I like to leave a few sprigs of mint leaf in bottled water overnight to give it some extra flavor. It's delicious, but recently I left one in the fridge while I was on vacation for five days. I tasted the water and it still tastes great, but I'm curious how long something like mint needs to soak in (refrigerated) water before it becomes a safety concern?
I recently asked this question to my dietitian friend at work, and she advised fruit/herbs last about 3 to 5 days in water in the fridge before becoming soft and mushy. If your mint leaf still looks nice and pretty, you are most likely OK. She also recommended a website to me: www.infusedwaters.com/faq for recipes and advise.