The instant and active dry yeast you use for baking is actually a living microorganism (Saccharomyces cerevisiae). This organism is very sensitive and can die if kept in the wrong storage conditions.
Dead yeast won’t work so it’s important that you store yeast in a way which keeps it alive.
Shelf Life of Yeast
Fresh yeast has a very short shelf life of just about 3 weeks in the fridge. By contrast, active dry yeast and instant yeast are freeze-dried. Freeze-drying puts the yeast in a sort of hibernation so it lasts much longer. Unopened, packets of instant and active dry yeast should last 2 years.
Red Star yeast, for example, puts the “Best If Used By Date” for their dry yeast at two years from the date the yeast was packaged. Once opening dry yeast, they recommend using the yeast within 4 months if it was kept in the fridge or 6 months if it was kept in the freezer.
Can You Use Expired Yeast?
Yeast generally doesn’t go bad in the sense that it becomes dangerous to eat. Rather, when yeast goes bad, it means that the microorganisms have died and will no longer help dough rise.
It varies depending on the storage conditions and strain of the yeast, but you can expect yeast to lose 10-25% of its viability per year at 68 degrees F (20C). At higher temperatures, the yeast will die even faster.
However, there are plenty of accounts of expired yeast still working years after it expired. I even heard one story of dry yeast working fine 13 years after its best-by date.
Tips for Using Expired Yeast:
- Perform a yeast test before using: Dissolve 1tsp of sugar in ¼ cup of warm water (105-115F). Add one packet of yeast. Within 10 minutes, the mixture should foam up to twice its volume. If it doesn’t, the yeast has lost some of its potency.
- Feed the yeast some sugar first: Put the yeast in a bowl with some sugar and warm water. The yeast will activate, start to eat the sugars, and have a chance to multiply before you add the other dough ingredients.
- Use more yeast: Depending on how old the yeast is, you might need to use much more to get the same rising effect.
How to Store Dry Yeast Long-Term
The key to storing yeast is to keep it away from moisture, heat, and air. These are the elements which could “wake up” the yeast and cause it to start dying off.
Unopened packets of dry yeast can last approximately 5 years in the refrigerator. Once the yeast pack or jar has been opened, it should be good for approximately 2 years in the fridge.
The important thing to know about storing yeast in the refrigerator is that the air inside can be very moist. Don’t just put the open yeast packets directly in the fridge: they will start to absorb moisture and die off faster. Instead, put the open yeast packets in an air-tight container first.
Storing yeast in the freezer is even better than keeping it in the fridge. The low temperature keeps the yeast cells in “hibernation” mode so they live much longer. It’s not clear how long frozen yeast will last but it should be much longer than 5 years.
Dry yeast is usually packaged in a metallic-type material which keeps out moisture. Air is usually removed from the package with a process called nitrogen flushing. So, yeast packets are already mostly safe from air and moisture. However, the packaging doesn’t protect the yeast from high temperatures.
If you want your instant or active dry yeast packets to last more than 2 years without keeping it in the fridge or freezer, you’ll need to keep it as cool as possible. Don’t keep it near the stove (which tends to get much warmer than other areas of your home), heating vents, or other warm areas.
If you can’t keep your dry yeast in the fridge or freezer after opening the package, then you can keep it in a sealed container. These containers will help protect from the elements. For example, you can put the opened yeast in:
- Mason jars
- Buckets with gamma lids
- Air-tight plastic containers
- Sealed Mylar bags
Should I Use Oxygen Absorbers when Storing Dry Yeast?
Yeast will deteriorate faster in the presence of oxygen. Steps should be taken to keep air away from your opened yeast, such as keeping the opened yeast in small air-tight containers without a lot of headroom.
However, you do NOT want to store yeast with oxygen absorbers. The reason for this recommendation seems to be related to how yeast respires differently in the presence or absence of oxygen.
Best Yeast for Long Term Storage
If you want to store yeast long-term for emergency preparedness, it’s really important that you pay attention to the way the yeast is packaged.
I recommend getting yeast which is:
- In smaller packets: While this is ultimately more expensive than buying bulk packages of yeast, it is easier to store because you don’t have to worry about repackaging the yeast once you open it.
- Nitrogen-flushed packaging: Nitrogen flushing removes oxygen from the packaging. This is usually only done on smaller packets or jars of yeast. For example, Red Star’s 3-pack strips and 4oz jars are nitrogen-flushed but their 2lb bags of yeast are not. Fleishmann’s doesn’t give any info about whether their yeast is nitrogen-flushed or not.
- Sturdy packaging: Ideally you get the small packets of dry yeast which are packaged in metal-like materials which keep out moisture. If you must go with a vacuum-sealed package, make sure the material is thicker and has a strong seal.
Below are some recommendations for dry yeast in small packets which have been nitrogen-flushed.
Alternatives to Yeast
Instead of worrying about long-term storage of yeast for emergencies, you can also look at yeast alternatives. Check out these posts for more info: