The Right Temperature

The kombu should be removed from the pan when small bubbles begin to appear in the water. The temperature of the water at this stage is 60-65°C, which is an ideal temperature at which to stop applying heat. If heated to a higher temperature than this, unwanted substances contained within the kombu will begin to emerge into the dashi, tainting its quality. Notably, the polysaccharides which give the kombu its glutinous texture, the aldehydes and sulphates with their distinctive smells, and minerals, especially iodine, which become scum on the surface of the dashi, all have a tendency to come out when the kombu is heated excessively. This temperature of around 60-70°C is also ideal for adding the bonito flakes. At this temperature, the complex natural fragrance of the bonito flakes, which is actually made up of over 200 different kinds of organic acids, organic bases, alcohols, phenols and so on, will not be lost through evaporation. It also prevents the release of those elements contained in the bonito flakes which give unwanted pigments, unpleasant smells or stand in the way of the umami taste.