Why Do Dried Prunes Swell When Soaked in Pure Water?
Prunes are dehydrated plums. The process of dehydration removes the majority of the moisture content from foods. This can occur by drying them either in a dehydrator with hot air that flows around the pieces, leaving them in the sun or freeze-drying. Conversely, when moisture is returned to the prunes, they will swell. Does this Spark an idea?
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History
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Many cultures have been known to dehydrate foods to retard spoilage. Prehistoric people dried seeds, North American Indians made jerky from strips of meat and the Japanese dried fish and rice using this method. Today, commercial dehydrating mostly takes place using mechanical dehydrators, but some foods and condiments are still sun-dried, such as sea salt, herbs and roots. You can also dry your own, bypassing any commercial involvement.
Benefits
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One of the oldest forms of food preservation, dehydration has many benefits. These include the inability of bacterial organisms to form on the food thereby boosting its shelf life to almost unlimited; concentrated or sometimes better flavor due to removal of moisture and the remaining natural fructose becoming more condensed; and a higher nutrient level when compared ounce for ounce to their fresh counterparts. But be forewarned that the calories per serving of dried fruit are significantly higher in comparison with fresh fruit of the same type.
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Significance
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Dehydrating food creates less expensive shipping and handling by using less fossil fuels for transport, and requires less storage due to a reduction in bulk and weight by up to 90 percent. For example, it takes three pounds of plums to make one pound of prunes. In addition, there would be no refrigeration costs. This makes food dehydration an attainable way of living "green."
Rehydration
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Placing dehydrated food in water and allowing it to soak will force it to rehydrate and "plump up," returning to a similar state as it was originally and becoming bigger, heavier and softer. However, rehydrated food will never be exactly as it was when it was fresh. Rehydration can take hours or up to several days, depending on how much moisture was originally removed from the food.
Other Liquids
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Pure water is not the only liquid that can be used to rehydrate a dried prune or other dried food. You can also rehydrate with liquids like simple syrup (water with sugar); water with additives like various extracts or citrus zest; rosewater; fruit or vegetable juices; milk or cream; alcoholic beverages such as wine, liquor or brandy; or broth. These liquids will impart different flavors to the food, which can make for interesting food experiences.
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