Why did my granulated white sugar go brown in the container? I am not talking about caramelization. This sugar was just stored in the cabinet for about a month; when I poured it into a meauring cup, I saw it had gotten a little clumpy here and there and started to go light brown at room temperature. Then I looked more closely through the clear plastic container and saw the entire bottom of the sugar was brownish in streaks. It was Target brand.