Miso paste is a simplistic product, considering the use of only three ingredients: beans, grain koji, and salt. In Japan, the citizens of particular regions of the country express preference towards one of three types of miso: kome (rice-based), mugi (barley-based), or hatcho (soybean- based). Within the three categories, there are more varieties, resulting in at least 12 main types of miso. The method of cooking beans, specific ratios of the ingredients, and the time of fermentation allows producing pastes with different colour, flavour, and aroma. As with cheese or wine, the diversity of miso pastes creates the whole portfolio of products. The composition of each of the main categories of miso was presented in the table below.
Traditionally soybeans were the only type of beans used for miso production. It has been known as the cheapest plant-based source of food energy in relation to the costs of cultivation. Different varieties of this legume (produced in Japan, China, or the USA) were characterized with various compositions of nutrients (protein and fat), but also different water content – an important factor in miso making. From the 1950s, miso producers started using defatted soybean and soybean grits, being satisfactory to make specific types of miso.
The second ingredient (koji) is made from grains, usually rice or barley. Historically, rice miso was in scarcity due to its reservation for the aristocracy. Nowadays miso based on rice koji is a dominant category produced in Japan. Koji (and resulting miso) made with barley has more deep, earthy notes and is preferred in southern parts of Japan. In Denmark, restaurant Noma and distillery Empirical base their production of fermented food and beverages on barley koji. It is a local grain, easily available and desirably more complex in flavour.
Hatcho miso is exceptionally made with soybean koji. Mixed with cooked soybeans this low-carbohydrates combination requires the longest time in fermentation and is the least popular type of miso.
Salt is the last crucial ingredient in the production of miso paste. The long fermentation process in open vessels allows for exposure of miso to the environment risking cross- contamination and spoilage of the product. Salt allows promoting the growth of the desired lactic acid bacteria while preventing the unwanted microbes from developing. Sodium chloride is used commercially for making miso. Some artisanal miso producers use sea salt for its flavour characteristics.
Different ratios of used salt allow modulating the final product toward more salty or more sweet pastes. Generally, mixtures low in carbohydrates contain 10-14% of salt. Miso with over 30% of the carbohydrates can contain less than 7 percent salt and is sweeter.
Another aspect that determines final miso products is colour. Depending on the type of bean and method of processing (grinding and cooking), different varieties can be produced. Categories of miso differed by colour are presented in the table below.
Red, yellow and white miso pastes are among the most popular categories. Red miso is made through the longest process of fermentation, taking from one to three years. It is rich and deep in flavours, often with a chunky texture. It has a low proportion of carbohydrates and a high concentration of salt. Yellow miso is made with slightly less salt and has a more subtle, tart flavour. White miso (both sweet and salty) is the most popular category of amino pastes. Highest in carbohydrates and lowest in salt, it requires from a few weeks to a few months of aging. The bright colour of miso has been perceived as a standard of high quality and purity of the product. Paradoxically, commercial producers in Japan started adding bleach to cooked beans, deteriorating the quality, yet giving the final product desired appearance.
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Japanese Ministry of Agriculture, F. and F. (2008). Rice and wheat processed food production dynamic statistics survey. Food Self-Sufficiency Rate Report.
Japanese Ministry of Internal Affairs and Communications. (2019). “Ministry of Internal Affairs and Communications household survey”
Shurtleff, W., & Aoyagi, A. (2001). The Book of Miso: Savory, High-protein Seasoning: Vol. II