This is the corn relish recipe I use which I've put together from several different ones. We like our relish spicy, but you can always tone down the heat by cutting back on the Jalepenos and leaving out the red pepper flakes. Serve it chilled. It's always a hit and it looks so pretty on the shelf, too! Since it has a vinegar base, you can water bath can it safely. You can also refrigerate it for up to two weeks.
Sterilize jars and keep warm. Immerse lids and rings in very hot water and leave them there until you're ready to use them.
Combine corn, onions, bell peppers, hot peppers, vinegar, sugar, salt, mustard, celery seed, turmeric and red pepper flakes (if using) in a large, non-reactive pot. Bring to a boil over medium-high heat. Reduce heat to low and simmer for 15 minutes stirring occasionally.
Fill the hot jars with the relish leaving 1" head space, run a small spatula around the inside of the jars to remove air bubbles and wipe rims and jar threads with a damp paper towel. Please lids on jars and tighten rings to fingertip tightness.
Lower jars on a rack in the canner using a jar lifter. Make sure the jars are covered with at least 3-4 inches of water. Return to a boil and boil gently for 15 minutes.
Remove jars and place on a clean dish towel out of direct sunlight. Let rest for 24 hours. Test jars for seal and refrigerate any unsealed jars. Store sealed jars in a dark cupboard for up to one year.