The miso used in Mitoku Instant Miso Soup is freeze-dried rather than dehydrated. This method of preserving food is possible because under the right conditions water molecules in foods can change directly into a gas without first passing through a liquid phase. This process, called sublimation, involves freezing food under a vacuum, which allows the water to vaporize at a very low temperature. Freeze-dried miso retains an excellent flavor profile, because very little of the fresh taste is lost during the process. Moreover, along with the microorganisms, most of the medicinal components of miso are also preserved, because this type of drying removes water molecules from bioactive compounds without destroying their chemical integrity.
Freeze-dried miso, which is also an ingredient in Mitoku's instant ramen broth, is sometimes called a "space age food," because freeze-dried foods are often used by NASA for space travel. However, this type of food preservation has been used by the Japanese to make snow-dried tofu for hundreds of years. Freeze-dried foods were also a staple of the Peruvian Incas who freeze-dried vegetables at high altitudes in the Andes. However ancient, freeze-drying is a much better way of preserving miso and other fermented foods than simple heat dehydration, which works fine for fruits and vegetables, but greatly reduces the quality of delicate fermented foods.