I recently bought Ginger Kombucha for the first time in a reputable health food store. I'd never heard of it, but my doctor feels the probiotics will help my chronic digestive problem. Because of the strong taste, I only drank a small amount each day. I did this by pouring some out, not by drinking from the bottle. On the fifth day, it smelled and tasted so much like alcohol I was afraid it was rancid. I took it back to the store for advice. One clerk told me it was supposed to smell like that, just to use it for seven days and discard any remainder. Another clerk said it can't spoil, and as long as I keep it refrigerated it will last indefinitely. Can someone with experience please help me? It's expensive, so I don't want to throw it away if I don't have to, however I don't want to poison myself or use something that's no longer effective. Thank you!
When they say "probiotic", what they mean is that there are microbe cultures present in the kombucha. It's really nothing more than a sweetened tea which has been fermented by a symbiotic mix of yeast and bacteria. The odor and distinctive flavor is the result of a low alcohol content and acetic acid (the same acid found in vinegar) produced by the fermentation process.
While these cultures do tend to edge out other bacteria that would spoil the drink and potentially cause illness, it can eventually go bad like anything else. More to the point, because the cultures are still alive, they'll continue the fermentation process as long as they can, especially once you open the container and start introducing oxygen. This can throw off the balance of the culture, but it can also just make the kombucha unpleasantly acidic. Once it gets to that point, it might still be effective from a probiotic stance, but the acid could have an adverse effect on your digestion.
If you keep it sealed and refrigerated, it'll last a couple weeks, but a week or so is probably the effective maximum when you're opening the container frequently. You'll want to stick to purchasing an amount that you can drink within a week or so, but don't worry overmuch if it has a slightly vinegary tang and odor.
If you're talking about raw kombucha (rather than pasteurized) then the answer is yes, inevitably, in the sense that it loses its desired probiotic properties. The kombucha will start to grow its own culture (though small), more commonly referred to as a mother or a scoby, which forms at the top of the bottle (container) and in time will take on both the look and feel of a jellyfish (tendrils hanging down). At this stage it can be harmful to consume, especially if discolored. Gauging however when it is that your purchase has crossed over from being beneficial to not beneficial, (meaning not good for you but not bad for you either), would probably require lab equipment and a working knowledge of microbiology. Refrigeration greatly slows down the culturation process but does not bring it to a halt.
When Kombucha gets old it turns to vinegar, then one can make salad dressing out of it. I have been brewing booch for while now and that has been the ultimate out come. I double ferment with ginger and home grown berries so when mine get old, i all ready have a vinegarette waiting for me. Hope that helped