Rainey's professional areas of interest include designing national sample collections and analyses of commodities to develop nutrient and residue databases for submission to the Environmental Protection Agency, the Food and Drug Administration and the U.S. Department of Agriculture.

In 1981, she began a nutrient composition sampling design on all varieties of potatoes. She now has experience in designing statistical sampling for FDA approval to isolate nutrient variables on over 100 produce commodities in their fresh and processed forms.

Rainey developed Nutrition Facts '95 for Windows, an FDA-approved modeling program on the nutrition information of processed foods from a database of ingredient nutrient information.

She is the principal investigator of an eight-country study on boron in foods and dietary consumption, using consumption data from Germany, Egypt, Kenya, Mexico, China, Japan, Great Britain, and the United States.

As a director for "Build a Wider Bridge," a nonprofit organization that collects used food science reference books and journals and delivers them to universities internationally, Rainey recently presented 6,000 titles to the University of Santiago.

Rainey was awarded a scientific lectureship by IFT and provides short courses on nutrition labeling regulations for the Food Laws and Regulations Division. She is a regular contributor to Nutrition Today and has published over 75 scientific articles and reports.