How long is yeast good for after opening?

January 17, 2005 7:05 AM

My father in law is one who can never pass up (in his mind anyway) a bargain. He likes to make bread so instead of buying the small packets of yeast, he buys the big, CostCo, industrial size bag of yeast. Once he opens that, how long until the efficiency of the yeast is diminished?
posted by ShawnString to Food & Drink (14 answers total)

4 months at room temperature, longer in the fridge or freezer. (I have a bag of dry active yeast in the fridge that's about a year old, and it's still effective though not as aggressive as it used to be.)
posted by headspace at 7:11 AM on January 17, 2005

Put some of it in a resealable container for use -- look at the use-by date, if it has one, or assume a year, and try to figure out how much he'll use in that time.

Divide the rest into similar amounts, put into ziplocs, and into the freezer with it. Should be fine for a few years at least.
posted by ROU_Xenophobe at 7:12 AM on January 17, 2005

I've had the Costco yeast for well over a year in the refrigerator without any diminution of potency. It is a tough bargain to pass up because even if you end up throwing half of it away, you've saved a whole lot of money compared to those little packets. You can always proof the yeast if you doubt its efficacy, but I think in the active dry form, it lasts a long, long time.

My only problem with it is that it's such quick acting yeast that I don't think the bread has enough time to develop flavor, even if I let it have three risings. I would love to have a source for larger quantities of slower yeast.
posted by anapestic at 7:33 AM on January 17, 2005

anapestic: I've had that same problem, and I've found that you can get some of that flavor if you make a french loaf of it- knead hard, folding the top over the bottom several times, then let it rise the third time inside a floured piece of cotton or cheesecloth.

Put a pan in the bottom of your oven, and when you slip the loaf in to bake, throw a half a cup of water into the hot pan to create steam. Shut the door quickly! Most of the flavor is in the crusty rind of this bread, but it's nice and sharp, and distinctive.
posted by headspace at 7:43 AM on January 17, 2005

anapestic: You can ask a local bakery where they get bricks of fresh yeast (if they use it), but it really doesn't last as long as dry yeast, so you probably don't actually want to buy it in large quantities.
posted by transient at 7:56 AM on January 17, 2005

Of course, you could just go sourdough, too.
posted by transient at 7:59 AM on January 17, 2005

In lab, we've kept yeast for 5 or 10 years and it's still fine. It's just the normal stuff bought at the store and kept in its jar in the fridge. We use it for fungus demos and yes, for making bread. The only thing is, if it's truly ancient I might add more sugar or let it go for a little longer. Can't say I've noticed a difference in taste, but we make very simple bread rolls.

You'd be surprised how many college kids have never made bread before.

It seems to me that if the yeast quit working well, you'd notice. Plus, Saccharomyces has spores and those are designed to last for quite a while.
posted by arabelladragon at 8:57 AM on January 17, 2005

anapestic: Have you tried just letting it rise in the fridge? I've let dough hang out in there for 24 hours, sometimes 48.

FWIW, I had a large jar of yeast that my grandma gave me that had "July 1998" written on it that performed well for me into late 2003, when I ran out of it. I just kept it in the freezer.
posted by milkrate at 9:02 AM on January 17, 2005

I keep my bulk, dry active yeast in the freezer. The current batch has been there for 3 years that I know of. However, I have not yet seen a need for longer rising times or additional yeast. If you decide to use additional yeast, don't immediately jump to double the called for amount. Add a little for the batch at hand. If the results aren't what you're looking for, add a little more the next time you bake. You'll eventually find the level needed with your remaining yeast that doesn't leave your bread tasting too "yeasty".
posted by onhazier at 9:06 AM on January 17, 2005

In addition to ROU's suggestion of dividing it up, and everyone's suggestion of keeping it cool, don't forget to keep it DRY. That's the biggest problem with keeping large amounts in the fridge or freezer, you get condensation inside each time you open the cold package. If you divide it up though, it shouldn't be a problem.
posted by spaghetti at 9:33 AM on January 17, 2005

For freezing food effectively, I swear by vaccuum sealers like this one. Meat and other things that would normally keep a few months keeps 1-2 years.

Granular stuff, like yeast, shouldn't be put in the vaccuum seal apparatus unprotected, plus if you need only a bit at a time, continually reopening and resealing can be a pain. Instead, put yeast into a collection of small plastic bags, then slip all the bags into the freezer bag(s) and suck out the air. At intervals, remove several small packages for fast access and fridge storage, then reseal the bag and put it back in the freezer. You get longterm storage, fast access, and much fewer problems with condensation.
posted by maudlin at 10:10 AM on January 17, 2005

I put my yeast in an old jar, put the lid on and keep it in the freezer, along with the other big bags of yeast I bought at Sam's. Works fine.
posted by konolia at 10:52 AM on January 17, 2005

If you are ever uncertain as to whether yeast is still good, put a little bit of yeast and a little bit of sugar in a spoon, mix it up, and see what happens. If nothing happens, toss the yeast. If it turns to bubbling liquid, you're aces.
posted by jennyjenny at 12:18 PM on January 17, 2005

You can buy normal dry yeast (ie, non-fast) from King Arthur Flour. They have a lot of interesting things for making bread.
posted by Goofyy at 2:45 AM on January 18, 2005