Pickles of the World: Why Does Suguki Become Sour in the Kyoto Winter?

Around December, when the Kyoto winter truly deepens, if you visit a pickle shop in places like Nishiki Market, you will see rows of uniquely rounded turnip pickles, freshly taken from barrels and glowing with an amber hue. This is suguki, a seasonal tradition of Kyoto's winter. While suguki is counted among the "Three Great Pickles of Kyoto" alongside senmaizuke and shibazuke, what sets it apart from the other two is its "intense, refreshing acidity."

The only ingredients are "sugukina," a traditional Kyoto vegetable, and salt. No seasonings like vinegar are added at all. Even more mysterious is why such intense lactic acid fermentation occurs in the freezing Kyoto winter, where lactic acid bacteria should not be active. Breathing within this process is an extremely unique thermal fermentation technique known as "tenbin-shibori" (lever pressing) and the use of a "muro" (chamber), which were devised and stubbornly protected by the priests of Kamigamo centuries ago. In this article, we will explore the charm and science of suguki, a traditional fermented food that is the pride of Kyoto and a closely guarded secret.

1. Introduction: A Fruity and Sharp Acidity Overflowing from Amber Flesh

Those who eat suguki for the first time will be amazed by its sharp, sophisticated acidity, reminiscent of citrus, the moment they put a slice in their mouth.

And its texture is also exceptional. The flesh of the whole-pickled sugukina is tightly firm, and every time you bite into it, a light "crunch, snap" sound resonates. Furthermore, from deep within the fermented fibers, the subtle sweetness inherent to the turnip and the savory flavor of aging drawn out by the salt gradually seep out.

This acidity, which is not an artificial coating of seasonings but rather overflows with vitality from within the vegetable, is the true essence of suguki. We will unravel the mystery of this supreme fermented delicacy that calls for hot tea and white rice, born precisely because of the biting winds of a Kyoto winter.

2. Suguki Born from History and Climate

The history of the birth and spread of suguki is deeply intertwined with the religious mysticism of the Kamigamo region of Kyoto and the memories of a strict class society.

Kamigamo Shrine and the "Shake" (Shrine Priest Families) Secret

The raw material for suguki, "sugukina," is a type of turnip and an indigenous variety that has been cultivated only in the fertile sandy soil of the Kamo River basin in Kamigamo, Kyoto.

The history of making suguki is ancient, passed down from the Momoyama period through the Edo period by the "Shake," the families of priests at the World Heritage site Kamigamo Shrine. At the time, the production of suguki was permitted only within the residences of the Shake, and the method was considered a "secret" passed down to only one child. The suguki made in this way was used as a high-class "gift" for the Imperial Court, court nobles, and temples and shrines. It was a pickle that was "not to be taken out," strictly forbidden for commoners to eat, and even the seeds were strictly prohibited from being taken out.

Since the Meiji era, with the collapse of the Shake system, the traditional manufacturing method was passed on to local farmers, and it finally became widely available for sale. However, even today, only a limited number of farmers in the Kamigamo district continue to protect the traditional method.

3. The Science of Sugukina Transformation: The Mechanism of Lever Pressing and Thermal Fermentation

The process of causing powerful lactic acid fermentation with only salt and sugukina in a freezing land, and creating that unique texture, involves a precise combination of physical dehydration and thermal management.

Limit Dehydration via "Tenbin-shibori" (Lever Pressing)

After harvesting, the sugukina is peeled and undergoes "arazuke" (rough pickling), which is the first salting. After that, it enters the "tenbin-shibori" process, which is the greatest feature of suguki.

This is a huge, uniquely Japanese pressing device that uses the principle of leverage by using the end of a thick log as a fulcrum and hanging heavy river stones on the opposite end. Sugukina are lined up in a barrel without gaps, and the powerful pressure of the lever is applied to squeeze out the moisture over the course of a night. This physical high pressure causes the cell walls of the sugukina to tighten to the limit, squeezing out the moisture. This is the scientific factor that creates the dense, "crunchy" texture that pushes back when you bite into it.

The Magic of Thermal Lactic Acid Fermentation via the "Muro" (Chamber)

From December to January, when suguki production reaches its peak, temperatures in Kyoto drop to near freezing. General lactic acid bacteria (with an optimal temperature of 30°C to 40°C) stop working in such cold conditions. Therefore, the squeezed suguki is placed in a barrel inside a special greenhouse called a "muro" (formerly charcoal fire or rice straw, now electric heaters).

The temperature inside the room is kept at about 35°C to 38°C, and it is heated there for about one week to ten days. This "artificial thermal environment" causes the wild lactic acid bacteria attached to the sugukina to proliferate explosively all at once. Through this thermal fermentation, the sugar in the turnip is rapidly broken down into lactic acid, the pH drops sharply in a short period, and a refreshing acidity is completed.

The Vitality and Health Benefits of 'Labre Bacteria'

In 1993, a groundbreaking vegetable lactic acid bacterium was discovered within suguki. It is known as 'Lactobacillus brevis subsp. coagulans' (commonly referred to as Labre bacteria).
Because Labre bacteria have survived the harsh environment of suguki, which has a high salt concentration and extremely high acidity, they possess very tough characteristics. It has been scientifically proven that they can withstand strong digestive fluids such as human gastric acid and bile, reach the intestines alive, improve the intestinal environment, and boost immunity (such as by promoting the production of interferon), which has led to suguki gaining significant attention as a health food.

4. The Role of Suguki in Local Dining: Kyoto's 'Bubu-zuke' Culture

Suguki is treated as a top-tier 'kono-mono' (pickle) in traditional Kyoto dining and high-end restaurants.

The Star of 'Bubu-zuke' (Ochazuke)

In the ochazuke known as 'bubu-zuke' in Kyoto, suguki is an indispensable element.
Well-chilled suguki is finely chopped (kizami-suguki), placed on top of warm rice, and hot bancha or hojicha tea is poured over it. The sharp acidity of the suguki and the natural sweetness of the turnip combine with the savory aroma of the tea to refresh the palate, making it easy to eat bowl after bowl of rice. People in Kyoto also eat the leaf part of the suguki (ha-suguki) finely chopped together with it. The leaf part has an even stronger acidity than the flesh, with a unique bitterness that is a more mature flavor.

The Conclusion of Taste in Kyoto Cuisine

At the end of a Kyoto kaiseki meal, when rice and red miso soup (tome-wan) are served, suguki is presented on an elegant small plate alongside senmaizuke and shibazuke. It serves as the perfect piece to cleanly tighten the lingering richness of the delicate dishes that came before it and to beautifully conclude the meal.

5. Recipe and Safety Management for Home-Made Suguki-Style Turnips

While it is difficult to prepare authentic suguki greens or a traditional 'muro' (fermentation room) at home, you can safely make delicious 'suguki-style warm lactic acid fermented turnips' by using 'small turnips' or 'daikon radish' available at supermarkets and utilizing home heating appliances (ovens, rice cooker warming functions, yogurt makers, etc.).

For Home Use: Suguki-Style Turnip Warm Lactic Acid Fermentation Recipe

【Ingredients】

• Small turnips (or daikon radish): 2-3 pieces (approx. 500g)

• Coarse salt: 25g (5% of weight)

• Turnip leaves: A small amount (finely chopping and adding them makes it authentic)

【Steps】

1. Preparation and Rough Pickling: Peel the turnips and cut them into wedges (or bite-sized pieces). Place them in a bowl and rub the salt into them thoroughly. Put them in a bag such as a Ziploc, place a weight (such as a plastic bottle) about twice the weight of the turnips on top, and leave them overnight to thoroughly draw out excess moisture.

2. Alternative to Tenbin-shibori (Pressing): The next day, discard the moisture that has come out of the bag, wrap the turnips in paper towels, etc., and squeeze them firmly by hand, removing as much moisture as possible.

3. Warm Fermentation (Recreating the Muro): Place the squeezed turnips into a clean, heat-resistant airtight container or Ziploc bag.

   • Fermentation Method: Set it in a yogurt maker (set to 35°C), or use the warming function of a rice cooker (*adjust by opening the lid slightly so the temperature does not exceed 40°C), and maintain a temperature of 35°C to 38°C and warm for about 36 to 48 hours.

4. Checking Taste and Aroma: If a slightly sweet and sour yogurt-like aroma drifts and the turnip flesh has become slightly translucent, it is proof that the lactic acid fermentation was successful.

5. Cooling and Maturation: Once finished, place in the refrigerator immediately and let it cool before serving. It can be stored refrigerated for about one week.

Safety Management and Precautions at Home

The process of heating to ferment carries the risk of explosively increasing miscellaneous bacteria and putrefactive bacteria (especially Bacillus cereus, which is common in leaf mold) if temperature control is handled incorrectly.

• Strict Temperature Control: If the fermentation temperature exceeds 42°C, the lactic acid bacteria will die; conversely, if it is below 25°C, fermentation will not progress, resulting in simple salting, from which putrefaction will proceed. Please maintain the 35°C–38°C range accurately.

• Importance of Salt Concentration: In accordance with traditional methods, the salt concentration is set relatively high at about 5%. If the salt concentration is too low, "butyric acid fermentation" will occur during heating, causing a strong foul odor (the smell of a rotten rice bran bed) or off-flavors.

• Disposal Criteria:

  • If, during or after heating,a foul odor like a dirty rag or a seweroccurs (this is clearly different from the sweet and sour aroma of lactic acid fermentation).

  • Ifwhite, green, or black moldappears on the inside of the container or the surface of the turnip.

  • If the turnip flesh has melted into a mushy, soft state.
    If any of these signs are present, lactic acid fermentation has failed and harmful bacteria have proliferated, so please do not eat it under any circumstances and discard it.

6. Summary: The Wisdom of Food Culture Told by a Small Dish

Suguki is a unique wisdom of thermal fermentation born from the cool climate of Kamigamo, Kyoto, and the prestigious historical background of the shrine families. It is a sophisticated traditional technique that tightens the tissue through physical pressing called "Tenbin-shibori" (lever pressing) and explosively multiplies wild lactic acid bacteria (Lactobacillus brevis) through an artificial thermal environment called a "muro" (chamber).

Its sourness is not a chemical seasoning from vinegar, but the acidity of living lactic acid itself, created by robust vegetable lactic acid bacteria decomposing natural sugars. When we learn and reproduce this "mechanism of heating and pressing" in a modern, clean kitchen, we are benefiting from the great wisdom of dialoguing with nature and controlling microorganisms that the Shinto priests of Kyoto once carefully kept hidden.

References and Sources

• Kyoto Prefectural Agriculture, Forestry and Fisheries Technology Center, "Historical Changes and Manufacturing Survey of Kamigamo Suguki"

• Yoshida Kosan Bio Research Institute, "Survival Characteristics and Functionality of Lactobacillus brevis Derived from Suguki Greens"

• Japan Society for Food Microbiology (Supervised), "Microbial Control Effects of Heating Processes in Fermented Foods"

• Search keywords: "Suguki recipe," "Suguki Kyoto," "suguki pickle," "Kamigamo Suguki."

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