Gunma Prefecture, Japan — over 90% of Japanese konnyaku production
Konnyaku (konjac, Amorphophallus konjac) has been cultivated in Japan for over 1,500 years and is produced almost entirely in Gunma Prefecture (which supplies 90% of Japan's konnyaku). The processed corm produces a firm, gelatinous block with a neutral, slightly earthy taste, distinctive rubbery snap when chewed, and the remarkable property of being nearly calorie-free (98% water and glucomannan fibre). Konnyaku forms include: grey block (ita konnyaku) with darker specs from nori ash that give the 'speckled' appearance; white block (shiro konnyaku); shirataki (thread konnyaku, used in sukiyaki and nabe); ito konnyaku (slightly thicker threads); and tsukurizume (moulded specialty shapes). Konnyaku absorbs flavour from its cooking medium beautifully — in oden it absorbs the rich oden broth; in sukiyaki it takes on the sweet warishita. Its textural properties make it irreplaceable as both a filler (providing satisfaction without calories) and a textural element in mixed preparations.
Neutral, mineral-earthy in raw form; in cooking it absorbs surrounding flavour completely, becoming a vehicle for dashi, soy, miso, and tare — the flavour is always its cooking medium
Konnyaku must be parboiled and rinsed before use to remove the alkaline lime (cal) used in processing — this also improves texture by firming it; 'tearing' konnyaku by hand rather than knife-cutting creates a rougher surface that absorbs more surrounding flavour; scoring cut surfaces with diagonal crosshatch pattern dramatically increases surface area and flavour absorption; konnyaku does not cook — it only absorbs; long simmering improves flavour absorption but does not change the fundamental texture.
The best konnyaku preparation: tear into rough pieces, parboil 3 minutes, drain and pat dry, then pan-fry briefly until the surface develops slight colour (the Maillard browning creates micro-texture that holds sauce far better); konnyaku steak (ita konnyaku pan-seared with soy-butter-mirin glaze and topped with kona-sanshō) is one of Japan's great vegetarian comfort dishes; in Gunma Prefecture, traditional konnyaku is eaten as sashimi — sliced cold with soy and mustard — a flavour test of the quality of the product itself.
Skipping the parboiling step (retains alkaline lime taste and odd smell); cutting with knife when hand-tearing would produce better flavour absorption; using konnyaku in raw applications that rely on flavour (it is nearly tasteless raw — it must be cooked in flavoured liquid); expecting konnyaku to soften over time (it maintains its rubbery texture regardless of cooking duration — that is its fundamental character).
Japanese Cooking: A Simple Art — Shizuo Tsuji