Anything with pasta, rice, and barley cannot be canned safely. These low-acid ingredients common to soups, stews, and other convenience meals need to be pressure processed at length. During this time they break down and may, in fact, make the foodstuff too dense for the heat to safely kill the botulism spores.

Second, any dairy products like eggs, milk, cream, cheese, and butter are not safe to can. You can make pickled eggs and refrigerate them, but they need to be used within two weeks. Oils also aren’t good candidates. While flavored oils can be made for short-term use, oils generally get rancid very quickly.

Anything heavy in fats doesn’t can well. Excess fat should be removed from meat and ground beef should be sautéed and drained of excess fat. Allow soups and stocks to cool, skim the fat off, and then reheat and process them. Like oils, fat tends to go rancid.

Last but not least, don’t can anything thickened with flour, cornstarch, arrowroot, or breadcrumbs. ClearJel A, which is a modified cornstarch, may be used for safely canning pie fillings, but is not safe for thickening sauces or gravies.