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As raspberries are highly perishable, they should only be purchased one or two days prior to use. Choose berries that are firm, plump and deep in color, while avoiding those that are soft, mushy or moldy. If you are buying berries prepackaged in a container, make sure that they are not packed too tightly, since this may cause them to become crushed and damaged, and that the container has no signs of stains or moisture, indication of possible spoilage. Raspberries are generally available from midsummer through early fall. Red raspberry is most often the source of a dietary supplement sold in many health food stores called ellagic acid.