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Health & Nutrition: Food Preservation

Do I really need to leave a certain amount of head space in the jar?

Yes, leaving the specified amount of head space in a jar is important to assure a vacuum seal. If too little head space is allowed the food may expand and bubble out during processing when air is being forced out from under the lid. Bubbling food may leave a deposit on the rim of the jar or the seal of the lid and prevent the jar from sealing properly. If too much air space is allowed, the food at the top is likely to discolor. Also, the jar may not seal properly because there will not be enough processing time to drive all the air out of the jar.