April 13, 2024


Food & Travel Enthusiast

The Importance of Properly Sealing Glass Jars for Food Safety

When properly sealed, jars create an airtight seal that prevents food spoilage and microorganisms from entering the food. Food safety is a multifaceted practice that includes food processing and handling, cooking at the correct internal temperature, avoiding cross-contamination, and storing chilled foods.

Glass jars and lids are an essential tool for canning foods at home. Before reusing jars or lids, examine them for nicks, cracks, and rough surfaces that may prevent an airtight seal.

Air and Moisture Resistant

Glass jars for food products are popular because it’s durable and versatile. Its clarity enables users to see the contents of their jars, and it’s available in a wide range of shapes, sizes, and rings with different opening diameters.

When a lid seals properly, it creates an airtight, water-resistant barrier that prevents spoilage and odors. However, jars that are not sealed properly can allow moisture and air to get into the jar. If this occurs, the contents of the jar will spoil over time.

After a jar is cooled, test the seal by gently jiggling or tapping on the rim. A clear ringing noise indicates that the jar has been sealed correctly. If the jars do not jiggle or only jiggle a few times and then stop jiggling, it’s safe to assume they have not sealed correctly and must be reprocessed. Also, remember to remove the jars’ screw bands before storing them in a cool dark place.


Glass jars can be sterilized and pasteurized to guarantee a long shelf life. The high temperature and time required for sterilization is a sure way to kill many pathogens on inanimate objects. This sterilization method uses ionizing radiation (beta particles and gamma rays) that bombard the object’s atoms, producing secondary electrons that ionize the target material’s molecules, ultimately killing the microorganisms.

Once the jars have been properly processed, remove the screw bands and let them cool for 12-24 hours on a rack or towel at room temperature. Once cooled, the center of the lid should be concave and will not spring up when pressed.

A good test for a seal is to tap the lid with the bottom of a spoon. A ringing, high-pitched sound indicates that the jar is sealed correctly; a dull sound means that food has expanded to touch the underside of the lid and has not been sealed.

Easy to Open

Often, it’s a matter of having a strong grip. The seal can weaken if your hands are wet or the jar has been stored in a drafty area. Luckily, several kitchen items you can reach for will help you get the extra leverage you need to open a stubborn lid.

Before storing, examine the lids for a concave center and a tight, firm seal. If there is an air bubble, the jar was improperly processed and should be labeled for use first. Also, check the jars during storage for signs of unsealing, such as rising gas bubbles or unnatural colors on the food and jar rims.

Easy to Clean

The right container can keep food fresher longer, but the wrong container can contaminate and harm the foods stored inside. To ensure that the contents of glass jars are safe, they must be sterilized.

New jars straight from the box are not sterile. They can pick up dust particles, tiny bits of glass, and other debris as they go through all the steps from factory to store to your kitchen.

Before using a glass jar:

  1. Wash it and the lid with soapy hot water and a scouring pad or steel wool.
  2. Soak the jar and the lid in hot water to help remove stubborn labels. If you’re dealing with a particularly sticky label, try using white vinegar.
  3. Be patient; it might take a while to peel the label cleanly.
  4. Once the label is off, rinse the jar and dry it completely before using it.

Dirty jars can be recycled, but they must be clean to prevent contamination of the recycled materials.