Chapter 16: Postharvest Handling:Dried Root

The majority of ginseng root consumed in the world today has first been dried down to moisture content of approximately 10-12%. A pound of fresh root will consist of approximately 72% water, with the remaining 28% solids.

For each acre of 4-year old ginseng root, we hope to dig 10,700 pounds of fresh root to end up with approximately 3,000 pounds of dried root. As mentioned previously, there have been gardens in the northwest that have yielded as much as 4,400 pounds of dried root, the equivalent of no less than 15,700 pounds of fresh root per acre! Using these numbers, growers will be able to estimate the amount of drying space that will either need to build or lease from other growers.

Dried root principals
Simply stated, the process of drying fresh ginseng root involves placing it on wire racks which are stacked inside a room held at a temperature between 95 F and 100 F for approximately 2 weeks until it is dry. The slow even drying conditions will leave the roots with a brittle exterior and a creamy-white interior. Once dried the roots can be stored for a relatively long period time, or until they are ready for sale.

Historical drying practices
Many of the modern day ginseng drying practices are steeped in tradition. Early settlers to the United States dug wild root as they hunted and gathered food. Ginseng root was collected over a period of time in the fall and dried in warm attic spaces. The roots were allowed to wilt before they were lightly washed, and then were allowed to dry on their own for a few days before being placed in a warm room. None of the steps in this process were hurried. As a result the roots took on a rich brown, tawny color. As tradition has it, the world still expects dried ginseng to have the same characteristics today as it had in the past.

Dryer designs
There are three different types of dryers used in the ginseng. In Ontario ginseng growers use converted tobacco dryers, which look very similar to 60’ semi trailers as seen on highways. Roots are loaded onto shallow screened trays on carts, which are wheeled into one end of the trailer. Accessibility is a problem with this type of dryer. Once the trailer has been loaded, there is really no way to examine the root as it is drying.

The British Columbia industry has developed contained drying systems where the root is placed once again onto screened trays, which are placed into heated cabinets. Warm air is introduced into the base of the cabinet. As the warm air rises it extracts the moisture from the roots slowly and evenly. The advantage of this system is that large volumes of roots can be dried in a relatively short period of time. This system is relatively expensive however, as it does require the installation of a number of cabinets, each with their own heat source. For a detailed description of how to build such as system contact Bert van Dalfsen (bvandalfsen@galaxy.gov.bc.ca), with the BC Ministry of Agriculture, Fisheries, and Food in Abbotsford, British Columbia.

The third type of dryer is really nothing more than an insulated shed, or garage equipped with wall heaters, a thermostat, and a series of exhaust louvers to allow for the escape of the moisture laden air. Once again, root is placed on shallow screened trays, which are placed on carts. The carts are simply wheeled into the shed where inexpensive household room fans circulate warm dry air (see Figure 1). The beauty behind this system is that the room used for drying root in the fall can also serve for a multitude of different farming uses the remainder of the year. The principal disadvantage of this system is that it will take longer to dry the roots than in the case of the contained system described above.

Root handling
Following careful root washing (see Chapter 15: Ginseng Harvest) done outdoors, roots are loaded no more than 3 deep into 3' by 5' frames constructed using 1" by 3" lumber, with hardware-cloth screening stapled on as a base. Don't handle the roots roughly at this time as bruises will be reflected in the dried root as light spots.

As seen in Figure 1, the trays can be designed so that they can be stacked one upon another. Trays can be stacked onto pallets with wheels to facilitate handling. The loaded stacks should be allowed to air dry completely for 2 days before being wheeled into the drying shed. Any surface water on the roots will simply slow down the time to dry the roots.

Temperature management
Growers will need to understand the importance of temperature management when drying their roots. If the temperature in the shed is allowed to drop below the roots can develop a green coloring, as well as begin to mold, both of which markedly reduce the eventual sale value. Conversely, if the room temperature is allowed to rise above 100 F for any length of time the roots can become too hard and develop a brown color indicative of the sugars haven become caramelized. The danger of brown root developing is greater towards the end of the drying process. Don't try to accelerate the drying process by turning up the heat late in the drying process.

Three or four thermometers placed throughout the shed will help in monitoring the room temperature. Be sure to monitor the temperature near the floor, where the temperature will be lower.

In practice, drying sheds can be heated by natural gas or electricity. Some growers prefer electric wall heaters as there is no chance of the roots taking on an odor from the gas heat.

Figure 2 is a hypothetical illustration of drying rates for 3 different sized roots. As seen in the illustration the percentage moisture in the roots will decline rapidly during the first four days in the shed. By day 7 the smaller roots will have nearly attained the recommended percentage moisture content for long term storage. The medium and large size root, with their smaller surface area to volume ratio, will have lost a considerable amount of moisture but not nearly enough to be considered dry.

During the first week of the drying cycle more heat will be required to keep the shed warm enough, as the water vapor given off by the roots will lower the air temperature due to evaporative cooling. During the second week of the cycle less heat will be required as the moisture content of the air will have dropped significantly. The larger 'bullet' roots (see Figure 3) take the longest longest to dry.

Tray management
In a shed type dryer the moister laden, heavier air will sink to the lower levels of the room. If the upper trays are drying too fast, the stacks can be rebuilt to move the dryer roots to a lower level. Alternatively, upper trays can be loaded with larger roots to begin with. Trays with smaller roots can be removed from the shed sooner and more attention could be devoted to the larger more valuable roots.

Air exchange
An exhaust fan will need to be built into one of the walls of the dryer shed. During the first week of drying cycle, when the roots are still moist, the exhaust fan should have enough capacity to completely change the air in the shed every 10-15 minutes. As for an intake, mount a louvered shutter into one of the walls of the shed. Whenever the exhaust fan starts up the shutter will automatically open on its own to bring in air from outside.

Estimating dryer capacity
As mentioned previously, the principal disadvantage of the shed dryer is the time it will take to dry a given amount of root. The contained drying units being employed by the British Columbia industry are noted for their speed and efficiency. In research trials in Ontario, fresh root loading rates of between 25-40 lbs/sq.foot where found acceptable. Any attempts to expedite root drying, in order to reduce energy expenditure, needs to be balanced by concerns for root deformation and the possibility of green root developing. In trials in British Columbia, using contained drying units, loading rates where as high as 75 lbs./sq.ft. with no loss of quality.

Higher loading rates however, are just not feasible with shed dryers. A large clump of roots will simply slow down the over-all drying time as the movement of the moist air will be slowed considerably. A good analogy here can be taken from work with cooling berries. If a flat of fresh picked warm berries are placed in a refrigerated room it may take as long as 8 hours to remove their field heat. Over that time some of the interior berries will actually start to spoil due to the fruit sweating. However, if the field flats are placed in front of a suction fan in the cold room, with the room air forced to travel through the fruit as opposed to around it, the field heat can be removed within 45 minutes.

For shed dryers used with the smaller ginseng farms here in the Northwest, a suggested loading rate is 25-30 lbs. of fresh root per square foot of drying rack surface. However, since this is a shed dryer, the roots should not be stacked more than 3 roots high. Each 3’ by 5’ tray should not be filled with more than 45 lbs. of fresh root. A stack of 10 trays could then hold approximately 450 pounds of fresh root. By using some of these simple calculations it is possible to estimate the size of the dryer for a given amount of dug root.

It will be very important to ensure good air movement through the shallow trays. As seen in Figure 1 ordinary swivel fans can be placed throughout the shed to help even out any temperature gradients in the drying room. The fans should be aimed in the general direction of the exhaust fans. Note how the stacks of trays are not placed closely together. Once again this is to ensure even air flow throughout the dryer. It also allows for workers to move between the stacks to handle trays and inspect the roots over the 14-16 day drying period.

Drying end point
The industry rule of thumb to estimate the end of the drying time is to take one of the largest roots and try to break it in half. The root is dry if it snaps in half and feels hard. Since most Asian root buyers prefer to purchase un-sorted dried roots, the entire batch of field dug roots will have to be dried until the largest root snaps. The conventional storage container for finished whole root is a 40 gallon cardboard container (see Figure 4). Normally a large, clear plastic bag is first placed within the barrels. Then the root is loaded in. The plastic bag prevents the roots from taking up moisture in the air during the time the root is stored. In storage, place a pallet under the barrels so that the cardboard barrels don't absorb moisture from the floor they are sitting on.

After the drying process is complete there will be a certain amount of scrap and fiber root left over (see Figure 5). This material can be ground up to make powder (see Figure 6) which can then be sold to tablet manufacturers

All the fresh dug root does not have to be dried at once. If the roots are laid out to wilt on their own in the fall they can be dried in batches. If fall temperatures are too high, or if rain threatens, the root can be stored in a refrigerated room as outlined in the following chapter (see Chapter 17: Postharvest Handling: Fresh Root).

Add value to dried root
During slow times of the year 'bullet' roots can be cut from the larger whole root pieces as seen in Figure 7. The resulting large carrot shaped pieces can be boxed up for retail sales (see Figure 8) either on the farm, which would be the most lucrative approch, or sold to a wholesaler.