And while I love the taste of freshly baked banana nut bread or zucchini bread, I wouldn’t recommend it – and here’s why …
While I’ve heard several times of people/groups “canning” bread such as zucchini, banana nut, etc. I know that some folks have done this as a fundraiser stating that the canned bread is good for months/years. The process that they use is baking the bread (which contains eggs, fat, and other potentially hazardous ingredients) in a canning jar (not supported by the jar manufacturers). The hot jar is then removed from the oven and the lid and ring applied. The lid appears sealed because the heat from the jar and food soften the compound enough for it to adhere to the jar and the lid will indent when this happens. I do not believe that this is a safe product and I personally would not consume it. I do know that one of the major canning companies at one time had recipes for these products in their publications; they have since pulled them saying the process is unsafe.
Further, the following information is from the National Center for Home Food Preservation where much research on canning safety occurs:
Can I can bread or cake in a jar?
These products are not recommended for canning; choose recipes that you can freeze. In fact, most of these products are not really “canned.” The directions call for baking in the jar and then closing with a canning lid. Many recipes for quick breads and cakes are low-acid and have the potential for supporting the growth of a bacteria like Clostridium botulinum if it is present inside the closed jar.
One university’s research showed a high potential for problems. You will see these products made commercially; however, additives, preservatives and processing controls not available for home recipes are used. Canning jar manufacturers also don’t endorse baking in their canning jars.