Mochi Gome Zu – Rice Vinegar

What do sushi and fish and chips have in common? It is often said that Japan and England are similar, both being small island nations, but similarities in their cuisine is not usually the first thing that springs to mind when comparing Japan and England. However, these two dishes, representative of each country, do have something in common, and that is vinegar.

The su in sushi means vinegar, and shi is a contraction of ‘meshi’ meaning cooked rice – so ‘sushi’ is vinegared cooked rice (not raw fish as many assume).

And, just as there is good reason for taking vinegar with deep fried fish and chips, to help digest the oil, the vinegar in sushi rice is there for a reason: vinegar is an anti-bacterial, and it helps to preserve the fish and the rice.

You won’t be surprised to learn however, that Japanese vinegar is a rather more refined product than English malted vinegar: it’s made from rice, in a two part process that is similar to making sake. In fact the first stage is making a type of sake but, in the case of rice vinegar, the rice used contains more protein. And the best rice vinegars use glutinous rice – mochi kome.

As in sake-making, first the rice is steamed and mixed with the rice koji to make the mash; the enzymes in the koji convert the starch in the rice into sugar; and yeasts convert the sugar to alcohol.

In vinegar-making this initial sake-like mash, or moromi, is called su moto moromi – ‘sake base for vinegar’, or ‘vinegar mash’. This mash is then combined with spring water, and with something that would be deadly for sake production – acetic-acid: either in the form of a bacteria or a vinegar mother. After several weeks, when the alcohol content has reached 20% and fermentation has ceased, the liquid is filtered and left to mature.

Rice vinegar barrels in Japan
Rice vinegar barrels in Japan. Image courtesy of The Wasabi Company and Marusho Jozomoto.

The southern island of Kyushu is home to many of the top producers of rice vinegar.

Marusho Jozomoto is one of these companies. They produce a dizzying variety of top class vinegars, available here in the UK from The Wasabi Company. Skilled craftsmen rely on four generations of family experience to create Marusho fermented vinegars, using the same techniques that were employed 200 years ago. The quality of the ingredients makes for a premium product: water from the nearby Kumamoto mountains, and rice grown on their own family-managed fields.

Marusho’s Nachi Kurokomeshi vinegar is left to ferment for a minimum of ninety days. Then after filtering it’s left to mature for a further five hundred days (a year and a half!) using Japanese cedar casks. So the whole process takes almost two years. Artisan indeed, as are all their vinegars, more of which are described below.

Iio Jozo is not one of the Kyushu producers but they have been making traditional rice vinegars in Kyoto Prefecture, for over a hundred years. The brewing of the initial sake (su moto moromi- vinegar mash) takes place at a distance from the vinegar fermenting area, so the yeast and bacteria don’t contaminate each other. In the vinegar producing area the su moto moromi is heated and mixed with spring water, and an acetic-acid forming bacteria called sakusankin. The liquid is then left to ferment for three to four months, during which time a mother grows on the surface, converting the alcohol into vinegar, and covering the entire factory in an unmistakeable vinegar aroma. After filtering it’s left to mature, in concrete vats, for a further four months.

Brown rice vinegar

Iio Jozo makes superior white rice vinegar, using milled rice, but also Brown Rice Vinegar, called genmaisu, and Black Vinegar (kurozu).

As we know from sake making, amino acids (which give flavour) are a result of two things: proteins and minerals in the rice, and the length of fermentation. In making Brown Rice Vinegar the rice is not milled, so the proteins, fats and minerals that remain create high levels of amino acids; this, together with a long fermentation, gives the vinegar depth and complexity, and flavour. (In the case of kurozu, which is often matured for years, this complexity is even greater.)

Maruboshi Vinegar Company in Fukuoka, Kyushu make the brown rice vinegar for Clearspring, and this long-established company ferments their vinegars in clay crocks, which are half-buried in the ground positioned to catch the warmth of the sun in winter, and shade in summer. This time consuming process contributes to the creation of numerous amino acids which, as well as enhancing taste, are beneficial to health.

Kurozu black vinegar – the ‘Rolls Royce’ of brown rice vinegar

There is brown rice vinegar and there is black vinegar. Black vinegar became fashionable as a health drink in Japan some years ago, and now, with the increasing interest in gut health in the west, it is here. Special points about black vinegar:

  •  Always made with brown rice
  •  Higher ratio of rice used in the production
  •  Fermented for longer – 1 to 3 years

Uchibori Rinkosan Kurozu, from Kagoshima, is aged for one to three years, and is readily available here in the UK (from Japan Centre, Ichiba and Natural Natural). Wasabi Company’s black vinegar is made by the aforementioned Iio Jozo in Kyoto Prefecture, where it is fermented for up to three years, resulting in a vinegar which adds flavour and complexity to food, but which also makes a pleasant drink, simply diluted with water.

Other Marusho vinegars sold by Wasabi Company are Dentojozo komezu, a blend of black vinegar (made from unpolished sticky rice, and fermented for 500 days) and pure rice vinegar, which is then seasoned with amazake and mirin. Tosazu/dashi vinegar is Marusho’s own top-grade rice vinegar seasoned with soy sauce, bonito, kombu and mirin. Use for dishes which are enhanced by a touch of dashi (most things!) such as dressings; and it’s perfect for the nanbanzuke – pickled fish – see below.

Caution! Do not confuse these superior artisan-made vinegars with industrially-produced products, which are made in factories with a variety of inferior ingredients, such as rice powder, or even different starches altogether, and sugar: apart from the paucity of taste, these do not have the same health benefits as artisan-made products.

Health benefits of Brown Rice Vinegar and Black Vinegar

Wash a very fresh egg, being careful not to break the shell. Immerse the egg in a cup of brown rice vinegar for two to three days, or until the shell dissolves leaving the inner soft skin. Discard the skin and mix the egg and vinegar well. Drink a sake cup of this liquid three times a day after meals” John and Jan Belleme, Culinary Treasures of Japan (Avery).

This ancient folk remedy may sound unappealing but it is said to prevent a hangover – if drunk before a drinking session!

A tablespoon of brown rice or black vinegar simply diluted in water makes a delicious non-sweet drink, for those who want to eschew alcohol; I sometimes even drink it from a wine glass!

The amino acids produced during long fermentation stimulate appetite and aid digestion, so a glass before a meal, or a vinegared appetizer, supports a healthy stomach; and a daily drink of vinegar and honey is said to relieve symptoms of arthritis, or even allay its onset.

Particular health benefits of kurozu black vinegar are said to include increased blood circulation and stabilised blood pressure; some studies have even indicated anti-cancer properties: “kurozu has been reported to have anti-cancer activity in vivo in rats, and in vitro in human cancer cells” (cited in Molecular innovations Novi, MI, USA).

A bottle of kurozu then almost belongs in the medicine cupboard as well as the pantry.

In the kitchen though, is where rice vinegar, white, brown or black, really shines.

As demonstrated by the recipe for Tamago-su above, vinegar dissolves calcium – so small fish marinated in rice vinegar become digestible and therefore a good source of dietary calcium (important in a food culture which doesn’t include dairy).

To stop discolouration of certain vegetables – root vegetables such as burdock, lotus root, Jerusalem artichoke, taro, but also aubergine, place them in water with a dash of rice vinegar. Vinegar also brings out sweetness in root vegetables (try a miso and vinegar dressing with simmered daikon or carrot).

Green vegetables though discolour when cooked with vinegar, so only dress greens after they have cooled. Interestingly, the pleasant pink colour of sushi ginger is a result of the pigment anthocyanin in ginger, which is activated by the vinegar used in pickling.

Rice vinegar increases the potency, and slows the destruction, of Vitamin C, so it’s good to add a little rice vinegar to grated daikon (which is always best grated just before serving for the same reason).

And you can even try some on your fish and chips!

© Shirley Booth 2021

Recipes using Mochi Kome Zu

The simplest dressings are made by combining vinegar and sugar, as in sushi rice, which becomes a kind of short term pickle. Use a ratio of 5:2 vinegar to sugar, and add a little salt to balance. This can be used to ‘pickle’ root vegetables, as well as cucumber and Chinese leaf, which will keep for up to a week, refrigerated.

Vinegar and soy sauce dressing. Use a 4:2 ratio of vinegar to soy sauce. Drizzle over fish and shellfish, or vegetables, and use as a dipping sauce for fried food such as gyoza.

More complex flavours are achieved by combining vinegar with mirin, miso, and mustard – even egg. ‘Japanese hollandaise’ is made by combining egg yolks with sugar and rice vinegar. Use three eggs, two tablespoons sugar and three of vinegar, add a little salt, and cook slowly over a bain marie to thicken.

Mustard and Vinegar Dressing

  • 1 tablespoon Dijon mustard
  • 1 tablespoon brown rice or barley miso
  • 3 tablespoons tosazu – Wasabi Company’s dashi vinegar (or other rice vinegar)
  • 1 tablespoon mirin
  • 1 tablespoon barley malt syrup, or coconut sugar syrup
  • 5 tablespoons rapeseed (or other vegetable) oil

Mix all the ingredients together, whisking or shaking thoroughly to combine. Can be used on western salads, or on Japanese style vegetable dishes. Try it on simmered daikon radish, or steamed carrots.

Korean Coleslaw salad

  • Half a Chinese Leaf cabbage (hakusai)
  • 1 small Iceberg or Cos lettuce, sliced (but not too thinly)
  • 2 medium carrots, coarsely grated
  • ½ teaspoon salt for the dressing
  • 1 teaspoon minced or grated garlic
  • 1 teaspoon grated ginger
  • 1 tablespoon rice vinegar
  • 2 tablespoons toasted sesame oil
  • 1 teaspoon gochugaru, Korean chilli powder (or use a little less paste if that is all you have)
  • toasted sesame seeds to serve (optional)

Finely chop the Chinese leaf, using only some of the thick white stem (keep the rest for another dish). Mix the grated carrot and Chinese leaf with the salt and leave for fifteen
minutes. Make the dressing by mixing together all the other ingredients. Combine the salted cabbage and carrot with the sliced lettuce, then pour over the dressing. Mix well, using chopsticks. Sprinkle over toasted sesame seeds before serving. This can be eaten immediately, but will also keep a few days in the fridge.

Nanban-zuke Deep fried fish in vinegar

This method of pickling deep fried fish in vinegar has the same origins as tempura – almost certainly introduced into Japan by the Portuguese in the sixteenth century. The word nanban-jin means ‘southern barbarian’ – used by the Japanese to describe westerners at the time. Nanban then came to be associated with their cooking styles – in particular the use of chilli, which indicates something ‘foreign’ or barbarian!

  • 4 large fillets of white fish (or small whole whitebait or sardines, cleaned and gutted)
  • salt
  • 4 spring onions
  • 1 ½ tablespoons mirin
  • 1 tablespoon caster sugar
  • 180 ml tosazu rice vinegar (or 120 ml brown rice vinegar and ¼ tsp dashi granules dissolved in 4 tablespoons water )
  • 2 tablespoons light soy sauce
  • 1 red chilli, de-seeded and sliced into rings (OR a pinch Korean chilli powder, or dried chilli pepper flakes if you like very spicy food – to taste)
  • oil for deep frying
  • flour to coat

First prepare the fish by lightly salting and leaving for fifteen minutes. Then prepare the marinade: Grill the spring onions until limp (slightly charred is OK). Cut into thin slices on the diagonal. In a small saucepan combine the marinade ingredients and the sliced onion. Bring to a simmer then keep hot whilst you fry the fish. Bring about 2-3 inches depth of frying oil to a temperature of 160C (not too hot as you want the fish to cook through). Wipe the fish clean of salt, and then coat in the flour. Deep fry the fish for about five minutes, depending on size. When cooked, remove from the oil and place in a shallow dish. Bring the marinade up to a simmer again and then immediately pour over the fish.

If using whole fish, pour over the marinade whilst warm, and leave to cool; then refrigerate for a day or two to allow the bones to soften. If using fillets the dish can be eaten after a couple of hours in the fridge, to allow the flavours to be absorbed.

Black Vinegar drink

  • Milk
  • Black vinegar
  • 5:1 ratio of milk to vinegar
  • Honey to taste

This is a wild sort of a drink – but surprisingly good. The vinegar of course slightly thickens the milk; and it’s best to use runny honey so it dissolves more readily (you could try maple syrup, which will give it an extra taste).

© Shirley Booth 2021

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