Miso pastes are fascinating not only because of their taste and possibilities of use in the kitchen but also because of their composition. We will try to introduce them here both in general terms as well as to the level of detail that might be of interest to you as our customers.
Miso is a phenomenon, especially in Japan, where you can find dozens to hundreds of different variations and recipes. Typically, it uses soy as the legume and rice as the cereal on which koji, a noble fungus that is an essential reagent in the fermentation process through its enzymes, is grown. In some cases, the cereal is barley, and specific misos are also fermented completely without any cereal.
Traditionally, miso pastes are classified according to the length of the fermentation process and the ingredients used.
- Shiro miso is a light, briefly (2-3 months) fermented miso paste with a typically milder and sweeter flavor. The standard basis is polished white rice, but our production also includes variations made from buckwheat, millet, or spelt.
- Genmai miso is the name for miso made from whole grain rice, which is responsible for its brown color. These misos usually take around six months to age and are rich in flavor. We offer them coarsely ground.
- Aka miso ages for at least one year, and has a more intense flavor and a typical reddish tone. In Japan, it is one of the most popular miso.
- Mugi miso refers to miso pastes based on barley instead of rice. It ages from six months to a year and is also considered to be one of the types with a distinctive flavor.
- Hatcho miso is usually completely black, very intense, with a strong flavor, and ages for 2-3 years. There are no cereals in its composition, the koji culture in this case is cultivated directly on the fermented soy.
We like to play around with miso and also ferment other legumes instead of the traditional soy and other cereals instead of the most commonly used rice. Therefore, you can also find misos made from peas, chickpeas, lentils, buckwheat, and more. Also, the nomenclature of our miso pastes always includes the dominant ingredient for better customer orientation.
There are many myths about what miso contains, what it cures, how it's alive, and so on. For many reasons we want to be clear about this, so we decided to explore miso from the inside, so to speak. We'll tell you upfront that it's going to be a long haul, but what we're continuously discovering is more than interesting.
Google helper and scientific studies
The first thing that comes to one's mind is to google. So he looks up a few articles, reads them, and can't shake the feeling that he is reading the same thing. Yes, unfortunately, most of the sources in Czech only copy from each other and so you will read general or unsubstantiated information. For that reason, we will not even quote them.
The second thing one does is to start googling foreign language sources, ideally various studies and articles in reputable journals and publications. And this is where you get stuck for a long time.
We have read and studied a few dozens of studies (unfortunately, most of them are in Japanese) and we have the ambition to translate them over time, but for the time being, we will be satisfied with just links to their English versions.
Before we start listing what the studies say and get you so excited that you'll buy out your nearest health food store and start putting miso, even on your toothbrush, we have to warn you. Although the studies have fascinating findings, they are being conducted on specific samples of miso. However, there are hundreds and thousands of varieties of miso pastes out there, varying in the quality and type of input ingredients, as well as in the quality and type of koji (noble fungus) used, the length of aging, the method of preservation (we'll get to that later), the method of preparation, and so on...Miso pastes available on the market vary so significantly that we simply can't mindlessly apply the results of any particular study to every single one of them.
Among the findings of one of the most recent (from April 2021) and quite comprehensive studies  is that a lot of investment in miso research will still be needed to prove all its health benefits.
Thus, if you read scientific studies published in Japan's academic journal, Journal of Food Science, Journal of Fungi, and others, you will find, for example, that:
- Using miso lowers or at least does not raise (depending on the source) blood pressure, especially compared to regular salt
- By adding miso to rice, you lower its glycemic index (which can be anticipated for other high glycemic index foods)
- Miso reduces the risk of reflux problems and digestive problems in general (dyspepsia)
...and it's getting better! It's worth pointing out that we are drawing mostly from Japanese studies and that there are hundreds of types of miso and what is true for one may not be true for another...
- Miso has positive effects in cases of radiation exposure (Japan has a rich experience), colon, breast, liver, and stomach cancer, and so far only experimentally observed protection against lung cancer
- Miso protects against stroke
What else can be learned from the studies...
Significant attention is typically given to the probiotic effects of miso. According to the findings of the last mentioned comprehensive study , miso cannot be considered to have a probiotic effect according to the WHO definition. This is confirmed by our own analyses, which we will come to later.
Miso is salty, and the common lactobacilli known from fermented vegetables or yogurt simply cannot survive the high saltiness of miso. According to the studies, miso most often contains the bacteria Tetragenococcus halophilus and the yeast culture Zygosaccharomyces rouxii, which are not formally considered probiotic cultures according to the WHO.
So if you are expecting miso to be probiotic, you will be disappointed. You're better off with fermented cabbage, kimchi, or homemade yogurt. But you don't have to give up on miso, because it's prebiotic  (it's a source of fiber and other substances that support the growth and life of probiotic cultures in the intestine) and contains a variety of vitamins, minerals, and fiber. The particular substances depend on the composition of miso, e.g.:
- In addition to fiber, soy contains calcium, vitamin E, potassium
- Rice is a source of vitamins B1, B2, B3, minerals, magnesium, potassium, and zinc
- In addition to fiber, peas contain vitamins B1, B2, B3, B5, B6, minerals, selenium, calcium, iron, magnesium, and others
- And so we could go on... we recommend looking, for example, at calorie charts  and on the labels of miso you buy
What about enzymes?
This is probably the most interesting characteristic of miso pastes, but also the one least described. Koji (Aspergillus oryzae) is a noble fungus grown on cereals (typically, but not necessarily, rice) that is the input ingredient for miso. Koji produces a wide variety of different enzymes that are catalysts for various biochemical processes (allowing them to happen). Part of this enzyme cocktail is used to break down proteins, starches, and fats during the fermentation of miso, while a significant amount naturally remains in miso. White miso has most of them, given its recipe, which contains more enzymatic rice. On the other hand, red or dark miso is richer in protein.
The structure of these enzymes has not been thoroughly mapped yet. It was only in 2005 that the molecular analysis of the Koji genome was completed, and 13,572 genes were identified, of which 25% were new and previously unknown genes.
Amylases break down complex carbohydrates into simple sugars (typically e.g. glucoamylase).
Proteases break down complex proteins into more digestible peptide chains, which is especially appreciated in legumes, given their significantly improved digestibility and the elimination of bloating and other undesirable characteristics. Koji produces a variety of such enzymes, some of which (e.g. glutaminase) result in the release of glutamic acid, which plays a key role in achieving the umami flavor of miso.
Lipase plays a key role in breaking down fats into fatty acids, which again helps make miso paste more digestible.
Koji is therefore rightfully called an enzyme bank, and how it can be used not only for making miso is still far from being fully described.
Own analyses of miso
And if you are not satisfied with googling in Czech or English, there is nothing left than doing your own biochemical and microbiological analyses. We continuously do this, although it is certainly not a cheap affair. We also have all other miso pastes on the domestic market analyzed so that we can keep up to date and objectively compare the composition of our miso pastes with, for example, the Japanese ones.
Therefore, we prefer to publish the results of our analyses. We comment on the interesting findings of our own miso pastes and then point out in general what to look out for when choosing miso available on the market.
Conclusions of analyses of selected Kojibakers miso pastes:
- Soy and pea miso does not contain histamine
- Both soy and pea miso contain:
- 1,57-1,79 mg/kg of vitamin B1
- 1,03-1,10 mg/kg of vitamin B2
- 1,32-2,39 mg/kg of vitamin B6
- Soy red miso contains 0,233 micrograms/100 grams of vitamin B12 (cobalamin)
- So we have a proven non-animal source of B12
- Vitamin B12 is also expected in other soy miso but has not been proven in pea miso
- There was evidence of low levels of lactic acid bacteria and lactobacilli, which is consistent with findings from Japanese scientific studies and no different from other miso pastes we have sent for analysis.
- This also applies to our miso kimchi soup (as well as competing products of similar composition). Kimchi, otherwise highly probiotic, is overwhelmingly deprived of its probiotic effect when mixed with miso.
When choosing between the various miso pastes on the market, we recommend that you consider the following:
- Is miso pasteurized? If the answer is yes, you don't have to give up on it, many of its qualities and especially the taste will remain. It also depends on the temperature and length of pasteurization, as the enzymes are denatured gradually, but this topic is beyond the scope of our article. We recommend miso unpasteurized!
- What is the value of sugars listed in the nutrition facts? Koji breaks down complex carbohydrates into simple sugars during fermentation. If the values of sugars listed are in the range of 0,5-1,5g/100g of product, you can be sure that the manufacturer is only using calculated values, but has not done his own analysis of the values. If the sugar values are at 15-25g/100g of product, this corresponds to the actual breakdown of carbohydrates by the amylases produced by the noble fungus koji, therefore the manufacturer could not have calculated this value and spent the time and money to analyze it. So you can probably trust the other values on the label as well.
- Read the label. You will read interesting information, for example, about alcohol stabilization or additives that have no place in miso.
Miso is a phenomenon that we still can't appreciate. In Asia and Japan, in particular, it is valued regardless of facts, figures, and analyses. It was superseded by at least 2,000 years of using miso in daily diet. In Japan, Koji even has its annual holiday and probably all this is no coincidence. And the fact that it is not just an Asian affair is demonstrated by the explosive growth of interest in koji and miso around the world, in Europe, and eventually even here.