I like to buy bananas in, say, Costco, where they sell for 4 lbs for $1.33 but they're totally greeen. I keep them in my kitchen on a banana stand, and they start to brown before they've become yellow. This happened in both the summer and in the winter here in New York, so I can't imagine temperature is an issue. Does anyone have any suggestions for making my bananas go from green to yellow to brown? Thanks.