Mandai (fermented cempedak rind)

What is mandai?

Mandai is a traditional fermented food made from the inner rind of the cempedak fruit, an aromatic tropical fruit closely related to jackfruit.

Cempedak belongs to the mulberry family, Moraceae. Its accepted botanical name is generally Artocarpus integer, although Artocarpus champeden appears frequently in older literature and contemporary research.

The fruit contains sweet aromatic flesh surrounding its seeds, enclosed within a thick, textured rind.

Mandai uses the pale, firm inner part of that rind rather than the sweet fruit flesh.

The rind is cleaned, salted and left in a covered container, sometimes submerged in brine, until it develops a different flavour and texture.

Fresh inner cempedak rind is relatively bland and firm. Fermented mandai becomes sourer, saltier and more savoury, with a fibrous texture that makes it particularly suitable for frying.

Its Indonesian name is simply mandai. In Banjar usage, mandai tiwadak associates the preparation with cempedak, which is locally called tiwadak.

This specific recipe is a short household preparation documented by a cook in Pontianak, West Kalimantan.

It is not the same as the substantially saltier, longer-aged preparations documented elsewhere in Kalimantan.

History and cultural setting

Mandai is strongly associated with the Banjar people of South Kalimantan, although cempedak-rind dishes and related methods occur elsewhere on the island.

The food developed as a way to use a portion of the fruit that might otherwise have been discarded.

Cempedak flesh is sweet, aromatic and immediately attractive to eat. Its rind is less appealing when fresh, but still contains useful plant material.

Fermentation transforms this part of the fruit into a separate savoury ingredient.

The practice belongs to a broader tradition of preserving seasonal foods through salting and fermentation.

The exact date of mandai's invention is not known.

There is evidence of intergenerational transmission and established regional use, but no verified first manufacture or historical document fixing its origin to a particular century.

The continued sale of mandai in jars and its presence in home cooking demonstrate that it remains a living food rather than an obsolete preservation experiment.

What part of the fruit is used?

The important distinction is between three portions of cempedak:

The outer skin is tough and often covered with small raised projections.

Beneath it lies the paler inner rind or pith.

Inside the fruit are the sweet edible portions surrounding the seeds.

Mandai uses the inner rind, sometimes called dami in regional descriptions.

The outer rough skin is removed.

The sweet flesh and seeds are separated for other uses.

This matters because a photograph of fried cempedak fruit flesh is not necessarily a photograph of mandai.

The two can look superficially similar after frying, but they are different foods.

Ingredients

Pontianak household batch.

Ingredient: Prepared cempedak inner rind — Quantity: 1 kg

Ingredient: Salt — Quantity: Approximately 50 g, described as about 3 tablespoons

Ingredient: Water — Quantity: Approximately 1 litre, or sufficient to cover

The tablespoon measure and gram quantity come from the same household account, but their equivalence depends on the type of salt.

For reproducible measurement, the 50 g mass is the clearer quantity.

The water amount is approximate. The actual requirement depends on the container and the way the rind is packed.

There is no separate bacterial starter.

The process relies on spontaneous fermentation.

Cempedak rind

The rind provides plant carbohydrates, fibre and residual nutrients.

Its structure is more fibrous than the fruit flesh.

That structure contributes to the chewy texture of the finished food.

Salt

Salt draws water from the rind and influences the organisms capable of growing in the ferment.

The household recipe uses approximately 50 g salt for 1 kg rind and approximately 1 litre water.

This should not be simplified into a guaranteed final 5% salt concentration.

Water enters and leaves the rind, and the salt distributes between the liquid and plant tissue.

The final concentration in the brine and in the rind is not measured.

Water

Water helps keep the pieces submerged.

Submersion restricts exposure to surface air and creates an environment in which particular microorganisms can become dominant.

The water must be suitable for food preparation.

Equipment

The household process uses a cutting board, knife, washing equipment and a clean jar with a lid.

Cempedak releases sticky latex.

Oil applied to a knife or gloves can make preparation easier.

The oil is a handling aid and is not included as a measured fermentation ingredient.

The jar must be able to accommodate the rind and covering liquid.

1. Open the fruit

Cut through the cempedak rind and separate the inner fruit contents.

Remove the sweet fruit flesh and seeds.

These can be used separately.

2. Trim the rind

Cut the empty rind into manageable sections.

Remove the rough outer skin, retaining the inner pale material.

The source does not specify one universal piece dimension.

3. Wash

Wash the trimmed rind to reduce sticky latex and surface residues.

Drain the pieces.

The rind should no longer be heavily coated in sticky sap.

4. Apply salt

Rub approximately 50 g salt through 1 kg prepared rind.

The source allows the salted rind to rest for approximately one hour or overnight.

These are alternative household resting periods, not two consecutive stages.

Salt begins drawing moisture from the plant tissue.

5. Pack the jar

Place the salted rind in a clean jar.

Add approximately 1 litre water, or sufficient water to cover the pieces.

Keep the rind below the liquid surface.

6. Ferment

Close the jar as described in the household recipe and leave it under ambient conditions.

The recorded preparation takes 3–4 days.

The cook reports that some people prefer the product after two or three days, while the characteristic flavour is especially noticeable by day four.

No numerical fermentation temperature is given.

The record also does not supply a measured final pH.

A vessel should not be permitted to build dangerous pressure; fermentation containers need an appropriate gas-management arrangement.

7. Remove and prepare for cooking

Take out the amount of mandai needed for cooking.

Depending on how salty it tastes, it may be rinsed or otherwise prepared for the dish.

The original household recipe is a preservation preparation, not a fully specified cooking recipe for fried mandai.

The microbiology of mandai

Mandai is associated with lactic-acid fermentation.

Lactic-acid bacteria can metabolize available carbohydrates, producing lactic acid and other metabolites.

Research on mandai has identified organisms historically called Lactobacillus plantarum and Lactobacillus casei, as well as other lactic-acid bacteria.

Current taxonomy places some of these organisms in revised genera, including Lactiplantibacillus.

These names identify microorganisms detected in studies, not a guarantee that every jar will contain the same strains.

Why the rind becomes sour

As suitable bacteria metabolize available sugars, organic acids accumulate.

This can lower the pH and create the characteristic tartness.

Salt concentration, temperature, raw material and competing organisms influence the process.

Because the household recipe is spontaneous, its microbiology can vary.

Changes in texture

Salt and fermentation alter the plant tissue.

Water movement changes the condition of the cells.

Microbial and endogenous enzymes may further influence the material.

The final texture is often flexible and chewy rather than freshly crisp.

Does it become probiotic?

Some mandai studies have investigated lactic-acid bacteria with probiotic potential.

That is not equivalent to demonstrating that every traditional jar of mandai provides a clinically validated probiotic benefit.

Strain identity, viability, dose and health outcomes would need to be established.

Cooking mandai by frying also changes the survival of microorganisms.

A major regional difference: salt concentration

The short Pontianak recipe uses approximately 50 g salt and 1 litre water for 1 kg rind.

Published traditional-process reviews describe substantially different conditions.

One research summary records 25% salting and seven days of fermentation.

Another documents 12–14 days or longer, sometimes extending toward a month.

Salt concentrations ranging approximately 5–25% appear in descriptions of different methods.

These are not minor seasoning substitutions.

High salt concentrations can inhibit many microorganisms, including some lactic-acid bacteria, and change the balance between fermentation and salt preservation.

The result can be much saltier and develop different flavour characteristics.

The different methods belong on the same mandai page as documented variants, rather than being falsely combined into one standardized recipe.

Modern starter-culture studies

Researchers have investigated producing mandai with selected lactic-acid bacteria.

One study used Lactobacillus casei strain Shirota as a starter, with separate spontaneous-fermentation batches for comparison.

Its process included blanching or boiling pieces of rind, cooling, inoculating selected batches and controlling the fermentation environment.

Other studies have investigated drying mandai after fermentation to make powders or seasoning ingredients.

These are experimental modifications intended to improve consistency or examine changes in composition.

They should not be treated as evidence that every traditional Banjar preparation uses commercial cultures.

How mandai is eaten

Mandai is normally cooked before serving.

Fried mandai

A familiar preparation involves draining and frying pieces of mandai.

The exterior becomes browned while the interior retains a distinctive fibrous bite.

Fried mandai is commonly eaten with rice, chilli relish and other accompaniments.

Oseng mandai

Mandai can be stir-fried with onion, garlic, chilli and soy sauce.

This combines the sour, salty preserved ingredient with aromatic seasonings.

Sambal mandai

Mandai may be incorporated into a chilli-based sambal.

The fermented rind contributes both texture and flavour.

Mandai serundeng

Another preparation involves cooking or drying seasoned mandai into a relatively dry shredded mixture.

Crispy mandai

Pieces can be coated with seasoned flour and fried.

This creates a crisp exterior around the fermented rind.

These dishes are related applications of one ingredient. They are not separate fermentation methods.

How to judge the batch

A characteristic sour aroma and progressive texture change can indicate fermentation is occurring.

The pieces should remain recognisable as cempedak rind.

The appearance of bubbles may indicate gas-producing microbial activity.

However, the household method does not provide an objective, measured safety endpoint.

A sour smell alone cannot prove that the product is safe.

Problems

Pieces floating above the liquid: Exposed surfaces can allow unwanted growth.

Unexpected mould: Fuzzy growth on the rind or surface requires rejection rather than casual removal.

Strong putrid odours: These suggest deterioration.

Excessive softening: The rind may become unpleasantly mushy.

Very salty flavour: High-salt variants may be intended to be rinsed or cooked before serving.

Pressure buildup: A tightly closed jar can accumulate gas.

No acidity development: This may indicate that the desired microorganisms did not become dominant, but the source provides no numerical correction procedure.

Safety and storage

The original household recipe does not establish a final pH, storage temperature or validated shelf life.

Its creator states that the household batch was consumed in less than a month and mentions adding salt for longer keeping.

That is not a tested instruction for room-temperature storage.

The short fermentation, approximate saltwater formulation and uncontrolled ambient temperature require caution.

For modern commercial production, the process should be validated for the actual substrate, salt concentration, fermentation conditions and intended storage.

The household recipe is valuable documentation, but it has not been validated as a safe process.

Why mandai matters

Mandai demonstrates how fermentation can transform an overlooked part of a tropical fruit into a valued regional ingredient.

Its identity depends as much on the fruit anatomy and later cooking as on microbial activity.

The different Banjar and Kalimantan preparations also show that mandai is not one rigid salt-and-time formula.

It is an evolving food tradition with short household ferments, heavily salted preserved forms and modern starter-culture research.