Why do raspberries seem to rot or mold within a day or two after bringing them home? "Red raspberries will mold while you stand there watching them," says Querencia. "I have given up on them and use the frozen when I need raspberries. For fresh, blackberries keep for weeks in the refrigerator."
But you don't have to give up on fresh berries if you're willing to give some attention to how they're stored. "Check over and discard any moldy berries," says pikawicca. "Do NOT rinse. Put in wide-mouthed Mason jar (or other glass container with a tight-fitting lid). Refrigerate. Keeps a long time." walker confirms that this berry-preserving strategy works: "Yes ... in a glass jar with the lid on works ... really!"
One explanation for this problem, says greygarious, is that "being moister than other berries, raspberries will easily 'sweat' in their plastic-topped containers if they go from a warm car into a cool house and are not uncovered while they acclimate to the cooler room before being refrigerated."
greygarious has an elaborate but proven method for keeping the fruit fresh: "I like to put all berries in front of a fan for a couple of hours before placing them in a paper-towel lined Rubbermaid container. I leave the cover open at one end and after a few hours in the fridge, take it out and dry off any condensation on the lid. Then lay a dry paper towel over the berries and seal completely. That works for 10+ days for strawberries, and close to a week for raspberries that were in top condition when purchased. I do this ONLY with unbruised berries. Any that have a soft spot get eaten right away, or are placed at the top of the Rubbermaid container so they get eaten soonest."