Reducing post-harvest losses in tomatoes

Backgrounder

Introduction

Why is this subject important to listeners?   

Because farmers and processors who handle fresh tomatoes after harvest need to know:

• When tomatoes are ready for harvesting and how to properly harvest them.
• How to reduce on- and off-farm tomato losses.
• The right environmental conditions for storing fresh tomatoes.
• The degree of perishability of tomatoes at different harvesting stages.
• When to pick tomatoes meant for processing, and when to pick tomatoes for nearby and distant markets.
• Methods of reducing postharvest loss.
• The best methods of handling tomatoes during and after harvest.
• Cost-effective organic solutions to protect maturing tomatoes.

What are some key facts?

• Tomatoes have a life cycle of 3-4 months, depending on the variety, and harvesting can continue for up to a month or more.
• Tomatoes should be harvested in the early morning or late evening, ideally when the temperature is around 20 degrees Celsius and the weather is dry.
• Good quality tomatoes are firm, juicy, and, in higher or middle-income markets, uniform in colour and medium-sized or larger. Fruits intended for export should also be uniform in ripeness, colour, and size.
• Tomatoes to be processed into ketchup, chutney, puree, or juice should be harvested when fully red.
• Tomatoes meant for fresh marketing to consumers can be harvested while still green and ripen later. However, tomatoes harvested early have lower nutritional values.
• The recommended conditions for storing tomatoes are 12 degrees Celsius and 86-90% relative humidity. Tomatoes spoil if stored at temperatures below 10 degrees Celsius for over 2 weeks, or if kept at 5 degrees Celsius for more than 6-8 days. Tomatoes can be stored for 2-3 weeks in temperatures not lower than 10 degrees Celsius.
• Tomatoes are sensitive to weather conditions such as wind, moisture, temperature, and chilling, which causes colour to be irregular. Also, tomatoes soften prematurely and may fail to ripen properly and decay when kept at below recommended temperatures.

What are the big challenges with reducing postharvest loss in tomatoes?

• African farmers often lack the right containers for harvesting tomatoes, and instead use wooden crates or woven baskets that injure fruits.
• Poor road infrastructure results in delays in transporting tomatoes to market, which increases postharvest losses.
• Lack of facilities where tomatoes can be stored at the recommended cooling temperature, which minimizes spoilage.
• Using inappropriate methods to transport tomatoes to market. This includes motorbikes, which vibrate and wobble, resulting in mechanical damage to fruits.
• Tomatoes are highly perishable, and a lack of readily accessible markets results in spoilage, increasing postharvest losses for farmers.
• Farmers tend to produce tomatoes all at the same time rather than staggering their planting. This creates a glut in the market, resulting in serious postharvest losses.

Gender aspects of reducing postharvest loss in tomatoes

• In Mbeya, Tanzania, women dominate the sale of tomatoes because they are responsible for household food security, while men prefer not to be involved with sales.
• In the Brong–Ahafo region of Ghana, men and women of all ages produce tomatoes, and large numbers of young men specialize solely in tomato production.
• In the Imeko Afon region of Ogun State, Nigeria, men dominate tomato production.
• In Koluedor, Ghana, it’s fairly common for a wife and her husband to grow their own tomatoes in different fields.
• In Kwara State, Nigeria, 70% of tomato sellers are women.

For further information, see documents 3, 4, 5, 6, 8, 9, 10, 11, and 12.

Predicted impact of climate change on postharvest losses in tomato production

• Increased temperatures affect fruit development, resulting in reduced yields.
• Increased temperatures can result in soil salinity, which reduces tomato productivity. This is more serious in soils that are already high in salt.
• Temperatures above 25 degrees Celsius interfere with pollination and fruit development in tomatoes.
• High temperatures result in smaller tomatoes.
• Climate change may result in more frequent or severe droughts, which cause tomato plants to shed flowers.

For further information, see documents 1 and 2.

Key information about reducing postharvest loss in tomatoes

Pre-harvest

As tomato fruits mature, they become more susceptible to pests and diseases. Farmers can minimize tomato losses in the field by:

• Closely observing tomato growth to pinpoint the occurrence of diseases or pests, and to identify crop stress due to lack of nutrients and over- and under-watering.
• Adherence to an integrated pest management program which includes chemical, mechanical, cultural, and other effective tools
• Engaging in preventive measures to ward off diseases before they attack:
  • Installing traps and bait to capture pests and fencing the field to keep out animals.
  • It may be necessary to apply pesticides on a preventive basis for some pests, for example, Tuta absoluta and blight, especially if nearby farms have been infested

Here are some “homemade” methods farmers can use to control tomato pests in the field:

• Kerosene-soap solutions help to manage aphids, mites, thrips, and leafhoppers.
• Liquid soap solutions help manage aphids and thrips.
• If cow urine is stored for two weeks and then diluted, it is effective at controlling aphids, mites, thrips, and other insects, as well as mosaic virus and fungal diseases.
• Spraying an extract of neem seeds soaked in water manages the pests mentioned above, as well as nematodes.
• Three parts of cow dung mixed with a bucket of water, stored for two weeks, stirred daily, then diluted before spraying, is effective as a spray for tomato pests and fungal diseases.

Harvesting

Since over-mature fruits are easily damaged and then rot, harvesting tomatoes at the right time helps minimize postharvest losses. Tomatoes can be harvested at the pale green stage, early light red stage, light red stage, or at the red or ripe stage.

Because tomatoes are fragile, it’s important to take the following precautions during harvest.

• Clean hands and containers before picking tomatoes.
• Harvest tomatoes by gently twisting them off the plant.
• Plastic buckets and nylon net bags are ideal containers for picked tomatoes.
• Gently place tomatoes in picking containers—do not throw or drop.
• Transfer harvested tomatoes from picking containers to larger containers. Larger containers should be wide, shallow, and stackable to avoid putting pressure on fruits.
• Large containers should not weigh over 25 kilograms when fully packed with mature, ripe, and undamaged tomatoes.
• Do not expose harvested tomatoes to direct sunlight.
• If tomatoes will be shipped long distances, harvest at a less mature stage, and harvest tomatoes for local markets at a mature ripe stage.

For further information, see documents 4, 5, 6, and 9.

Sorting

After harvesting, wash and sort tomatoes according to size, colour, and quality. Ensure that the sorting area is cool, clean, and shaded from direct sunlight. To prevent contamination, people sorting tomatoes should have clean hands and clothes.

Packaging

Packaging adds value and increases the lifespan of harvested tomatoes. Well-packaged tomatoes are less prone to damage, seen as more desirable by consumers, and fetch better prices for the farmer. Proper packaging protects tomatoes from disease organisms, predators, moisture loss, high temperatures, crushing, and damage during transport.

Tomatoes can be packed in the following ways:

• In cartons, sisal baskets, customized wooden boxes and crates, cardboard boxes and crates, plastic bottles or jars, and clay pots.
• You can use green leaves or banana leaves to pad packaging containers and cushion tomatoes from crushing.

Transport

When transporting tomatoes, farmers should not use motorbikes because their vibrations damage tomatoes. Whenever possible, farmers should use refrigerated trucks to transport tomatoes, and ensure they are well packaged to protect them from damage when vehicles are in motion. In non-refrigerated transport, cover vehicles with jute spreads or tarpaulins to reduce evapotranspiration* from tomatoes.

Farmers should use returnable plastic crates to ensure safe transportation of their produce.

Drying

Drying is a basic form of processing. If farmers overharvest, they can dry tomatoes to preserve them and minimize postharvest losses. The best tomato varieties for drying are firm plum or paste varieties, for example, Roma. Before drying, dip tomatoes in boiling water for 1-2 minutes to disinfect them. Tomatoes can be sun-dried in the open air or artificially dried.

• Open air drying: Wash tomatoes, cut in halves or quarters, and place on clean, flat surfaces with the cut side facing the sun. Place tomatoes on trays covered with plastic mesh and on a raised surface. Cover with a mosquito net or cotton muslin cloth to prevent contamination by insects, dirt, and dust. Open air drying takes 2-5 days when it’s windy and the air is less humid. The results are dark, red, leathery tomato pieces with 15-20% moisture content. If dried further, moisture content is reduced to 5% and the dried, hard, brittle tomato pieces can be crushed to obtain powder or flakes for use in soups and sauces. It’s easy to store tomatoes as powder or flakes.
• Artificial drying: In artificial drying, solar-powered driers or driers powered with various fuels are used to dry fresh tomatoes. Ensure that temperatures in driers don’t exceed 65 degrees Celsius, as excessive heat interferes with the taste of the dried tomatoes.

Processing

Processing tomatoes reduces postharvest losses and results in products that last up to a year without spoilage. It also removes micro-organisms that cause spoilage and ensures that tomato products are packaged in containers that prevent contamination. In homes, tomato pulp can be processed as a base for tomato juices, sauces, puree, and pastes.

Preparing tomato pulp

• Make tomato pulp only with ripe tomatoes.
• Wash tomatoes and dip in boiling water for two minutes to kill harmful micro-organisms on skins.
• Pulp tomatoes with a pestle and mortar.
• Remove skin and seeds by straining through a coarse 4-millimetre sieve and then a finer sieve with 1-millimetre holes.
• The pulp is now ready for processing. Heat pulp immediately to destroy micro-organisms and enzymes. Heat deactivates the enzymes that cause tomato cells to separate into pulp and water in storage.
• Heat pulp over a fire in a stainless steel or aluminum pan, stirring continuously. After all the tomatoes are added and heated, let the mixture simmer for five minutes before making it into juice.
• Refrigerate fresh tomato pulp for future use.

Tomato pulp products

You can make tomato juice by adding salt and lemon juice to tomato pulp. Tomato puree and highly concentrated tomato paste are made by boiling the pulp until water evaporates, constantly stirring to preventing burning. The resulting paste has a dark red colour, and salt can be added to taste.

Storage

If fresh tomatoes do not have a ready market, store in cool conditions to minimize spoilage / postharvest losses.

• Different storage conditions are recommended for tomatoes at different stages of ripeness. For example, it is recommended that green tomatoes ripen at temperatures between 13.9 to 15.6 degrees Celsius after being cooled at 10 degrees Celsius for two weeks.
• In general, store tomatoes at 12 degrees Celsius, and at 86-90% relative humidity.
• To minimize spoilage in storage, wrap ripe tomatoes in clean, green leaves. Change the leaves every 2-3 days until the tomatoes are sold.
• Do not allow the storage temperature to fall below 10 degrees Celsius.
• Mature tomatoes can last for 2-3 weeks if stored in the right conditions.

For further information, please see document 4, 5, 6, and 9.

Definitions

Evapotranspiration: Transferring water from land to the atmosphere through two processes: evaporation from soil and other surfaces, and transpiration from plants.

Transpiration: The process through which moisture is carried through plants from roots to small pores on the undersides of leaves, where it changes to vapor and is released to the atmosphere. Transpiration is essentially evaporation of water from plant leaves.

Where can I find other resources on this topic?

Documents

1. Abewoy, D., 2016. Advances in Crop Science and Technology. https://www.omicsonline.org/open-access/review-on-impacts-of-climate-change-on-vegetable-production-and-itsmanagement-practices-2329-8863-1000330.pdf  (372 KB)
2. Abou-Shleel, S.M., and El-Shirbeny, M.A., 2014. GIS Assessment of Climate Change Impacts on Tomato Crop in Egypt. https://idosi.org/gjer/gjer8(2)14/2.pdf (930 KB)
3. Ayandiji A., Adeniyi O.R., Omidiji D., 2011. Determinant Post Harvest Losses among Tomato Farmers in Imeko-Afon Local Government Area of Ogun State, Nigeria. https://globaljournals.org/GJSFR_Volume11/5-Determinant-Post-Harvest-Losses-among-Tomato.pdf  (487 KB)
4. Arah, I.K., et al, 2015. An Overview of Post-Harvest Losses in Tomato Production in Africa: Causes and Possible Prevention Strategies. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.862.3331&rep=rep1&type=pdf (2.42 MB)
5. Cantwell, M., undated. Post Harvest Handling of Tomatoes. http://ucce.ucdavis.edu/files/datastore/234-1362.pdf (1.92 MB)
6. Department of Agriculture Forestry and Fisheries, Republic of South Africa, undated. Production Guidelines for Tomato.  (2.48 MB)
7. Food and Drug Administration, UC Davis, Western Institute for Food Safety and Security, undated. Tomatoes. https://www.wifss.ucdavis.edu/wp-content/uploads/2016/10/Tomatoes_PDF.pdf (6.20 MB)
8. Issah, M., 2007. Right to Food of Tomato and Poultry Farmers Report of an investigative mission to Ghana. http://germanwatch.org/handel/ffm-ghana.pdf (644 KB).
9. Naika, S., et al, 2005. Cultivation of tomato production, processing and marketing. https://publications.cta.int/media/publications/downloads/1296_PDF_1.pdf (767 KB)
10. Okali, C. and Sumberg, J., 2012. Quick Money and Power: Tomatoes and Livelihood Building in Rural Brong Ahafo, Ghana. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.880.2808&rep=rep1&type=pdf (390 KB).
11. Salau, S.A., and Salman, M.A., 2017. Economic analysis of tomato marketing in Ilorin metropolis, Kwara State, Nigeria. https://scindeks-clanci.ceon.rs/data/pdf/1450-8109/2017/1450-81091702179S.pdf (241 KB).
12. Sanga, A., and Mgimba, C., 2016. An Analysis Of Constraints That Affect Smallholder Farmers In The Marketing Of Tomatoes In Mbeya Urban And Peri-Urban, Tanzania. https://www.onlinejournal.in/IJIRV2I3/106.pdf (257 KB).