Methods for Cooling Tomatoes After Harvest

Tomatoes are an extremely popular type of produce that are used in a wide variety of dishes and which may be eaten fresh and raw, turned into paste or sauce, or of course used for America’s favorite condiment: ketchup. However, for optimum taste and quality it is very important that the temperature of tomatoes be closely regulated. What follows is a discussion of general tomato information, factors that affect cooling and storage, and proper cooling methods.

General Facts About Tomatoes

One of the most popular tomato-related debates is whether tomatoes are fruits or vegetables. Botanically they are fruits of the nightshade family, specifically Solanum lycopersicum. In terms of culinary practices they are often used in ways similar to a vegetable. Tomatoes as a food originated in Mexico. However, due to their versatility, taste, and ability to grow in different regions, they quickly spread throughout most of the world following the Spanish colonization of the Americas in the 1500s.

Tomatoes are renowned for their nutritional value. They contain an important and powerful antioxidant known as lycopene. Lycopene has been shown to have a number of health benefits including possible prevention of cancer, particularly prostate cancer, and skin protect against UV rays. There is also research being conducted into whether or not tomatoes have heart-healthy benefits for people with type 2 diabetes and whether or not tomatoes can improve urinary tract function.

General Information About Cooling and Storing Tomatoes

Tomatoes are more complicated to cool and store than many other types of produce because there is a very wide variation of correct storage temperature depending on the ripeness of the tomatoes. Tomatoes also vary in shelf life depending on ripeness at the time of harvest and storage conditions.

Ripeness/Color – Tomatoes are often graded on ripeness based on the color of their skin. The colors and criteria are as follows:

• Green – Green tomatoes have a surface that is completely green. The particular shade of green may range anywhere from light to dark. Tomatoes are called “mature green” when they have reached the stage of ripening that will allow them to fully ripen into red tomatoes. Immature greens are tomatoes that are not yet mature enough to ripen fully and should be avoided. Mature greens on the other hand will be indistinguishable from vine-ripened tomatoes by the end of the ripening process and come with the added benefit of a longer shelf life.
• Breakers – Tomatoes are called breakers when their green skin features tannish yellow skin with pink or red spots that do not cover more than 10% of the tomato’s surface.
• Turning – Tomatoes are said to be turning when they have tannish yellow, pink, or red skin that makes up more than 10% of their surface but less than 30%.
• Pink – Tomatoes are said to be pink when they have more than 30% but less than 60% of their skin a pinkish red or red color.
• Light Red – Light red tomatoes have a pinkish red or red skin that comprises more than 60% of their surface but less than 90%.
• Red – Red tomatoes are those with more than 90% of their surface red.

Temperature – The correct storage temperature for tomatoes varies based on their ripeness/color. As a general rule the more ripe the tomato the cooler its correct storage temperature. Tomatoes stored at temperatures too cold for their ripeness stage will suffer cold damage, reduced taste and quality, and may never fully ripen. By contrast tomatoes stored at temperatures too high for their ripeness stage may be subject to premature spoilage, decay, and damage. Mature greens may be stored at 58°F to 60°F, while pink tomatoes may be stored at 48°F to 50°F. Fully ripe tomatoes may be stored at temperatures as low as 40°F.

Humidity – The correct humidity level for storing and cooling tomatoes is about 85% to 95%, with lower humidity levels running the risk of drying out or dehydrating the tomatoes and higher humidity levels making the tomatoes more susceptible to rapid decay. Some studies suggest an even more narrow range of about 85% to 90% with concerns that even humidity levels over 90% could hasten decay.

Ethylene – Like many other fruits and vegetables tomatoes produce and release ethylene as they ripen, which in turn further hastens the ripening process. Unripe tomatoes may be intentionally treated with ethylene to bring about more rapid ripening prior to being sold to consumers. By contrast unripe tomatoes not yet ready to be sold should avoid contact with ethylene.

Storage – Because tomatoes are sensitive to ethylene it is typically a good idea to keep them separate from other fruits and vegetables since these other types of produce may unintentionally hasten ripening or, likewise, ripe tomatoes may hasten the ripening of other produce. Along the same lines ripe tomatoes may also need to be kept separate from unripe tomatoes. Once a tomato fully ripens its shelf life is much lower.

Shelf Life – The shelf life of tomatoes varies based on their ripeness, as well as the other factors discussed above. Generally mature green tomatoes will have a shelf life of about 21 to 28 days. Pink tomatoes have a shelf life of about 7 to 14 days. Fully ripe red tomatoes only have a shelf life of about 2 to 4 days.

Methods of Cooling Tomatoes

Tomatoes should be cooled using the room storage method, which involves placing the tomatoes in a refrigerated room or cooler set to the correct temperature for the tomato’s given ripeness level. It is important to ensure that the tomato boxes are well ventilated to allow heat to escape and for proper air circulation. Tomatoes should also be handled carefully as they are very prone to physical damage due to bruising, dropping, or general mishandling. SEMCO/SEMCOLD LLC offers industry-leading cooling equipment that can be customized to handle the unique demands and cooling sensitivity of tomatoes.