By 1929, Duke tired of the food business and sold her secret mayonnaise mix to Sauer and the sandwich recipes to her bookkeeper. The sandwich spreads are still controlled by the bookkeeper's family.

Duke's mayo ingredients include soybean oil, eggs, water, distilled and cider vinegar, salt, oleoresin paprika, natural flavors, and calcium disodium EDTA to protect flavor.

In addition to the flagship mayonnaise, which is still made according to the founder's original recipe, Duke's offers light, olive oil, and flavored mayonnaises, tartar sauce, sandwich relish and ...