Miso

 is a traditional Japanese seasoning produced by fermenting soybeans with salt and "kōji" (the fungus "Aspergillus oryzae") and sometimes rice, barley, seaweed, or other ingredients. The result is a thick paste used for sauces and spreads, pickling vegetables, fish, or meats, and mixing with dashi soup stock to serve as miso soup, a Japanese culinary staple. High in protein and rich in vitamins and minerals, miso played an important nutritional role in feudal Japan. Miso is still widely used in Japan, both in traditional and modern cooking, and has been gaining worldwide interest.
Typically, "miso" is salty, but its flavor and aroma depend on the ingredients and fermentation process. Different varieties of miso have been described as salty, sweet, earthy, fruity, and savory.
History.
The origin of the miso of Japan is not completely clear. 
In the Kamakura period (1185–1333), a common meal was made up of a bowl of rice, some dried fish, a serving of miso, and a fresh vegetable. Until the Muromachi period (1337 to 1573), miso was made without grinding the soybeans, somewhat like "nattō". In the Muromachi era, Buddhist monks discovered that soybeans could be ground into a paste, spawning new cooking methods using miso to flavor other foods. In medieval times, the word "temaemiso", meaning home-made miso, appeared. Miso production is a relatively simple process, so home-made versions spread throughout Japan. Miso was used as military provisions during the Sengoku period, and making miso was an important economic activity for "daimyō"s of that era.
During the Edo period (1603–1868), miso was also called "hishio" (醤) and "kuki" (豆支) and various types of miso that fit with each local climate and culture emerged throughout Japan.
Today, miso is produced industrially in large quantities, and traditional home-made miso has become a rarity. In recent years, many new types of miso have appeared, including ones with added soup stocks or calcium, or made with beans other than soy, or having reduced salt for health, among other varieties, are available.
Ingredients.
The ingredients used to produce miso may include any mix of soybeans, barley, rice, buckwheat, millet, rye, wheat, hemp seed, and cycad, among others. Lately, producers in other countries have also begun selling miso made from chickpeas, corn, azuki beans, amaranth, and quinoa. Fermentation time ranges from as little as five days to several years. The wide variety of Japanese miso is difficult to classify, but is commonly done by grain type, color, taste, and background.
Many regions have their own specific variation on the miso standard. For example, the soybeans used in Sendai miso are much more coarsely mashed than in normal soy miso.
Miso made with rice such as "shinshu" miso (信州味噌) and "shiro" miso (白味噌) are called "kome" miso (米味噌).
Types and flavor.
The taste, aroma, texture, and appearance of miso all vary by region and season. Other important variables that contribute to the flavor of a particular miso include temperature, duration of fermentation, salt content, variety of "kōji", and fermenting vessel. The most common flavor categories of miso are:
Although white and red ("shiromiso" and "akamiso") are the most common types of misos available, different varieties may be preferred in particular regions of Japan. In the eastern Kantō region that includes Tokyo, the darker brownish "akamiso" is popular while in the western Kansai region encompassing Osaka, Kyoto, and Kobe, the lighter "shiromiso" is preferred.
A more nuanced breakdown of the flavors is:
Chemical properties of flavor and aroma compounds.
The distinct and unique aroma of miso determines its quality. Many reactions occur among the components of miso, primarily the Maillard reaction, a non-enzymatic reaction of an amino group with a reducing sugar. The volatile compounds produced from this reaction give miso its characteristic flavor and aroma. Depending on the microorganism in combination with the variety of soybean or cereal used, many classes of flavor compounds are produced that give rise to the different types of miso. Fermentation products such as furanone compounds, including 4-hydroxy-2(or 5)-ethyl-5(or 2)-methyl-3(2H)-furanone (HEMF) and 4-hydroxy-2,5 dimethyl-3(2H)-furanone (HDMF) are novel flavor compounds of miso. HEMF is especially known for its sweet aroma and is very important for the sensory evaluation of the aroma of rice miso.
The unique sensory properties of miso are complex; however, the key factor involved in the overall quality of the final product is the enzymatic activity of microorganisms. They use the composition of miso (rice, barley, and soybeans) to produce different pigments, flavor and aroma compounds.
Proteolysis of soybean protein produces constituent amino acids that impart an umami taste that enhance the relatively dull taste of soybean by itself. Soy protein contains a substantial amount of glutamate, the salt of which is known as MSG or monosodium glutamate, a popular ingredient used by food manufacturers to improve the taste of their products. The umami effect of MSG itself is one-dimensional; however the umami taste of miso is multi-dimensional because of the myriad of different amino acids and fermentation products present.
Barley miso is a traditional farmhouse variety made for personal use. Often called "rural miso", domestic barley is more often used than imported barley. Containing glutamic acid and aromatic compounds such as ferulic acid and vanillic acid, barley miso is distinguished by a characteristic flavor.
Fermentation.
Miso's unique properties and flavour profile can be attributed to the compounds produced through the fermentation process. Miso, depending on the variety, consists of a starter culture called koji (麹), soybeans, and usually a grain (either rice, barley, or rye). The miso goes through a two step process; first creating the koji, and second the koji is combined with the other components and the mixture is left to be enzymatically digested, fermented and aged.
Creating koji.
Koji is produced by introducing the mould "Aspergillus oryzae" onto steamed white rice. This mould culture comes from dried "A. oryzae" spores called "tane-koji" or "starter koji" and is isolated from plant matter (usually rice) and cultivated. In the past, the natural presence of "A. oryzae" spores was relied upon to create koji, but because of the difficulty of producing the culture, tane-koji is added almost exclusively in both industrial and traditional production of miso. Tane-koji is produced much in the same way as koji, but also has a small portion of wood ash added to the mixture which gives important nutrients to the fungus as well as promoting sporulation.
"A. oryzae" is an aerobic fungus and is the most active fermenting agents in koji as it produces amylolytic, and proteolytic enzymes which are essential to creating the final miso product. Amyloytic enzymes such as amylase aid in the breakdown of starch in the grains to sugar and dextrin, while proteolytic enzymes such as protease catalyze the breakdown of proteins into smaller peptides or amino acids. These both aid in the enzymatic digestion of the mixture of rice and soybeans. Depending on the strain of "A. oryzae", enzymatic composition varies thereby changing the characteristics of the final miso product. For example, the strain used to create the sweeter white miso would likely produce a higher content of amylolytic enzymes, while comparatively a soybean miso might have a higher content of proteolytic enzyme.
To create optimal conditions for enzymatic production and the growth of "A. oryzae", the koji's environment must be carefully regulated. Temperature, humidity and oxygen content, are all important factors in not only maximizing mould growth and enzyme production, but to prevent other harmful bacteria from producing. Once the koji has reached a desirable flavour profile it is usually mixed with salt to prevent further fermentation.
Although other strains of fungi have been used to produce koji, "A. oryzae" is the most desirable because of a number of properties, including the fact that it does not produce aflatoxin.
Storage and preparation.
Miso typically comes as a paste in a sealed container requiring refrigeration after opening. Natural miso is a living food containing many beneficial microorganisms such as "Tetragenococcus halophilus" which can be killed by overcooking. For this reason, the miso should be added to soups or other foods being prepared just before they are removed from the heat. Using miso without any cooking may be even better. Outside Japan, a popular practice is to add miso only to foods that have cooled to preserve "kōjikin" cultures in miso. Nonetheless, miso and soy foods play a large role in the Japanese diet, and many cooked miso dishes are popular.
Usage.
Miso is a part of many Japanese-style meals. It most commonly appears as the main ingredient of miso soup, which is eaten daily by much of the Japanese population. The pairing of plain rice and miso soup is considered a fundamental unit of Japanese cuisine. This pairing is the basis of a traditional Japanese breakfast.
Miso is used in many other types of soup and soup-like dishes, including some kinds of" ramen, udon, nabe", and" imoni". Generally, such dishes have the title "miso" prefixed to their name (for example, "miso-udon"), and have a heavier, earthier flavor and aroma compared to other Japanese soups that are not miso-based.
Many traditional confections use a sweet, thick miso glaze, such as "mochi and dango". Miso-glazed treats are strongly associated with Japanese festivals, although they are available year-round at supermarkets. The consistency of miso glaze ranges from thick and taffy-like to thin and drippy.
Soy miso is used to make a type of pickle called "misozuke". These pickles are typically made from cucumber, daikon, Nappa cabbage, or eggplant, and are sweeter and less salty than the standard Japanese salt pickle.
Other foods with miso as an ingredient include:
Nutrition and health.
Claims that miso is high in vitamin B12 have been contradicted in some studies.
Some experts suggest that miso is a source of "Lactobacillus acidophilus". Miso is relatively high in salt which can contribute to increased blood pressure in the small percentage of the population with sodium-sensitive prehypertension or hypertension.