Potato Grower

December 2018

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TOP 5 By Mike Machurek, IVI DIAL IN ON TEMPERATURE CONTROL Several factors influence temperature management for stored potatoes: • Whether the potatoes are to be marketed for processing, table stock or seed • Tuber temperature at the time they are placed in storage • The length of time tubers are to be stored • The extent of tuber at harvest • The presence of disease organisms Low temperatures enhance sugar formation. If the storage temperature is maintained below 45 degrees for a long time, accumulated sugars in the tuber do not readily reconvert to starch (recondition). High-reducing sugar concentrations result in undesirably darkened chips and fries. Some varieties recondition better from low temperatures than others. In general, the optimum long- term storage temperature for processing potatoes is approximately 45 degrees. For fresh market potatoes, a storage temperature of 40 degrees is recommended. Seed potatoes may be stored at slightly lower temperatures (38 to 40 degrees) for better weight loss and sprout control. Raise the temperature just prior to storage removal. Cold potatoes are brittle and may easily bruise or shatter during handling. Before removing the tubers from storage, raise the temperature to 50 to 55 degrees. This can sometimes be accomplished by removing ventilation, which allows the heat from tuber respiration to accumulate. More frequently, however, heaters and/or forced ventilation of warm air are necessary. WOUND HEALING Bruising and cuts can occur during harvest and handling. Wound healing is critical in order to minimize the entry areas for ever-threatening organisms of potato diseases. Temperature is critical at this phase of initial storage, as healing proceeds most rapidly at temperatures of 60 to 65 degrees Fahrenheit. In order to achieve the healing of any wounds, this temperature, plus high humidity, facilitates the forming of a suberin layer in three to five days. Cell regeneration, or complete wound healing, can take place beneath this suberin layer within 10 to 20 days, depending on the condition of the potatoes. When potatoes are placed in storage, rapid cooling can result in more rot- forming organisms in the tuber because entry points remain unhealed. Rapid cooling, particularly in the absence Key Factors to Successful Storage The two critical environmental factors involved in properly storing potatoes and preventing common potato diseases are temperature and humidity. Adequate, unrestricted air movement is also necessary to maintain constant temperature and humidity throughout the storage pile—and to prevent excessive shrinkage from moisture loss and decay. With some help from our friends at Industrial Ventilation, Inc. (IVI) and utilizing information from studies performed by University of California Cooperative Extension, we've put together these tips for making sure your storage is a happy place for your potatoes. More helpful storage information can be found at www.ivi-air.com/ivi-blog. 16 POTATO GROWER | DECEMBER 2018

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