Kasam Sabi: Exploring Bornean Fermented Mustard Greens
Savor centuries-old fermentation techniques for a tangy, nutrient-rich accompaniment.
Kasam Sabi: Borneo’s Beloved Fermented Mustard Greens
Kasam Sabi is a traditional Bornean delicacy of fermented mustard greens that captures the vibrant taste and history of Indigenous Dayak cuisine. This dish, a staple of Sarawak kitchens, offers a combination of tangy, savory, and umami notes created through a natural fermentation process. Kasam Sabi exemplifies how fermentation not only preserves but transforms ingredients, making them more nutritious and deeply flavorful.
The Cultural Roots of Kasam Sabi
For generations, Kasam Sabi has played a crucial role in the culinary traditions of Borneo, especially among the Dayak people. In an environment rich with wild and cultivated greens, preserving food was vital for survival during periods of scarcity or unpredictable weather. The fermentation of mustard greens into Kasam Sabi reflects the resourcefulness, community spirit, and taste preferences of the region.
The tradition is rooted in seasonal harvests. When mustard greens, known locally as sabi, are abundant, families prepare large batches of Kasam Sabi to enjoy over several months. This preserved vegetable is often served as a condiment or side dish, accompanying rice and freshwater fish, or enriched into comforting stews.
Why Mustard Greens?
Mustard greens (Brassica juncea) are prized for their sturdy leaves, health benefits, and peppery flavor. Their robust texture holds up to fermentation exceptionally well, while their natural glucosinolates contribute to Kasam Sabi’s distinctive taste and sharpness.
Ingredients and Variations
The beauty of Kasam Sabi lies in its simplicity. At its core, the recipe calls for just a few essential ingredients:
- Mustard greens (preferably fresh and thick-stemmed)
- Cooked rice (white rice is typical, offering starch to fuel fermentation)
- Salt (preserves and seasons; sea salt is traditional)
- Water (boiled and cooled to ensure a clean environment)
Some families add extra flavorings, such as crushed garlic, sliced bird’s eye chili for heat, or a handful of Korombot (wild ginger). Each household’s Kasam Sabi may taste slightly different, reflecting local ingredients and preferences.
Optional Additions
- Chopped chilies for heat
- Smashed garlic for pungency
- Sliced ginger to add warmth
- MSG for extra umami (controversial, but sometimes added)
Step-by-Step: Making Kasam Sabi at Home
Replicating Kasam Sabi is approachable, provided you follow these steps:
1. Prepare the Mustard Greens
Wash the greens thoroughly, paying close attention to the stems, which often trap grit.
- Remove any wilted or blemished leaves.
- Cut into 2–3 inch sections for more uniform fermentation and easier packing.
2. Salt Massage
Rub a generous amount of sea salt (about 2–3% of the greens’ weight) into the leaves and stems. This step draws out excess water, softens fibers, and kicks off an environment where beneficial bacteria flourish.
3. Create the Rice Starter
Cook plain white rice and allow it to cool to room temperature. The cooked rice adds not only starches to feed fermentation but also helps initiate a more complex tangy flavor.
Use approximately half a cup of cooled, cooked rice for every kilogram of greens.
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4. Layer and Pack
- In a sterilized glass jar or traditional earthenware crock, alternate layers of seasoned greens and small amounts of rice.
- Press each layer down firmly to expel air and ensure the greens remain submerged in their own juices as much as possible.
- For extra flavor, add pieces of chili or ginger between some of the layers.
5. Add Brine (Optional)
If the greens are not completely covered by their own liquid, prepare a brine (2–3% salt in boiled, cooled water) and pour over the greens until they are just submerged.
6. Ferment
- Seal the container with a lid or plastic wrap. Traditional methods might use a banana leaf weighted down with a clean stone.
- Leave at room temperature—ideally 25–28°C (77–82°F)—out of direct sunlight for 5–7 days (sometimes longer during cool weather).
- Check the greens daily to ensure all bits remain submerged. Skim off any foam or harmless surface mold; discard greens if foul odors develop.
7. Taste, Store, and Use
After several days, Kasam Sabi should taste pleasantly sour, slightly funky, and aromatic. The color will change from bright green to olive or slightly yellowish. When fermented to your liking:
- Store jars in the refrigerator to dramatically slow further fermentation.
- Kasam Sabi will keep its flavor for several weeks, gaining depth over time.
Fermentation Science: What’s Happening to the Greens?
Like all lacto-ferments, the transformation of Kasam Sabi is powered by lactic acid bacteria naturally present on the vegetables. These beneficial microbes break down plant sugars and starches from the rice, producing acid and creating an environment hostile to spoilage organisms.
Key biochemical changes include:
- Softening of the vegetables due to acid and enzymatic activity
- Development of tangy, sharp flavors
- Enhanced probiotic content for gut health
The combination of salt and limited oxygen ensures food safety while fostering deep, complex flavors.
Kasam Sabi Throughout Borneo: Regional Diversity
Although the basics of Kasam Sabi remain constant, regional nuances yield intriguing variety across Borneo:
- Some communities favor a more sour, slightly fizzy Kasam Sabi, emphasizing longer fermentation.
- Others add spices or mix in other greens for a multi-layered taste.
- Variations are also found in container types—from traditional earthenware crocks, imparting more earthiness, to modern glass jars offering clarity in monitoring fermentation.
Serving Suggestions: How to Enjoy Kasam Sabi
Kasam Sabi’s strong, tangy kick makes it a perfect pairing for rich, meaty dishes and plainer staples. Popular approaches include:
- Chopped and stirred through steaming hot rice as a refreshing palate cleanser
- Tossed with boiled fish or fish head curry to add tart balance
- Added to stir-fries alongside pork, chicken, or tofu for depth and aroma
- Mixed into soups and broths for a subtle, fermented complexity
- Served as a small side salad—perhaps with a squeeze of lime and a dash of chili
Table: Classic Pairings with Kasam Sabi
| Dish Type | Description | How Sabi Enhances |
|---|---|---|
| Rice & Fish | Steamed rice with grilled or boiled fresh river fish | Cuts through oil, adds tang and saltiness |
| Meat Stew | Pork or chicken cooked with ginger, spices | Brings freshness, aroma, and light acidity |
| Sour Soup | Soup with fish, tomatoes, and kasam sabi | Increases sour complexity and depth |
Tips for Successful Homemade Fermentation
- Use only clean, sterilized equipment to prevent contamination.
- Weigh the greens down to ensure full submersion and minimize risk of mold.
- Be patient: Temperature fluctuations may speed up or slow down fermentation. Warmer rooms mean faster, more vigorous fermentation.
- If you’re new to fermentation, start with a small batch and taste daily to develop your palate and confidence.
Frequently Asked Questions (FAQs)
What type of mustard greens is best for Kasam Sabi?
Traditional recipes favor thick-stemmed Asian mustard greens (such as Gai Choy), but other varieties—including curly or broad-leafed types—can also be used with slightly different flavors and textures.
Can I use brown or wild rice instead of white rice?
White rice is preferred for its neutral flavor and soft texture, but you can experiment with other cooked grains—just note that flavor and fermentation speed may vary.
How do I know when Kasam Sabi is ready?
The greens will appear duller in color and become distinctly tangy and slightly salty. Taste is the best indicator: When the flavor is pleasantly sour but not harsh, it’s ready for refrigeration.
Is Kasam Sabi good for gut health?
Yes, like other fermented vegetables, Kasam Sabi provides lactic acid bacteria that can benefit the digestive system and enhance nutrient absorption when eaten as part of a balanced diet.
How long does Kasam Sabi last?
Properly fermented and refrigerated, Kasam Sabi will keep for several weeks or even months. Its flavor intensifies with time, but if it develops discoloration, an off smell, or signs of spoilage, it should be discarded.
Fermentation in Borneo: A Living Heritage
Fermentation is central not just to Bornean cuisine but to food cultures worldwide. The practice of preserving mustard greens, as with so many traditional foods, is as much about community and ritual as it is about sustenance. In villages across Sarawak and Sabah, making Kasam Sabi is often a group activity, with elders passing down ratios, tactile tips, and anecdotes to younger generations.
By mastering Kasam Sabi, you connect not only to the flavors of Borneo but also to an ancestral knowledge that celebrates patience, simplicity, and the abundance of the land.
Kasam Sabi Recipe (Step-by-Step)
- 1 kg mustard greens (preferably thick-stemmed Asian variety)
- 2–3 tablespoons sea salt
- 1/2 cup cooked white rice (cooled)
- Optional: 2 chilies, sliced; 2 garlic cloves, smashed; 1 small piece of ginger
- Wash and drain the mustard greens thoroughly. Cut into 2–3 inch pieces.
- Massage salt into the greens and let stand for 30–60 minutes until slightly wilted.
- Squeeze out excess liquid, reserving as much as possible for brine.
- Pack greens into a clean glass jar or earthenware crock, layering with rice and optional seasonings. Press down between layers.
- Pour any reserved brine (from salted greens) over all. If needed, add more salted, boiled, and cooled water to ensure everything is submerged.
- Cover and ferment at room temperature, 5–7 days. Once tangy and aromatic, refrigerate.
Conclusion: Taste the Tradition
Whether you’ve grown up eating Kasam Sabi or are trying it for the first time, this Bornean fermented mustard green is a celebration of both flavor and ingenuity. Let it enliven your meals, connect you to a living cultural heritage, and deepen your appreciation for the wonders of fermentation.
References
- https://www.whiskeyandbooch.com/blog/pickled-mustard-greens-dua-chua-fermented-mustard-greens
- https://tastecooking.com/recipes/fermented-mustard-greens/
- https://stefangourmet.com/2025/02/07/homemade-thai-pickled-mustard-greens/
- https://www.thehongkongcookery.com/2023/06/chinese-pickled-sour-mustard-greens.html
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