Recommendations for Maintaining Postharvest Quality
Trevor V. Suslow and Marita Cantwell
Department of Plant Sciences, University of California, Davis
Maturity & QualityGeneral Information
Sweet corn postharvest expectations have changed dramatically with the increased availability and popularity of super sweet varieties based on the shrunken-2 gene (sh-2) and other naturally-occurring sweetness enhancing mutations. Although there is no relation to sweetness, regional consumer perceptions and preferences for kernel color have also caused significant shifts from traditional yellow corn to white and bicolor corn.
Sweet corn is considered mature for fresh market consumption or "baby kernel" processing when the pollination silks are dried and the kernels are still immature. The husk leaves remain tight and have a good green appearance. The ear is firm and turgid. The kernels are plump and appear 'milky', and not doughy, when squeezed. At this point the kernels of standard 'sugary' corn are 70-75% water content and kernels of sh-2 corn are at 77-78% water content.
Quality of fresh market sweet corn is judged by its fresh, uniform appearance, uniform and well filled rows, plumpness of kernels, milky kernel contents, and freedom from damage and defects (discoloration, harvest injury, worm damage, live insects, decaying silks or kernels). Trimmed, husked, or minimally processed whole-ears (i.e. microwave consumer packs) have additional grade standards for husk cover, husk appearance, length, and other quality indicators.
Temperature & Controlled AtmosphereOptimum Temperature
Rapid removal of field heat and continuous and proper refrigeration are essential to the maintenance of sweet corn quality. Sweet corn is generally hydrocooled and packed with ice and/or top-iced. After thorough cooling and icing, storage and transit temperatures are held slightly above 0°C (32°F) to prevent freezing of the ice layer and "capping-off" of the container, which could reduce proper air circulation. Handling in bulk containers should be avoided unless provisions for generous and uniform icing can be assured.
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.
Exogenous ethylene is not considered an important postharvest handling factor.
Controlled or modified atmosphere storage or shipping offer moderate benefits to sweet corn quality maintenance. Low O2 levels (3%) and elevated CO2 (10%) delay loss of sucrose content and maintain appearance of husks. CA at 5°C (41°F) is superior to storage in air alone, but sugar content is not retain-ed as well as corn stored at 0°C (32°F). Sweet corn does not tolerate low 2 (<2%) or elevated CO2 (greater than or equal to 20%).
Physiological and Physical Disorders
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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.