Digression alert: Before fermentation can happen, complex carbohydrates or starch have to be converted to fermentable sugars. All cultures somehow figured this out to make alcohol. The most primitive form is to chew cooked grains and spit the masticated starch out into a vessel. Diastase in saliva will convert starch into sugar and fermentation can produce a primitive “jungle” beer. For true beer making, enzymes formed during sprouting of barley (malting) is used to convert starch in the barley and other grains to sugar (“mash). The Japanese/Chinese figured out that certain mold (yes, “mold” called Aspergillus oryzae, which produce several enzymes including amylase) can convert the starch of cooked rice into fermentable sugar. Many Japanese food items are based on “Koji” to produce; sake 酒, chochu 焼酎, miso 味噌, and shouyu 醤油 (soy sauce). But koji or cooked rice inoculated with this mold by itself can be used in different dishes. If this was used in pickling or “tsukemono” the vegetables, sugar will mostly ferment into acid (lactic acid by lactobacillus) rather than alcohol. Thus, it imparts sweet (sugar), sour (from lactic acid) and salty (from added slat) and additional “je ne sais quoi” components from whatever develops during fermentation.When I was growing up in Hokkaido, there was a fermented and preserved condiment/side dish called “Nishin-zuke” 鰊漬け or Herring pickles (picture below) and my mother used to make it. Essentially, vegetable and filets of dried herrings were mixed with “koji” and salt and left to ferment for several months in a cold place (there were many “cold” places in winter in Hokkaido houses).
In recent years, “koji” is making a big come back especially as “shio-koji” in Japan as a magical marinade and meat tenderizer. Since I found dried “koji” in the near-by Japanese grocery store, I decided to prepare “shio koji”. After making “shio koji”, this is the first dish I made.
I used daikon cut into quarter circle (1/4 inch thick), cucumber (1/2 inch thick), radish (a kind called “French breakfast” which is small, elongated and a bit sweeter than regular radish with red and white color, cut into thin slices). The amount was totally arbitrary but I weighed the entire amount of the vegetables, and it was about 500 grams. The reason I weighed the vegetables was because the recipe calls for 10% of shiokoji to the weight of the vegetables. I just wanted to get the feel for what constituted 10% of the weight. I mixed and kneaded the vegetable and shiokoji. The recipe said just massage the vegetables with shiokoji in a Ziploc bag and leave it in a refrigerator for half a day but I decided to use a “Tsukemono” pot with a plunger to apply pressure and left it overnight in the refrigerator until ‘water” came out and submerged the vegetables (or “mizu ga agaru” 水が上がる meaning the water is up).
You could see the fragments of rice kernels from the shiokoji attached to the pieces of vegetables. This is good but we did not think it was all that different from simply salted asazuke 浅漬け. This version adds a slight sweetness and some complexity to the taste. The addition of thinly cut kelp, red pepper, ginger to the simple salted version also can give a different kind of complex flavors to the asazuke. If you already prepared shiokoji, this is a good use for it but I would not make this dish with shiokoji just for the sake of making it.
Shiokoji preparation: I bought pre-made and dried koji and simply followed the instructions that came with the product. As I said you could get the koji mold ( from a home brewing place) and make koji from scratch. In Japan, I was told that a ready made shiokoji is readily available in a jar but I have not seen it sold here in our area. Here, I bought premade and dried koji (#1). I added the amount of water and salt as per the instruction which came with this (#2).