I am new to brewing but I have worked in the food industry most of my life. The white that you see could be the sugar crystalyzing. When sugar gets old, it crystalyzes. If you were to leave a chocolate bar in your refrigerator for a long time, it will start to turn white. Being that extracts are sugar, it could be the sugar crystalyzing. Extracts are sweet like sugar, try tasting the extract and see how it tastes. If it is mold, it wont hurt you(unless you are alergic to pennicillin), it will just taste funny. If it tastes moldy, scrape off the white part and toss, if its sweet, just use as normal. Like I said, I am new to brewing so there may be experts who have seen this before.