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Duckweed Nutrient Preservation Tips

March 13, 2012

Sun-dried Wolffia : Two days in partial sun. One would have been sufficient had it not clouded over in the afternoon of the first day and decided to rain!

A reader recently asked,”What is the best way to dry and store duckweed without nutritional loss?”

Good news: Duckweed dries easily due to its biomass surface to air ratio and stores well.

Bad news: There are always some losses in vitamins when converting a fresh plant material to that of a dried state.

This is why I advocate using fresh duckweed whenever possible. However, there will be times when supply exceeds demand and you will be wanting to dry and store duckweed for later use. Given the myriad of growing conditions and applications of subsequent dried duckweed, I’m going to focus on generalities.

– Drying duckweed in temperatures over 140 degrees F will cause accelerated vitamin B and C losses.  Maintain a drying temp of 110-115 degrees F to ensure optimal vitamin retention.

– Conventional solar drying of duckweed can destroy 1/3 to 1/2 of its beta carotene content. To minimize losses, dry duckweed in a ventilated, sun-protected environment such as a shaded tunnel of black plastic with a solar-driven fan placed at one end. Monitor interior air temps to insure you don’t reach 140 degrees either by increasing fan speed or covering a portion of the tunnel.

Low temp mechanical heat drying will work, but for every one pound of duckweed, it will take approximately 1,000 btu’s.  That’s why I always opt for sustainable solar drying techniques.

– Pelletization of dried duckweed is reportedly an easy process due to the waxy coating on the fronds that act as a binding agent. I would venture to guess that some vitamins would be lost due to the heat generated during compression. Still, duckweed pellets have been incorporated  in research settings as  animal supplements or feedstocks with very good returns on digestion ratios and overall health.

– Protein content of dried duckweed will remain quite stable, given the context of the above drying processes and temps.

– For optimal shelf life, always store dried duckweed in any form away from sunlight and in air and moisture-proof bags.

Hope this helps.

Ciao,
Tamra

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