Varieties
Yellow, White and Bicolor. Recent varieties, known as the Supersweets, are rapidly gaining market acceptance. These varieties are sweeter and have longer shelf lives than their predecessors. Since sugar begins turning to starch immediately after harvest, Supersweets will maintain their desired taste several days longer than their conventional cousins.
U.S. Grades
U.S. Fancy, U.S. No. 1 and U.S. No. 2.
Storage Conditions
USDA recommended storage 32° to 34° F. (0° to 1.5° C.) Approximate freezing point 30.9° F. (-0.6° C.) Moisture and cool temperatures are essential in maintaining freshness and retarding the sugar to starch metabolism. Corn is either hydrocooled or vacuum cooled immediately after harvest and maintained as near 32° F. as practical.
Top ice is recommended and used by most shippers. Vacuum cooling is accomplished by placing the product in a rigid structure and reducing the atmospheric pressure within the chamber. Under this reduced pressure, water vapor is given up by the product. This results in cooling of the product in much the same manner as sweating cools your body. Shippers who use vacuum cooling generally top ice and set refrigeration temperatures somewhat warmer than 32° F. A temperature close to 36° F. will allow some melting into the corn to replace moisture lost during the vacuum cooling. If top ice is used, care should always be taken not to run temperatures below 32° F. In addition to possibly freezing the corn, the ice will form a crust and inhibit air circulation throughout the load. Corn has a high rate of respiration and at room temperature, up to one half of the sugar can be metabolized into starch in 24 hours. Top icing and proper temperatures will slow respiration dramatically.
