Friday, May 1, 2009

Tapioca starch film


I love tapioca. Tapioca pudding is the obvious preparation of this starch derived from the root of the cassava plant. But I also like two other qualities it has which aren't as well known: tapioca is flavorless, but you can cook it in a flavored liquid and it will take on that flavor. This results in neutral chewy vessel for practically any flavor.


The second less known quality is the actual thickening strength it has. Because tapioca is in fact a type of starch,You can purchase tapioca flour but this can yield a cloudy thickened liquid. You can also purchase a modified version of the tapioca flour (commercially known as Ultratex 3... really good if used in moderation; it thickens hot and cold preparations and is virtually flavorless. It is great for flavoring a liquid that you do not wish to adulterate with anything else. For example, you can make a basil water or cucumber water with a sauce-like consistency. Really any liquid for the matter.) But one of the most exciting findings I've had came from cooking it over the stove with a small amount of water. I put about 400 g inside a pot with enough water to cover the tapioca by 2 inches. I cook it over high heat and stir it occasionally. There, the starch on the surface of the tapioca dissolves into the water and begins to thicken almost immediately. When the water has been completely thickened, I strain the tapioca pearls out. The mucilaginous liquid is what I discovered to be a great by-product of cooking tapioca. At this point, the actual tapioca pearls are still uncooked. I use this method because I was always annoyed by this snotty liquid. So I would cook the tapioca in an initial amount of liquid, strain it, rinse the pearls out in hot water, and then put them back in the pot with a much larger amount of fresh water, and then finish cooking them on the stove. In both cases, you can add a flavored liquid.

What I had discovered during this process was that the initial thickened water that I had drained, when it was spread out very thin and dried out, it was transparent and crisp. If I had added a flavor, there would be a transparent crisp sheet with that flavor. I really noticed this by accident, since some of that thickened liquid had remained on the side of the pot as I had strained it, and when I had placed the tapioca back in the pot with the second amount of water to finish cooking it, the heat on the side of the pot would dry out the liquid and turn it into a film.

I decided to see if this could be taken further. That mucilaginous liquid that I always discarded could now be used, I hoped. I spread it very thinly over sheets of Plexiglas and let it dry out overnight. The next day, it peeled right off and it looked like plastic wrap. If I then placed it in the dehydrator it would become crisp and shatter like glass if handled improperly.

In the picture at the beginning of the posting, I added soy sauce to the pot along with the water. The next day I took the dried out film and wrapped fleur de sel caramels. I placed them in the dehydrator to crisp up the film. What resulted was a soft, warm chewy caramel, wrapped in a salty, crisp film. A very nice balance.

The second item I made (below) is a little more complicated but with two of the previous elements. I wrapped a cube of foie gras mousse in the tapioca film, topped it with the cooked soy tapioca and served with with a strand of fleur de sel caramel. Sweet, salty, crisp, smooth, chewy.


6 comments:

  1. very nice technique -- it reminds me of a thinner, more pliable version of yuba or mung bean sheets, yet much more fragile when dried.

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  2. Interesting.I used mung bean starch recently; it yielded a somewhat chewy product. A little crumbly, almost like agar which doesn't strech as much as tapioca starch does. I have never seen mung bean sheets though. How is it made or is it bought as is?

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  3. We picked up the mung bean sheets in a small Korean grocery a few years back -- the sheets are circular and roughly 10 inches across, sort of like a larger rice paper.

    After soaking them in warm water for a minute or so (also like rice paper), you can then shred them like noodles for soup. We rolled tofu in ours, and pan-fried it for a crispy outer skin. Like these two versions:

    http://www.flickr.com/photos/tofu/126463817/

    http://www.flickr.com/photos/tofu/80063800/

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  4. I just discovered your blog, looks awesome.
    It's funny you reminded me when I was playing around with tapioca pearls. I was able to pull off this thin sheet of something. You toke it to the next level. I will revisit after looking at these pictures. Thx.

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  5. Hello Daniel
    Is this the Daniel I think it is? DL?

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  6. Perhaps what is happening is that a portion of the amylose fraction of the tapioca (which usually consists of about 15 to 18% % amylose, the remainder being amylopectin) is being extracted out of the pearls. Amylose has good film-forming ability, compared to amylopectin.

    Crisp Film(R) is an example of a commercially-available modified high-amylose corn starch that can be used to make flavored films.

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