Traditional Fermented and Preserved Fish Products

TRADITIONAL FERMENTED AND PRESERVED FISH PRODUCTS

Ngari · Hentak · Tungtap · Gnuchi

 

The Eastern Himalayan area - eastern Nepal, Bhutan, Darjeeling, Sikkim, and the North-Eastern Indian states of Assam, Arunachal Pradesh, Meghalaya, Tripura, Mizoram, and Manipur - have historically lacked access to refrigeration. Freshwater fish caught from rivers, streams, and lakes are highly perishable, so indigenous communities in these areas developed low-cost biopreservation methods using natural ingredients (salt, turmeric, smoke).

Four Broad Categories of Traditional Fish Products

Category	Examples	Basic Principle
Smoked & sun-dried	Gnuchi, Suka ko maacha	Salt/turmeric cure + slow smoke-drying above a hearth
Sun-dried / salted (non-fermented)	Sidra, Sukuti, Karati, Bordia, Lashim	Washing, salting, and open sun-drying only
Fermented (paste/whole)	Ngari, Hentak, Tungtap, Shidal	Anaerobic packing in sealed earthen pots; microbial fermentation

 

Microbes involved in fish fermentation

• Lactic Acid Bacteria (LAB): Lactococcus lactis (subsp. lactis & cremoris), Lactobacillus plantarum, Leuconostoc mesenteroides, Enterococcus faecium, E. faecalis, Pediococcus pentosaceus, Weissella confusa.

• Spore-formers / Micrococci: Bacillus subtilis, Bacillus pumilus, Micrococcus spp.

• Yeasts: Candida spp. (C. chiropterorum, C. bombicola), Saccharomycopsis spp.

• Halophiles/others (in deep-fermented pastes such as ngari): Staphylococcus cohnii, Staphylococcus carnosus, Tetragenococcus halophilus.

These organisms carry out proteolysis, acid production, and flavour/aroma development, while simultaneously suppressing spoilage and pathogenic organisms.

 

 

1. Ngari

A non-salted, long-fermented whole-fish product which is the signature flavour base of Meitei cuisine (Meitei community).  These are eaten daily as a side dish with cooked rice and are a key flavouring base for Eromba and Singju, which are traditional Manipuri dishes.  Sold in local markets, typically packed inside earthen pots.

 

Prepared by Anaerobic solid-state fermentation of whole fish, Puntius sophore (this is a small freshwater fish, locally known as Phabou nga)

1. Fish are rubbed with salt and sun-dried for 3–4 days.

2. Dried fish are washed briefly and spread out on bamboo mats.

3. The inner wall of an earthen pot is coated with a layer of mustard oil (to seal pores and aid anaerobic sealing).

4. The pot is filled with the dried fish, which is then pressed down tightly by foot to remove air pockets.

5. The pot is sealed airtight and stored at room temperature for 4–6 months (can be kept for over a year).

Characteristics include Soft texture with a strong, pungent, distinctive aroma, light brown to golden-brown colour, and whole fish remain visually intact but softened by fermentation.

Microflora involved

Bacteria: Lactococcus lactis subsp. cremoris, Lactobacillus plantarum, Enterococcus faecium, L. fructosus, L. amylophilus, L. coryniformis subsp. torquens, Bacillus subtilis, B. pumilus, Micrococcus sp.

Yeasts: Candida spp., Saccharomycopsis spp.

 

 

2. Hentak

This is a fermented fish-and-plant paste with therapeutic/nutritional value used in Manipur, consumed as a curry ingredient and used as a condiment, and traditionally given to women in the final stages of pregnancy or to patients recovering from sickness/injury.

 (Image Credit: The Manipuri Foodie @facebook)

Prepared by Solid-state paste fermentation of fish, Esomus danricus (finger-sized freshwater fish) and petioles of Alocasia macrorhiza (giant taro)

1. Finger-sized fish are washed thoroughly, sun-dried, and crushed into a fine powder.

2. Petioles of Alocasia macrorhiza are cut into pieces, washed, and exposed to sunlight for 1 day.

3. An equal amount (roughly 1:1) of cut petiole pieces is mixed with the powdered fish.

4. The mixture is made into a ball-like thick paste.

5. The paste balls are kept in an earthen pot, sealed tightly, and fermented at room temperature for 7–9 days.

Characteristics of Hentak are paste-like consistency with a strongly pungent aroma and are ball-shaped when freshly prepared.

Microflora involved

Bacteria: Lactococcus lactis subsp. cremoris, Lactobacillus plantarum, Enterococcus faecium, Lactobacillus fructosus, Lactobacillus amylophilus, Lactobacillus coryniformis subsp. torquens, Bacillus subtilis, Bacillus pumilus, Micrococcus sp.

Yeasts: Candida spp., Saccharomycopsis spp.

3. Tungtap

This is a salted, short-fermented fish paste used in Meghalaya by the people of the Khasi Hills. Consumed as a pickle and used in curries and often ground/mixed with chillies and other spices before serving as a side condiment.

 

Prepared by salted fermentation of whole fish, Danio spp. (small freshwater fish)

1. Sun-dried fish are washed briefly and mixed thoroughly with salt.

2. The salted fish are packed into an earthen pot, which is sealed airtight.

3. The pot is left to ferment at room temperature for 4–7 days.

Characteristics of Tungtap: a semi-solid paste with a sharp, salty-fermented aroma.

Microflora involved

Bacteria: Lactococcus lactis subsp. cremoris, Lactobacillus plantarum, Enterococcus faecium, L. fructosus, L. amylophilus, L. coryniformis subsp. torquens, Lactobacillus puhozihii (identified specifically from tungtap and shown to have bacteriocinogenic potential), Bacillus subtilis, B. pumilus, Micrococcus sp.

Yeasts: Candida spp., Saccharomycopsis spp.

4.   Gnuchi

This is a smoked and dried (not fermented) fish product of the Lepcha community of Sikkim & Darjeeling hills.  They cook this into traditional fish curries and soups

Prepared by Smoking and slow drying of fish, Schizothorax richardsonii, Labeo dero, Acrossocheilus spp., Channa sp. (riverine species)

1. Fish are collected from river and kept on a large bamboo tray to drain off water.

2. Fish are degutted, then mixed with salt and turmeric powder, and separated according to size.

3. Bigger fish are spread in an upside-down manner on a bamboo rack called sarhang, positioned above the earthen kitchen oven.

4. Smaller fish are hung one after another on a bamboo strip above the same oven.

5. Fish are smoked continuously above the earthen oven for 10–14 days.

6. The finished gnuchi is kept at room temperature for 2–3 months and eaten as curry.

Characteristics of Gnuchi - Firm, chewy texture with a smoky aroma.

Microflora Identified

Bacteria: Lactococcus lactis subsp. cremoris, L. lactis subsp. lactis, Lactobacillus plantarum, Leuconostoc mesenteroides, Enterococcus faecium, Enterococcus faecalis, Pediococcus pentosaceus.

Yeasts: Candida chiropterorum, Candida bombicola, Saccharomycopsis spp.

 

Feature	Ngari	Hentak	Tungtap	Gnuchi
Region and Community	Manipur Meitei	Manipur	Meghalaya Khasi	Sikkim/Darjeeling Lepcha
Fish used	Puntius sophore	Esomus danricus	Danio spp.	Schizothorax spp., Labeo dero
Plant additive	None	Alocasia macrorhiza petioles	None	None (salt + turmeric)
Process type	Anaerobic pot fermentation (whole fish)	Paste fermentation (powder + petiole)	Salted pot fermentation (whole fish)	Smoking + sun/hearth drying
Duration	4–6 months	7–9 days	4–7 days	10–14 days smoking
Physical form	Whole soft fermented fish	Moist ball-like paste	Semi-solid paste	Firm smoked whole/degutted fish
Special uses	Daily staple, Eromba, Singju	Given to pregnant women/convalescents	Pickle/curry base	Curry, soup

 

Biochemical Changes

• Proteolysis and flavour development - During fermentation, endogenous fish enzymes (cathepsins, calpains) and microbial proteases from Lactobacillus and Bacillus species break down muscle proteins into peptides and free amino acids (e.g., glutamic acid, lysine, glycine). This is the main source of the characteristic umami taste and strong aroma of ngari, hentak, and tungtap.

• Mechanisms of bio preservation –

1. Lactic acid accumulation: LAB ferment residual carbohydrates into lactic and acetic acid, lowering pH and inhibiting spoilage/pathogenic organisms.

2. Salting & drying: Reduces water activity (aw), suppressing growth of pathogens.

3. Anaerobic packing: Tight compaction in sealed earthen pots (ngari, hentak, tungtap) creates an oxygen-free environment that favours facultative/obligate anaerobic LAB over aerobic spoilage flora.

4. Bacteriocin production: Certain isolated strains (e.g., Lactobacillus puhozihii from tungtap) produce antimicrobial peptides that further suppress competing and pathogenic bacteria.

5. Smoking (gnuchi): Deposits antimicrobial phenolic compounds and reduces surface moisture, extending shelf-life without a sealed anaerobic fermentation step.

 

References

Thapa, N. (2016). Ethnic fermented and preserved fish products of India and Nepal. Journal of Ethnic Foods, 3(2), 69–77.

History and Evolution of Fermentation Technology

 History and Evolution of Fermentation Technology

In human history, fermentation existed as an empirical art—a domestic craft passed down through generations, driven by tradition rather than scientific understanding. Early civilizations successfully produced bread, beer, cheese, and wine by following precise, repetitive rituals. They knew that mixing grain mash with a portion of an older, successful batch of beer would initiate the reaction, but they had no concept of the microscopic life forms carrying out the transformation. Over the past two centuries, this field has undergone a dramatic transformation, shifting from an empirical domestic art into a highly engineered molecular science.  The evolution of fermentation technology is organized into five distinct chronological phases, shifting from empirical art to molecular precision.

Era 1: The Empirical Era (Pre-1800s)

For millennia, fermentation was practised purely as a domestic art form. Civilisations exploited microbial pathways without knowing that living organisms were driving the process.

• Ancient Brewing (4000–6000 BC): Sumerians, Babylonians, and Egyptians utilized wild yeasts to ferment grain mash into beer and grape sugars into wine. Fermentation was viewed as a divine or spontaneous magical event.
• The Orleans Vinegar Process (14th Century): Developed in France, this was the earliest recorded semi-continuous open commercial fermentation method. Wine was introduced into shallow wooden vats exposed to air, allowing a surface mat of wild acetic acid bacteria (Acetobacter) to convert ethanol into vinegar.

Era 2: The Physiological Foundations (1800–1900)

This era transformed fermentation from mystery into science. It was defined by intense academic conflict regarding the true nature of chemical conversions.

·       The Spontaneous Generation & Vitalist Controversy

During the mid-19th century, a fierce scientific debate erupted between two schools of thought - The Mechanistic View - Fermentation is a dead, purely chemical decay process driven by molecular tremors and The Vitalist View - Fermentation is a    physiological process driven strictly by living organisms

The Mechanistic (Chemical) View: Liebig, Berzelius, and Wohler

Liebig argued that fermentation was a form of slow, dead decay. He believed that nitrogenous plant or animal matter (like albumin or gluten), upon exposure to air, entered a state of internal instability and decomposition. This decomposing, dead material supposedly generated atomic vibrations or "tremors." When these vibrations came into contact with stable molecules like sugar, they mechanically shattered the sugar apart, forcing it to rearrange into ethanol and carbon dioxide.  While Liebig acknowledged the presence of yeast in brewing vats, he dismissed it as an accidental, lifeless byproduct of vegetation or a dead precipitate.

The Vitalist (Biological) View: Latour, Schwann, Kutzing and Pasteur

In the late 1830s, Charles Cagniard-Latour, Theodor Schwann, and Friedrich Kutzing independently used early microscopes to observe yeast. They noted that yeast cells were globular, grew by budding, and behaved like microscopic plants. However, their ideas were aggressively ridiculed by the chemical view.  In 1857, Louis Pasteur adopted the Vitalist perspective, aiming to prove that fermentation was an unyielding biological consequence of cellular life.

Pasteur’s entry into the debate was through by a practical industrial crisis. In 1856, a beet-root alcohol manufacturer in Lille, faced a major economic problem. many of his fermentation vats were mysteriously failing, producing a sour, slimy, non-alcoholic grey broth instead of ethanol. Pasteur systematically disproved Liebig's chemical assertions through a series of experiments.

Step 1: Microscopic Differentiation  - Pasteur sampled the contents of both healthy and failed industrial vats and examined them under the microscope. In the healthy vats, he observed large, plump, spherical or oval budding cells—yeast (Saccharomyces cerevisiae). These vats produced abundant ethanol.  In the sour vats, the large yeast cells were absent or dying. Instead, the broth was crowded with vastly smaller, thin, rod-shaped microorganisms (now known as lactic acid bacteria).

Pasteur deduced that fermentation was not a uniform, random decay of dead matter. Specific chemical products were produced by specific, living microorganisms. If dead chemical vibrations were responsible, the same sugar substrate should not yield completely different chemical compounds based on which microscopic shape was present in the broth.

Step 2: Synthetic or chemically defined media experiments - Liebig had asserted that fermentation required the presence of complex, unstable, decaying organic nitrogenous matter (like albumin) to trigger the reaction. Pasteur formulated a completely synthetic, transparent growth medium containing pure distilled water, sucrose, ammonium salts, and ash from burned yeast to provide essential inorganic trace minerals like potassium and phosphate.  He inoculated this transparent, inorganic fluid with a microscopic trace of pure yeast.  The yeast did not decay. Instead, it multiplied, consumed the sugar, and generated a healthy alcoholic fermentation.  Because there was no complex, decomposing organic matter present to provide Liebig's "atomic tremors," the fermentation could only be attributed to the metabolic activities of the growing, living yeast cells assimilating simple nutrients to build their biomass.

Step 3: Demonstrating anaerobiosis (life without air) - Liebig claimed that oxygen from the air was the indispensable trigger that initiated the chemical decay of nitrogenous substances. Pasteur disproved this by demonstrating that yeast could thrive and ferment in the absence of atmospheric oxygen.  He introduced the concept of anaerobiosis, discovering that yeast is a facultative anaerobe. In the absence of oxygen, yeast cells converted sugar into alcohol with higher efficiency. He summarised this phenomenon with his famous declaration: "Fermentation is life without air".

This has resulted in the birth of Industrial Biotechnology.  By establishing that distinct microbes produce distinct products, Pasteur taught industries that they must maintain pure cultures. To prevent "diseases" of wine and beer (souring), he introduced Pasteurization (heating fluids to 55–60°C in the absence of air) to selectively kill bacteria before inoculating with pure yeast strains.

· The Buchner Revolution (1897)

The Vitalist theory held that fermentation could only happen within an intact, living cell body. Eduard Buchner disproved this. By grinding yeast cells with quartz sand and diatomaceous earth, he prepared a completely cell-free yeast juice.  When he added this sterile juice to a concentrated sugar solution, it bubbled vigorously, producing carbon dioxide and ethanol. Buchner discovered cell-free fermentation mediated by a soluble intracellular enzyme complex (he called it as Zymase). This discovery bridged biochemistry and microbiology, proving that cells are chemical engines powered by enzymes. Buchner was awarded the Nobel Prize in Chemistry in 1907.

Era 3: True Industrial Scaling & Solvents Era (1900–1940)

The pressures of World War I forced countries to scale up fermentation from small glass bottles to massive industrial operations to produce raw materials for military weapons.

The ABE Fermentation - During World War I, the British military faced a critical shortage of acetone, an essential solvent used to manufacture cordite (smokeless gunpowder). A severe blockade cut off Britain's traditional imports of wood-derived acetone. During this time, Chaim Weizmann isolated a novel anaerobic bacterium, Clostridium acetobutylicum. He developed a massive, large-scale fermentation process that converted grain starch into Acetone, Butanol, and Ethanol (ABE) at a specific ratio ().  This  acetone yield provided exactly what the British military required.

The ABE process required the design of large, sealed fermenter tanks ( to  liters). Clostridium acetobutylicum is an obligate anaerobe—even trace exposure to atmospheric oxygen stops its growth and kills active vegetative cells. Furthermore, wild airborne bacteria (like lactic acid producers) could easily outgrow the clostridia if given the chance.  To overcome these hurdles, engineers built the world’s first dedicated, large-scale industrial fermentation facilities.  This marked the birth of modern industrial biotechnology, demonstrating that bacteria could replace traditional chemical synthesis for bulk solvent production.

Fed-Batch Cultivation of Baker’s Yeast - During the same period, the production of Baker's yeast (S. cerevisiae) faced a major biological barrier: the Crabtree Effect. When yeasts are given high concentrations of sugar, they automatically switch to fermenting it into ethanol, even if there is plenty of oxygen around. This caused waste of sugar and lowered cell biomass yields.  To bypass this, engineers invented Fed-Batch cultivation. Instead of dumping all the sugar into the tank at the start, nutrients are pumped in incrementally at low concentrations. This keeps the cells locked in pure aerobic respiration, maximizing biomass output while completely preventing the formation of toxic alcohol.

Era 4: Submerged Aerated Engineering Era (1940–1970)

The urgent demand for mass-produced penicillin during World War II completely reshaped bioprocess engineering, driving the creation of the modern bioreactor.

The Penicillin Scale-Up Crisis - When Alexander Fleming discovered penicillin in 1928, it was produced in minute amounts by the mold Penicillium notatum. Early attempts to harvest it required growing the fungus on the surface of thousands of shallow bottles, which was slow and highly prone to contamination.  To solve this crisis, Howard Florey, Ernst Chain, and a team of engineers revolutionized the process between 1940 and 1945:

1. Strain Switch: They replaced Fleming's original strain with a high-yielding version of Penicillium chrysogenum.
2. The Submerged Bioreactor: Because this fungus requires massive amounts of oxygen, scientists could no longer use shallow pans. They engineered deep, enclosed steel vessels where the mold grew fully submerged throughout the liquid broth. 

3.     Penicillium is an obligate aerobe. It requires enormous amounts of dissolved oxygen to synthesize its secondary metabolites. If the mold was submerged in liquid without a constant air supply, it literally suffocated and stopped producing the drug.  To deliver oxygen to these deep tanks without introducing contaminants, engineers invented the Sparger - A perforated ring at the base of the tank that continually pumps sterile, pressurized air into the broth and

4.     The Mechanical Agitator (Impeller): High-speed internal blades that break up incoming air into tiny bubbles, ensuring maximum oxygen distribution while blending the thick fungal growth.

5.     Sterilization Protocols: Systems designed to sterilize large volumes of media using high-pressure steam, along with specialized air filters to prevent contamination over long fermentation runs.

Era 5: The Biotechnology & Molecular Era (1970–Present)

The birth of genetic engineering completely separated fermentation technology from its traditional reliance on natural, wild-type microbes.

• Recombinant DNA (rDNA) technology (1973): Herbert Boyer and Stanley Cohen successfully sliced a specific gene out of one organism and pasted it into a bacterial plasmid. This technological leap allowed scientists to turn simple microbes into highly specialised cellular factories.
• Insulin (1978/1982): Scientists successfully inserted the human insulin gene into Escherichia coli. By 1982, Humulin became the world’s first commercially approved recombinant pharmaceutical product made via fermentation, replacing insulin extracted from pig and cattle pancreases.
• Modern Metabolic Engineering: Today, industrial microbiologists do not just rely on random mutations. They use precision tools like CRISPR-Cas9 and computer-guided metabolic models to completely modify a cell's metabolic pathways. By deleting genes that make unwanted side products and overexpressing target genes, we can engineer microbes that convert cheap sugars into complex bioplastics, biofuels, monoclonal antibodies, etc with near-perfect efficiency.