Avoid Sweetpotato Chilling Injury

The next few days will be abnormally frigid in North Mississippi.  This increases the risk of chilling injury to sweetpotatoes in storage, and those being transported to or from packing sheds.  Chilling injury occurs when roots are exposed to temperatures between 32 and 55°F.  (The ideal storage temperature for sweetpotatoes is 55 to 60°F. Freezing injury occurs when temperatures are below 32°F).

Symptoms of sweetpotatoes exposed to chilling temperatures include:

• Pitting and sunken lesions on storage root surface.
• Internal flesh darkening.
• Accelerated weight loss and root shriveling.
• Increased incidence of post-harvest decay.
• Hardcore.

Often chilling injury is only evident after the ambient temperature of the storage roots warms to above chilling levels, and then symptoms will develop rapidly.  Symptoms are often more pronounce in noncured roots than in cured roots.

Hardcore is a physiological disorder where areas of the sweetpotato flesh remain hard after cooking.  Hardcore cannot be detected prior to processing/cooking.  It can develop when roots are exposed to 50°F for as little as 3 days.  Storage roots can develop hardcore in a single day if exposed to 35°F.

Chilling injured sweetpotato saved for seed often produce fewer sprouts than healthy roots.

What you can do:

• Monitor storage house temperatures and provide supplemental heat when necessary.
• Remember: Combustion air for gas and oil heaters should come from outside the storage room. Unvented gas heaters can quickly deplete storage room oxygen, which results in incomplete combustion and increased levels of carbon monoxide. Gas heaters also produce ethylene as a biproduct. Ethylene gas in excess will negatively affect storage root quality.
• Repair sills around doors and damaged insulation.
• Full sheds retain heat better than emptier sheds because the high specific heat of water in the sweetpotato storage roots.
• Keep an eye on humidity. Sheds with appropriate humidity (85%) will retain heat more efficiently than those with drier air.
• Limit the exposure of sweetpotatoes to chilling temperatures during transport from storage shed to packing house.