Harvesting on time and proper post-harvest treatment of the fruit is very important. The high water content of tomatoes makes them vul-nerable to post-harvest losses. Over-mature fruit gets easily damaged or starts rotting. The first measure to help limit the extent of post-harvest damage is harvesting at the right moment. It will be necessary to harvest several times as the fruit of tomato plants do not all ripen at the same time. The first tomato harvest is possible 3 to 4 months after sowing. Harvesting will continue for about one month depending on climate, diseases, pests, and the cultivar planted. During one season tomatoes must be harvested 4 to 15 times.
Quality tomatoes are firm and are uniform in colour. If the tomatoes are to be used for the production of, for example, ketchup, chutney, purée or juice, the fruit must be picked when it is red and completely ripe. If the tomatoes are to be sold as vegetables on the market, they can be harvested while still green. Green tomatoes can be ripened after picking, until they are red. A few red, ripe tomatoes will speed up the ripening process. One disadvantage of early picking is that the nutritional value of the tomatoes is lower. One advantage is that green tomatoes are less likely to get damaged or to rot.
To uphold the quality and ensure a good harvest some simple and easy guidelines can be followed when harvesting:
- Workers need to know which tomatoes are to be harvested and what end use they will have.
- Harvesting needs to be carried out in dry weather and cool temperatures, hence in the early morning.
- Tomatoes must be picked with clean hands and twisted gently off a plant and not be squeezed or damaged by fingernails.
- Tomatoes must be gently placed in the container and not thrown in or dropped.
- Containers must be clean nylon net bags, plastic buckets, or wood or plastic crates.
Harvesting will continue for about one month, depending on climate, diseases and the cultivar planted. Tomatoes can be classified in four stages of maturity:
- Stage 1: Seed are white in colour (immature) and can be cut when the tomato is sliced. There is no juice inside the tomato.
- Stage 2: Seeds have a tan colour (mature) and some juice present.
- Stage 3: Seeds are pushed aside when cut. The colour inside is still green.
- Stage 4: Juice becomes red in colour.
Tomatoes that are harvested at the first stage of maturity will ripen into poor-quality tomatoes. Tomatoes harvested at third and fourth stages of maturity will ripen into good-quality tomatoes.
It is also good to look carefully at how ripe the tomatoes are. How ripe a tomato is when it is harvested affects the fruit composition and tomato quality. Tomatoes accumulate acids, sugars and ascorbic acid when they ripen on the plant. Field-ripened tomatoes have a better flavour and overall quality than tomatoes that ripen after picking. Hence it is important to understand ripeness stages. A simple colour index for red tomatoes can be given to the tomato pickers so that they are familiar with this.
- Green ripeness stage: Fruit surface is completely green. The shade of green may vary from light to dark.
- Breaker ripeness stage: Break in colour from green to tan yellow, pink or red on not more than 10 % of the tomato skin.
- Turning ripeness stage: 10% to 30% of the tomato skin is not green. It can be tan yellow, pink or red.
- Pink ripeness stage: 30% to 60% of the tomato skin is not green. It can be pink or red.
- Light red ripeness stage: 60% to 90% of skin colour is not green. It can be pinkish red or red.
- Red ripeness stage: 90% of the tomato skin is not green. It shows a red colour.
Tomatoes are delicate fruits and need to be sent to the market quickly. If they are not handled carefully they decay easily, which affects their taste, flavour and nutritional value.
Post Harvest Handling
Tomatoes are picked in picking containers (nylon net bags or plastic buckets). These picking containers need to be emptied into larger con-tainers placed in picking areas. The large containers must be trans-ported frequently to the sorting areas on the farm. Therefore they must not weigh more than 25 kg. The containers need to hold only tomatoes that are mature, ripe and free from damage. When the field containers are full, they should be transported to a sorting area located on the farm.
In sorting areas, the fruits are washed and sorted by size, colour and variety. Sorting areas need to be out of direct sunlight, preferably cool and clean. People working in the sorting areas, must have clean hands and clothes. It is important that each worker is trained regarding his or her task.
In some small-scale handling and sorting operations, machines are used for washing, sorting and grading of tomatoes. Such machines cost a lot of money and are a fixed cost to handling operations.
Efficient washing and sorting can be done with ‘sorting canals’. These are long water containers in the reception areas that look like livestock drinking troughs. They have several advantages. Tomatoes can be off-loaded more quickly from field containers, for tomatoes can be gently poured into the water. The water prevents the tomatoes from hitting a hard surface, so fewer will be damaged. Water cleans the dirt off the tomatoes. It is also possible, to add a permissible amount of chlorine solution to the water, to disinfect the tomatoes. It may also be possible to heat the water to several degrees above the temperature of the tomato pulp. This will prevent the tomatoes from absorbing water and will also counteract pathogens. It is important to use clean and good quality water in sorting canals. The water must also be changed regularly.
Once the tomatoes are taken out of the sorting canal they must be dried and carefully placed in a container, ready for dispatch to their final destination.
Grading simply consists of arranging the tomatoes into a number of uniform categories according to the economically important physical and quality characteristics. The process involves identification, classification and separation.
Grading has advantages:
- Uniformity is one of the first attributes that buyers look for. Appearance comes before aroma and taste.
- Tomatoes of different qualities can be sold to different customers.
- Setting standards will create customer confidence in the product and more importantly in the producer.
In some cases farmers may be able to pool their financial resources so that they are able to buy a washing and sorting machine.
Badly packed tomatoes will not only ruin the tomato crop for sale, but will also mean lower prices. How tomatoes are packed depends on the end use to which they will be put. For example, some buyers may want fresh table tomatoes to be packed in small containers; other buyers may require dried tomatoes or tomatoes for processing. Even if tomatoes are just being sold at the farm gate, they will require some form of packaging, which can be a simple traditional basket.
Packaging is convenient for handling, transporting and storing toma-toes. It protects against pathogens, natural predators, loss of moisture, temperatures, crushing, deformation of tomatoes and bruising. It also has an aesthetic function.
Fresh tomatoes are often packed without stems. Mature green mature tomatoes can be stacked on top of one another in a package, since they are firm, but remember that not too many must be packed all at once, or the tomatoes at the bottom of the package will be deformed or bruised due to excessive weight on top of them. In all cases it is a good idea to use padding material at the bottom of packages and in between layers of tomatoes. Packaging material is expensive, in terms of total costs, and must not be wasted.
Some of the most common packaging materials:
- large green leaves
- clay pots
- wooden crates
- cardboard crates
- cardboard boxes
- glass bottles or jars
- plastic bottles
- tin cans
It may be possible to form formal or informal associations with other farmers to organise packaging operations.
Storing tomatoes in tropical and subtropical climates can be difficult without cold storage. Sometimes fast marketing is the only solution.
Tomatoes that are to be sold fresh for table consumption must not be stored for long. Tomatoes that have been processed, for example into tomatoes purée or juice, or dried or pickled can be stored from several months to a few years.
Storage facilities will vary according to marketing demands. Fresh table tomatoes will need to be stored somewhere where they can ripen or be stored for a short amount of time. At other times cold storage rooms are required. Processed tomatoes can be stored in typical stor-age rooms. Tomatoes often need to be stored at different points while they are in transit to a final destination. For example the tomatoes are picked when ripe and stored for a few days in a cool room, after which they transported to distant markets. During the journey the tomatoes will ripen to the market stage. Tomatoes that go for export are often transported in large containers that have cold storage facilities and ethylene treatment units.
Fresh tomatoes can be stored after they have been harvested and sort-ed or they can first be packaged before storing. Cooling before and during storage is important.
Tomatoes are sensitive to chilling. Tomatoes that suffer chilling injury fail to ripen, and do develop full colour and flavour. Their colour de-velopment is irregular, and they are likely to suffer premature soften-ing, browning of seeds and increased decay. Tomatoes will deteriorate if they are kept at temperatures below 10°C for longer than 2 weeks or if kept at 5°C for longer than 6 to 8 days.
Clearly it is difficult to keep tomatoes at cool temperatures without the aid of cold storage facilities, especially in the tropics and subtropics. Hence storage methods have to be adapted to methods used locally. For example, one method of storing nearly ripe tomatoes is to place them in green leaves that have been washed. The leaves must be changed every 2 or 3 days until the product is sold. These operations need to be conducted in a cool location that is ventilated. Other forms of storage are tomato drying and purée production.
It is important to estimate what the costs of storage are likely to be, both for fresh tomatoes and well as for processed tomatoes. Costs will vary depending on the situation. For example if a farmer has her own storage facilities, she will have to calculate the costs for maintenance of the building, cleaning, loss of produce, etc. If a farmer does not have her own facilities she will have to calculate the costs of renting storage space and loss of produce.
To work out storage costs, first list all costs and then do the calculations. For example a simple cost calculation for storage space could be: