Jump to content

Course:FNH200/Projects/2026/Tai O shrimp paste

From UBC Wiki

Shrimp paste (Chinese: 蝦膏 / 蝦醬; Jyutping: haa1 gou1 / haa1 zoeng3) is a salt-fermented condiment central to Cantonese cuisine, made from small planktonic shrimp of the genus Acetes and salt, with no other additives. This article focuses on the version produced in Tai O, a stilt-house village on Lantau Island, Hong Kong, where the craft is recognised as intangible cultural heritage but is now practised by only a small number of producers. Tai O shrimp paste offers a compact case study in salt-based preservation, uncontrolled fermentation, and the difference between a food that is shelf-stable and a food that is safe.

File:Jars of shrimp paste / bamboo drying trays

History and cultural context

Tai O developed as a fishing and salt-production settlement, and shrimp paste emerged as a way for the Tanka boat-dwelling community to preserve a seasonal krill catch using the one preservative available locally in quantity: sea salt.[1]

The industry peaked in the mid-twentieth century. Around ten shrimp paste factories operated in Tai O in the 1960s, and the nearby settlement of Ma Wan produced tens of thousands of kilograms annually; Ma Wan's factories are now derelict, and press reporting indicates that roughly two producers remain active in Tai O.[2][3] The oldest surviving business, Cheng Cheung Hing, was founded in 1920 and is now in its third generation.[4]

The product has a documented Canadian connection. Tai O paste was historically exported to Chinatowns in London, San Francisco and Vancouver, with Taishanese immigrant communities in North America forming a significant market, particularly for steamed minced pork cakes seasoned with salted shrimp.[5] Shrimp-paste making was included in Hong Kong's first intangible cultural heritage inventory of 480 items, announced in June 2014.[6]

Production and preservation science

Production uses two inputs. Acetes krill are washed, mixed with coarse salt, ground to a paste, fermented in vats for roughly one to two months, then spread on bamboo trays and sun-dried, with the trays turned regularly.[7]

The primary preservation mechanism is reduction of water activity. Salt binds free water osmotically, lowering aw below the range in which most spoilage organisms and vegetative pathogens can grow, and simultaneously selecting for halophilic and halotolerant bacteria that tolerate the resulting environment. Sun-drying adds a second hurdle by removing water directly. Neither step involves heat processing, so the product is preserved rather than sterilised.

Flavour develops through proteolysis. Endogenous proteases from the shrimp, together with enzymes from surviving halophilic bacteria, break shrimp protein into peptides and free amino acids.[8] Liberated glutamate is the main contributor to the paste's umami intensity, which is why a small quantity flavours an entire dish. Sequencing studies of comparable Asian shrimp pastes identify Tetragenococcus as a dominant genus during fermentation, alongside other salt-tolerant taxa.[9]

Because fermentation is uninoculated and takes place outdoors, producers control it by adjusting salt rather than by instrumentation. One Tai O maker has described adding several extra pounds of salt to a batch when rain is forecast, then blending that batch with one made in fair weather to even out the final flavour — an intuitive form of water-activity management.[10] The same producer reports that his family lowered the recipe's salt level in the late 1990s in response to public health reporting on sodium, an example of consumer-driven reformulation in an artisanal product.[11]

Safety, labelling and regulation

Biogenic amines

Salt and drying suppress spoilage organisms but do not prevent the accumulation of biogenic amines, which form when bacterial decarboxylases act on free amino acids released by proteolysis. Histamine, cadaverine and putrescine are all reported in fermented shrimp products, and studies of Chinese shrimp pastes have found biogenic amine levels that are not consistently within recommended limits; the European Food Safety Authority has suggested 50 mg/kg as a reference threshold for histamine in fish.[12][13] Biogenic amines are heat-stable, so cooking the paste does not remove them. This makes shrimp paste a clear illustration that preservation and safety are distinct properties.

Sodium

The product is, by design, very high in sodium, and research on shrimp paste explicitly notes the tension between the salt required for fermentation and dietary sodium reduction goals.[14] Reduced-salt formulations shift the microbial community and are an active research area.

Comparison: Cantonese salted fish

A related Tai O product illustrates that traditional salt preservation is not uniformly benign. Chinese-style salted fish is classified by the IARC as a Group 1 carcinogen based on its association with nasopharyngeal carcinoma, with N-nitroso compounds as the proposed mechanism and a dose-response relationship strongest for consumption during childhood.[15] The Hong Kong Centre for Food Safety advises moderation on this basis.[16] This classification applies to salted fish specifically and has not been extended to shrimp paste.

Canadian labelling requirements

Shrimp paste sold in Canada is a prepackaged imported food subject to the Food and Drugs Act and the Food and Drug Regulations. Crustaceans are one of Canada's priority allergens, and must be declared either by common name in the list of ingredients or in a "Contains" statement immediately following it.[17] Because Acetes krill are crustaceans and are the sole protein source, a compliant Canadian label cannot omit this declaration. File:Photograph of a Canadian retail label, taken by team member

Decline and competing pressures

Hong Kong banned trawling — including shrimp trawling — in its waters under the Fisheries Protection Ordinance (Cap. 171), effective 31 December 2012, across roughly 1,700 km² of territorial waters.[18]

The measure has measurable ecological benefits: post-ban surveys found large increases in predatory crab densities in both eastern and western Hong Kong waters.[19] It also removed the local krill supply. At least one Tai O producer responded by moving early-stage production to Yangjiang and Taishan in Guangdong, retaining only final processing in Tai O.[20] Commentators have since asked whether a paste made from non-local shrimp and processed largely off-site can still be described as a Hong Kong product.[21]

Other pressures run in both directions. Cheaper factory-made paste from mainland China and Southeast Asia has displaced Tai O producers in the local market, while also keeping shrimp paste affordable and widely available. Reporting attributes the remaining decline chiefly to a lack of successors willing to enter the trade.[22]

See also

References

  1. ↑ Zolima CityMag. Hong Kong's Salty History: Rebellion, Smuggling and Shrimp Paste. https://zolimacitymag.com/hong-kongs-salty-history-rebellion-smuggling-and-shrimp-paste/ Accessed August 2026.
  2. ↑ Localiiz. Hong Kong Shrimp Paste: A history of local shrimp paste. https://www.localiiz.com/post/food-drink-history-shrimp-paste-hong-kong Accessed August 2026.
  3. ↑ Localiiz. 10 intangible cultural heritages to see and experience before they vanish from Hong Kong. https://www.localiiz.com/post/culture-history-hong-kong-intangible-cultural-heritage-traditions-to-see-before-they-vanish Accessed August 2026.
  4. ↑ The Industrial History of Hong Kong Group. Cheng Cheung Hing Shrimp Paste Factory, Tai O. https://industrialhistoryhk.org/cheng-cheung-hing-shrimp-paste-factory-tai/ Accessed August 2026.
  5. ↑ SBS Food. A taste of the sea: Tai O's famous shrimp paste. https://www.sbs.com.au/food/article/a-taste-of-the-sea-tai-os-famous-shrimp-paste/s831heim3 Accessed August 2026.
  6. ↑ South China Morning Post. Tai O is losing its taste for century-old shrimp paste flavour. https://www.scmp.com/news/hong-kong/article/1593980/tai-o-losing-its-taste-century-old-shrimp-paste-flavour Accessed August 2026.
  7. ↑ Kingcha, Y. et al. Microbial diversity during processing of Thai traditional fermented shrimp paste, determined by next generation sequencing. LWT. https://www.sciencedirect.com/science/article/abs/pii/S0023643819313313 Accessed August 2026.
  8. ↑ Sang, X. et al. Assessment of the Distribution and Safety of Tetragenococcus muriaticus for Potential Application in the Preparation of Chinese Grasshopper Sub Shrimp Paste. Frontiers in Microbiology. https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.628838/full Accessed August 2026.
  9. ↑ Rahayu, E. S. et al. A review: amino acids, biogenic amines, and microbial diversity in traditional Asian fermented shrimp-based products. https://www.researchgate.net/publication/398707829 Accessed August 2026.
  10. ↑ Goldthread. In Hong Kong's Tai O, making shrimp paste by hand is a dying trade. https://www.goldthread2.com/food/hong-kong-tai-o-making-shrimp-paste-hand-dying-trade/article/3088577 Accessed August 2026.
  11. ↑ Goldthread, as above.
  12. ↑ Sang, X. et al., as above.
  13. ↑ Sang, X. et al. The Impact of Microbial Diversity on Biogenic Amines Formation in Grasshopper Sub Shrimp Paste During the Fermentation. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7193991/ Accessed August 2026.
  14. ↑ Rahayu, E. S. et al., as above.
  15. ↑ IARC Monographs, Volume 100E. Chinese-Style Salted Fish. https://www.ncbi.nlm.nih.gov/books/NBK304384/ Accessed August 2026.
  16. ↑ Centre for Food Safety, Hong Kong SAR. Group 1 Carcinogens in Food – Are You Eating Them? https://www.cfs.gov.hk/english/multimedia/multimedia_pub/multimedia_pub_fsf_115_02.html Accessed August 2026.
  17. ↑ Health Canada. Food Allergen Labelling. https://www.canada.ca/en/health-canada/services/food-nutrition/food-labelling/allergen-labelling.html Accessed August 2026.
  18. ↑ Agriculture, Fisheries and Conservation Department, Hong Kong SAR. Conservation of fisheries resources. https://www.afcd.gov.hk/english/fisheries/fish_cap/fish_cap_con/fish_cap_con.html Accessed August 2026.
  19. ↑ Biodiversity Information Hub, Hong Kong SAR. Ecology and Biodiversity of Benthic Marine Ecosystems. https://bih.gov.hk/en/feature-studies/index-id-8.html Accessed August 2026.
  20. ↑ The Industrial History of Hong Kong Group, as above.
  21. ↑ Things To Do In HK. Shrimp Paste Factories: The Fading Culinary Heritage of Shrimp Paste. https://thingstodoinhk.com/article/shrimp-paste-factories Accessed August 2026.
  22. ↑ Localiiz, intangible cultural heritages, as above.
====================================================================

PROPOSED FINAL EXAM QUESTION

====================================================================

Question

Tai O shrimp paste contains no preservatives beyond salt, is never heat-processed, and remains shelf-stable for years at ambient temperature. (a) Explain the principal mechanism responsible for this stability. (b) Identify one food-safety hazard that this mechanism does not control, and explain why cooking the product before consumption does not eliminate it.

Answer

(a) Reduction of water activity. Salt binds free water osmotically and sun-drying removes water directly, lowering a_w below the level required for growth of most spoilage organisms and vegetative pathogens, while selecting for halophilic and halotolerant bacteria.

(b) Biogenic amines, particularly histamine. These are produced by bacterial decarboxylation of free amino acids liberated during proteolysis, a process that continues in the salt-tolerant microbial population that the preservation method actively selects for. Biogenic amines are heat-stable, so cooking does not degrade them.

Why this question should be on the final exam

Students routinely treat "preserved," "unspoiled," and "safe" as interchangeable. This question forces the three apart using a single product, and requires transfer of the water activity concept to an unfamiliar food rather than recall of a lecture example. Part (b) additionally tests the understanding that a preservation hurdle can select for the very organisms responsible for a chemical hazard — a point that applies well beyond this product, to salted fish, cured meats and fermented sauces generally.

Retrieved from "https://wiki.ubc.ca/index.php?title=Course:FNH200/Projects/2026/Tai_O_shrimp_paste&oldid=902715"