Do you have the right jar?
When it comes time to putting delicious produce in jars to preserve make sure you have done your homework on selecting a canner safe jar.
Not all canning jars are the same, especially when it comes to preserving your delicious produce. You want to make sure you are using a Mason-type jar. According the National Center for Home Food Preservation, a Mason-type jar is specifically designed for home canning and is the best option. Commercial mayonnaise jars may not seal and may break, especially in a pressure canner.
Looking in the store you will notice that canning jars come in a variety of sizes from half-pint jars to half-gallon jars. Pint and quart jars are the most common used sizes. Many foods do not have processing times for the smaller jars as they are typically used for jams and jellies. If a recipe does not specify a processing time in one of these jars, process the half-pint and 12-ounce jars for the same time as pints. Half-gallon canning jars are recommended only for very acid juices.
In 2014 you will also notice in the canning jar aisle there are blue and green canning jars. These newer versions of jars are fine to use, but the older versions (blue, purple, green and various shapes) are no longer recommended for use in processing. They have had years of use and stress, possibly weakening the glass in places that could cause breakage. Save the antiques for decorating!
If you are a bargain hunter and have found jars at an estate sale or garage sale, proceed with caution, you have no idea of how they were stored and if the glass has been placed under stress which could result in breakage. Question the seller to see if you can get the story on how the jars were used and stored. Examine the jars for nicks, cracks and chips.
Using jars from commercial foods is not a recommended practice. There are some jars that even say “Mason” on them but they are not a true pint or quart jar and do not have the flat rim for a lid to tightly seal. Quite often they are considered “one time” use jars and have seams making them weak for our method of processing, that may result in breakage.
Food safety educators are often asked how long a Mason jar is good for, which depends on how you treat them. If they are stored carefully at proper temperatures, not knocked together and kept clean, they will last you several canning seasons. Remember to start out every season by checking the jars for chips, nicks and cracks.
There are also some “designer” jars available quite often online. Currently, the U.S. Department of Agriculture doesn’t recommend using anything other than the standard pint or quart sized jar to process foods in. The shape and size of a jar does have an effect on the safety of the canning process, and on how the heat penetrates the jar. It should not be assumed that our recommended processes can be used with jars other than the standard sizes and shapes of Mason-type jars manufactured for home canning.
The most common type of canning lid sold today is a two piece, self-sealing lid. This type consists of a flat, metal disc which has a sealing compound around the outer edge and a separate metal screw band. The lid is only used once but the band may be used multiple times, unless it begins to rust. One piece lids are not recommended for the home canner at this time because there is not enough research to determine if they are allowing enough air to escape and create a safe vacuum-type seal.
Michigan State University Extension recommends following research based recipes to get the best results with your canning efforts. By taking a few steps and ensuring your containers are safe you will have wonderful products to enjoy.