David Ehrlich
Sun, 03 Apr 2011 17:14:26 PDT
Both yacón (Polymnia sonchifolia) and topinambur (Jerusalem artichoke, Sunchoke, 
Helianthus tuberosus) have tubers composed mainly of inulin rather than starch.  
This is the part that is usually eaten, though young stems can also be eaten.  
Raw, these tubers are somewhat sweet and crunchy, but the skin has a stronger 
more resinous taste, so you might want to peel it.  Because humans lack an 
enzyme to hydrolyze inulin, these vegetables pass through the body mostly 
unmetabolized, so they make ideal diet foods.  I like them raw with lime juice 
and a sprinkle of salt as a snack, or sliced and sautéed as a dinner vegetable.  
They can also be baked or boiled, but they lose their crispness.  I would not 
bake them in a pie.

Oca (Oxalis tuberosa) can be bitter or sweet.  The bitter varieties can contain 
up to 500 ppm oxalic acid (that's like spinach leaves).  However, the sweet 
varieties contain only 79 ppm acid, which is 1/20 the amount found in a standard 
white potato.  So, get a sweet variety; it'll be perfectly safe to eat.

David E.

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