Thursday, May 5, 2011

Solar Dehydrator

There were few different reasons that encouraged me to take up the challenge of building the solar dryer (dehydrator, in the picture). I wanted to try and promote a simple food processing method; and use it for drying currently my favorite fruit – mango. At the moment we are in the mango season and the fruit is in abundance but it will be over in several months.
So with the help of my host brother, Sana, we finished the dehydrator last week. I was anxious to test it out and see if it works. It did but only partially. The mango slices that I placed in the dryer did not dry out completely. I have been trying to figure out its problems and came up with the several:
  • The temperature does not raise significantly due to gaps in the box and/or inefficiently build inclination (I used clear plastic bag for the top part and black plastic for the bottom)
  • The airflow to take the moisture out is not nearly non existent even during high winds
I would really appreciate input and suggestions or if you know anyone who built a solar dehydrator and can throw my way few advices. Thank you kindly!!

 
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Here, in the Gambia, food processing is nearly non existent from what I heard and experienced. Also I have not yet seen any adequate food storage facility of large or small scale. Therefore, rotting, spoiling and parasite infestation of different foods and grains is widely spread. To address the food security and self-sustainability problem the promotion and implementation of appropriate food processing and storage; and seed storage techniques is essential. It is also one of the areas that Peace Corps volunteers are working on.

Currently there is a project lead by Department of Agriculture which consists of building 10 fenced-in community gardens (size of 5 acres each) each equipped with a reliable water supply for watering and a storage building. The building will be used to store produce when the market is overloaded with it. Lack of adequate storage facilities require everything that is harvested to be sold right away. Sometimes women loose a significant portion of earnings due to low prices of the produce which is caused by the surplus.

I have visited two food processing facilities which process only small amounts of fruits and vegetables. One of them I mentioned in previous entry and the second one is called REFESA, which is also lead by the group of women. Their activities include the trainings and workshops for women kafos (associations) of different villages. They also make pepper sauce, cashew jam and mango jam and prepare/process coos and rice for the consumption. They have done some batik (tie and dye) too. The biggest challenge, the same as most of the local organizations have, is the funding. However, they are very passionate and determined women who want to teach other women and empower them in the areas of gardening, food production and other income generating activities. I am very much looking forward to working with them and learning from them!  

As for me, I have never given much thought to food processing and food preservation before I came to the Gambia because most of foods were readily available anywhere I travel in Lithuania or the United States. Here I can only buy foods that are not perishable, can be stored at room temperature or would be consumed promptly. I have not had much desire to cook for myself because there is no cool place to store leftovers. Such situation also requires frequent trips to the market.
Hence, we are so fortunate to live in the places where the stores are overflowing with goods and houses have fridges!      

5 comments:

  1. Hmmm - I think I'll have to get some apples and experiment. Without researching, I'd think you'd want some mass warmed up - black rocks or black bags of water or some sheet rock painted black. I think you'd want air flow to release some of the humidity and to aid in the drying process and I think it'd be a good idea to give condensation an escape route.

    The dehydrating book we have upstairs says apples (no section for mangos) are best dehydrated at 65 C for 2 - 3 hours and at 55 C until they are "done".

    I'm going to use "the Google" and see what turns up for solar dehydrators.

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  2. You must have seen this article: http://homepower.com/view/?file=HP69_pg24_Scanlin

    Your design is similar. Peaches have the same "65C for 2-3 hours and 55C until done" recommendations in the dehydrating book, BTW. I thought peaches would be closer to the consistency of the mangos, so I checked.

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  3. The initial article is here: http://homepower.com/view/?file=HP57_pg62_Scanlin

    I have the PDF's downloaded and I will probably print them and mail them to you. They are 11 pages each.

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  4. I would expect the airflow issue to become moot once you get the "engine" of the thing optimized. If the top plastic is clear enough and the bottom is dark enough, that leaves leaks, I'd think. The heat differential will drive the airflow and I would expect high ambient temperature to affect the delta very much - the "engine" would just get hotter as a result. Perhaps too hot to effectively dry the fruit evenly? Have you got a way to vary the venting at the top? Have you got a way to measure the internal temperature?

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  5. Very inspiring to have something as important as food supply to work on!!!!

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