Produce Compatability In Storage
February 11, 2013 Just like people, not all produce items are compatible. It is important to know which products should never be mixed, and which can be mixed for short periods of time to avoid product damage. Generally, the longer the product is stored under incompatible conditions, the greater the chance for injury to develop. This is especially problematic for mixed shipping loads, and at distribution and retail.
Incompatibility can be related to storage temperature, ethylene gas, and odor emission. For storage or transit periods of up to seven days, fruits and vegetables can be divided into three temperature categories:
• The lowest temperature range, 32°F to 36°F with 90% to 95% relative humidity, is for the majority of green, non-fruit vegetables and temperate fruits. If possible, store fruits and vegetables separately within this temperature category and maintain a higher relative humidity (95% to 98%) around the vegetables to prevent wilting.
• The intermediate temperature group (45°F to 50°F and 80% to 85% relative humidity) is for many subtropical products that are moderately chilling sensitive. This includes products like summer squash, cucumber, eggplant, citrus, avocado, cranberry, and guava.
• The third group is at the highest temperature (55°F to 65°F and 85% to 95% relative humidity) and is for very chilling sensitive tropical products including potato, sweet potato, winter squash, tomato, mango, papaya, and banana. This temperature can also be used to ripen products.
Many green vegetables and most floral products are very sensitive to ethylene gas and ethylene must be kept away from these products. Minimize exposure to ethylene by keeping ethylene producing fruits (apple, pear, guava) away from green vegetables and sensitive fruit (kiwifruit, Fuyu persimmon, watermelon). As little as 1 part per million (ppm) of ethylene can be damaging to sensitive products and in some cases, even 0.01 ppm ethylene is problematic. Gas-powered forklifts should not be used in areas where sensitive products are stored, and all combustion products should be avoided, such as vehicle exhaust.
Tips For Treatment
Treatment of products with SmartFresh gas will reduce or, in some cases, eliminate product sensitivity to ethylene. Use of ozone in the storage room will destroy ethylene gas and is useful when production of ethylene is not too great. Also, regular venting of the storage space and introduction of fresh, ethylene free air can be used to keep ethylene low. Be careful in areas where air pollution is heavy as the outside air may have more ethylene! All of these methods can be helpful when mixed storage or transit is essential.
Finally, some products produce odors that, if absorbed by other produce items, are harmful to the sensory quality or flavor of those products. This includes potatoes, which impart an earthy aroma and flavor, as well as onions and garlic. Many produce items, such as strawberries and apples, absorb these odors to the detriment of their own flavor quality. Potato, onion, and garlic should always be stored separately or packaged to inhibit aroma emissions.
When mixed loads are essential for long-distance shipments, such as sending food to overseas military bases, special practices can be used to avoid some incompatibility problems. Wrapping pallets of chilling sensitive product with plastic wrap can slow the rate of cooling when sensitive product is mixed with temperate products at low temperature. Care must be taken to avoid damaging atmosphere modifications if the wrapping is done too thoroughly.
A compatibility chart for storage of produce can be found on the Postharvest Technology Center’s website at http://ucce.ucdavis.edu/files/datastore/234-102.pdf and a wall poster can be purchased for your storage facility or loading dock. Go to postharvest.ucdavis.edu and click “Online Bookstore.”
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