Blueberry flavor is related to degree of ripeness. Fruit that is harvested at full ripeness will have the highest sugar content and flavor. Fruit that is not fully ripe will have low sugars, higher acid, and lack flavor.

Blueberry fruit should be firm. Excessively ripe fruit can be too soft.

Blueberry varieties vary in color from light blue to purple to nearly black. Most varieties have a waxy "bloom" on the fruit that makes it appear lighter in color. For a given variety, fruit should be fully colored, without red or green areas on the back of the berry near the stem scar.

Blueberries are bright colored at harvest. Water loss will cause the fruit to become wilted and dull. Excessive handling can cause the waxy bloom to be wiped off, giving the fruit a dark, dull appearance.

Blueberry fruit range is size by variety and as the season progresses. Many new varieties produce very large fruit that are over 3/4 inch in diameter. Large size is often more favored for fresh consumption, but not for processing uses. There are size standards for blueberries based on the number of berries that will fill a cup measure. Extra large fruit takes less than 90 berries per cup; Large, 90 to 129 berries per cup; Medium, 130 to 189 berries per cup; and, Small, 190 to 250 berries per cup.

Defects

Soft fruit, wet stem scars, attached stems, and green berries are common defects of blueberries. These must be graded out during packing.

Disease

The most common diseases affecting blueberry fruit are anthracnose and Alternaria. Control recommendations can be found in the Midwest Small Fruit Pest Management Handbook and Midwest Small Fruit and Grape Spray Guide for Commercial Growers, or through your local Cooperative Extension Service.

Gray Mold (Botrytis cinerea) and Penicillium fruit rots can occur in storage.

Insects

European Japanese beetle, blueberry maggot, and cherry/cranberry fruit worms are the most common pest that affects fruit quality. There are grade standards that cover allowable insect damage. Tolerances vary depending on the pest.

Decreased quality during postharvest handling is most often associated with water loss and decay. Blueberries have a longer shelf life than most other berry crops and can be stored for as much as 6 weeks. Storage for up to 2 weeks is most common. Some use of controlled atmosphere storage has been attempted, but off-flavors can develop.

It is important to remove field heat as soon as possible to prevent water loss and retard decay. Most shippers will use forced air cooling to achieve temperatures of 31-32˚F. Maximum shelf life of can be expected if these temperatures are maintained at 90% to 95% humidity.