Thap: The Yeast Starter Culture of the Karbi Community of Assam

Thap is the traditional starter culture used by the Karbi people of Assam, one of the major indigenous tribal communities of Northeast India. While previous entries have described starter cakes from the Ahom and Deori communities, Thap serves a distinct yet analogous role for the Karbis. It is the essential inoculum for producing Hor Alank, the traditional rice beer of the Karbi community, and also for distilling Hor Arak, a concentrated alcoholic spirit . Thap represents a unique microbial ecosystem preserved in dried cake form, representing centuries of ethnobotanical knowledge and fermentation expertise.

Unlike many other starter cultures that rely primarily on filamentous molds for starch saccharification, Thap is described in scientific literature as a potential yeast medium that has been known to the Karbis since time immemorial . This distinction highlights the sophisticated understanding of the Karbi people regarding fermentation microbiology, long before the scientific discovery of yeast.

Cultural Roots and Nomenclature

The Karbis are one of the major hill tribes of Assam, largely concentrated in the hill districts of Karbi Anglong and West Karbi Anglong, with significant populations in Dima Hasao and the neighboring states of Nagaland, Meghalaya, and Mizoram . They belong to the Mongoloid racial stock and speak Karbi, a Tibeto-Burman language belonging to the Kuki-Chin subgroup . Historical and oral traditions suggest that the Karbis migrated from the Chindwin river valley in western Myanmar to their present locations .

The term Thap refers specifically to the dried starter cake. The Karbis also use the term Thap Aphi to refer to previously prepared starter cake that serves as the inoculum or yeast spawn for new batches . The final fermented rice beer is called Hor Alank, while the distilled spirit is known as Hor Arak .

Traditional Significance

Hor, meaning alcohol in the Karbi language, is an integral part of the socio-cultural life of the Karbis . Both Hor Alank (rice beer) and Hor Arak (distilled liquor) are used in virtually all important social and religious contexts.

Marriage Ceremonies (Adam Asar)

Hor is traditionally used during the Karbi marriage ceremony known as Adam Asar . The beverage is considered essential for the proper observance of wedding rituals.

Religious Worship (Seh Karkli)

Hor is used during Seh Karkli, the traditional worship ceremonies of the Karbi people . The offering of alcohol to deities and ancestors is a customary practice.

Death Ceremonies

Hor Arak is used in all death ceremonies, where it is offered to guests as a mark of respect .

Hospitality

Both forms of the beverage are consumed daily as a refreshing drink and are offered to guests as a sign of respect and welcome .

Medicinal Uses

Highly concentrated Hor Arak is used in small quantities among rural Karbi communities to cure dysentery, pharyngitis, and cholera . Hor Alank is used as a preservative and for flavoring dried fish, a product known as manthu .

Sacred Origins

The Karbis believe that Thap Aphi (yeast spawn) is God gifted. According to oral tradition, a Karbi woman was told in her dream to make Thap from leaves of Marthu and uncooked rice, using the fecal matter of a bird locally known as Vokongching as the yeast spawn. The Hor Alank produced from this fermentation was then to be used during marriage and worship ceremonies .

The Microbiology: A Yeast Driven Consortium

Thap is distinguished from other starter cultures in the region by its primary reliance on yeasts rather than filamentous molds for fermentation. While molds play a role in some Asian starters (such as koji for sake production), Thap is explicitly described in the scientific literature as a potential yeast medium .

Dominant Microorganisms

The key functional microbes present in Thap include:

Yeasts

The primary fermenting microorganisms are various yeast species, chiefly Saccharomyces cerevisiae (brewer's yeast) and potentially Pichia species. These yeasts convert the sugars present in cooked rice into ethanol (alcohol) and carbon dioxide. The drying period of Thap coincides with the active growth of yeast cells in the medium, and the yeast cells remain dormant during storage, becoming active again when mixed with cooked rice .

Lactic Acid Bacteria

While yeasts dominate the fermentation, Thap, like other traditional starters, also contains various LAB species that contribute to the flavor profile and produce beneficial postbiotics. The presence of LAB makes the final Hor Alank a source of probiotic bacteria despite being an alcoholic beverage.

Expected Probiotic Bacteria

Based on analysis of similar starter cultures from the Karbi and neighboring communities, Thap is expected to contain the following LAB strains:

· Lactiplantibacillus plantarum

· Levilactobacillus brevis

· Lactococcus lactis

· Leuconostoc species

· Weissella species

Filamentous Molds (Minor Role)

Unlike starters such as Haazor Pitha which rely heavily on Aspergillus and Rhizopus for saccharification, Thap appears to rely less on molds. However, some mold species may be present on the plant materials used in the starter preparation.

The Herbal Composition

What distinguishes Thap from commercial yeast and even from other traditional starters is its extensive use of medicinal plants. The herbs and plant parts used in Thap serve not only as substrates for microbial growth but are also believed to impart specific functional properties to the final Hor Alank and Hor Arak .

Comprehensive List of Plants Used in Thap

The following table presents the extensive list of plants used in the preparation of Thap by the Karbi community, compiled from multiple scientific surveys .

Plant Name Family Part Used Vernacular Name (Karbi/Assamese)

Croton joufra Roxb. Euphorbiaceae Leaves Marthu

Phlogacanthus thyrsiflorus Nees. Acanthaceae Leaves Jockan

Solanum viarum Dunal Solanaceae Whole plant Hisou-kehou

Acacia pennata (L.) Willd. Mimosaceae Bark Themra

Amomum corynostachyum Wall. Zingiberaceae Leaves Ku-eng

Clerodendrum viscosum Vent. Lamiaceae Leaves

-

Ricinus communis L. Euphorbiaceae Leaves Castor

Cymbopogon citratus (DC) Stapf Poaceae Leaves Lemongrass

Ananas comosus (L.) Merr. Bromeliaceae Leaves, Fruit Pineapple

Saccharum officinarum L. Poaceae Stem Sugarcane

Solanum indicum L. Solanaceae Whole plant -

Artocarpus heterophyllus Lam. Moraceae Leaves Janphong (Jackfruit)

The Chief Constituents

The primary and most traditional ingredient for Thap is Marthu (Croton joufra) . Leaves of this plant are pounded together with water soaked rice to form the base of the starter cake. To this mixture, a small amount of previously prepared Thap called Thap Aphi is added as the microbial inoculum.

Substitutes and Admixtures

Several plants are used as substitutes or additional ingredients depending on availability and local preferences :

Leaves of Ku-eng (Amomum corynostachyum Wall.)

Thap prepared with this ingredient is reported to produce Hor that is most favored by the Karbis because it is fragrant, cooling, and refreshing .

Bark of Themra (Acacia pennata Willd.)

This is used as a substitute for Croton joufra, particularly by non Karbi people living in and around Diphu town .

Leaves of Janphong (Artocarpus heterophyllus)

Jackfruit leaves are added to the herbal mixture in some Thap preparations .

The combination of these herbs creates a complex phytochemical profile that influences both the fermentation process and the organoleptic properties of the final beverage.

Preparation Guidelines for Thap

The traditional preparation of Thap follows a specific methodology documented in ethnographic and ethnobotanical studies .

Raw Materials

Glutinous rice

Quantity: Sufficient quantity of rice, typically of inferior quality or any available variety. The rice is soaked in water for 24 hours prior to use .

Fresh plant leaves and bark

Quantity: A substantial quantity of mixed leaves, primarily from Croton joufra (Marthu), along with other optional herbs including leaves of Phlogacanthus thyrsiflorus (Jockan), whole plants of Solanum viarum (Hisou-kehou), bark of Acacia pennata (Themra), leaves of Amomum corynostachyum (Ku-eng), and leaves of Artocarpus heterophyllus (Janphong) as available .

Previously prepared Thap (Thap Aphi)

Quantity: A small amount of old starter cake powder. This acts as the yeast spawn or microbial inoculum for the new batch .

Water

Quantity: As needed for soaking and grinding.

Equipment

Wooden mortar (Long)

A traditional wooden mortar used for pounding the ingredients together .

Wooden pestle (Lengpum or Lingnum)

The corresponding pestle used in conjunction with the Long mortar .

Bamboo sieve (Ingkrung)

Used for drying the formed cakes, which allows air circulation on all sides .

Banana leaves

Used for wrapping or covering the cakes during the initial stages.

Step by Step Recipe for Thap

The following recipe is based on ethnographic documentation of traditional Karbi practices .

1. Soak the rice

Take the required quantity of rice and soak it in clean water for 24 hours. The soaking softens the rice grains, making them easier to pound into a paste.

2. Harvest and prepare the herbs

Collect fresh leaves and bark from the required plant species. For Croton joufra (Marthu), harvest tender leaves. For other plants, collect the appropriate parts as listed above. Wash all plant materials thoroughly to remove soil and debris.

3. Combine ingredients in the mortar

Place the soaked rice along with the drained water and the fresh plant leaves and bark into the wooden mortar called Long.

4. Pound the mixture

Using the wooden pestle (Lengpum or Lingnum), pound the mixture of rice and herbs vigorously. Continue pounding until the ingredients form a sticky, cohesive paste . During this process, add small amounts of water as needed to achieve the correct consistency.

5. Add the Thap Aphi inoculum

To the sticky powdered mass, add a small amount of previously prepared Thap, known as Thap Aphi . This old starter cake should be powdered before addition. The Thap Aphi acts as the yeast spawn, providing the microbial consortium for the new cakes. Mix thoroughly to distribute the inoculum evenly throughout the paste.

6. Shape the cakes

Take portions of the sticky paste and shape them into round, flat cakes. The traditional size is approximately 6 cm in diameter and 0.5 cm in thickness .

7. Dust with Thap Aphi powder

Sprinkle or overlay the formed cakes with additional powder of previously prepared Thap . This ensures that the surface of the cakes is also inoculated with the desired microbial community.

8. Arrange for drying

Place the cakes on a bamboo sieve called Ingkrung . The bamboo sieve allows air to circulate around all surfaces of the cakes, promoting even drying. If a bamboo sieve is not available, a clean bamboo mat or a wire rack can be used.

9. Dry the cakes

Dry the cakes for 2 to 5 days, depending on the prevailing ambient temperature . The drying can be done either in direct sunlight or above a traditional fireplace . Both methods are traditionally employed, with sun drying preferred during the dry season and fireplace drying used during rainy weather.

10. Monitor the drying process

During the drying period, the yeast cells in the cakes become actively metabolizing before entering a dormant state as the cakes dry completely . The cakes are ready when they are completely hard and dry to the touch.

11. Store the finished Thap

Once fully dried, store the Thap cakes in a dry place. The cakes can be kept near a fireplace for future use, which helps maintain dryness and may impart additional aromatic compounds from the smoke . Thap is reported to be effective for up to twelve months when properly stored .

Signs of Success

A properly made Thap is a hard, dry, round flat cake approximately 6 cm in diameter and 0.5 cm thick. The color ranges from off white to light tan or grey, depending on the specific herbs used. The aroma should be complex, combining the scents of dried herbs, yeast, and a faint sour note reminiscent of bread dough or beer. There should be no signs of live insects, moisture, black mold, or rancid odors. When used to ferment rice, a good Thap will produce a bubbling, alcoholic fermentation within 2 to 3 days.

Troubleshooting Common Issues

Cakes develop black or green mold

Cause: Contamination by undesirable fungi due to insufficient drying, high humidity during storage, or unclean equipment. Solution: Discard all contaminated cakes. Ensure the drying environment has good air circulation and that the cakes are completely hard before storage.

No fermentation activity when used

Cause: The microbial community in the cake has died, possibly due to overheating during drying or prolonged storage in poor conditions. Thap stored beyond 12 months may lose viability. Solution: Obtain fresh Thap cakes from a reliable source or prepare a new batch. The drying period must coincide with active yeast growth, and the cakes must not be overheated.

Cakes have a rancid or ammonia like smell

Cause: Overgrowth of undesirable bacteria during the drying process. Solution: Discard the batch. Ensure the cakes are dried quickly and thoroughly, and that the Thap Aphi used as inoculum came from a successful previous batch.

Cakes crack or crumble during drying

Cause: Dough too dry or insufficient pounding to form a cohesive paste. Solution: Add slightly more water to the dough in the next batch and pound more thoroughly to develop a cohesive sticky mass.

The Role of Thap Aphi (Yeast Spawn)

A critical element in Thap preparation is the use of Thap Aphi, the previously prepared starter cake . This practice of back slopping, using a portion of a previous successful fermentation to inoculate a new batch, is a sophisticated microbial management technique. The Thap Aphi provides:

A reliable source of the desired microbial consortium, including specific yeast strains adapted to the local environment. A competitive advantage against undesirable microbes, as the high population of desired microbes outcompetes contaminants. Consistency in fermentation outcomes across batches. The preservation of strain specific characteristics that contribute to the unique organoleptic properties of Hor Alank and Hor Arak.

The traditional belief among the Karbis that Thap Aphi is God gifted reflects an understanding that the microbial culture is a valuable resource to be preserved and passed down through generations .

Social and Cultural Restrictions

Interestingly, for historical reasons, women belonging to the section Bey Ronghang of the sub clan Bey and the clan Hanjang consider the preparation of Thap a taboo . This restriction highlights the complex social organization surrounding traditional food and beverage production among the Karbis, where knowledge and practices may be restricted to specific lineages or individuals.

Storage and Shelf Life

Properly dried Thap stored in a dry place, preferably near a fireplace to maintain dryness, will maintain its viability for up to twelve months . The cakes should be kept in a container that protects them from moisture, insects, and direct sunlight. Traditional bamboo containers lined with leaves are used, but modern airtight glass jars stored in a cool, dry cupboard work equally well. Do not refrigerate Thap, as condensation can introduce moisture and cause mold growth.

Usage Note

Thap is a traditional starter culture and is not meant to be consumed raw. To use, powder the dried cake and mix it into cooled, cooked rice. The typical ratio is approximately 40 grams of powdered Thap for 5 kilograms of rice, yielding about 5.5 liters of alcohol after distillation . The fermentation for Hor Alank typically takes 3 days during summer and up to 4 days during winter . For Hor Arak distillation, an adequate quantity of water is added after fermentation and the mixture is allowed to rest for one more night before distillation.

Individuals with mold allergies or compromised immune systems should avoid handling raw Thap cakes, as fungal spores may become airborne during the powdering process. Always wash hands thoroughly after handling Thap.

Hor Alank prepared from Thap using Amomum corynostachyum (Ku eng) is reported to be most favored as it is fragrant, cooling, and refreshing . The fermented rice left over after distillation, known as Hor Sera, is used as feed for pigs and sometimes as a fish attractant , demonstrating the zero waste approach of traditional Karbi food processing.

x x x