Hmmm, a mother who keeps a bottle of corn syrup sitting in her cupboard for a decade, and a daughter with no Internet access. Sounds like two variations of the same problem – failing to keep up with changing times. And while we can provide an answer, that’s never a guarantee that it will settle an argument.
ACH Food Companies, Inc., the conglomerate that owns and markets Karo syrup, says, “Karo syrup is safe to eat for an indefinite period of time, whether it has been opened or not opened. Light corn syrup may turn slightly yellow with age, but this is normal and not harmful. Storage conditions affect product quality. Before or after opening, Karo syrup may be stored at room temperature. Bottles may be refrigerated after opening, however, the syrup will be thicker and slower to pour.”
To us, 10 years fits within an “indefinite period,” so we’re not going to argue with mom or ACH Food Companies, Inc. But we think it’s time mom used up her corn syrup by increasing her baking activities a bit, and your friend found out for herself how to ask cooking questions online.