With an index of 240 ppm, Honjuku water is particularly hard for Japan. This figure may not mean much to you, but it directly determines the quality and originality of the products from the brewery we wanted to talk to you about today, the Iwase Shuzo brewery.


Founded in 1723 in the coastal area of Chiba, Iwase Shuzo is recognized by sake connoisseurs as being out of the ordinary, precisely because of the water used in its production.


Through two emblematic references, Iwanoï sakes, we invite you to find out a little more about this parameter.

Why is Onjuku water so hard ?
The water used for brewing is drawn from the immediate underground reserves of the Chiba coast. Before accumulating in aquifers, this water has passed through the shell mounds found in large numbers in this coastal region.
Called Kaisou (貝層) in Japanese, it corresponds to a stratum rich in mollusc shells. Over time, the shells dissolve and release calcium carbonate, making the soil more calcareous. The water passing through this environment becomes loaded with minerals, reaching a degree of hardness considered one of the highest in Japan.

Water hardness
This corresponds to the quantity of calcium and magnesium ions dissolved in a liter of water. Water containing high levels of these ions is said to be “hard”. Conversely, water containing low levels is “soft”.
Most water in Japan is soft, while in Europe and North America, water is more mineralized, and therefore harder.

What does i240 mean ?
240 ppm is the hydrometric titre of the water in question. It corresponds to 240 mg of limestone per liter of water. To measure it, determine the amount of calcium and magnesium present, then perform the following calculation :
Titre hydrométrique = (quantity of calcium x 2.4) + (quantity of magnesium x 4)

Hard water and fermentation
The minerals present in large quantities in hard water promote yeast growth and enzymatic activity, accelerating the fermentation process. The end result is a sake with a stronger, richer, drier taste (conversely, fermentation with soft water generally produces a sake with delicate flavors, which is lighter and rounder on the palate).

Iwanoi i240 sakes

Yamahai Junmai Ginjo Nama Yamadanishiki

The nose is rather pronounced, with lactic, yogurt, yeast and candy notes. As soon as it hits the palate, a pleasant sensation of mellowness emerges. This is followed by a rise in intensity accompanied by lively alcohol peaks and, above all, high acidity. A superbly balanced sake with a creamy, spicy finish, bitterness and tension.

Best served chilled (8°C), with fish, shellfish, seafood or vegetables.

Junmai Ginjo Nama Gohyakumangoku

A sweet nose, marked by notes of strawberry candy, rice and mochi. The attack on the palate is fairly light. It quickly gains in strength and liveliness, as this is a nama, an unpasteurized sake. The finish is long, emphasizing the herbaceous side and adding a nice freshness.

Pairings : A sake that gains in strength and vivacity once on the palate, it's best served chilled (8°C), with small blue fish such as horse mackerel, sardines or mackerel.