Potatoes are related to tomatoes, capsicums and eggplants. They can vary in size and shape and also have varying skin and flesh colour, from creamy-to-white, yellow, red to even purple. They should never be green though. Different varieties can be starchy or waxy, which affects their ideal uses. Check which variety is best suited to the use you intend.
Potatoes are generally harvested once tubers have reached a desirable size for the variety or market. Irrigation and planting bed management, along with vine-killing treatments are used to manage harvest maturity. Immature potatoes are easily bruised and 'skinning' leads to shrivelling or decay. Quality traits include tuber shape, brightness of colour (especially reds, yellows, and whites), uniformity, firmness, freedom from adhering soil, freedom from bruising, scuffing or skinning, growth cracks, sprouting, insect damage, rhizoctonia black scurf, decay, greening, or other defects.
Postharvest storage temperature
Optimum storage conditions depend on the intended use of the potato. Table potatoes should be stored at 7°C at 98% relative humidity, potatoes for frying stored at 10–15°C at 95% relative humidity and potatoes for chipping at 15–20°C and 95% relative humidity.
Controlled atmosphere storage
Controlled or modified atmospheres offer little benefit to potato. Periderm development and wound healing is delayed at atmospheres below 5% O2. Injury from low O2 (<1.5%) or elevated co2 (>10%) will induce off-odours, off-flavours, internal discolouration and increased decay.
Potato tubers are not very sensitive to external ethylene, although low levels have been shown to elevate respiration, especially in immature potatoes, resulting in weight loss and mild shrivelling. After aging for 2–3 months at temperatures above 5°C and in the absence of sprouting inhibitor application, low levels of ethylene may retard sprouting. High concentrations of external ethylene may induce sprouting.
Potatoes should be stored at 95–98% relative humidity.
Disease & infection
Diseases are an important source of postharvest loss, particularly in combination with rough handling and poor temperature control. The major bacterial and fungal pathogens that cause postharvest losses in transit, storage, and to the consumer are bacterial soft rot, ralstonia, solanacearum, pyhytopththora infestans, fusariam rot, pink rot and water rot. Occasionally serious diseases of immature tubers include pink eye and grey mould.
Try to leave the skin on when eating potatoes for added fibre and nutrients. If you must peel them, only remove a thin layer of the skin.