Sweet potato storage
The sweet potato (Ipomoea batatas) is a very important crop for subsistence farmers in Africa and developing countries in other regions.
[1][2] Its relatively short growing period, tolerance to drought and high yield from poor soils lead to its use as a famine reserve for many of these households.
[3] Most subsistence farmers who eat sweet potato do not use a storage technique of any kind, instead using a method of continuous cultivation and leaving the tubers in the ground until they are ready to be used.
[3] Curing can toughen the skin and heal minor physical damage, while drying can reduce spoilage and inactivate metabolic degradation.
[3] Optimum storage of sweet potatoes occurs at 12–16 °C (54–61 °F) and 85–90% relative humidity (RH) and requires proper ventilation to remove excess carbon dioxide (CO2) and bring in oxygen (O2) for respiration.
[4] This is mainly due to their high moisture content, metabolic activity following harvesting and thin, permeable skin.
[3] Following harvest, sweet potatoes are susceptible to spoilage by physical, physiological, pathological and environmental means, including by pests.
Physical losses occur when sweet potatoes are damaged by mechanical force during harvest, handling, and transportation of the tubers,[3][8] including injury by cutting, bruising, and skinning.
[3] Infection can result in the production of toxins, pathogens, bitter flavours, surface blemishes, and decayed tissue.
[3] Damage to tubers by physical and physiological means can increase the chance of pathological infection and pest infestation.
[3] Other signs of chill injury include production of off flavours; internal cell structure breakdown; and increased rotting due to reduced skin formation, which allows fungal infection.
Because of a lack of proper equipment, maintaining adequate temperature conditions is the largest hurdle that farmers in developing countries face.
[3][failed verification] In developed countries, proper refrigeration technology is used to store sweet potatoes for long periods of time.
In areas with reliable rainfall patterns, farmers can maintain a supply of fresh sweet potatoes for most of the year by continuous cultivation and harvesting.
The construction of the pit can vary with what materials are available, but those commonly used include grass, soil, wood, lime, sawdust, and ash.
[3][4][12] Grass is typically used to line the bottom and sides of the pit to insulate the tubers from temperature changes and to absorb moisture.
[12] Wood ash can applied to potatoes prior to storage and has shown some effectiveness in protecting against attack by insects and mould.
[3] Commonly the pit will be sealed shut in order to maintain a good RH, which has the disadvantage that CO2 will collect and cause spoilage.
[3] Pits can be reused, but they should first be cleaned and the soil turned over and disinfected with fire or sulphur to rid the area of microorganisms.
[3][12] In clamp storage, another simple and low-cost method, sweet potato tubers are stored in covered piles.
[3] In homes, the tubers are typically stored in straw woven baskets, cloth bags, or wooden boxes.
[3] This protects against excessive moisture loss, reduces entry of microorganisms into the plant, and facilitates healing of mechanically damaged tubers.
