History of the Plum

What is a Dried Plum?

By definition, a prune is a dried plum.  All prunes are plums, but not all plums are prunes.  Prune plum varieties can be dried without fermenting while still containing the pits.  This is not true of all varieties of plums.  The California dried plum is an offshoot of La Petite D'Agen, a prune plum native of Southwest France.  At maturity, it has a royal purple outer skin and amber colored flesh.

History of the Dried Plum

Dried plums are fruit with an ancient heritage. Western Asia, more specifically an area near the Caucasus Mountains bordering the Caspian Sea, is the recorded point of origin.  From there, prunes were carried westward and eventually found their way into South Central and Western Europe and the Balkans where they have thrived ever since.  Prune trees were introduced to North American soil in 1856 by Louis Pellier, a French nurseryman who had come to California in 1848 in search of gold.  After his unsuccessful mining venture, Pellier purchased land in the fertile Santa Clara Valley (1850) brother, Pierre, joined him in 1851, and in 1854 Pierre returned to France to secure a variety of fruit cuttings for nursery stock.

The original D'Agen prune graft stock was in the selection he brought back to California in 1856.  By 1900, prune orchards in California covered approximately 90,000 acres.  Today, as technology has greatly improved yield per acre, there are more than 80,000 high production acres concentrated in the Sacramento, Santa Clara, Sonoma, Napa and San Joaquin Valleys.

Currently, these acres produce more than twice as many prunes as the rest of the world combines: approximately 99% of the United States production and an average of 70% of the world supply.

Today the D'Agen prune coming from California constitutes approximately 99% of the state's production.  Here, the rich valley soil, the long, warm and clear growing season, abundant supply of irrigation water and the application of the most modern agricultural practices, enable the fruit to reach full maturity on the trees under continuous ideal growing conditions.  Thus, these orchards produce fruit with maximum flavor, ideal fruit size, find texture, high sugar content, and smooth, small pits – all characteristics inherent in high quality dried plums.

Other commercial varieties produced in California are Imperials, Robes de Sergeant, Sugar, and other varieties, all of which constitute less than 1% of the state's production.

Growing

Ordinarily, a prune tree starts to bear fruit four to six years after planting – and reaches its full production capacity (150 to 300 pounds of raw fruit per year)  some time between its eighth and twelfth year in the ground.  The orchards will then continue to bear fine quality fruit on a commercial basis for about 30 years.

The prune tree is deciduous and goes dormant during the winter months.  It is at this time that the grower cuts back and prunes each tree to regulate shape, control fruit size and maintain a healthy growth pattern.

While much of the nations still shivers under a blanket of snow, springtime literally explodes in the California Valleys.  Blossoms burst in orchards stretching over more than 80,000 acres, producing a fragrant mantle of white as far as the eye can see.  The blossoms last for about a week, and as they fall, white translated to a deep chartreuse as the new fruit begins to form and the leaf buds burst.  It is at this time that irrigation has to take over for natural rainfall - in that the California valleys have a Mediterranean-type climate that pretty well confines its total rainfall to the late fall, winter and early spring months.  Only rarely does it rain during blossom time or thereafter.  While this necessitates the inconvenience and added expenses of irrigation, it also contributes to "fruit quality" assurance.

California prune growers can plan and execute irrigation programs to eliminate the "chance" element inherent in an agricultural operation that is dependent on natural rainfall.  In this way, the trees are given jus the amount of water they need to augment the available ground water.

Harvesting

By mid-August, the orchards are ready for harvesting, which generally takes about 30 days.  The predeterminant of harvest time for prune plums is ripeness, in that they are one of the few fruits allowed to fully tree ripen before they are picked for processing.  Fruit firmness and natural sugar content determine the picking date.

Today, most of California's prune production is harvested by machine.  In this process, a mechanical shaker takes hold of a main limb or the trunk - a fabric catching frame is spread under the tree – and in a matter of seconds the fruit is shaken off the tree and transferred via conveyor belt into bins in which it goes to the dehydrator.  Because of the ever-increasing industry emphasis on fruit quality, the historical method of allowing fruit to ripen and drop before gathering has disappeared.

Formerly, the ground under the tree was smoothed and the soil pulverized to a powder to provide a soft blanket to catch the fruit as it fell.  Then it was gathered and taken to the dehydrator.  This method required three to four "pickings" to completely strip an orchard of its fruit and is now obsolete.

Processing

Immediately after the harvesting, the orchard-ripe fruit is taken to the dehydrator yard where it is washed, placed on large wood trays and dehydrated – in a series of scientifically controlled operations.  Fully automated – strictly sanitary – and highly efficient.  Here, super-sensitive thermostats take over and produce the uniform, high quality prune.  This is where three pounds of fresh fruit become one pound of dried plums.

Packing

From the dehydrator, the dried plums go to modern packing plants where they are graded for size, inspected and put into storage to await final processing and packaging.  Unlike most of the processed fruits, most dried plums are still packed to order.  They remain stored in what is known as "natural condition" until the order comes in.  Then they are rehydrated – re-inspected – and packaged for the customer's order.

Since dried plums store best when their moisture content has been reduced to about 21% - they are dehydrated to this degree immediately after picking. 

This is what is generally referred to as a "Natural Condition Dried Plum".  Then they remain in cool storage facilities until they are needed for further processing. Since dried plums are packed to order, they are rehydrated, sterilized, put through a final inspection and packaged when the order is received.  This procedure is followed whether the order is packaged in 25 or 30 pound bulk cases or the 1 or 2 pound containers sold through the retail grocery outlets.

Today the dried plum industry is devoting much more time and energy to producing pitted dried plums than ever before.  Innovations and improvements in equipment and fruit handling techniques have upgraded the end products, providing many new marketing opportunities. 

Preservative

The only preservative used in processing dried plums is potassium sorbate (the potassium salt of sorbic acid), which is used to protect against mold and yeast spoilage.  Sorbic acid is the safest preservative known to food science, since it is a food itself found in nature in the European sorb apple and in rowanberries.  It is a polyunsaturated fatty acid, completely metabolized by the human body.  Hence the system does not have to detoxify the material prior to elimination, a feature unique to sorbic acid.  Nothing else is added to dried plums except pure water during processing.

Nutritional Facts

California dried plums are naturally sweet and chewy, adding a vanilla-like flavor enhancer when used as an ingredient.  Dried plums are a smart choice for today's healthful lifestyles since they're a quick energy source with no fat or cholesterol.  A serving of dried plums is a good source of vitamin A and fiber and container iron and potassium.