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Does opened tahini go bad?

post #1 of 12
Thread Starter 
This might be the stupidest question ever. If so, I apologize for being a dunce. I have a barely used jar of tahini in my fridge, and I don't know if I should toss it out or make hummus. How long with tahini keep? I don't think it's been in there for years or anything, but a few months definitely.



Advice?
post #2 of 12
If it smells ok.. make hummus! If it smells funky... don't. We've had tahini around forever in the back of the fridge at my parents house... Always seems ok, no one's gotten sick or died. Treat it as you would natural peanut butter.
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post #3 of 12
You're more at risk of the oils going rancid and making it taste bad than of actually getting sick from it. As long as it tastes good you should be fine.
post #4 of 12
I left an opened jar of tahini in the fridge for over two years once. I didn't even unscrew it when I discovered it because I knew I wasn't going to use it.
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"They call this war a cloud over the land. But they made the weather and then they stand in the rain and say '$#!±, it's raining!'"  Ruby, in "Cold Mountain"
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post #5 of 12
I've also had it around for a couple of years with no problems.
post #6 of 12
Quote:
Originally Posted by thebelovedtree View Post

You're more at risk of the oils going rancid and making it taste bad than of actually getting sick from it. As long as it tastes good you should be fine.



Quote:
Originally Posted by thebelovedtree in another thread View Post


That said most of the things that make us sick aren't going to make the food look, smell, or taste different. You could eat most strains of mold, etc. and make food look and taste gross and be fine (well, other than being grossed out). Bacteria, etc. generally don't spoil food as they build up over time, so even if it looks good, it may still make you sick.



So these rules aren't hard and fast?
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post #7 of 12
Quote:
Originally Posted by rabid_child View Post

So these rules aren't hard and fast?



Well Rancid oils won't make you sick, the taste is just really unpleasant so most people wouldn't eat them. There are a few strains of mold that will make you sick, but other than that if it looks gross it probably won't hurt anything other than your taste buds. Most of the "sickness" people experience from spoiled food is in their head.



Nut and seed butters generally have too low a water activity (Aw) to support bacterial growth, so as long as they've not been contaminated by an outside source they'll keep for quite some time. The minimum water activity for bacterial growth is 85, though some bacteria need more than that. I couldn't find the AW for tahini, but peanut butter has an Aw of 70, so there is a wide margin of error there.
post #8 of 12
Oils seem to preserve foods well. Tahini would fall into this category. Like others have said, you can probably use it if it does not seem rancid. Would you use peanut butter that you kept this long? It's basically the same thing.
post #9 of 12
Quote:
Originally Posted by froggythefrog View Post

Oils seem to preserve foods well.



This is true to a point, in foods that would otherwise support the growth of bacteria (high protein, neutral to slightly acidic, moist) oil limits oxygen. That will prevent the growth of aerobic bacteria, but allow anaerobic bacteria to grow in places they normally wouldn't. Anaerobic bacteria are less common than aerobic bacteria but they tend to make you sicker, so while you're less likely to get sick, it's more likely to be serious if you do.



Tahini, etc. doesn't go bad because if you removed the oil, which won't support bacterial growth, it would be very dry.
post #10 of 12
An opened jar of tahini will taste good for about 4 or 5 years if stored in the fridge, covered. If stored in a dark place at room temp it should last about 2 or 3 years without much of a flavor change. In the fridge it will be safe to eat for about 15 years, about 6 years unrefrigerated. Obviously if you see stuff growing on it, don't eat it. The first thing to go will be the oil will turn rancid. It will taste rancid, but it won't harm you. There is almost no moisture in tahini, so nothing will live in it. The problem of it eventually becoming unpalatable is due to rancidity, not bacterial action. Of course, always use a clean spoon when taking tahini from the jar. Transfer to a glass jar if it came in a metal can (the metal from the can will give the tahini a metallic taste, as the metal slowly dissolves in the oils, but it will take about 60 years before there is enough metal in it to harm you). Make sure there is no food or moisture on the spoon you stick into the jar of tahini. Keep it covered of course.
post #11 of 12
thebeloved tree
Quote:
The minimum water activity for bacterial growth is 85,



I never heard of "water activity" before. What units is this measured in? 85 what?
post #12 of 12
Quote:
Originally Posted by soilman View Post

thebeloved tree



I never heard of "water activity" before. What units is this measured in? 85 what?



Its a measure of how much of the water in an item is "free". It has to do with the pressure of water vapor with in the cells. I don't have my food science books with me now, but I'll pull it out and go into more detail when I can get to them.



Here's the wikipedia article about it: http://en.wikipedia.org/wiki/Water_activity



Their numbers seem to be a bit different than the ones in "Foods, Experimental Perspectives" which is where I pulled mine from.
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