Nabak Kimchi: The Watery Probiotic Kimchi of Korea

Nabak kimchi is a traditional Korean watery kimchi, known as mul kimchi, distinguished by its refreshing broth and mild, balanced flavor. Unlike the pungent, spicy baechu kimchi made with napa cabbage, Nabak kimchi features thinly sliced radish and napa cabbage as primary vegetables in a vibrant, often pinkish orange liquid. It is a seasonal variety, most commonly prepared in spring and autumn, offering a lighter probiotic alternative to the heavier, fully fermented winter kimchis. The name Nabak is believed to derive from nabok, the Korean pronunciation of the Chinese character for radish, reflecting its central ingredient. This kimchi serves as a versatile banchan side dish and is also poured over cold noodles such as naengmyeon or eaten alongside tteokguk rice cake soup during the Lunar New Year celebrations.

Cultural Roots, Ingredients, and Probiotic Profile

Cultural Roots

Nabak kimchi has been prepared for centuries across the Korean peninsula, with particular prominence in the Chungcheong province. Historical records from the 1400s describe a proto version of this dish, while cookbooks from the 1700s and 1800s show the addition of red pepper powder and aromatic spices like ginger and garlic. Unlike dongchimi, a winter radish water kimchi, Nabak kimchi is considered a fast kimchi, or fast food kimchi, designed to ferment quickly and be consumed within days rather than months. It is often made in large batches for festive occasions, including the Lunar New Year and major ancestral rites called jesa, where it fulfills the requirement for a chae, or pickled vegetable side dish.

Raw Ingredients

The key components for a standard batch of Nabak kimchi include:

Korean radish (mu): The primary ingredient, peeled and sliced into thin, flat squares approximately 2 by 4 cm.

Napa cabbage (baechu): Cut into similarly sized square pieces, contributing sweetness and texture.

Korean red pepper powder (gochugaru): Provides the characteristic color and mild heat, suspended in the broth.

Aromatic vegetables: Finely minced garlic and ginger, along with chopped green onions.

Water parsley (minari): An optional addition that imparts a fresh, herbal note.

Brining liquid: Filtered non chlorinated water and coarse sea salt (cheonilyeom).

Sweetener: A small amount of sugar, honey, or sliced apple or pear to balance flavors.

Probiotics Isolated from Nabak Kimchi

The microbial ecology of Nabak kimchi is distinct from other kimchi varieties due to its high moisture content and specific vegetable composition. Scientific studies have identified the following lactic acid bacteria (LAB) and microbial groups during its fermentation:

Leuconostoc mesenteroides

Lactobacillus sakei

Weissella koreensis

Lactobacillus plantarum

Lactobacillus brevis

Lactococcus lactis

Enterobacteriaceae family (present in early fermentation, declines rapidly)

Approximate CFU per ml or gram

A well fermented Nabak kimchi contains a substantial probiotic load. Research data documents the following quantitative ranges:

Total lactic acid bacteria count

Quantity: 5.52 to 6.24 log CFU per gram at the start of fermentation, equivalent to approximately 330,000 to 1,700,000 colony forming units per gram. After 28 days of storage at 4 degrees Celsius, populations exceed 9.0 log CFU per gram, reaching over 1 billion colony forming units per gram.

Total aerobic bacteria

Quantity: 5.57 to 6.25 log CFU per gram initially, increasing alongside LAB populations.

Yeasts and molds

Quantity: Detected at low levels between 2 and 3 log CFU per gram, equivalent to 100 to 1,000 CFU per gram.

Coliforms

Quantity: Not detected in properly prepared samples during storage, indicating food safety.

Peak Probiotic Diversity and Count

The stage when probiotic diversity as well as count is at its highest occurs at a specific temperature and time point. According to fermentation studies, the peak for Nabak kimchi is reached after 4 to 7 days of fermentation at a consistent temperature of 10 degrees Celsius. At this stage, the population of lactic acid bacteria surpasses 8 log CFU per gram, exceeding 100 million colony forming units. Microbial diversity is also maximal here, with a balanced consortium of Leuconostoc, Lactobacillus, and Weissella species actively coexisting. Beyond this window, the population begins to shift towards acid tolerant Lactobacillus species, reducing overall diversity. Fermentation at lower temperatures of 4 degrees Celsius slows this process, delaying the peak to approximately 14 days but yielding a similar final diversity profile.

Preparation Guidelines

Raw Materials and Quantities for 2 Liters of Broth

Korean radish (mu)

Quantity: 300 grams, approximately half of a medium radish, peeled

Napa cabbage

Quantity: 200 grams, approximately 4 to 5 inner leaves

Korean red pepper powder (gochugaru)

Quantity: 2 to 3 tablespoons, adjust to taste

Garlic

Quantity: 6 to 8 cloves, finely minced

Ginger

Quantity: 1 tablespoon, finely minced

Green onions

Quantity: 4 to 5 stalks, chopped into 3 cm lengths

Water parsley (minari) – optional

Quantity: 30 grams

Coarse sea salt (cheonilyeom)

Quantity: 2 tablespoons for the initial brine, plus 1 tablespoon for the final seasoning

Filtered non chlorinated water

Quantity: 2 liters

Sweetener – sugar or honey

Quantity: 1 tablespoon

Pre processing Guidelines

Radish preparation

Peel the Korean radish and slice into thin, flat rectangular pieces of approximately 0.3 cm thickness, 2 cm width, and 4 cm length. The uniform shape is characteristic of Nabak kimchi.

Cabbage preparation

Cut napa cabbage leaves into square pieces of approximately 3 by 3 cm, discarding the tough white core.

Initial brining

Dissolve 2 tablespoons of coarse sea salt in 500 ml of water. Submerge the sliced radish and cabbage pieces for 30 to 40 minutes. Drain and rinse lightly under cold water to remove excess salt. This initial brining softens the vegetables without making them overly salty.

Seasoning paste

In a small bowl, combine the minced garlic, minced ginger, Korean red pepper powder, and 1 tablespoon of sweetener. Add 2 tablespoons of warm water and mix into a smooth paste.

Water preparation

Use boiled and cooled filtered water. Chlorinated tap water inhibits fermentation. Allow the water to reach room temperature before use.

Vessel selection

Use a clean sterilized glass jar of 3 liter capacity or a traditional Korean onggi earthenware pot. Avoid metal containers.

Step by Step Recipe

1. Sterilize the vessel: Clean the jar or onggi with boiling water, then allow it to air dry completely.

2. Layer the vegetables: Place the brined and rinsed radish slices and cabbage pieces into the vessel. Add the chopped green onions and water parsley if using.

3. Add the seasoning: Add the prepared red pepper paste to the vessel.

4. Dissolve remaining salt: Dissolve 1 tablespoon of coarse sea salt in 500 ml of room temperature filtered water.

5. Combine the broth: Pour the salted water and the remaining 1.5 liters of plain filtered water into the vessel. Stir gently to distribute the seasoning paste, which will suspend in the liquid creating a translucent pink broth.

6. Submerge ingredients: Ensure all vegetable pieces are fully submerged in the liquid. Use a clean weight or a plate if necessary to keep them below the surface.

7. Seal and ferment: Cover the vessel with a lid, but do not seal it airtight. Alternatively, cover with a clean muslin cloth secured with a rubber band.

8. Ferment: Keep the vessel in a cool, dark place. The ideal temperature for optimal probiotic development is 10 degrees Celsius. For a household setting without a kimchi refrigerator, a cool cellar or a consistently cool corner of the kitchen between 15 and 18 degrees Celsius works well.

9. Daily check: After 24 hours, open the vessel to release accumulated gas. Taste a piece of radish. For a mildly sour Nabak kimchi, ferment for 2 to 3 days. For the peak probiotic diversity and maximum count, ferment for 4 to 7 days at 10 degrees Celsius. The liquid should develop a clean, sour aroma with a slight effervescence.

10. Signs of readiness: The broth turns a clear pinkish orange color. The radish pieces are slightly translucent and crisp tender. The taste is refreshingly sour with a mild, peppery warmth from the gochugaru and a faint garlic ginger note. The pH typically decreases from an initial value near 6.0 to approximately 4.0 to 4.5.

11. Store: Once ready, transfer the entire contents including the liquid to a clean container. Refrigerate immediately to slow further fermentation. Unlike thicker kimchis, Nabak kimchi is best consumed within 2 to 3 weeks, as the radish can become overly soft and the broth excessively sour beyond this period.

Medicinal and Nutraceutical Benefits

Nabak kimchi functions as a functional food offering several evidence based health benefits derived from its live probiotics, postbiotic metabolites, and bioactive vegetable compounds.

Contribution of Probiotics

Cardiovascular health

Recent research using Mendelian randomization analysis on large scale Korean population cohorts has demonstrated a causal effect of kimchi consumption in preventing reduced high density lipoprotein cholesterol levels. A higher intake of kimchi, including varieties like Nabak kimchi, is associated with lower odds of low HDL cholesterol in middle aged men. This effect is attributed to specific bioactive compounds including 3-(4′-hydroxy-3′,5′-dimethoxyphenyl)propionic acid, capsaicin from red pepper, and allicin from garlic, all of which modulate cholesterol metabolism.

Gut health regulation

The Leuconostoc and Lactobacillus species in Nabak kimchi survive gastric transit and contribute to a healthy gut microbiota. The high water content and mild acidity make Nabak kimchi particularly well tolerated by individuals with sensitive digestive systems who might find traditional spicy kimchi irritating.

Antimicrobial action

The rapid decline of Enterobacteriaceae populations observed during Nabak kimchi fermentation at 4 degrees Celsius indicates potent antimicrobial activity of the developing LAB community. This natural competitive exclusion helps ensure the safety of the product.

Antioxidant properties

The combination of gochugaru, garlic, and ginger provides a rich source of antioxidants. The fermentation process may increase the bioavailability of these compounds.

Vital Postbiotics and Bioactive Metabolites

The fermentation of Nabak kimchi produces several key postbiotics:

Lactic acid and acetic acid

These organic acids lower the pH of the broth, creating an environment that inhibits pathogenic bacteria while promoting mineral absorption.

Short chain fatty acids (SCFAs)

Produced by LAB, these compounds including acetate, propionate, and butyrate strengthen the gut barrier and exert anti inflammatory effects.

Exopolysaccharides (EPS)

Produced primarily by Leuconostoc mesenteroides, these compounds have prebiotic properties and may contribute to cholesterol lowering effects.

Bioactive peptides

Generated during fermentation, these peptides can exhibit antioxidant and ACE inhibitory activities.

Additional Nutraceutical Highlights

Hydration and electrolyte balance

As a watery kimchi, Nabak kimchi provides hydration along with natural electrolytes from sea salt and minerals from vegetables.

Low calorie density

A typical 50 gram serving contains approximately 5 to 10 calories, making it a virtually calorie free source of flavor and probiotics.

Vitamin contribution

The raw vegetables contribute vitamins A and C, while fermentation may enhance B vitamin availability including folate.

Usage Note

Nabak kimchi is generally well tolerated due to its mild acidity and lower histamine profile compared to aged, fermented fish products. However, individuals with histamine intolerance or severe SIBO should begin with small servings of 30 to 50 ml of the broth.

Enjoy Nabak kimchi as a refreshing soup with meals, poured over cold buckwheat noodles, or as a hydrating probiotic drink on its own. A daily serving of 100 to 150 ml provides significant probiotic benefits.