The secret to successful freezing is to use berries that are unwashed and completely dry before placing them in the freezer. Completely cover the blueberry containers with plastic wrap, store in an airtight, resealable plastic bag, or arrange dry berries in a single layer on a cookie sheet. When frozen, transfer berries to plastic bags or freezer containers.

Blueberries should be kept frozen and any unused portion promptly returned to the freezer. If not used immediately, cover and refrigerate thawed berries and use within three days.

Source: Michigan Blueberry Growers Association