Is A Hot Water Bath Necessary?
The answer is no.
You have to make sure that you maintain 190 degrees Fahrenheit at fill. It is also important that you invert the jars so the glue seal on the lid will adhere to the glass properly.
There is unfortunately a downside to hot water bathing, the minor being extra time and processing. The major downside is, with certain pectin's, if your product cools down and starts to set before you put it into a hot water bath. The temperature will increase to the point where the pectin molecule chain can break a lot of times and it will not relink.
So, from a processing standpoint, hot water bathing is not necessary if your maintaining 190 degrees at fill and it’s often times problematic in breaking the pectin down. The majority of our customers use this method and prefer it as well.
If you do not feel confident in having a controlled and sanitized environment while filling, pressure canning is also an option. The only unfortunate thing is you can end up with the same results in hot water bathing, and end up with a bad set from the reheating.