Commodities / Strawberries
Defects and Disease |
Shelf Life |
Strawberry quality is a combination of appearance and flavor. According to grade standards, the berries should be of one variety or similar varietal characteristics with the cap (calyx) attached, which are firm, not overripe or undeveloped, and which are free from mold or decay and free from damage caused by dirt, moisture, foreign matter, disease, insects, or mechanical or other means.
Strawberry flavor is related to degree of ripeness. Fruit that is harvested at full ripeness will have the highest sugar content and flavor. However, fruit is often harvested prior to full ripeness so that it is firm enough to be shipped. New varieties have improved firmness for shipping. Additionally, improvements in post harvest handling and shipping conditions have allowed growers to ship fruit that is more ripe.
Strawberry fruit should be firm but not crunchy. Excessively ripe fruit can be too soft.
Strawberry varieties vary in color from deep red to red-orange. For a given variety, fruit should be fully colored, without white or green tips. Calyx color is also important. The calyx should remain green and healthy.
Strawberries are bright colored at harvest with healthy green calyxes. Water loss will cause the fruit to become wilted and dull.
Strawberry fruit range is size by variety and as the season progresses. Many new varieties produce very large fruit that are over 2 inches long and more than an inch in diameter. There are grade standards for strawberries related to diameter. U.S. No. 1 fruit must be at least 3/4 inch in diameter and U.S. No. 2 fruit must be at least 5/8 inch in diameter.
Strawberry fruit should be well developed and normally shaped. Varieties vary slightly in shape, but most are conical. Occasionally fruit is misshapen due to lack of seed development, which results in differential growth of fruit flesh. Grade standards state that “undeveloped” means that the berry has not attained a normal shape and development due to frost injury, lack of pollination, insect injury, or other causes. "Button'' berries are the most common type of this condition.
Strawberries grown under normal conditions will have fully developed fruit. Frost injury is a common cause of undeveloped fruit. Frost injury is avoided through site selection and overhead irrigation during frost events. Undeveloped fruit can also be caused by tarnished plant bug feeding on developing fruit and flowers. Damage can be avoided by scouting for insect pests and well-timed insecticide applications. 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. Lack of pollination can also lead to undeveloped fruit but it is a less common cause. Installation of beehives can improve pollination.
Soft fruit, wet stem scars, attached stems, and green berries are common defects of blueberries. These must be graded out during packing.
The most common diseases affecting fruit is gray mold (Botrytis). 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) can occur in the field or in storage. Gray mold is most likely to develop when there is a full canopy of leaves creating a micro-climate with high humidity. Infection occurs primarily during bloom, so control measures are timed accordingly.
Tarnished plant bug is the most common pest that affects fruit quality. This pest feeds on developing flowers and fruit causing seed abortion and subsequent lack of fruit development. Other insect pests such as spittle bug and root worms affect plant vigor.
Decreased quality during postharvest handling is most often associated with water loss and decay.
It is important to remove field heat as soon as possible to prevent water loss. Most shippers will use forced air cooling to achieve temperatures of 32-34˚F. Berries freeze at 31˚F. A shelf life of 5-7 days can be expected if these temperatures are maintained at 90% to 95% humidity.
|Strawberries, Raw 1 cup|
|Weight of Household Measure||% Water||Food Energy
|Protein||Fat||Saturated Fatty Acid||Mono - unsaturated Fatty Acid||Poly - unsaturated Fatty Acid|
|Cholesterol||Carbohydrate||Calcium||Phosphorus||Iron||Potassium||Sodium||Vitamin A (IU)|
|Vitamin A (RE)||Thiamin||Riboflavin||Niacin||Ascorbic Acid|
|(Source: USDA. Nutritive Value of Foods (HG-72), Release 3.2. 1990.)|
Content author: B. Bordelon, 2003. Links updated: January 2012.