Harvesting and Handling Tomatoes

Since tomatoes are perishable, proper after-harvest handling is very crucial for maintaining quality and increasing shelf life.

Cleaning

Tomatoes should be washed in clean water to sufficiently remove dust and foreign material, then wiped dry with a clean soft cloth. To eliminate the problems with disease build-up that normally occur, wash water should not be reused. When washing ensure the wash water is several degrees warmer than the pulp temperature of the tomatoes to avoid drawing water and disease organisms into the fruit.

Grading

During grading of fruits, damaged, rotten and cracked fruits should be removed. Only healthy, fruits should be selected. The grades are mostly based on the condition and the quality of the fruits and not specifically on their size. However, on the basis of the size, three grades are formed: small (less than 100g), medium (100–255g) and large (over 255g). Retailers normally do size-grading for the local market.

Storage: Temperature and Humidity Management

Immediate and thorough post-harvest cooling to remove excessive field-heat aids greatly in maintaining quality and substantially lengthens the shelf-life of tomatoes. Cooling and washing can reduce the effects of dehydration and minimize decay. Though post-harvest cooling is essential for maintaining quality, it will not improve the quality of a poor product. Pink or light red tomatoes destined for distant markets should be cooled immediately after harvest to avoid becoming overripe before reaching the consumer. Placing containers of warm tomatoes in a refrigerated space, known as room cooling, is recommended. To aid room cooling and prevent the buildup of respiration heat, containers of tomatoes should be loosely stacked with space between the containers to allow for sufficient air circulation.

Tomatoes are very sensitive to chilling injury. The recommended storage temperature varies with the maturity of the fruit (for mature green, 14°C; for pink, 10°C). Proper temperature control is critical to quality and shelf-life. Mature green tomatoes should not be held at temperatures that delay ripening. When they are stored for several weeks at 12.7°C, they often fail to ripen properly instead developing decay due to Alternaria. Chilling injury is cumulative and is a function of both temperature and exposure time. The optimum temperature for ripening mature green tomatoes is from 18°C to 21°C at temperatures above.

26.7°C, mature green tomatoes will appear to ripen but may not have the best eating qualities. A temperature of 14.4°C to 15.6°C is best for slowing the ripening of mature green tomatoes and preventing existing decay. Light red tomatoes can be stored for two weeks or longer at 10°C. Longer storage may result in reduced retail shelf-life. Ripe tomatoes may be stored at lower temperatures than mature green tomatoes. Several days at 4.4°C may be acceptable, but longer storage at this temperature will result in loss of color, firmness, shelf life, and especially taste. Under extreme circumstances, firm yet well-ripened tomatoes may be stored for as long as three weeks at 0.6°C to 1.6°C. Pink to firm-red greenhouse grown tomatoes may be stored at temperatures of 10°C degrees to 12.7°C. Less mature tomatoes should be ripened at 21°C before being stored at 10°C to 12.8°C.

Packaging and Transportation

For local markets, the fruits are packed in wooden or plastic crates. The packing should be rigid enough to protect the fruit from being crushed. Plastic crates can be conveniently stacked one on the other as the contoured rim keeps the product safe and allows sufficient air circulation. For exports, the fruits are packed in cardboard telescopic boxes with capacities of not more than 15kg. Size graded tomatoes are pattern packed in layers to make best use of the box. Tomatoes are highly perishable in nature hence quick means of transportation is necessary.

Cool Chain

Maintaining a cool chain is essential during the transport of export quality commodity all the way from the farm to the customer. This helps in maintaining the temperature inside the box at the same low level as is found in cold storage.

The various stages of the cool chain are:

1. Cold store at the farm

2. Refrigerated truck from farm to the airport

3. Cold store at the airport

4. Building up of the pallet in a cold store at the airport

5. Loading the aircrafts directly from the cold store in a short time

6. Cargo aircraft maintains cold store temperature in hold

7. Off loading direct into a cold store in the receiving country

8. Refrigerated truck to the customers

Post-Harvest Disease Management

Tomatoes are subject to a large number of post-harvest diseases such as alternaria rot (Alternaria alternata), gray mold or botrytis (Botrytis cinerea), rhizopus rot (Rhizopus stolonifer), and sour rot (geotrichum candidum). Although the skin of tomatoes offers some protection against infection, it is easily damaged by rough handling.

Pathogens can enter tomatoes through a variety of openings. Wounds such as punctures, cuts, abrasions, and cracks as well as stems and stem scars provide potential points of entry. The entry of pathogens into a surface injury is nearly a certainty. Therefore, tomatoes with surface injury should be separated promptly from sound fruit and discarded before decay can spread.