Published on Wednesday, 30 November -0001 00:00
By Debbie Botzek-Linn,
U of M Extension
Whether you are processing pickles in a boiling waterbath or canning green beans in a pressure canner, the amount of headspace in the canning jar is important. Headspace is the space in the jar between the top of the food or liquid and the inside of the lid.
Recently, in judging home food preservation at a county fair, a concern was the number of jars entered that did not have the recommended amount of headspace. Jams and jellies overall had too much headspace resulting in some unsealed jars. This will lead to mold and lost product. Some of the pickled foods did not have enough headspace as a cucumber or beet was touching the lid and above the brine. These cucumbers may discolor and will not pickle when not submerged in the brine. Canned vegetables, pickles or fruit need to be covered by brine, liquid, or syrup.
If jars are overfilled, the contents may boil out during the processing and cause solids or seeds to be caught under the sealing compound and prevent an airtight seal from forming. When too much headspace is left at the top of the jar, the processing time may not be long enough to drive out all the extra air, thus preventing an airtight seal. Excess air inside the jar also causes food discoloration.
The amount of space to leave at the top of the jar is determined by the type of food being processed. As a general rule when canning, allow 1-inch headspace for vegetables and meats; 1/2 inch for fruits, tomatoes, pickles and relishes and 1/4-inch headspace for jams, jellies, juices, pickles and relishes.
As a home canner you invest time and resources in preserving so do be mindful of headspace in canning for quality foods and to prevent loss of product.