Every tablespoon of oil you use for popping adds around 100 calories, as does every tablespoon of melted butter added after popping. More than two-thirds of the popcorn sold today comes already buttered and salted and ready to microwave-pop in two to three minutes.
Calories for microwave popcorn vary from 40 per cup for "light" varieties to 60 or 70 per cup for "regular" versions. Sodium levels also vary highly: from 50 to 150 milligrams per cup.
To control the fat and salt in your popcorn, start with plain kernels and an air-pop machine. The two main types of popcorn, yellow pearl and white rice, pop differently. Yellow pearl kernels produce a greater volume of popcorn per kernel than do white rice ones. On the other hand, white rice popcorn does not produce any hulls to get stuck in your teeth.
How well your popcorn pops depends to a great extent on the moisture content of the popcorn and the temperature of the popper. A moisture content of 14 percent seems to work best when popping corn with oil in an electric popper. A slightly higher moisture content is helpful for dry popping in an air-popper.
Popcorn that has been processed by a reliable processor and packed in an airtight, undamaged container or package should be at the proper moisture level for perfect popping. Once you open the package, store the unused portion in an airtight container, such as a glass jar, to help preserve the natural moisture.
If your popcorn doesn't pop into fluffy, crisp kernels, it may be because the moisture level of the dry corn has dropped too low. To recondition the kernels, fill a quart jar three-fourths full with dry popcorn kernels and add one tablespoon of water. Cover and shake often, every five or 10 minutes, until all of the water has been absorbed.
After two to four days of storage in the closed jar, the corn should be ready for perfect popping.
Lynn F. Little is a family and consumer sciences extension educator for Maryland Cooperative Extension, Washington County.