Posted: June 19, 2012
Choose berries that look plump and firm with a light silvery bloom. Select fully ripe fruit because unripe berries do not become sweeter after they are picked. Ripe blueberries have a light blue to blue-black color. Red or green berries have a sour flavor. The bigger the berry, the sweeter it will be. That doesn’t necessarily mean the flavor is better as part of the appeal of any berry is its tartness.
Blueberries are delicate. Examine the berries carefully and remove squashed, diseased or moldy berries. Don’t wash fresh blueberries until you are ready to use them. They will spoil quickly if they are refrigerated while wet.
Because moisture on the surface of a frozen berry toughens the skin, some sources recommend freezing blueberries without washing and then washing them before being used. Another option is to wash the berries before freezing, but they must be thoroughly dried. Lay them out in a single layer on a towel and blot dry. To freeze blueberries, spread dry berries on a flat tray and place in the freezer. Once hard, transfer the frozen berries to any closed container or freezer bag. Do not thaw when you are ready to use them.
Blueberries may also be frozen crushed or pureed. Crush or press washed berries through a fine sieve, or puree in a blender or food processor. Mix 1 to 1⅛ cups of sugar with each quart (2 pounds) of crushed berries or puree. Stir until sugar is dissolved. Pack into freezer containers, leaving head space.
It is best to freeze only the amount that will be used within one year. Properly frozen berries will be safe to use for longer periods of time, but signs of quality deterioration such as freezer burn and textural changes will begin to show.
Blueberries may be canned in light or medium sugar syrup or may be covered with water, apple juice, or white grape juice. To make light syrup for a canner load of quarts, mix 2¼ cups sugar in 9 cups water and heat to dissolve or mix and dissolve 3¾ cups sugar in 8¼ cups water to make medium syrup.
To hot pack, place drained berries in boiling syrup, juice, or water and boil 30 seconds. Fill clean jars, with hot berries and cooking liquid, leave ½ inch headspace. To raw pack, place drained berries in jars and cover with your choice of boiling water, juice, or syrup, leaving ½ inch headspace. Process hot packed pints or quarts and raw packed pints for 15 minutes in a boiling water bath. Process raw packed quarts for 20 minutes. Altitudes above 1000 feet require additional processing times. Start counting processing time after the water comes to a vigorous boil.
Find recipes for preserving blueberries at this Penn State Extension publication: Let's Preserve Blueberries