Cola by citric or other isolated acids. Coca-Cola's recipe is maintained as a corporate trade secret. A variety of different sweeteners may be added to cola, often partly dependent on local agricultural policy. High-fructose corn syrup (HFCS) is predominantly used in the United States and Canada due to the lower cost of government-subsidized corn. In Europe, however, HFCS is subject to production quotas designed to encourage the production of sugar; sugar is thus typically used to sweeten sodas. In addition, stevia or an artificial sweetener may be used; "sugar-free" or "diet" colas typically contain artificial sweeteners only. In the 1940s, Coca-Cola
Drink can Fraze (1913–1989) of Dayton, Ohio, United States, invented the similar integral rivet and pull-tab version (also known as "ring pull" in British English), which had a ring attached at the rivet for pulling, and which would come off completely to be discarded. He received US Patent No. 3,349,949 for his pull-top can design in 1963 and licensed his invention to Alcoa and Pittsburgh Brewing Company, the latter of which first introduced the design on Iron City Beer cans. The first soft drinks to be sold in all-aluminium cans were R.C. Cola and Diet-Rite Cola, both made by the Royal Crown