For Cesar Ojeda Linares, supporting traditional fermentation techniques in Mexico is a way to preserve culture and environment.
Interview by Maribel Alvarez
(Lea el articulo en español aqui.)
Cesar Ojeda Linares is an ethnobiologist and fermentation adviser researching traditions of fermentation of maíz, agave, cactus fruits, and other foods among rural and Indigenous communities in Mexico. Linares will participate in the second annual Pueblos del Maiz festival in Tucson in early May 2023 .
It is an honor to talk with you, Cesar. Tell me, where are you located and what is your work affiliation right now?
I’m working part-time at a brewery in Mexico City as a fermentation advisor and I’m about to start a post-doctoral stay at UNAM, at the Botanical Garden. I am a biologist. During my master’s degree research I did evolutionary biology, trying to understand how plants responded to environmental effects. In my PhD program, I decided that I was going to study something I was passionate about—fermented beverages. There was a great gap in research on the associated microorganisms, especially on our conception of them—how we humans work with something we cannot see. And since we can’t name these phenomena exactly, we end up using other things like textures, smells, and flavors to describe them.
It occurs to me that the recent interest—both in Mexico and elsewhere—in native crops and in paying attention to popular knowledge about food, comes from a crisis perspective, a realization of our own vulnerability. How do you see the study and documentation of fermentation under this somewhat apocalyptic umbrella?
I see fermentation as a process of resistance. Beyond the techniques, which focus on fermenting to provide better nutrients and diversify foods, fermenting is a way of resisting the system that increasingly limits our diets, reducing their range. I see fermentation as a tool and a way of thinking. My goal is to make microorganisms become the vehicle that helps us realize we have to take care of the environments where the foods we ferment come from. These fermented products foster identity. Communities identify themselves as fermenters of a certain product that not only offers the pleasant effects of intoxication, but also gives food, vitality.
Fermentation has become somewhat of a trend. We see it in the popularity of Kombuchas. Yet you come at it through the back door, where the original sources of fermentation knowledge lie.
Yes, totally. Kombucha, for example, is already quite a profitable business. But fermentation is a technique is accessible to all, one that also makes it possible to resist homogenization of the diet. My focus is not on how to do business, but to try to ensure that the communities continue to have access to these things, that they continue to maintain them. At the same time, it is difficult for the communities to have the capacity to develop these products because they do not have the capital. My hope is that the academic research offers them tools with which they can make better decisions.
Fermentation is a process of nature; it is found everywhere. It is one of the oldest human practices, and you have documented it very well. There is popular knowledge about some forms of fermentation. People know that bread is fermented and so is beer. But certain fantasies and fears also circulate because fermentation has to do with bacteria, with microorganisms. How do you see this ambivalence playing out?
We’ve just experienced a pandemic. The whole world suddenly saw microorganisms as something terrible, as something that had to be avoided. I observed this wave of obsession about reducing risks—the madness of cleaning the body with chlorine. The idea of sterilizing our surroundings grew during this time. But I also think people began to recognize microorganisms as something valuable. In fact, I heard that during COVID the term “sourdough starter” (in Spanish “masa madre”) was among the most searched topics on Google. Microorganisms started to be seen as important entities, especially in diet. But they have other biotechnological applications such as the preparation of medicines, biofuels, bioremediation.
I see an opportunity for dialogue opening up. In your work, you focus on the integral relationship between biological processes and cultural processes. In the world of fermentation there are those who reach high levels of expertise—craft beer brewers, for example. But your work focuses on the knowledge that lives among common people, which is often ancestral and kept alive in the oral history of a community. How do people in these areas react when you show up with a microscope?
I didn’t take a microscope with me to community research sites until my second year in the project. The first year I simply asked, “How do you make this liquid change composition? What is it that transforms it?” Many times, they offered me their unscientific but very accurate conceptions. They told me, for example, “Well, there is something there that allows it to boil.” It makes sense that they say “boil,” because the word ferment comes from the Latin “fervere,” which means to boil. They may not tell you about yeast, or bacteria, or lactic acid, but they know a lot.
When we brought the microscope, they saw for the first time the living organism they knew was present but was invisible. They also know a lot about how to handle fermentations. The Rarámuris (in Chihuahua) who make a fermented corn drink don’t wash the pots with soap in order to maintain the community of microorganisms for the next batch. But they also have this conception that other things can be added, such as pasture grasses that carry other yeasts and bacteria and promote fermentation in a different way.
In what ways do people adapt the primary inoculation (or adding of yeast) to influence flavor? I’ve heard of honey being added, for example.
Yes, but in the case of added sugar, it is also to raise the level of alcohol they want in the drink. In most of the cases that I have recorded, materials were added to prevent a certain group of bacteria or yeasts from flourishing; in other words, to keep products from spoiling. Pulque, a very popular fermented drink, is an example. It is made with the sap of the agave and is fermented. But when the producer sells it to someone who might not drink it within two hours, people add the peel of a tomatillo, Physalis philadelphica, which inhibits the growth of certain microbial groups, so the pulque doesn’t arrive over fermented.

There is creativity and innate genius in human beings. In your most recent publication, you organize the types of fermentation into groups of substrates[1] and name 16 traditional drinks, their origin, and use. Explain to me how you discovered these.
We organized drinks by the “core” plant used in their fermentation. To be honest, we chose those 16 because they are the drinks for which there are academic records. The truth is that we fall very short in “found drinks,” which do not appear in any journal but that are still valid in memory or community uses. In an article that just came out in January, we talked about the loss of two fermented beverages in the Tehuacán Valley, “tolonche” and “lapo,” that have never been documented. In some cases, these drinks have been marginalized because they are frowned upon by certain class and racial dynamics, because they are consumed by the poor or by Indigenous communities. The marginalization also comes from the Academy because sometimes the primary intention of scholars is to find products that have biotechnological applications. Their interest is in identifying strains that may have probiotic potential. Also, there are drinks we have not been able to register or study well because there is still a secrecy on the part of certain cultural groups to share knowledge with outsiders.
There have been cases where the intellectual property of Indigenous or native knowledge has not been respected, resulting in harm.
In the case of plants, it is very clear when these biopiracy problems happen. But in the case of microorganisms, it is more difficult since we are talking about microscopic levels. How do you protect what is not seen? The Kyoto Treaty includes this protection of biodiversity and especially agrobiodiversity. But that protection is not so easy. To protect, you must make records and you have to generate public policy that defends fermentation as intellectual property.
Let’s talk about the maize substrate, and the fermentation of beverages based on this grain. You locate the origin of these beverages as northern Mexico, among the Indigenous groups of Sonora and Chihuahua.
We focus on a drink called “tesgüino.” It is a drink generally associated with cultural groups such as the Rarámuris. It is a drink that is shared, sought after, and causes happiness. Not only the happiness of intoxication, but of wellness. The belief is that consuming this drink promotes being healthy. To make tesgüino, certain varieties of grains are collected, especially very local corn. The planting of this corn is promoted solely to produce this drink. And within these varieties, one is preferred because it is sweeter. The grains are selected, the corn is shelled, and then it is put to soak and store in the dark. After three days they have radicles, the initial root of the germinated seeds. Then they grind these grains and put them to ferment in pots called tesgüineras. The tesgüinera is also a form of identity. Every house has one of these.
Made out of clay?
Yes. These clay pots are taken care of year after year. They are not washed; no other chemical is added. However, if at some point the fermentation changes and does not look good, infusions of different herbs are applied, which bring alkaloids that serve as antimicrobials. Within the production process, they use wild grasses that grow around the milpa, which they take care of and promote. These grasses end up working as catalysts, bringing up certain yeasts or promoting the growth of certain enzymes to better break down the sugars in the drink.
The point I want to make is that drinks must be understood holistically–what human beings want as a final product, the environment where these resources come from and the knowledge.

The names of the fermented drinks that make up your analysis are super interesting. They have a very special sound. From the well-known mezcal, pulque, and tepache to others I had never heard of: chorote, colonche, balché, pox, and sour atole (“atole agrio”). I saw a drink called “tejuino” on the list. What is the difference between that drink and the “tesgüino” you were talking about?
The difference is significant. Sometimes the word tesgüino stands for Indigenous beer as a generic name. But “tejuino” is widely consumed in the states of Nayarit, Jalisco, and Colima. It is a refreshing drink. It is not alcoholic. It has a slight fermentation, but it is very basic and largely a lactic fermentation. The tejuino consists of nixtamal dough, the same process that is used to make tortillas or atole. You have this used nixtamal dough and add water, dissolve it, ferment it for a while and then prepare it with lemon, with salt. You put it on ice in frosted glasses to enjoy it on a hot afternoon.
With the commercial pressures of producing grains and corn that are modern and high yielding, how are the substrates for these highly specialized beverages preserved in terms of soil, breed, biological variety?
When I worked in Michoacán, my friends told me that it was common for people to plant certain varieties of corn that they liked to make atole or some kinds of tamale. Maybe it’s because it gives the dough different textures or because it gives them a different flavor or a different color. So, generally, communities try to maintain these substrates. In the case of sour atole, which is known in central Mexico around Tlaxcala or Puebla, people maintain the production of blue or black corn to make atole. But there’s also a lot of market pressure at the end of the day, where the buyer says to the farmer, “Hey, you committed to planting this entire plot of this same species.”
What gives you hope in this work and what worries you?
I would love to look for financing to continue this work. There are many gaps in this topic. I am also interested in generating workshops where fermented experiences are shared across the US-Mexico border. But I want to work with people who are not motivated by cultural appropriation, because I think this is very common now. I am referring to instances where people start selling these ancestral products that have been used for years as if they were a merchandise that they are just discovering. I would like to make the invitation to create cooperatives and civil associations so that these marketing offers do not in effect fragment the communities due to external interests.
[1] Substrate refers to the medium in which a chemical reaction occurs. In yeast fermentation, yeast operates on the substrate of sugar to produce fermentation.
A terrific article.. deep knowledge being shared here. Many thanks to Sr. Cesar Ojeda Linares for the insights and the writer as well,