Corn - Postharvest Care
Postharvest temperature management is imperative to maintain ear quality. Ears will be 15 to 30°F cooler in the morning than at midday, so pick ears early, if possible. Chill corn as soon as possible after picking. Standard sugary (su) types lose sweetness in just a few days. In fact, half of the sugar in su kernels is lost within 24 hours when stored above 86°F. When kept near freezing, only 8% of the sugar is lost each day. Extra sweet and super sweet types remain sweet for a longer period, but cooling the harvested ears is still critical to maintain quality
When sweet corn is shipped or stored for more than 2 to 3 days, maintain the corn at 32°F. Cooling with air is common but not as effective as other options because it often takes 24 to 48 hours for ears to become sufficiently chilled.
In larger operations, hydro-cooling (soaking or sprinkling ears in chilled water) and then top-icing is commonly used to reduce ear temperatures quickly. Temperatures can be reduced by 20°F in as little as 20 minutes if ears are immersed. When using sprinklers, one gallon of water is needed for every 4 lbs of corn.
Hydro-cooling and ice making systems are expensive, costing several thousand dollars for refrigeration units and assembly. Refrigeration systems that produce crushed ice will dissipate heat more quickly than those producing cubed ice. For shipping, add one lb of ice for every five lbs of pre-chilled corn in the shipping containers. Contact the local health department or government food safety administrator for potential restrictions, building codes, and other safety issues.
If using an air refrigeration system, immerse sweet corn ears in tanks of pre-chilled water to lower their temperature quickly. After the initial bath, store the ears in the cooler at approximately 98% humidity to maintain ear quality.