Recipes from So Easy to Preserve: Fall Garden Relish, Curry Relish, Marinated Mushrooms, Baked Beans, Rummage Relish.
All jars of preserves meant for shelf-stable storage require processing of the filled, sealed jar. No matter how much you sterilize a jar in advance, or how much you cook the food before, or how tight you screw a lid on, or how much sugar or vinegar is in the recipe, or whether your Great-Aunt Matilde did or not. None of that counts: filled jars intended for shelf-stable storage must be processed.
It is not acceptable to just whack a lid on, let a jar cool, and if a seal, however weak, forms, call it a day.
In terms of kitchen sanitary practice, it’s the equivalent of licking a raw chicken.
A seal does not indicate that a canned product is safe. A seal indicates that new contaminants cannot get in, but it tells you nothing about the presence of microorganisms (mold, yeast, bacteria) that were already in the jar. Heat from a proper canning process is needed to make sure any microorganisms in the jar of food are killed.”  Christian, Kasey. Your Favorite Salsa Recipe…Is it Safe to Can? Preserving Food at Home blog. 13 August 2013. Accessed January 2016.
The ‘canning’ process you describe is not actually a recommended canning method — it is sometimes called “open-kettle canning”. In open kettle canning, food is cooked in an ordinary stockpot or kettle, then packed into hot jars and sealed without processing. The temperatures obtained in open kettle canning are not high enough to destroy all spoilage and food poisoning organisms that may be in the food. Also, microorganisms can enter the food when it is transferred from the kettle to jar and cause spoilage.”  Christian, Kasey. Your Favorite Salsa Recipe…Is it Safe to Can? Preserving Food at Home blog. 13 August 2013. Accessed January 2016.
Note as well that scientific testing has shown that sterilizing preserve jars (except for jars processed for less than 10 minutes) doesn’t actually achieve anything. You’ve wasted your time. It doesn’t replace the need for proper processing of the filled jar, and, the jar gets sterilized anyway during the processing step. So, modern advice based on research says: don’t bother.
There are three acceptable ways to process your jars, depending on the food product inside the jars.
For low-acid foods, the jars must be pressure-canned.
Always use a tested recipe from a reputable source, which will give you the correct processing time and method for that particular food item being made. If a recipe doesn’t give you a processing time, run, don’t walk, away from that recipe source.
Don’t guess at a processing method. Do the method that the recipe says — pressure canning your jam is overkill.
Whether you call your craft “canning” or “bottling”, process your jars.
AND, as a minor point, prevents the embarrassment when a friend says that jar of unprocessed jam you gifted to them had lovely psychedelic blue mould growing in it.
How important is proper processing? It’s so important that — while in-the-know experts do have firm opinions on many other things such as what type of jars and lid closure systems are best from an operational point of view — when push comes to shove, their concern about properly researched canning (i.e. processing) procedures being used makes it to the very top of the list.
That’s just how important processing your jars is.
1, 2. ↑ Christian, Kasey. Your Favorite Salsa Recipe…Is it Safe to Can? Preserving Food at Home blog. 13 August 2013. Accessed January 2016.
3. ↑ ”More complete removal of oxygen from the headspace also offers some longer protection from undesirable color and flavor changes with some types of fruit products. The canning process is therefore a more foolproof method of making jams and jellies that will not spoil.” Andress, Elizabeth. Preserving Food: Processing Jams and Jellies. University of Georgia Cooperative Extension. June 2011.