How long does bicarbonate soda (baking soda) keep?

StillTasty provides a very conservative answer: 6 months at best quality. In my personal experience, it can last much longer and be just fine, though I think the longest I ever kept a box was a couple years, not 5 years like riotburn. StillTasty suggests that the concern after more than 6 months is lost potency, but I believe the potential to take on odors from the surroundings is much more of a concern; store it in something airtight like you said, and you should be pretty safe from that.

So I'm sure it'll last at least until next Christmas. And if you do get into baking, you might go through a box faster than you'd think. Otherwise, it's fortunately pretty cheap, and it does have other uses (e.g. cleaning) so it won't hurt you too much to just go for it.

Sodium bicarbonate is stable at room temperature. Above 70 or 80 degrees C, it will degrade into sodium carbonate, water and carbon dioxide. Keep it in a sealed container (esp away from the oven and acids such as vinegar) and it should last indefinitely.

I don't know if this is technically correct but I've had the same canister of baking soda in my house for at least 5 years and have not had any problems cooking with it.

Baking Soda (Sodium bicarbonate) is often mined from the ground, it's been there for millions of years, so a few years in a closed container in your cupboard should not be a problem :-)

Even though the baking soda won't decompose into hunks of salt and carbon within a year, it will lose the leavening power (potency and performance) that many baking applications (such as in cookies and quickbreads) rely on.

Baking is chemistry. To get the same outcome as the recipe intends, you need to use precisely the same proportions and ingredients as the recipe states. If the baking soda you use doesn't give the same rising power (leavening) at the same times as the recipe expects, then you will have different results.

Some resources suggest testing the efficacy of baking soda by putting some in water or vinegar and looking for fizzing. You can do this at home to see a difference between old and new baking soda. But there is no way quantifiable to quantify how much fizz occurs. Without quantifying the decrease in efficiency, you have no way of knowing how much more baking soda you might need to get the expected result.

When I bake cookies with baking soda older than 6 months, they are definitely flatter than when I use newer baking soda. Here are some cookies that I baked with new baking soda, and baking soda from last year.

(You can read more about my science experiment here.)

But, if you're just using baking soda to absorb odors or clean, you may not notice the reduced efficiency.

I realise you're asking about baking soda, but not being happy with the rise I was getting on American-style pancakes, I bought some new baking powder and instantly got that good ol' rise back. I'd had the previous baking powder for 6 months and it still had 6 months until expiry. I now keep the new powder in an airtight container now, not the cardboard cylinder it came in.

I did the fizz test KatieK talks of (but I think I used lemon juice), and the new powder easily fizzed twice as much.

It's dirt cheap and has so many other uses, I just wouldn't take the chance.

I'm also in Sydney, near the ocean.

Baking soda causes a flattening of baked goods. Baking powder gives baked goods a rise. So the older baking soda in the picture did exactly what it should have and there is no reason to discard the Nov 2010 baking soda.