Kudzu In Asia

Dear Newt and Barbara,

I've read with great interest the wealth of information gathered on the KOkudzu website.

I am now writing with a question about the size of the roots. In Vietnam kudzu roots can become quite big, as you can see on the [above] picture . . . , and I'm very curious to know if you encounter kudzu roots of similar size in South Carolina?

From the website, it seems that the plants' main activity is to produce stems and leaves, and not so much roots.

Looking forward to hearing from you.

Please let me know if you have questions about kudzu in Asia, I'd be happy to share.

Sincerely yours,

Dear Newt,

My apologies for the delayed reply. I have not been able to contact my friend who is the author of the photograph I sent you. I will let you know as soon as I hear from him.

My interest for kudzu is as a source of starch. I'm actually based at BIOTEC - Kasetsart University in Bangkok (Thailand), and part of my work is to gather information on the cultivation of kudzu and other marginal starchy plants in South-East Asia. The idea behind this is to find starches with different properties than the major starches (potato, corn, rice, wheat, tapioca). If the results are good enough, we may be able to catch the attention of the local food industry and create some economic activity around the starch in question (from farming to small scale starch extraction, to end-use in food products).

Regarding the proliferation of kudzu in the US, the problem in South-East Asia seems to be the opposite: In Thailand, I have heard of at least one wild starchy plant similar to kudzu that has been harvested to extinction in the last 20 years, and in Vietnam I understand kudzu needs to be farmed to meet the demand. I was thinking that, if immigration and costs could be sorted out (big IF!), enterprising farmers from Vietnam might be happy to dig out roots and extract starch during the winter months (they do have cheap, small scale extractors to do just that). That could help controlling kudzu if the process is repeated several years, but it's not as quick as going directly for the crowns, as explained on KOkudzu.com.

That's my snapshot on the kudzu situation in Thailand/Vietnam. Please do not hesitate to write if you have more questions.

With thanks and best wishes,

Regarding a comparison of kudzu starch compared to other starches, the basic properties have been published, including microscope pictures of the starch granules, how much viscosity develops during cooking in water, as well as characterizations of the crystallinity of the starch before cooking. These properties are the "standard" that starch people look first when they want to compare starches. With these, we know that kudzu starch is similar to other root starches such as cassava (tapioca) in terms of granule shape and size, and a bit less viscous than cassava but more viscous than cereal starches such as corn or rice during cooking.

However, this doesn't say much about the texture, appearance and flavour of products made from kudzu starch, compared to the same products made with other starches. For example, one of my pet ideas is to make noodles with kudzu starch and find out if they are similar to rice noodles, wheat noodles, or if they give a texture entirely different. I haven't found studies to answer this.

Another difference known about kudzu starch is that it contains some molecules (isoflavones) with medicinal applications, but I'm less familiar with this area.

I attach a recent publication on kudzu starch properties, by a Japanese-Vietnamese team . . .
There are various models of starch extractors described on the internet. The names used are "extractor", "rasper" or "grater".

A quick search led me to this description: http://www.foodnet.cgiar.org/agro_ent/process/Gratwdg.htm

I also have a photograph of the Vietnamese model (from Northern Vietnam), which you can see in the . . . [first photograph above, click it for a larger image]. Note that this particular one is used for cassava starch extraction, but I assume it can work with any starchy roots, provided they are cleaned and cut to a suitable size.
1. The main part of the machine is the extractor, which contains a wooden wheel covered with bits of metal wire to reduce the roots into a pulp (see pictures of the wheel . . . [above]).
2. The wheel is kept in motion by an electric motor (on the left of the machine).
3. The roots are fed into the machine from the top, and water is added through a pipe connected to the middle of the extractor.
4. The pulp is filtered through a cloth fitted at the bottom of the machine. The liquid passing through the cloth (starch slurry) contains most of the starch and is directed to two successive sedimentation tanks where further impurities can be removed and starch can settle for later collection. Fibers (cellulose, lignin . . . ) accumulate on the filter and are taken out from time to time through a small door (typically they are used for animal feed as they still contain some starch).
This type of machine can process 800 - 1000 kg of roots per day, and the fiber residue can make the work area quite messy! The water consumption is fairly high, estimated at 3 - 4 liters per kg of root to be processed (that's 4000 liters per day), if water from the sedimentation tank is re-used (if not water consumption is higher). Unfortunately I don't have the figures for electricity consumption. I should also mention that this information comes from a research project led by Le Thanh Mai and Guillaume Da at Hanoi University of Technology.

I hope this helps. I've only started to learn about this small-scale technology a year ago, but feel free to ask if you have more questions.

With best wishes,