High-fructose corn syrup (HFCS) (also called glucose-fructose, isoglucose and glucose-fructose syrup) is a sweetener made from corn starch  that has been processed by glucose isomerase to convert some of its glucose into fructose. HFCS was first marketed in the early 1970s by the Clinton Corn Processing Company, together with the Japanese research institute where the enzyme was discovered.