Preserving 101: Filling the Jar


Ok, so we have safe, sterile jars and the fresh, beautiful produce to fill them with. No matter what recipe you decide on, there are a few principles that always apply when filling your jars. These include:

Controlling headspace. Headspace is the unfilled space above the food and below the lid. It is needed for the expansion of foods to be processed and for forming vacuums in cooled jars. Directions specify leaving 0,5 to 2,5 cm headspace. After wiping the jar rim clean, place the lid on and tighten.

Process times. To destroy microorganisms in your food, you must process jars for the correct number of minutes in boiling water or a pressure canner.  Take into consideration that if you live more than 300 m above sea level, you will have to adjust processing times due to water boiling at lower temperatures as altitude increases. For determining proper process times, consult the set of tables provided by USDA here.

Cooling jars. After removing hot jars from a canner (preferably with a jar lifter – safety first!), cool them at room temperature for 12 to 24 hours. Don’t try to rush the procedure by putting jars in cold water! My mother even puts jars under thick blankets to further slow the cooling process.

Testing jar seals. When jars have cooled, press the middle of the lids with a finger. If the lid springs up when you release your finger, the lid is unsealed. You can also check by holding the jar at eye level and looking across the lid, it should be curved down slightly in the centre as vacuum pulls it inward. If a lid fails to seal on a jar, change the lid and reprocess the jar, or store the food in the fridge and consume within a few days.

Storing canned foods. Clean completely cooled, tightly sealed jars if necessary. Label and date them, and store in a clean, cool, dark and dry place. Avoid direct sunlight, dampness (may corrode metal lids) and accidental freezing and thawing (may soften food).

Identifying spoilage. Very important: do not taste food from a jar with an unsealed lid or food that shows signs of spoilage! Swelled lids are a sign of gas produced be bacteria or yeasts. Also look for unnatural color or mold growth, smell for unnatural odors.

Hope you find this useful! Play by the simple rules I posted in this blog series and you can enjoy the fruit of your hard work, both literally and figuratively speaking. 🙂


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