It is a well-known fact among Vietnamese that their home country has a rich portfolio of fermented food, from mắm chua (pickled shrimp) to mắm tôm (shrimp paste). Here is a comprehensive look into not only these funky condiments' history, taste and production, but also the emerging food science behind them.
For thousands of years, Vietnamese cuisine has taken great pride in its arsenal of preserved foodstuffs. Indeed, the category constitutes some of the most essential elements of Vietnamese flavors — think nước tương (soy sauce), nước mắm (fish sauce) or mắm tôm (shrimp paste) — these are condiments that few dishes go without.
Nước Mắm (Fish Sauce)
Fish sauce is fiercely coveted by diners across Southeast Asia and even in smaller pockets across the continent as a whole. For example, in Japan it is known as shottsuru and widely used in nabemono, the nation's version of a hotpot. Indeed, any self-confessed addict of Vietnamese cuisine must have a soft spot for the sauce. An iconic example was Anthony Bourdain imparting the flavors of Hanoian bún chả to former US President Barack Obama. It is incredibly versatile, useful to garnish any dish in its concentrated form and makes an exquisite broth on its own if diluted.
This origin and history of fish sauce is remarkably hard to pinpoint. Its distribution spans a great distance, even reaching parts of East Asia, as investigated in Ishige Naomichi's The History and Culture of Japanese Food. Academics believe that the origins of the condiment is lost in antiquity due to its existence predating written history:
"If salted fish were accidentally allowed to stand around before drying, autolysis would automatically occur. A keen observer would recognize that the salted fish had now acquired a new and appealing flavor," wrote the late biochemist Joseph Needham in the sixth volume of his Science and Civilisation in China (1954-2016). "He or she would be tempted to try the method again. In other words, the fermentation of salted fish was an invention that was just waiting to happen."
This sentiment is corroborated by other works on food cultures. In Salt: a World History, Mark Kurlansky proposes that in comparison to Western fish sauces, which are thought to have their roots in the Roman Empire, its Asian counterparts were likely to have developed separately:
"The Asian sauce is thought to have originated in Vietnam, though the Vietnamese must have taken it in ancient times from the Chinese soy sauce, in those early times when the Chinese fermented fish with the beans," Kurlansky writes, noting the historical and geographical relationship between the two countries. Thus, a state of aporia (Greek for "at a loss") surrounds the origins of the humble commodity, at least where written records are concerned.
Distribution of fish sauce in East Asia. Map courtesy of The History and Culture of Japanese Food by Ishige Naomichi.
Any mention of fish sauce must touch on its aroma. The light-to-dark amber liquid's scent was dissected in forensic details in a study shared by Pham AJ and Wes Schilling of Mississippi State University with Saigoneer:
"Aromas that were isolated and present in all four fish sauce samples at all concentrations included fishy (trimethylamine), pungent and dirty socks (combination of butanoic, pentanoic, hexanoic, and heptanoic acids), cooked rice and buttery popcorn (2,6-dimethyl pyrazine), sweet and cotton candy (benzaldehyde)." The authors, therefore, provided scientific confirmation of fish sauce's unmistakable kaleidoscope of smells. Or in layman's terms, it stinks, and is proud of it.
Which leads us to consider its fermentation process, or how exactly fish sauce gets its tell-tale stink. This is a procedure that requires approximately a whole year to complete, though the specifics vary by manufacturer thanks to today's copious availability of chemical catalysts, as noted in a literature review by Nguyen La Anh, who leads the Microbial Technology Center (MTC) in Hanoi:
"Fish and salt are mixed at a ratio of 25-33% in a vessel made of wood, ceramic, or cement depending on the local custom...The traditional method involves fermentation for 12-18 months. Nowadays, fermentation time is shortened to six months by addition of enzymes from external sources. Anchovy [cá cơm] is the most commonly used fish for making nước mắm. Temperature for fermentation and hydrolysis is in the range of 35-50 degrees Celsius."
Anh's observation that the Vietnamese version of the sauce primarily relies on anchovies is important, because it's the ingredient that ties nước mắm to its Southeast Asian siblings. For instance, Thailand's nam pla and the Filipino patis both employ anchovies as their star fish. In contrast, the Japanese shottsuru is made from hatahata (sailfin sandfish) while the Korean eoganjang — especially popular in Jeju — relies on godori, or young chub mackerels; thus, they each have a distinct flavor of their own.
Nước Tương (Soy Sauce)
Like its sister fish sauce, soy sauce is a key flavor in nearly any dish, not only for Vietnamese, but for almost everyone in East Asia. "With soy sauce you can cook an untiring series of Chinese dishes with nothing but those foods that you can get at any American chain market," Buwei Yang Chao wrote in her famed How to Cook and Eat in Chinese (1963) regarding the sauce's ubiquitous presence in Chinese and Asian cuisine.
The seasoning is made with soybeans, a legume bearing the scientific name Glycine Max. Soy sauce itself bears various labels from a variety of Asian cultures, in Chinese, it's known as jiang you (or chiang yu), shoyu in Japanese and nước tương here in Vietnam.
"Discovered in China more than 2,500 years ago, soy sauce is one of the world's oldest condiments," stated Keshun Liu in an essay included in the Handbook of Food and Beverage Fermentation by Y. H. Hui, et al.
This origin is corroborated by works of other academics involved in investigating the science and history behind the sauce, with the aforementioned biochemist Joseph Needham drawing the same conclusion:
"The earliest references to the term chiang yu [soy sauce] occur in two late Sung works. Lin Hung's Shan Chhing Kung (Basic Provisions for Rustic Living) gives four recipes in which chiang yu is used to flavor various vegetables and seafood." Needham remarked in his book on written evidence of the existence of soy sauce dating to China's Song Dynasty, which flourished between 960-1279 AD.
Traditional soy sauce fermentation in the early 20th century: incubating jars with bamboo covers. Photo courtesy of Joseph Needham in Science and Civilisation in China: Volume 6.
"Throughout the history of the Chinese language, yu has always meant the oily (or greasy), water insoluble substance derived from animal, vegetable or mineral resources, for example, chuyu (lard) or niuyu (butter)," Needham expounded in his book, of the linguistic curiosity that exists in the Chinese language where soy sauce is concerned. "It is an aqueous solution (or suspension) of a variety of substances, and by no stretch of any imagination can it be construed as a yu (oil)."
As a result, the Mandarin chiang yu stands in stark contrast to Vietnamese nước tương because the latter literally translates to "water from soy" which is, given its fluidity, more apt in describing the condiment itself. This naturally allows us to come to the process of making nước tương, paying particular attention to the following: the roles of rice and the amazing fungi Aspergillus oryzae.
Compared to its counterparts elsewhere around Asia, the modern way to produce nước tương relies heavily on rice or glutinous rice and often forgoes wheat, unlike other countries such as Japan, where household names such as Kikkoman are known for emphasizing wheat in their production.
The use of rice forms a foundation from which a fungi microbial culture is introduced to the rice, which is then allowed to incubate for a few days, as illustrated in a flowchart from Nguyen La Anh's research below. This is essential to produce hydrolysis, a chemical reaction between the mixture and water, in turn providing an ideal environment where beneficial mold and roasted soybeans mingle together to give birth to nước tương.
Here is where the funky science really kicks in, thanks to our little fungi, Aspergillus oryzae. Otherwise known as koji, this domesticated mold has been pivotal for centuries, not only to the cultivation of soy sauce, but also rice wine, Chinese Huangjiu beverage, and other liquids. The fact that it's categorized as a domesticated fungi is important, as it speaks volumes about the history of soybean fermentation, according to a study by John G. Gibbons of Clark University on the evolutionary pathway of the mold.
Flow chart illustrating the process involved in making nước tương (soy sauce). Image courtesy of Health-promoting microbes in traditional Vietnamese fermented foods: A review by Nguyen La Anh.
Mắm Tôm (Shrimp Paste)
The third member of the proverbial trinity of Vietnamese preserved foods is mắm tôm, or shrimp paste. In equal measure, it manages to live up to that accolade, bearing a distinctive stink entirely its own. On its own, the paste takes one's nose on a learning curve without the distraction of being accompanied by a main dish, often a hot bowl of broth like bún riêu.
Its smell and taste have even been compared to durian by Vietnamese food bloggers, like Vi Bi of Christina.vn. Although, on a personal level, it is best to compare mắm tôm to Marmite, the British fermented yeast spread that evokes very strong feelings.
In order to explore how the paste earned its odor, it's important to realize that mắm tôm has a non-identical twin in the form of mắm ruốc, which is extremely popular in northern communities in Vietnam such as Hanoi and Hai Phong. What separates the two from being the same lie wholly in their fermentation process, as detailed in a study sent to Saigoneer by Vu Nguyen Thanh, a researcher at Hanoi's Center for Industrial Microbiology:
"Mắm tôm is prepared in [a] similar manner but the salt concentration used is significantly lower (shrimp to salt ratio of 4-6:1 for mắm ruốc and 7-9:1 for mắm tôm). After grinding/pounding, the paste is transferred directly to the jars for fermentation (without partial drying)," Thanh elaborates on the stages necessary to prepare both condiments. "Instead of strict anaerobic fermentation, for mắm tôm production, periodic stirring and sunning is performed. The obtained product is more fluid and has strong odorous smell."
The anaerobic (no air) environment required for mắm ruốc is what separates it from its sibling, mắm tôm. Louis Pasteur, the father of microbiology, once proposed that fermentation was 'life without air'. It turned out he was partially wrong, as fermentation can continue in the presence of oxygen through rare aerobic respiration, as is the case for mắm tôm. A much lower salt content combined with deliberate, occasional exposure to air is responsible for its stronger pungency. A halophilic (salt-loving) microbe is essential for mắm ruốc .
A map of William Dampier's travels around Asia between 1679-91. Map courtesy of the Special Collections at King's College, Cambridge.
Similar to fellow traditional foods, tracing the footsteps of mắm tôm often requires delving into records of marine explorers, according to an entry in Gastronomica, a 2009 journal devoted to critical food studies, by Su-Mei Yu.
Yu wrote of the opinions held by various dignitaries on Thai cuisine of the time: "Their sauces are plain, a little water with some spices...They do much esteem a liquid sauce, like mustard, which is only crayfish corrupted, because they are ill-salted, they called it Capi."
Another explorer who commented on the paste was William Dampier, a British buccaneer in the 17th century, in an account of a trip to Tonkin (modern-day northern Vietnam):
"To make it, they throw the mixture of shrimps and small fish into a sort of weak pickle, made with salt and water, and put it into a tight earthen vessel or jar. The pickle being thus weak, it keeps not the fish firm and hard, neither is it probably so designed, for the fish are never gutted," Dampier recalls of his culinary adventure while visiting the region. "Therefore, in a short time they turn all to a mash in the vessel; and when they have lain thus a good while, so that the fish is reduced to a pap, they then draw off the liquor into fresh jars, and preserve it for use. The mash[ed] fish that remain is called balachaun, and the liquid poured off is called nuke-mum."
At first glance, one can have the impression that Dampier was referring to fish sauce when he wrote "nuke-mum," and that this was merely an interesting attempt at putting into words the pronunciation of nước mắm. Until he elaborated on its color: "The nuke-mum is a pale brown colour, inclining to grey," which strongly suggests an inference to mắm tôm with its grey hue or its close relative, mắm ruốc, a pulverized mixture of preserved shrimps and small fishes when Dampier referred to 'balachaun.'
A flowchart showing the steps involved in producing mắm tôm and mắm ruốc. Courtesy of Ethnic Fermented Food and Beverages of Asia by Vu Nguyen Thanh.
Gut science
In writing about fermented foods, it's always tempting to delve deeper into the science behind the beneficial microbes in each dish, be it the koji mold that gifts us soy sauce or different microorganisms inside both shrimp paste and fish sauce. An exciting frontier of research to which traditional Vietnamese fermented cuisine and Asia as a whole can contribute is probiotics.
This field investigates the range of bacteria that can make a positive difference on our gut's health, some of which have been mentioned in the academic works quoted this article, such as Nguyen La Anh's literature review and Vu Nguyen Thanh's investigation. Both have found that there exists bacteria that are recognized as probiotic.
Thus, the world inside our digestive system continues to surprise us. Terms such as bacteria and microbes often have negative connotations attached to them, yet those that live inside our stomach represent important symbiotic relationships that have span our own evolutionary pathway.
"Probiotic bacteria exert effects in many different ways depending on the health of the person consuming them. A bacterium itself will have no direct dietary - as in nutritive - benefit," Karen Scott — who is currently President of the International Scientific Association of Probiotics and Prebiotics and Senior Research Fellow at the Rowett Institute, Aberdeen — told Saigoneer in an email exchange. "They can also help restore the colonic pH thus enabling the normal microbiota to regenerate following periods of disruption due to infection - and again this has a health benefit to the host."
"The general benefits include enhanced food safety (preservative effects of fermentation), decreased allergenicity of these foods and increased nutrient availability," Paul Cotter, Head of Food Biosciences at TEAGASC, Ireland's agriculture and food development authority, told Saigoneer via email.
Ultimately, this is an area of research that is only beginning to be investigated," Cotter said, acknowledging the emerging body of research that lies behind our everyday foods, such as blue-veined cheese or fermented milk. Although it might seem that research is abundant in the fields of traditional fermented cuisine around the world, especially when it comes to the microbial environments they harbor, it is a field still in its infancy. This is often marked by the fact that food science, as a discipline, is primarily devoted to disseminating issues surrounding food security and safety. However, that can only mean the enthralling background behind three of Vietnam's most iconic fermented items remains a fertile venue where gourmet enthusiasts and scientists can collide.
Infographic on the effects of probiotics and how gut microbes affects our health. Image via ISAPP.
