Does store-bought Kombucha spoil? If so, how can I tell?
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.
Thank you for the link, as well as your personal advice. Since I've been opening it several times a day, I think I'll throw out unused portions after a week. Maybe I'll get used to the taste so I can drink it more quickly! Also, since there are things floating in the bottom, I assumed it's necessary to shake it to distribute those, however the bottle says not to shake it. If you feel differently, would you kindly let me know? Thanks!
Don't shake, for 2 main reasons. First, the fermentation will produce a small amount of carbonation. Second, the floating bits are actually parts of the microbial colony (called the "scoby"). I doubt they're actively harmful, but I'm not sure you'd want to drink the entire thing at once.
FYI - Most commercially available kombucha is now pasteurized, so it may not be likely that "the cultures are still alive" unless you specifically seek out the few brands that offer "raw" versions (which generally have "raw," "unpasteurized," or "live cultures" on the label). Many companies don't tend to advertise that their stuff is pasteurized, since consumers tend to want the raw stuff--but lots of commercial producers switched in 2010 after non-shelf-stable (i.e. live) kombucha was producing excess alcohol while it sat and going over the limit for unregulated beverages.