I was curious if I could further ferment store bought yogurt/kefir for a stronger taste. I make my own kefir and I make it pretty strong, but I'm away from home and was thinking that taking bottle of store bought kefir or yogurt and letting it sit unopened overnight at room temp would basically make a more intense kefir or yogurt. Anyone know if this would work? Or would the bacteria be too dormant after being refrigerated and made shelf stable to ferment any further, or possibly even be overcome by other bad bacteria?
Also, I know less about yogurt. If you think the above would work, would room temperature work or do I need to heat it up a bit?