Sterilizing a jar (canning jar) keeps canned food in a good condition for a very long time. If you’re processing any food, vegetables or fruits that the processing time is less than 10 minutes, you need to sterilize the jar first. The jar needs to be made from glass and make sure there’s no cracks or any sort of chips.
If you’re making jam (I have a strawberry jam recipe here Strawberry Jam (No Pectin and Low Sugar)), pickles, tomatoes or any home food, please sterilize your jar, unless you’re going to process the food for 10 minutes or longer that’s when it is advisable to skip the sterilization.
To sterilize you will need a canning kit, but if you don’t have don’t worry, just get a canning jar, a jar lifter or a tong, and a pot with a rack. Some people use an oven to sterilize their canning jar but it is not safe according to “National Center for Home Food Preservation” you can read more about sterilized canning jar and canned products on here https://nchfp.uga.edu/questions/FAQ_canning.html
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Fill a large with water and heat.
Place the jar in the pot and boil for 10 minutes, make sure the water covers the jar. When it gets to a boiling point, boil for additional 15 minutes then turn off the heat.
If you’re not ready to use the jar leave it in the hot water until you’re ready up to about 1 hour, but if it takes longer than that you’ll need to sterilize again.
Use a jar lifter or a tong (make sure the tong is sterilized; just dip the end of the tong into hot water for few minutes) to remove the hot sterilized jar.
Only add the lid to the hot water when you turn off the heat, if you boil it, the adhesive rings might be harmed, so it is better to drop it in the hot water when the heat has been turned off.
After the sterilization process, you can preserve your food.
Make sure you handle all the sterilized equipment properly. Your hands and the canning area are clean.