Q: I just noticed that there are expiration dates on my cans of soda. Other than going flat, what can go wrong with soda? Do I have to throw them away after that date, or will they still be safe for a while?
A: I suspect that what you see are "Use by" or "Best if used by" dates. Those dates refer to quality, not safety. You're right that the most common problem with soda is that it goes flat, and that's a quality issue, too. But if you have diet soda, what might happen if it's stored too long is that the sweetener breaks down, especially if the soda was stored outdoors or in an area without air conditioning. If the soda is sweetened with aspartame, for example, it breaks down into two amino acids. The body will use them to make protein, if you can get them past your mouth. Simple amino acids are terribly bitter. You'll know if you happen to take a sip of one, because you won't take another sip! It won't make you sick, it just tastes awful.
The other thing that can happen if soda is stored too long is that the acid in the soda gets to the can and starts dissolving the metal. In that case, you'll have pinholes or larger, puddles on the floor and stains on the carpet. Again, it's not a health and safety problem, but more than a taste issue.
So, no, you don't need to throw it away after the date. Just be aware that the longer you keep soda past that date, it might not taste as good, and might be flat.
Q: I've been trying to find a recipe for canned pumpkin butter. I'm getting ready for pumpkin season and remember the delicious stuff my mother used to make and can every fall. We'd have it through the year to spread on muffins or toast. All the recipes I find now say to refrigerate it, and I can't do that for a full year.
A: I remember pumpkin butter, too, with cinnamon and cloves. Yum! But unfortunately, you won't find any reliable recipes for canning it now. What happened was that as the National Center for Home Food Preservation (at the University of Georgia) was testing and updating all home canning recipes, it determined there was too much variation.
Even with the same recipe, if different people used different kinds of pumpkin, prepared the pumpkin by boiling, baking, microwaving or steaming, etc., the butter could come out different. Sometimes it would be thicker and need longer processing than the runnier version. The experts weren't able to determine how much lemon juice or vinegar different varieties needed to ensure they were acidic enough.
All those things — density, acid, sugar, etc. — help determine if a food can be canned and how it must be canned. So, the National Center for Home Food Preservation recommended that the U.S. Department of Agriculture withdraw the canning recommendations.
The same thing is true even of canning just plain pureed pumpkin. We used to have directions for that; now we don't. The safe recommendations now are for canning cubes of pumpkin and then making the pie filling or the butter in small batches as you're ready to use it. The pumpkin cubes must be canned in a pressure canner.
So, safe pumpkin butter will need to be stored in the refrigerator, unless you're buying commercially prepared products. Remember, commercial producers have a wider range of safe canning techniques and materials available to them than we do in a kitchen.