Use your own judgment. Bananas are a dense, low acid food, which opens up the risk of botulism. Certainly, there is no way to process them safely in a boiling water bath. As a note, Exile and I had slightly different experiences with canning bananas.
I recently decided to try pressure canning banana.
As prices go up, I suspect the cost of transporting bananas will rise to the point where it will become prohibitively expensive to ship them. Also the recent outbreaks of a new parasite is affecting the viability of banana crops in most of the major producing nations.
Our local grocery store bags up 2-3 bunches of bananas that are no longer yellow and sells them for $2.99 a bag. So thinking that I would store bananas now while they are still relatively cheap, I decided to look into how it should be done.
I found only a few recipes in all my collection of books that even had bananas as an ingredient and no information in the books or on the web on how to pressure can them.
I started with a single bag of bananas, over half of which where still yellow with no brown spots, I took the oldest ones and mashed up enough to get 11 cups mashed banana.
Then I added 1 cup lemon juice.
I mixed the two ingredients thoroughly until I had a soft mush. I added the lemon juice to keep the bananas from going brown and to increase the acidity of the mixture as a back up to the pressure canning.
I filled 6 jars (500ml) with about 2 cups of mixture and left 1” of head space. One jar ended up with about 2” of head space because I ran short of mixture. I wiped down all the rims carefully before sealing the lids.
I processed the jars at 15 PSI – I need at least 13 PSI because of my altitude but I usually use 15 to be extra safe.
It is important to know the recommended PSI for your altitude and the canner used.
I considered because of the density of the banana mixture that they had similar density to meat and so I processed them for 90 minutes which is my usual time for meat products and meat based pasta sauces.
After removing the jars from the canner I noticed two important things:
1) Some of the lids had creased but had still sealed. The one that didn’t crease was the one with 2” of head space. In the future I plan to leave 2” on all the jars.
2) The banana mixture had separated solids from liquids which was to be expected; but the mixture turned pinkish red. I have since found this is a reaction between the bananas, the lemon juice and high heat.
I waited a month before trying the mixture out. When I opened it the banana mixture was still red colored and had formed a solid mass floating in the liquid.
I tried a recipe that called for 2 cups of bananas.
This should have been a single jar but the separation meant there was now about 1 cup of bananas and 1 cup of liquid. I decided not to try to mix the liquid back in and instead used just the banana mixture which was very smooth and easy to mix into the bread ingredients. So I ended up using 2 jars for this recipe.
The bread turned out wonderful with a very good scent of bananas. The color was darker than normal because of the red color and I also used unbleached white flour as it was what I needed to use up at.
The bread was very popular with the kids and after I ate the first piece they quickly devoured the rest of the loaf in minutes.
Note from Marie: Again, please be aware that there are no USDA recommendations for safely canning bananas.
This does not mean that the USDA has declared it unsafe but that they have not properly tested it. Like pressure canning milk (which I do regularly) and pressure canning bacon, lard, cheese and other fatty foods, there has been no testing done for home-canning.
It is important to do your own research and come to your own decisions regarding the safety of this process. If in doubt, follow USDA recommendations.
As a comparison, the USDA has come out with very clear statements that it is unsafe to use a boiling water bath for low acid foods or open kettle canning for high acid foods. These processes have been tested extensively and, since the 1950s, have been declared unsafe.
With that said, the argument that the density and lack of acid in bananas makes it unsafe does not seem like a relevant argument to me.
Bananas have a pH of 4.5-5.2. With the addition of the lemon juice, they would drop below the 4.5pH mark, but not by much.
As for density, mashed bananas are actually less dense (7.94 oz/cup) than applesauce (8.68 oz/cup), chili con carne (8.54 oz/cup) or baked beans (8.92 oz/cup).
Update October 2015: I have now personally tried this. The jars that sealed turned out exactly like Exile’s jars. In each batch, however, I had one jar that popped its lid, spewing banana everywhere. The texture of the bananas is very different and they turn dark reddish pink. My children dislike muffins made with them, not because they are unpleasant but because the texture is different than typical banana bread.
I am calling this a mixed success. It is possible and most probably safe, but I am not likely to do it again.
For those who are not comfortable with it, sliced bananas dehydrate very well into delicious banana chips.