Sake Pressing: what method to use?

Sake Pressing: what method to use?

Recently one of the youtube channels I follow, SakaguraKaetsu’s channel, has had a few short videos on pressing. Specifically, they have a couple on filling a fune (P1020493.MOV, P1020548.MOV) and a couple showing the Fukurozuri – 袋吊り- drip process (P1020495.MOV, P1020553.MOV). Watching the great care taken to fill the bags with moromi is really impressive. They leave no wrinkles at all in the bags as they lay down one bag at a time; again, very impressive and labor intensive.

As an aside, SakaguraKaetsu’s channel has hundreds of short videos on just about every aspect of the brewing process. Some are very good while others are not, but all in all, their willingness to take these videos and make them available is a huge service to the community.  Back to the topic at hand…

When it comes to pressing, if you want to get the absolute best sake out of a batch you should use the fukurozuri method to produce Shizukazake – 雫酒 – or Shizuku – 雫 – for short. This method is very simple, just fill a bag with the fermenting moromi, tie it up so that it hangs above a collector for the dripping sake and let it drip. The resultant sake, slightly greenish yellow is by no means clear. Time will clear much of this as suspended matter precipitates out of solution. Sake, separated from the kasu (lees) in this manor is the best it can be!

The use of the fune – 槽 – is more common than the use of the fukurozuri method. It was once the main method used for pressing the moromi, shibori – 搾り- but has now been mostly replaced by the Assaku-ki. Fune pressed sake is second to shizuku in quality. It is close though and extracts much more of the sake than can be collected using the drip method. The first extracts of the fune, shown at the end of the second video, is very similar in color and clarity to what is produced in the fukurozuri method. However, what we are looking at in this case is sake only under the weight of other bags of moromi. Eventually a lid will be placed on the fune with a tremendous force used to press down on the lid and squeeze the sake from the kasu.

Joso -上槽 – the more formal name for shibori, is now most commonly done using an assaku-ki -圧搾 機 – press. The most well-known producer of assaku-ki is Yabuta. This method is far more efficient in pressing the sake from the kasu than these other two methods but still maintains a reasonably high degree of quality. There is almost nothing to see when a Yabuta is in use but I did find one video of an active Yabuta and one with the kasu being removed (Yabuta in action, P1000134.MOV). The reason there is nothing to see is because of the way the Yabuta works. It uses air pressure to squeeze the kasu, forcing the sake out through the mesh. The loud noise is the air compressor. Yabuta’s chart on the functioning of their machine is quite informative. For the most part, a pocket between two filters is filled with moromi and a bladder is then filled with air to force the sake from the lees. With the sake removed, the kasu is scraped off the filter and the process is repeated until all the moromi has been processed.

Homebrewers are unlikely to have an assaku-ki available for their use but the other two methods, modified for scale are well within reach. The fact that these methods tend to produce better sake does not hurt either. The only down side is the lower efficiency but in small batch production quality over efficiency is usually a good trade-off.

Measuring your Sake – Part four: Amino San-do (アミノ酸度)

Measuring your Sake – Part four: Amino San-do (アミノ酸度)

In part one I talked about how to measure the Nihonshu-do or Sake Meter Value (SMV) or your sake. In part two I covered how to measure the Arukoru bun (アルコール度数) or Alcohol percent by volume (%ABV). In part three I covered how to measure the sando or acidity of sake. In this part, part 4, I will cover how to measure the amino sando of your sake.

As is the case for measuring the sando, you will need some Sodium Hydroxide (NaOH) solution usually at a concentration of 0.1 Molarity (M), phenolphthalein, a small beaker to mix the sample and chemicals in, and a syringe to measure with. All of this can be purchased as a wine acid test kit. In addition you will need some formalin1 solution. As is the case in measuring sando, you can use the phenolphthalein as an indicator or a pH meter to determine the point at which the pH reaches 8.2.

The method used to measure the amino sando is very similar to the method for measuring sando. In fact, it incorporates the sando method as the first step in measuring the amino sando. This is because amino sando is just a specialized acid that is locked up and hidden in the structure. To measure the amino sando we must first remove or neutralize other acids so that they are not counted along with the amino acids. This is accomplished in the first titration step which determines the amount of base require to neutralize the acid. After our sample solution has been neutralized there are no more extra H+ to worry about and we can focus on how to make the amino acids visible, or at least measurable in some fashion. This is done with a formalin solution. The formalin solution reacts with the amino acid freeing an H+ from each amino acid structure. This free H+ can then be locked up using a base just as we did to measure the acid levels. So, one more round of titration using our base solution, sodium hydroxide (NaOH) will give us the level of base needed to neutralize the newly exposed acid so we can calculate the amount of amino acid as glycin, the simplest amino acid.

If that seems a bit intimidating, don’t worry, we will take it step by step from here.

OK, first we need to measure out 10ml of sample sake to evaluate. Place this in a beaker and add a few drops of phenolphthalein. The drops are not needed if you will use a pH meter. Load the syringe with about 10ml of NaOH and record the exact amount in the syringe for later reference; call it R1.

At this point, it is time to add, drop by drop the NaOH from the syringe to the sample watching for the indicator to change color to a light ping for at least 30 seconds. Swirl the sample after each drop as you go. If on the other hand you are using a pH meter you should gently stir the sample with the meter probe to get a correct reading. Once the color changes and holds its light pink color for at least 30 seconds you have neutralized the sample. Record the NaOH level now present in the syringe; call it R2. The difference between this and the earlier recorded level, (R1-R2) can be used to determine the sando (acidity).

Up until this point the procedure has been the same as measuring the sando. It is at this point that we depart from the sando method. Set the neutralized sample aside for use once we have a mixture based on the formalin ready.

Mix 50ml of formalin with 50ml of distilled water. Using the same titration procedure, neutralize the mixture at a pH of 8.2 or where the indicator turns light pink for at least 30 seconds. Remember to add several drops of phenolphthalein if you are using the indicator. There is no need to record the amount of NaOH used for this procedure.

OK, we are ready for the final step. Measure 10ml of the neutralized sample and 10ml of the neutralized formalin mixture and place in a beaker for a total of 20ml. Reload the syringe with NaOH and record the amount contained; call it R3. If you have been using phenolphthalein there should be enough present without any addition. Titrate this 20ml sample until it reaches neutrality at pH of 8.2 or until the color changes to a light pink for at least 30 seconds. Record the final level of NaOH in the syringe; call it R4. The difference between this and the previous recording will be the amount of NaOH required to neutralize the amino acid; (R3-R4).

Having completed all the measurements, it’s time to calculate the levels. First, as before for sando:

TA(g/L) = MoleRatio* (BaseMolarity * BaseVolume * MoleMass) / SampleVolume


Sando = TA(succinic g/L) = ½ * (0.1M*(R1-R2)ml*118) / 10ml

And similarly for amino acid:

TA(g/L) = MoleRatio* (BaseMolarity * BaseVolume * MoleMass) / SampleVolume


Amino Sando = TA(glycin g/L) = 1 * (0.1M * (R3-R4)ml * 75) / 20ml

Where the BaseMolarity is the concentration (moles / liter) of NaHO in distilled water, BaseVolume and SampleVolute are the amounts of NaHO and Sample solutions in ml.

Succinic acid, along with malic and lactic acid are the most abundant acids in sake. As discussed in part three, succinic acid has a reaction ratio, MoleRatio, with NaOH of 1:2 giving rise to the ½ in the Sando equation. The amino acid glycin reacts with NaOH in a 1:1 reaction giving rise to the multiplier 1 in the Amino Sando equation.

The molecular mass (MoleMass)of succinic acid is 118 while the molecular mass of glycin is 75. As you see, these have been substituted in the equations above.

Using a pH meter can be slower and more tedious than using phenolphthalein but the pH meter will be more accurate. In either case, any amount that you are off on any of the titration steps, first for sando, second for formalin or the final step for amino sando, will throw off the following step or be thrown off by the previous steps; that is, the error will accumulate with each step.

Another thing that should be understood and kept in mind when working with NaOH is that its concentration will change over time. NaOH reacts with CO2 in the air neutralizing its base character.  You can use Hydrochloric acid (HCl) to determine the strength of the NaOH solution. HCl is stable so, while NaOH is changing, HCl will remain constant and able to measure the new/ current strength of the NaOH concentration using the same titration methods used above. Maybe I will discuss this in more detail in a future article. [12-10-11, well I added a post on this. You will find it here]

Well, there you have it, the procedure to measure the sando and amino sando of your sake.

  1. Formalin is a saturated solution of formaldehyde at 40% by volume or 37% by mass.

Sake Filtering – Is this Muroka (無濾過)?

Sake Filtering – Is this Muroka (無濾過)?

OK, so the bodai moto based sake I am working on, rested for about 1 month after pressing. Normally, I would have racked it after a couple of weeks but the lees were just not dropping out. I have not had a sake that was so slow to drop its leas before. After one month the sake appeared as in the picture below:

Bodai-moto One Month After Pressing
Bodai-moto One Month After Pressing

Not very encouraging in turns of being able to recover a large percentage of the sake as clear sake. Anyway, I had been thinking about filtering sake and thought that this maybe a good batch to give it a try with. You may recall that the fermentation went very slow and I pressed it too early despite it having had more time to ferment than most. The moromi went through stages of smelling like green apples, strawberries and finally banana’s. These aromas have been very strong and are very evident the minute I open the cooler. At one month after pressing the banana aroma continues to be very strong; Ginjo-ka on steroids.

The equipment I used for filtering consists of a 5 gallon Cornelious keg, and a plate filter with a 7 micron filter paper. I also have 3 micron and 1 micron filter paper but I was afraid that the filter would clog and I would lose too much sake. As it turned out the filter was very close to being clogged if not actually clogged at the end of pushing about one gallon of sake with leas through it. The following picture shows the front and back sides of the 7 micron paper filter and the back plate of the filter housing. Continue reading “Sake Filtering – Is this Muroka (無濾過)?”

New Page on Koji Making with Video

New Page on Koji Making with Video

OK, so I have finally pulled together a complete page on making koji for sake brewing along with the videos. As with the videos for brewing sake there is nothing amazing here but that may, in fact, be the amazing thing. When it comes to making koji, like brewing sake, it is all very doable.

I believe the text for the koji making page is very readable and stands on its own without the videos. However, the videos may help to solidify what is said in the text. All in all I hope you find the page useful and enlightening!

Oh, FYI, I have linked the koji making  page into the top of the Recipe page for convenience.


Measuring your Sake – Part Three: San-do (酸度)

Measuring your Sake – Part Three: San-do (酸度)

In part one I talked about how to measure the Nihonshu-do or Sake Meter Value (SMV) or your sake. In part two I covered how to measure the Arukoru bun (アルコール度数) or Alcohol percent by volume (%ABV). In this part, part three I will discuss how to measure the san-do or acidity of sake.

To measure the san-do (acidity) of sake at home, there are two very closely related methods available. The easier and less expensive of the two methods is to use a wine acidity test kit. This kit contains almost every think you need to measure the acidity on sake. However, there is a difference getting from the physical test to the interpreted value, but I am getting a little ahead of myself. The second method differs from the first in that a pH meter is used rather than Phenolphtalein to determine the point of neutrality. Often the second method employs more sophisticated equipment for each of the components but this is not strictly necessary.

So, what do wine acid test kits come with? Well, they come with a small beaker to mix the sample and chemicals in, a syringe to measure with, a solution of Sodium Hydroxide, usually at a concentration of 0.1 Molarity (M) and Phenolphtalein. The idea behind the test is that we have some unknown amount of acid in our sample that we want to measure. To do this we add a known amount of base to neutralize the sample pH. When we have neutralized the sample pH with a known amount of base we can then work out the original amount of acid. Clear as mud? Perhaps an example will help.

Continue reading “Measuring your Sake – Part Three: San-do (酸度)”

Measuring your Sake – Part Two: Percent Alcohol by Volume

Measuring your Sake – Part Two: Percent Alcohol by Volume

In Part One we talked about measuring the SMV (Nihonshu-do) of your sake. In this part we will discuss two ways to measure the percent alcohol by volume for your sake. Because Heikou Fukuhakkou (並行複醗酵) or multiple parallel fermentation is used to make sake, we cannot employ the same simple method for determining the percent alcohol as is used for other fermented beverages. In particular, the simplest methods used for both beer and wine depend on knowing the initial specific gravity prior to fermentation. For sake, there is no point prior to fermentation when all the sugar is available for such a measurement. Rather, koji enzymes work side by side with yeast in the fermenting mash. Enzymes create sugar and yeast creates alcohol using the sugar; this is multiple parallel fermentation.

The first way to measure the alcohol level we will discuss uses what is known as the boiling method. It is a modified version of the distillation method that can be done at home with relative ease. The basic idea behind this method is that the alcohol in sake has a known specific gravity and a known effect on the specific gravities of substances it is in. Given this we can measure the specific gravity of our sake to get an initial state, replace the alcohol with distilled water and then take a new specific gravity reading. The difference between these two specific gravities can then be used to determine the percentage of alcohol by volume.

Continue reading “Measuring your Sake – Part Two: Percent Alcohol by Volume”

Measuring your Sake – Part One: the Hydrometer and SMV

Measuring your Sake – Part One: the Hydrometer and SMV

In this series on Measuring your Sake I will cover how to measure all the key characteristics of sake. These include:

–          Nihonshudo a.k.a. Sake Meter Value (SMV) and specific gravity
–          Alcohol percentage by volume
–          Sando or Acidity
–          Amino Sando or Amino acid levels

For Nihonshudo or SMV all that is needed is a hydrometer. The most commonly available hydrometers are for specific gravity though you can find other metrics. To simplify this discussion I will stick to specific gravity and SMV. A discussion of these other metrics is in the article: Nihonshu-do (日本酒度) or Sake Meter Value (SMV).

So, what are we talking about when we talk about specific gravity? Well, specific gravity is a measure of the density of a liquid compared to the density of distilled water at 60F. But what does that mean?

Continue reading “Measuring your Sake – Part One: the Hydrometer and SMV”

Time for shibori ( 搾り)

Description of the sake pressing process (shibori).

After the moromi (main ferment) has come to the stage where the ferment has run its course or it is time to stop it from going any farther, it is time for shibori; that is the pressing or squeezing of the moromi to separate the lees from the sake. This is mainly done in three different ways in kura (breweries) today and probably more ways than Sunday by homebrewers.

The most common way to press is to use a machine called Assaku-ki often referred to as a Yabuta; the name of the main supplier of assaku-ki machines. The moromi is pumped into these machines where it is squeezed by an air bladder to force the sake through a fine mesh that holds back most of the lees. As the lees build up on the mesh more and more of the lees are held back because the lees themselves become a part of the filter. In the most common configuration, the filtering action is so good that it filters out the yeast as well as the lees and hence stops all further fermentation. Continue reading “Time for shibori ( 搾り)”

Making Koji for Sake

Making Koji for Sake

In order to make koji for brewing sake we need to go through the same steps that we do to prepare rice for brewing sake. In fact, it is often the case that a portion of the rice goes directly into the brewing sake while another portion is used for koji. So, as always we begin by washing the rice. This is to remove all contaminates, including the powder (Nuka) that remains after milling and any material added by the miller, like iron. Removing the nuka lowers the stickiness we will have after steaming. And, as mentioned elsewhere, iron is very bad for sake as it darkens the sake and speeds a reaction of residual sugars with amino acids that harms the flavors and aromas.

Washing the rice is followed by steeping the rice until we reach the desired water uptake level, usually between 25% and 35%. If the uptake of water is too little the rice will not steam properly leaving a hard uncooked center that the koji mold will not penetrate. On the other hand having too much water uptake will cause the rice to be too mushy and sticky after steaming. This results in a base that is too easy for the koji mold to penetrate and this prevents or lowers the production of transformative enzymes we want. Most rice used for hombrew sake will need to steep between 30 minutes and two hours. As homebrewers we are more often than not more guilty of soaking too much than too little. Continue reading “Making Koji for Sake”

Protecting your HomeBrew Sake from light

Protecting your HomeBrew Sake from light

Sake, as with other beers, is sensitive to light and in particular ultraviolet light. Sunlight is the greatest offender having a much higher degree of ultraviolet light than most other sources. This is not to say that other sources are harmless, they can have a negative impact as well. Given that sake can be harmed by this light and light is all around us, what can we do to keep our sake safe from this harm?

We can choose to use bottles that have the best properties for filtering the light and specifically the ultraviolet light. Fortunately for us, Bradley E. Sturgeon, PhD1 recently did a study that examined which colors of glass bottles provide the best light filtering. Continue reading “Protecting your HomeBrew Sake from light”

  1. Bradley E. Sturgeon Supplemental paper to Basic Brewing Episode Airing April 10th 2008