The Path to Pasteurization: Why I Finally Decided to Pasteurize After Years of Sticking to Unpasteurized Sake and Bag-Dripping

Our brewery has held the policy of "no pasteurization" since before we even started making sake.

My philosophy for brewing sake was to deliver it to customers in its most natural state, with as little intervention as possible, by focusing on unpasteurized, unfiltered, and bag-pressed sake.

However, we are now finally ready to take the step of pasteurization.
I will frankly explain from the brewery's perspective why now, and what challenges we have overcome.

What is pasteurization? The difference from unpasteurized sake

Pasteurization (hiire) is the process of heating sake to about 60-65℃ for low-temperature sterilization.

By stopping the activity of lactic acid bacteria and enzymes, the sake quality becomes stable, and long-term storage becomes possible.

Most of the sake found on supermarket and liquor store shelves has undergone this pasteurization process.

On the other hand, sake that has not been pasteurized is called unpasteurized sake (namazake).

Raw doburoku, with its live enzymes, is characterized by a fresh and delicate flavor, but it is very sensitive to temperature changes, and fermentation continues even after bottling.

The best-by date for refrigerated storage is approximately 2 weeks. It is recommended to avoid storage at room temperature and to consume it as soon as possible after opening, but you can also enjoy the gradual changes it undergoes.

Some customers even prefer unpasteurized sake that has been left for about a month, allowing lactic fermentation to progress naturally, adding a subtle sourness.

While often described as "having turned sour," this is not a sign of the sake spoiling, but rather a unique characteristic of living sake.

However, this is an extremely rare case.

Reasons for avoiding pasteurization

To be honest, I initially had no intention of pasteurizing.

There were several reasons for this.

Firstly, we did not have the necessary pasteurization equipment.

Pasteurization requires specialized equipment, which represents a significant investment for a small individual brewery.

While heating in a hot water bath after bottling is common, there's a risk of bottles cracking during the rapid cooling process after heating.

This was a concern.

Secondly, we had experience that sake could be preserved sufficiently without pasteurization.

We had confirmed that bag-pressed sake could be stored long-term as unpasteurized sake by thoroughly managing refrigeration.

Thirdly, I disliked the change in flavor caused by pasteurization.

Adding the process of heating changes the delicate flavor of the sake, and I did not want to compromise the original taste of sake that had been meticulously brewed.

Compatibility of Bag-Pressed Unpasteurized Sake and Pasteurization: Hydrogen Bonds Hold the Key

What we prioritize most is sake pressed using the bag-pressing (fukurozuri) method.

This method involves putting the moromi (fermenting mash) into bags and hanging them, allowing the clear sake to drip out naturally by gravity alone.

Since no pressure is applied, it results in a very fine, delicate flavor without any off-flavors.

We have particularly avoided pasteurizing this bag-pressed unpasteurized sake.

The reason lies in hydrogen bonding.

The alcohol (ethanol) and water molecules in sake are loosely connected by hydrogen bonds.

These bonds contribute to the smoothness on the palate and reduce the sensation of alcohol as an irritant when consumed.

When sake undergoes heat treatment for pasteurization, some of these hydrogen bonds are broken, making the alcoholic sensation more prominent.

In short, pasteurization enhances the pungent taste of alcohol.

The delicate sweetness and umami of bag-pressed sake would be overshadowed, making all the effort in brewing go to waste.

After all, the unpasteurized state is the most delicious.

In fact, with proper refrigeration, bag-pressed unpasteurized sake can be stored for a long time.

Although not our brewery, there is a fact that another brewery using the same bag-pressing method has sake brewed seven years ago that is still being properly stored, which proves this.

 

 

Finally, a breakthrough: The idea of pre-bottling pasteurization

So, why have we decided to proceed with pasteurization now?

One reason is a growing desire to reach more customers.

Unpasteurized sake with a two-week shelf life is fine for local customers and direct sales, but when it comes to shipping long distances or using it as a gift, restrictions inevitably arise.

However, the biggest hurdle was the equipment.

The conventional method of pasteurization involves heating the bottles in a hot water bath after filling. However, rapidly heating and cooling glass bottles carries the risk of breakage due to temperature differences.

Preventing this requires rapid cooling equipment and precise temperature control, making a large-scale equipment investment unavoidable.

That's when it occurred to us: "Why not pasteurize before bottling?"

Heat-sterilize the sake while it's still in liquid form, then bottle it once it has cooled.

This eliminates the thermal stress on the bottles, significantly reducing the risk of breakage.

It also avoids the need for large-scale equipment like commercial pasteurizers, allowing for implementation on a compact scale.

You might think, "Why didn't they think of this before?" but because we had always approached it with the premise of "no pasteurization," we hadn't deeply considered the methodologies.

The moment we challenged that premise, the solution turned out to be surprisingly simple.

Another major hurdle: The doburoku bottling problem

As soon as the pasteurization policy was decided, another problem also showed signs of resolution.

That was bottling.

Doburoku is a cloudy fermented sake with rice grains remaining.

Due to its high turbidity and viscosity, bottling it by hand was extremely troublesome.

For sake bottling, if the number of bottles is small, it's quicker to do it manually than to set up a machine.

When bottling manually, a funnel is used, but with doburoku, the rice grains would clog it, stopping the work.

If you force it, foaming and splashing occur.

I keenly felt the need for a dedicated machine for bottling doburoku.

We considered commercial bottling machines (filling machines), but those for sake were not compatible with doburoku grains, and dedicated doburoku machines were too expensive to afford.

Therefore, we decided to build our own bottling machine.

The structure of the filling nozzle adapted to doburoku's characteristics, the flow path design to prevent grain clogging, and the selection of materials to ensure hygiene - there are many challenges, but like the pasteurization equipment, we are seeing a breakthrough.

Building this bottling machine ourselves is an unavoidable step in establishing a sales system for doburoku.

Which is the right answer, unpasteurized or pasteurized?

Enjoying it within a two-week shelf life, under refrigeration.

That freshness and delicacy are the true essence of bag-pressed unpasteurized doburoku.

We position pasteurized sake as a separate product line, offering a different way to enjoy it than bag-pressed sake.

For those who want to give it as a gift, enjoy it gradually for a longer period, or store it at room temperature.

Pasteurization exists to meet such needs.

We aim to be a brewery that can be closer to our customers' lives, utilizing the strengths of both unpasteurized and pasteurized sake.

Will taking a step towards pasteurization lead to new encounters?

My reluctance to pasteurize was by no means in vain.

Precisely because I was so dedicated to unpasteurized, unfiltered, and bag-pressed sake, I came to understand what pasteurization changes and what it doesn't.

The discovery of pre-bottling pasteurization, and the plan to build our own doburoku bottling machine.

Both are the result of a small brewery paving its own way with its own hands.

To not make large capital investments, not lose sight of the essence of brewing, and to remain honest with our customers.

That stance remains unchanged.

We will announce the release date of our pasteurized products on this blog again.

Thank you for your continued support.