Commercial postharvest handling of strawberries (Fragaria spp.)
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Strawberries are appreciated for their flavor and delicacy. They have very high respiration rates and therefore are highly perishable. They can be kept for up to 5 to 7 days if precooled immediately after harvest and kept at 32 degrees F.
Strawberries are usually hand-harvested, graded, and packed in the field. Harvest when temperatures are cool, either early in the morning or evening. Pick berries that are ripe but not over-mature (pink or red but not mushy), leaving only a short stem and the calyx, and place directly into pint baskets or flats. Berries that will be used for dipping should be harvested with long stems and placed into flats so that the stems do not touch other fruit. Avoid bruising or nicking fruit. Transport immediately to the shed or shade in the field if this is not possible.
Cool fruit immediately after harvest by forcing cool air through the flats. This is preferable to room cooling, as forced air can cool berries to 34 degrees F within an hour, whereas room cooling may take 9 hours.
Store strawberries at 32 degrees F and 90 to 95% relative humidity. After a few days in storage, fruit may lose some color, shrivel, and lose flavor. Berry shelf life can be extended by using 10 to 30% carbon dioxide in refrigerated storage, usually during transport. This can be done by packing berries in containers with dry ice or covering pallets with coated fiberboard or heat-shrink polyethylene film. Pallet loads can also be covered with polyethylene bags and injected with carbon dioxide gas. Off flavors can develop if carbon dioxide levels are above 30%.
The major postharvest diseases of strawberries are gray mold rot caused by Botrytis cinerea, Rhizopus rot, and leather rot caused by Phytophthora spp. The symptoms of gray mold rot are firm, brown, dry lesions covered by gray-brown spores, sometimes turning into fluffy white mold. It can spread in storage, even at low temperatures. Rhizopus rot causes juice leakage from fruit, developing into white mold with black spore-heads. Tissue affected by leather rot become discolored and tough, and may leak. Under humid conditions, a white mold may develop.
|Black spot||Colletotrichum spp.||circular, sunken, water-soaked, brown lesions, developing into pink, brown and black; does not spread from fruit to fruit|
|Cottony rot||Sclerotinia sclerotiorum||watery flesh; white, cottony mold|
|Rhizoctonia brown rot||Rhizoctonia solani||hard, brown rot on underside, with clear definition between healthy and diseased tissue|
For more information
For information covering related areas, consult the following Minnesota Extension Service publications. They are available from your county extension office or by writing to the University of Minnesota Extension Store, 20 Coffey Hall, 1420 Eckles Avenue, University of Minnesota, St. Paul, Minnesota 55108-6064.
Commercial Postharvest Handling of Fresh Market Asparagus (Asparagus officinalis)
Commercial Postharvest Handling of Fresh Market Apples (Malus sp.)
Commercial Postharvest Handling of Potatoes (Solanum tuberosum)
Nutrient Management for Commercial Fruit and Vegetable Crops in Minnesota