There is a lot to be said for Honjozo. It tends to be light and fragrant and can be exceedingly smooth. I was ecstatic with the first honjozo I tried. It was the Murai Family Tokubetsu Honjozo, light and smooth, fragrant but disappeared like a ghost. Very nice. Since then I have had other honjozos but this one remains one of my favorites.
Honjozo is a Special Designation Sake just as Junmai, Junmai Ginjo and Junmai Daiginjo. In fact Ginjo and Daiginjo without the Junmai designation are both honjozo. You can think about these special designation sakes as having three grades of Junmai (pure) and three parallel grades of Honjozo (brewer’s alcohol added). The top rung, Daiginjo, is one where the rice used has been milled to 50% or less with one pure and the other with added alcohol. The next rung, Ginjo, is with the rice milled to 60% or less with one pure and the other with added alcohol. Finally the entry rung to the special designation sake is Junmai (pure) and Honjozo (brewer’s alcohol added). When this system was put in place, to make this entry rung, the rice used had to have been milled to 70% or less. While this is still true for Honjozo, the milling requirement has been remove for Junmai.
In addition to the milling rate requirement, Honjozo is limited in the amount of alcohol that can be added. This is in stark contrast with Sanzo and Futsu which, by far have the greatest sales. The amount of alcohol for special designation sake is limited to 10% of the total weight of the white rice used.
Note: The specifics being spelled out with the term white rice is unclear to me. It may indicate the weight of the rice when milled to a specific seimai buai like 90% or it may mean the weight of the rice after all milling has taken place. Also, I believe that this includes the rice used to make koji as well. However, only when I assume that weight is limited to the actual weight of rice (excluding koji) can I reconcile with Philip Harper’s statement that this limits the added alcohol to less than a quarter of the total alcohol. If you know how it really is, please let me know. UPDATE: John Gauntner confirmed that all rice (regular steamed and koji) is included in this measure.
So, now that we know what it is that we like so much, how can we make our own Honjozo? Well, as you might guess it is very similar to how you brew Junmai sake. The only real difference is that we need to add the brewer’s alcohol just prior to pressing. The pure alcohol helps to draw out the aromas from the lees during pressing so the end product retains more of the fragrance. One other difference is the volume of water used to adjust the sake to have the desired alcohol level will also need to be adjusted.
The additional amount of alcohol and water thin the sake, leaving acid and amino acid levels lower than they normally are for a Junmai. While making the sake easy to drink it can also throw off the balance of the sake if too much alcohol is added. This is of course the art of the addition. Just how much should you add? Trial and error will get you to the amounts that you like the most. However, assuming you want to make a Honjozo and not just another sake you will need to stay within the milling rate and alcohol addition limits as defined. Using the most conservative assumption about the definition (and the one that agrees with Philip) we can calculate the maximum amount of alcohol you can add just prior to pressing.
I will assume you are using the recipe at: https://homebrewsake.com/recipe/ and using rice milled to at least 70%. With this we have 10 lbs. of milled rice and we will ignore the rice used to make koji. This gives an upper bound of 1 lb. of alcohol that can be added. A pound of alcohol is equivalent to 0.15 Gallons which is 4.9 cups. OK, so we can add up to 4.9 cups of alcohol and still have a Hanjozo. This all seems strait forward enough; now, where to get the alcohol. Pure alcohol is not easy to come by. A good substitute is Vodka, especially if you are planning to make a standard sake, one that is adjusted to have an alcohol content of around 16% ABV. An easy to find, 80 proof, Vodka will have 40% alcohol with the rest water. Dividing 4.9 cups by the 40% alcohol gives the amount of Vodka needed, 12.3 cups. Using this much will add 7.4 cups of water (~59.oz).
This is a lot of water to be adding, but is it too much to hit 16% ABV? Well, let’s assume we get 2 gallons at 20% ABV. This means we have .4 gallons of alcohol. To bring .4 gallons of alcohol down to 16.5% we need the amount of sake indicated by alcohol/16.5% or (0.4 / 16.5 = 2.42Gallongs). Taking the difference between this and what we have, 2 gallons, we find that adding 0.42 gallons of water (6.72 cups). However, because we are looking at adding 4.9 cups of alcohol we should have used this combined with the .4 gallons we have. Together this gives 0.7 gallons of alcohol. 0.7/16.5% = 4.28 gallons. Now the difference is 2.28 gallons. Given this there is no problem in adding 7.4 cups of water in the Vodka. In fact we will need to add much more than this to hit the target of 16.5% ABV. Not only will we have a nice Honjozo we will have a little less than twice as much sake.