Postharvest Handling and Storage
An important aspect of potato quality control is to provide a pathogen-free storage environment. All storage and potato handling equipment surfaces should be cleaned and disinfected prior to placing the crop into storage. Surfaces should be well moistened by the disinfectant spray. Spray bin walls until there is a slight runoff. Several disinfectant materials are available including quaternary ammonium compounds; (Prosan and Ster-Bac); sodium hypochlorite products (Agclor); and hydrogen dioxide products (Storox). Consult the labels for specific directions. Once the storage environment is clean and sterilized, it is ready for potatoes.
Healing of cuts and bruises that occur during harvest is most rapid in storage when the environment has a high relative humidity (95%), when tubers are at an appropriate temperature (50-60°F), and when adequate ventilation is provided throughout the pile. These conditions should be provided for 2 to 3 weeks at the beginning of storage and helps the tubers suberize. Effective suberization reduces tuber water loss and prevents rot organisms from entering damaged tubers. After suberization the temperature should be gradually lowered to 40°F (table stock or seed potatoes) or maintained at 50°F (chipping potatoes). When rot potential is high (field frost, late blight, or if ring rot is present) the curing period should be eliminated, the temperature dropped immediately, and the ventilation increased. Crops with these issues should be utilized as soon as possible.
Storage temperature control is best achieved with forced air ventilation. Storage relative humidity should be kept as high as possible without causing condensation on the storage walls and ceilings. Good insulation properly protected with a vapor barrier reduces the danger of condensation.
Once potatoes reach the long-term storage temperature, ventilate several hours per day or just enough to maintain pile temperature. Continuous ventilation is not necessary unless condensation or rot development occurs within the storage area or pile. Constant ventilation increases tuber weight loss and influences quality. A relative humidity of 95% is desirable for long term storage to maintain quality and minimize shrinkage.
For more detail on storage, handling and maintaining postharvest quality of potatoes, refer to the specific produce fact sheet available through the UC Davis Postharvest Technology website: http://postharvest.ucdavis.edu. These fact sheets are comprehensive guides to maintaining postharvest quality of the specific crop of interest.