Vegetables Produce Facts English
Recommendations for Maintaining Postharvest Quality
Maturity & Quality
Immature potatoes, generally harvested in spring or early summer, have a thin, poorly developed periderm, or skin. Irrigation and planting bed management, along with the option of vine-killing treatments, manage harvest "maturity". Harvest preparedness generally begins once tubers have reached a desirable size for the variety or market. Immature potatoes are easily bruised and "skinning" leads to shriveling or decays. They are very perishable relative to late-crop potatoes and are only stored for short periods. Curing potatoes for 8 days at 15°C (59°F) and 95% RH will allow extended storage of up to 5 months at 4°C (39°F) and 95 to 98% RH, depending on variety. More typically, early-crop potatoes are harvested, cooled to 15°C (59°F), treated with a sprouting inhibitor, packed and shipped in a short period of time (i.e. 1 to 5 days).
High quality traits, in commercial trade, include more than 70 to 80% of tubers well shaped, brightness of color (esp. reds, yellows, and whites), uniformity, firmness, freedom from adhering soil, freedom from bruising (black spot or shatter-bruising), scuffing or skinning, growth cracks, sprouting, insect damage, Rhizoctonia Black Scurf, decay, greening, or other defects. Commercial standards in use are typically higher than USDA grade standards. Differentiation of quality for potatoes is very complex.
Maturity & Quality Photos
Temperature & Controlled Atmosphere
Optimum Storage Conditions
At optimum conditions, potatoes should have good quality after storage of 3 to 5 weeks. Storing immature potatoes below 10-13°C (50-55°F) for as few as 3 days may cause the accumulation of reducing sugars leading to excessive browning during frying/chipping. Storage for less than 3 weeks is recommended to maintain good visual and sensory quality of immature potatoes.
To calculate heat production, multiply ml CO2/kg·hr by 440 to get BTU/ton/day or by 122 to get kcal/metric ton /day.
Very low; Bruised, cut or otherwise damaged tubers have greatly increased ethylene production rates.
Potato tubers are not very sensitive to external ethylene. Low levels of external ethylene have been shown to elevate respiration, especially in immature potatoes, and result in weight loss and mild shriveling. After aging for 2-3 months at temperatures above 5°C (41°F) and in the absence of sprouting inhibitor application, low levels of ethylene may retard sprouting. High concentrations of external ethylene may induce sprouting.
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 Atmosphere (CA) (<1.5%) or elevated CO2 (>10%) will induce off-odors, off-flavors, internal discoloration, and increased decay.
Temperature & Controlled Atmosphere Photos
Physiological and Physical Disorders
*Not found in California.
Use of Materials
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The information in this fact sheet represents our best understanding of the current state of knowledge at the time of the latest update, and does not represent an exhaustive review of all research results. Links to any of these UC Postharvest Technology Center pages are permitted, but no endorsement of the linking site or products mentioned in the linking page is intended or implied by such a link.
How to Cite
Author(s) names. Initial publication or update date (located at the top). Title. Link to the specific Produce Fact Sheet webpage (Accessed date)
Example: Cantwell, M. and T. Suslow. 2002. Lettuce, Crisphead: Recommendations for Maintaining Postharvest Quality.