If sweet corn browns during canning, it usually means that the temperature required for canning is too high for the sugar levels in the corn variety. This carmelization has become more of a problem as newer varieties of corn get sweeter and sweeter. You cannot, however, safely reduce the heat or processing time needed for canning corn; you can freeze that corn or find a locally grown variety that is recommended for canning. Though not an immediate safety concern, you might want to consider refrigerating these jars and/or consuming them more quickly since they may not maintain the best quality for long.
Learn more about preserving corn at Preserve it Fresh, Preserve it Safe: Sweet Corn.
