rot organisms: moulds and bacteria enter through cuts and soft spots.
• Pests: insects and rodents feed on stored produce.
• Ripening gas: ripe or rotting fruit gives off a gas (ethylene) that makes nearby fruit ripen and spoil.

How do we clean and sort harvested crops?

Cleaning removes dirt from the crop, and sorting removes damaged or rotten items from the batch.

What is cleaning?

Cleaning is the removal of soil, dust and insects from harvested crops.

• Root and underground crops (carrots, ginger): wash off the mud.
• Leafy greens: shake off sand and remove yellow or dead leaves.
• Soft fruits (tomatoes, strawberries): wash only shortly before eating, because moisture makes them rot faster.

What is sorting?

Sorting is the removal of bad items from the good ones.

• Remove any fruit with insect holes, bruises or soft spots.
• One rotten tomato in a basket gives off gas and germs that can spoil the whole basket by the next morning.

What is grading?

Grading is the grouping of good items into different levels of quality.

How do we grade horticultural crops?

There are three common ways of grading: by size, by ripeness and by appearance.

• By size: big “jumbo” onions go in one group and small onions in another.
• By ripeness: very ripe tomatoes go for immediate soup-making, and “green-turning-pink” tomatoes go for long-distance travel.
• By appearance: perfectly shaped, shiny peppers go into a “Premium” grade for hotels or supermarkets.

• Benefit of grading: the farmer sells Grade A items at a high price and still earns something from Grade B items at a lower price.

What is the difference between cleaning, sorting and grading?

Why do we package horticultural crops?

Packaging is the putting of crops into containers to protect them during handling and transport.

• Many crops travel long distances, for example tomatoes from the North to the South of Nigeria.
• Good packaging protects them from crushing, heat and dirt on the journey.

What are the common packaging materials?

The common packaging materials are plastic crates, raffia baskets, jute sacks and cardboard boxes.

• Plastic crates: the best option, with holes for air flow, and they stack without crushing the fruits at the bottom.
• Raffia baskets: cheap and common in Nigeria, but fruits at the bottom get squashed if packed too high.
• Jute sacks: good for tough items like onions or ginger, and bad for soft items like tomatoes.
• Cardboard boxes: used for high-value items like flowers or expensive fruits.

What are the rules for packaging?

1. Do not over-stuff: leave a little breathing room.
2. Ventilation: use containers with holes so heat does not build up inside.
3. Do not pack too high: heavy top layers crush the produce below.
4. Use clean containers: dirty containers carry germs and mould.

How do we store horticultural crops?

Storage is keeping produce safe and fresh until it is sold or eaten.

• In a hot climate like Nigeria, keeping crops cool is the biggest challenge.
• Farmers can also store crops until the market price is good.

What are the types of storage?

Three common types of storage are cold storage, evaporative cooling and dry storage.

1. Cold storage (refrigeration): the best way to keep produce fresh, because low temperature slows ripening and rotting.
2. Evaporative cooling (pot-in-pot): a traditional cooling method that needs no electricity.
3. Dry storage: used for onions and garlic, which are kept in a cool, airy place away from direct sunlight.

How does the pot-in-pot method work?

The pot-in-pot method keeps produce cool by using evaporating water to take heat away.

1. Place a small pot inside a larger pot.
2. Fill the space between the two pots with sand.
3. Wet the sand with water often.
4. Put the produce in the inner pot and cover it with a wet cloth.
5. Keep the pots in a shaded, airy place.

What are the post-harvest processes at a glance?

Evaluation

1. Define post-harvest handling.
2. State four reasons why post-harvest handling is important.
3. What is the difference between sorting and grading?
4. Why are plastic crates the best packaging material for tomatoes?
5. Describe the pot-in-pot method of storage.

Assignment

List the three ways of grading horticultural crops with one example of each. Then name the three types of storage and state one crop kept by dry storage.