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Strawberry Harvesting
and Postharvest
Handling for Improved Shelf Life

 

Dr. Charles F. Forney
Postharvest Physiologist
Atlantic Food & Horticulture Research Centre
January 1996

 

a.gif (364 bytes)s another strawberry season approaches it is a good time to reassess harvesting and postharvest handling procedures. If you are considering shipping fruit any distance proper harvest and postharvest management can make the difference in success or failure. Here are a few factors you might consider now before all of the demands on the harvest arrive.

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(photo:Andrew Jamieson)


Harvest frequency can have a major influence on strawberry fruit quality. Strawberry fruit ripen rapidly on the plant. Fruit color develops quickly going from first blush to fully red in only 24 to 36 hours. While the fruit is turning red other changes occurring include: increase in sugar content, loss of acidity, development of flavour compounds, and rapid softening.

A strawberry that is 50% red will lose 25% of its firmness in the 24 hours it takes to turn fully red and an additional 15% if it remains on the plant another 24 hours. When the strawberry is removed from the plant color and flavour development continue, but there is little change in firmness or sugar and acid content. The rapid changes occurring in ripening strawberries makes the timing of harvest a critical factor determining fruit quality. When the fruit has just reached full color it has developed acceptable flavour and appearance without becoming excessively soft. To harvest fruit at this peak maturity, fruit must be harvested daily and all ripe fruit must be removed. Any fully red fruit left on the plant will become soft and overripe and lower the quality of subsequent harvests. Uniform maturity obtained by daily harvests will give a high quality product with improved shelf life.

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(photo:Andrew Jamieson)

Postharvest cooling is essential to extend the market life of strawberries. Harvested fruit should be removed frequently from the field and cooled within 2 hours of harvest. Prior to cooling harvested fruit should be shaded to avoid heating from solar exposure.

Placing fruit in a cold room is not adequate to remove field heat. Cold air must be actively forced through the flats containing the fruit. If adequate refrigeration is available in a cold room, this can be economically accomplished by mounting a fan on an air plenum that can be constructed from plywood. Palletized fruit are placed against the opening in the plenum and the fan draws cold air from the room through the fruit. The fan should be positioned below the refrigeration unit so air warmed by the fruit will be cooled before mixing with the room air. Forced-air cooling will cool fruit to 1░ C in 1 to 2 hours. After fruit is cooled, it should be held at 0░ C throughout transportation and storage. Good refrigeration will reduce decay, maintain fruit shine, and prevent fruit from becoming dark and overripe.

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(photo:Andrew Jamieson)

After cooling, if cold fruit contacts warm humid air a temporary loss of shine will occur due to condensation on the fruit. As the fruit warms the condensation will dissipate and the shine will return. To prevent condensation plastic can be placed over the fruit to avoid it contacting humid air.