Strawberries are found in a variety of products, from food to beauty. Each require different methods to achieve, and processing can be vastly different. Varying grades of strawberries are used differently, and season can also determine the market at which the fruit is aimed.
Harvesting:
Strawberry harvesting has not changed much over the years, and are mostly done by hand. Some machines have been developed, such as the strawberry-picking robot, but they are not as effective as hand-picking. Strawberry picking is very labor-intensive, and requires skilled workers that can determine the ripeness of fruit that is still on the stalks. After picking, strawberries are processed differently for different uses.
Fresh Consumption:
Most strawberries go directly to the market and are eaten fresh by consumers. Because strawberries are highly perishable, the berries are packed into trays by the pickers immediately after removal from the plant. They are then sent to forced-air cooling facilities and cooled to 1 degree Celsius. The trays are stacked onto pallets and cool air is forced through the package to first lower, then maintain the temperature. Air should be pulled through the trays by pressure differentiation rather than blown through, to minimize damage. Since strawberries do not die after picking, and continue to produce heat, lowering the temperature is essential to ensure the natural heat doesn't ruin the fruit. Humidity must also be controlled, because dryness with dehydrate the fruit and moisture may accelerate decay. At these ideal conditions, strawberries have a maximum storage life of 5-7 days. After cooling, the pallets are loaded onto delivery trucks with similar cooling and humidity systems, and sent to the market. It is desirable for strawberries to be on the shelf less than 24 hours after picking, but due to distance factors, is only achievable in places with large strawberry industries.
automatic fruit washers are used
http://www.globaltrading.net/washer2.jpg
Frozen:
Frozen strawberries are cooled in a similar method as the fresh berries. Once cooled, they are sent to a cleaning and packaging facility, which includes a machine that moves the strawberries on a conveyor belt. The berries first pass through some workers that remove the stems by hand, a task the machine cannot accomplish. After stem removal, they are placed on a flumes that deliver them to the next step. A vibratory de-waterer is used to remove the water from the flumes, and the fruit is then passed through two bubble washes. The strawberries then go through a vibratory fruit sizer, that shakes the berries over variously spaced bars to determine size. The sorted berries are sent to different inspection belts and graded on inspection belts, where substandard fruit is also removed. They are then passed through a metal detector for safety reasons. Before freezing, the fruits are packaged in pallets, and stacked. Because it is dangerous to leave fruit at moderate temperatures for extended periods of time, the freezing process must be very fast. Blast freezers are used, which forces very cold (-35 to -40 degrees Celsius) air through the pallets very quickly (10 to 15 m/s). Essentially, is it an extreme version of the cooling system used after harvest. This makes the cooling procedure much faster, and can cool larger quantities. Once the fruit is frozen, it is loaded onto delivery trucks and sent to the market.
Freeze-drying:
Freeze-drying is the process in which the all the moisture is removed from the fruit, resulting in a completely dry strawberry that can be restored to its original properties with the addition of water. It is not used commonly; currently freeze-dried strawberries are only found in novelty foods, cereals, and snack bars. Although it is possible to reconstitute the berries with minimal alteration, it involves very specific and costly conditions that the average consumer will not be able to meet at home. Therefore, freeze-drying is not considered an effective method for maintaining strawberry freshness.
astronaut strawberries, a novelty food
http://www.edusci.co.uk/design/astronaut_strawberries_p.gif
To freeze dry, the strawberries are first flash frozen. This process involves exposing the fruit to temperatures well below freezing temperature. The strawberries are frozen very quickly with the process, and then placed in a vacuum. In the vacuum, the ice sublimates into vapor, without passing through the liquid stage. Temperatures are very low, and at -50 degrees Celsius, 98% of the moisture can be removed. Heat is then added to accelerate sublimation and then low temperature condenser plates solidify and remove the vaporized water from the vacuum. After freeze-drying, the product is sealed in moisture and water free packaging and sent to the market.
http://www.calstatela.edu/faculty/hsingh2/articles/strawberry.research.pdf
http://www.berries4u.com/harvest.htm
http://www.globaltrading.net/strawberry_processing_flowchart.htm
http://www.choicesmagazine.org/2004-1/2004-1-02.htm
http://www.bae.ncsu.edu/programs/extension/publicat/postharv/ag-413-2/index.html
http://books.google.ca/books?id=ERoAm13YF8IC&pg=PA188&lpg=PA188&dq=blast+freezer&source=bl&ots=H6-W2qj1h2&sig=ZvfRZufwjmiIs5l_UmmeGyxJAcE&hl=en&ei=tDMjSoHpKpL2tAOCroGMBA&sa=X&oi=book_result&ct=result&resnum=5#PPA188,M1
http://en.wikipedia.org/wiki/Flash_freezing
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