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I was cleaning out my spice cabinet and deep in the back I found two packages (e.g., six envelopes) of active dry Red Star yeast that expired in March 2009, 15 months ago as of writing this question.

With the thought that dry yeast is basically freeze-dried and should have a decent shelf life, I proofed one envelope in warm water with some sugar to see if it really "expires". It foamed right up, so it seems like the answer is, at least for one year after the marked date, no.

Although in this case, does "expired" really mean "less effective" or "will taste funny"?

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If you bake a lot (yeast baking), look around for Fleischman's Instant Yeast in 1 pound foil bags. Yes, 1 pound. Lasts forever and it's a lot easier to use than "active dry" yeast - it goes in like a dry ingredient, and there's no proofing. A pound makes a lot of bread and it should cost less than $5. –  Pointy Jul 21 '10 at 14:12
    
@Pointy: Fleischman's Instant Yeast is active dry yeast. Red Star works fine too, and is available in 1lb foil bags at Costco. –  derobert Jul 21 '10 at 22:35
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No, it is not active dry yeast. It's instant yeast. There is definitely a difference. The Red Star yeast is also instant yeast. The names are confusing; check McGee or something. –  Pointy Jul 21 '10 at 23:19
    
Here's a link: thefreshloaf.com/node/2815/active-yeast-vs-instant-yeast –  Pointy Jul 21 '10 at 23:20
    
And according to McGee, the difference is that "instant" yeast is dried a lot more quickly than "active dry" yeast, and the little particles are of a shape that absorbs water much more readily. Thus, it needs no proofing and can be added as a dry ingredient (which I've been doing for years with consistently good results). –  Pointy Jul 22 '10 at 1:16

15 Answers 15

up vote 17 down vote accepted

I've used yeast that was even older than yours and although the taste of the resulting bread was fine, and it foamed up properly when tested, I found I had to use about 50% more of it to get the same density of the bread. In the end, I threw it out because it was too much trouble to experiment with it every time.

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To note, yeast does expire; sort of. Cell viability goes down fairly quickly based on the age of the yeast from date of packaging: 1 month – 80% viable 2 months – 64% viable 3 months – 51% viable 4 months – 41% viable 5 months – 33% viable 6 months – 26% viable –  Matthew Jan 30 at 4:59

Expired yeast will taste less, and rise less or not at all.

I believe the expiration date is a conservative estimate for yeast stored sealed at room temperature to still rise reliably. If the storage environment is better and you're willing to test before every batch, and use more yeast if necessary, I don't see why you couldn't continue to use it.

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I've sucessfully used dry active yeast that is over five years old, keep it in the frige. When it's really old, I put a skosh of sugar in the proofing cup, to give the old fellers a bit of a leg up, and just wait till it's really foaming, then use it like usual, don't increase the quantities. It's the same bugs, and it tastes the same.

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Yeast expires because it's a micro-organism (a fungus, in fact) that eventually dies. Your foaming yeast is still alive and should be fine to use; the expiry date is a decent estimate of how long the yeast will last, but various conditions (where and how yeast is stored among others) affect how long it will live.

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Bottom line - 13 year old yeast works, here is the whole story - I am about to use some Fleischman's active-dry yeast that expired in 1999 (pre-millennium). I am feeling lucky because today is Christmas eve day (2012). I am using it in a bread machine (normal 4 hour bake mode) I will write back in 4 hours to tell you the results. Per my wife's advice, I tested it by putting a pinch in a small amount of warm sugar water. It was for sure doing something after about 5 to 10 minutes, not what you would call a foam, but it was generating a lot of opaque small masses and smelled yeasty. I also put in 50% more yeast (in the machine's special yeast receptacle) as recommended by answer 11. To make it interesting, I am also using some equally old dry milk. The "better for bread" flour is probably only 4 years old. The butter is less than a week old, the salt was bought about 6 months ago, and the water is 13.75 +/- 0.11 billion years old (per Wikipedia). The bread machine is approximately 15 years old. I am 54 years old. Wish me luck....OK, I'm back and I'm happy to report that I got a yummy 3/4 size loaf (served with real butter) enough for the family along with some soup I made from last Thanksgiving's Turkey stock.

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I realize that the original post was a "non answer", but in my first post I did promise to revise it in 4 hours with the final answer which I did (13 yr old yeast works). Mostly I am amazed and appreciative that someone already read my post (this was my first post) - Happy Holidays –  Bob Higbee Dec 24 '12 at 22:40

Weel, I tried to make pretzels and it never rose. And i was using old yeast so yes it does expires

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I just used a package of yeast that expired in 2007 for a belgian waffle recipe. It's been sitting in the kitchen, unrefrigerated. No movement—the bugs are dead!

Update—I hated to see the waffles go to waste, so I bought some more yeast. To whet the appetite of the yeast bugs, I gave them some sugar to feast on in addition to their milk meal. The Fleischmann's RapidRise yeast puffed right up, so much so that it even got pasty. 1⅓ hours later it had doubled in size. Guess we'll have waffles for dinner now!

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Old Active Dry Yeast:

Prehistoric yeast takes beer drinkers back in time:

The yeast was actually trapped in the gooey tree resin during the Eocene epoch, 20 million years after the last dinosaur perished. High temperatures and warm oceans created a balmy environment throughout the Earth, with palm trees growing in what’s now Alaska. And, fortuitously, the yeast is an ancient relative of today’s Saccharomyces, or brewer’s yeast.

If yeast can survive 45 million years trapped in Burmese tree sap, a couple decades sealed in a foil envelope should be no sweat.

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Tree sap is a totally different environment than foil packets. Things that would have totally degraded in open air can be preserved in amber for centuries. –  Yamikuronue Jun 25 '12 at 13:23
    
Foil packet isn't open air. It's sealed and likely anaerobic. Packet is Certainly drier than sticky tree juice starts out being. Lyophilized/anaerobic is a heck of a good way to preserve microorganisms. –  Wayfaring Stranger Jun 26 '12 at 1:14

Well, trying a packet from 1998 (in the freezer) today - seems to be rising - hope it tastes fine.

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I just baked a loaf of rye bread with dry yeast that had an expiration date of 2004 and the loaf turned out beautifully! All I did was mix 1 pkg of yeast with 1/4 c warm water and 1 tsp sugar and let it sit for 5 min. This was advice I'd read on the Internet, and it has worked. I'm thrilled bcse I have about 12 pkgs of expired yeast in my refrigerator!So don't let those dates intimidate you! Oh! I also have to let my bread rise in an oven that I've turned on to 250 degrees for 1 minute bcse I don't have a pilot light in my oven.Even without the optimal conditions for baking yeast bread, it can be done!

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Yeast does expire . Yeast will last longer than the date printed on the packet if it is kept in the refrigerator . It will last longer in the freezer (for up to a year or even more).

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Welcome to the site and thanks for the answer. –  BaffledCook Mar 29 '13 at 16:04

I've put a handmade loaf in the oven with Yeast that technically expired 2 months after I opened the tin (Allisons active dried yeast - granules)... it foamed up beautifully; 1 level tbsp (measuring spoon) in 150ml warm water (1 part boiling 2 parts room temp).

As for the loaf rising... The dough rose perfectly... Once in the oven? Not at all. Not beyond what it had already risen. It's now cooling, and is definitely loaf shaped and a decent size (despite looking slightly flat ontop), but I'm yet to know the density or crumb.

So overall, I would say just spend out on some new yeast, which is what I'll be doing.

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I forgot to say that I opened the tin 10 months ago now... time flies!!! –  Chloe Sep 2 '13 at 0:34

I had a several of packages of old yeast, the freshest best by date 5 years old and some 6 or more years old. It was just stored at room temp and that could be 90°+ in summer because we don't run the air conditioning much in summer.

I followed a yeast freshness test from http://www.redstaryeast.com/lessons-yeast-baking/yeast-shelf-life-storage/yeast-freshness-test to see if my yeast had any life.

I used 1/2 cup very warm water (110-115°F) in a 1 cup measure. I used a thermometer to be sure. I added a 1 tsp. sugar and the dry yeast packet (from 2009) and stirred together. The mixture should begin to foam after 3-4 minutes and after 10 minutes it should double to the 1 cup mark. My yeast mixture came to about 3/4 cup after 10 minutes. I didn't think this was good enough, so I proofed another batch with older yeast (from 2008) to see if it was any good. It had about the same result, so I threw in another packet of yeast, hoping yeast of the same date/storage conditions would work in my recipe if it had double strength.

You must use your proofed yeast immediately, so I made a batch of sweet roll dough. The dough took way longer to raise before punching down, and much longer to double after making rolls, about 7 hours before I baked them. I should have put them in a warmer spot, I just covered them and left them at normal room temp (about 72°F). I tucked them next to a pot of beef stew I was cooking on the stove for about an hour to help it along.

Summary: It took a long time, but we finally had cinnamon rolls at 9:30 p.m.! And they were delicious! Maybe it was 'cause we had to wait so dang long for 'em. I won't bother with yeast older than 5 years. I suggest storing your yeast in refrigerator or freezer, I heard that can extend the yeast life that way. Or make cinnamon rolls more often!!!

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I have a package of active yeast meant for commercial use that "expired" in 2009 (it's now 2014) and it still works as well as I expect it to. I have stored it in the freezer this whole time. I got mine at Smart and Final more than 5 years ago.

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Last year-I had positive and negative experiences both using expired yeast. Most of the batches didn't rise as well but still worked- the one batch that didn't -the individual packet of yeast was aobut a decade old. Still dissapointing because you go to all that extra effort of letting the dough rise, punching it down and rolling out to baste the butter, sprinkle cinnamon and sugar. Then roll it, cut it with dental floss and let it rise a again before baking. What I determined is to go ahead and use it if it's no more than five years expired for the individual packets and in the refrigerator for the jar or can. I'm going to try two batches today. The first batch with a jar of yeast 4 years old that has been sealed but NOT refrigerated "fast rising instant yeast" and one batch with a packet of yeast that is not expired and compare the rise times. Guess a little experiment will be the best way to determine if I'll be able to salvage the product and then bake more if it works to use it up- my lucky neighbors :)

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