As an example, Mission Organics White Corn Tortilla Chips list "trace of lime" as the last ingredient. This could indicate some part (or juice) of the citrus fruit, included as a seasoning (common in Mexican cuisine). On the other hand, there is a process for preparing corn (maize in some dialects) which involves cooking it in a calcium hydroxide solution. So if these chips are made using this process, "trace of lime" could refer to calcium hydroxide residues. Which is meant?
Calcium hydroxide is pretty much insoluble, so it's hard to get every last bit of it out after nixtamalizing. A trace always remains. If the maker were selling lime flavored tortilla chips, which are sold the ingredient list would say something like "lime extract" or "natural lime flavor".