History of Yoghurt, Part 2 - An exploration of our earliest relationships with yoghurt microbes.
History of Yoghurt, Part 3
While sour milk foods have been millennia in the making, the history of the yogurt found in a typical US or European supermarket traces its origins to the early 20th century. In the early 1900s, the Bulgarian researcher Stamen Grigorov was examining the yogurts of his home country and discovered a rod-like bacteria, now called Lactobacillus delbrueckii subsp. bulgaricus. We now know that this subspecies of bacteria is found in nature primarily as an intestinal microbe, such that it is reasonable to hypothesize that its originated from the gut of a yoghurt maker in Bulgaria or one of her or his animals. Inspired by his discovery of the Bulgarian gut-yoghurt microbe, the Nobel laureate Ilya Mechnikov connected the longevity of Bulgarian peasants with the central role of yogurt in this cuisine and postulated that the consumption of this bacteria played a role in maintaining health. Working at the Pasteur Institute in Paris, Mechnikov isolated pure cultures of this bacterial species, and his work caught the attention of Issac Carasso, who had recently moved his family from Thessaloniki to Barcelona to escape the Balkan Wars. There he opened a dairy factory and used Mechnikov’s cultures to create a commercial yogurt under the brand name Danone, later Americanized to “Dannon” in the United States. This historical isolation of a bacteria subspecies from a Bulgarian peasant yogurt (into which it may well have been inoculated from the body of a Bulgarian peasant) thus became the starter culture for the vast majority of subsequent commercially produced yogurts found in the US, Europe and Australasia. Odds are, if you have consumed a grocery store yogurt, you have consumed a descendent of one of Mechnikov’s original bacterial isolates.
Until recently, supermarket yogurt was fairly monotonous, with variations limited largely to the addition of different flavorings. However, increased connectivity in global cuisine has led to the awareness and rising popularity of different sour milk products, such as Greek-style yogurt, skyr, and crème fraiche. Greek-style yogurt is simply a richer yogurt that has been strained of whey to create a thicker texture with a higher fat content (around 10%), although due to market demand low-fat versions are also now available. In contrast, skyr, a yogurt-like product of Scandinavian origin, is traditionally made by straining skim milk fermented by thermophilic bacteria; it has a high protein but relatively low fat content. Creams can also be fermented to create products like crème fraiche, which is cream fermented with Lactoccus cremoris, L. lactis, and L. lactis biovar diacetylactis.
While consumers may be curious to try the flavors of new dairy products, a major driver in this sector is the booming “probiotics” industry. Although it might seem like a 21st century phenomenon, the link between diet, microbes, and health was first proposed more than a century ago by Ilya Mechnikov in his book The Prolongation of Life , which promoted the health benefits of consuming milk products soured by Lactobacillus. Mechnikov’s ideas were widely influential and adopted by physicians around the world, including the charismatic John Harvey Kellogg of breakfast cereal fame, who prescribed yogurt as both a tonic and an enema at his Michigan Battle Creek Sanatarium. Sour milk quickly became seen as a panacea by both medical professionals and the public, and it was reportedly used in preparation for surgery, as a disinfectant, as a digestive tonic, and to treat infections ranging from gonorrhea to typhus . Elite medical journals, such as the British Medical Journal, sought to tame some of this enthusiasm—promoting the consumption of “yoghourt,” but warning that one kilogram per day “should not be customarily exceeded”. As the movement continued to grow, many popular books followed, including one charmingly titled, “Intestinal Gardening for the Prolongation of Youth” . Yogurt rapidly became so entwined with ideas of medicine and longevity that when it was first commercially produced in the US, it was marketed as a health food and sold in pharmacies ; it wasn’t until after the 1970s that yogurt began to be widely consumed as a food in its own right.
Dairy probiotics first became commercialized in the first decades of the 20th century, initially though the sale of tablets, powders, and bouillons of Bulgarian Lactobacillus marketed under the brand names “Sauerin”, “Lactobator” and “Lactogenerator”, among others, and later as ready-made chocolates and candies innoculated with Lactobacillus . In Japan, the probiotic milk drinks Calpis (1919) and Yakult (1935) were developed, but while the thicker Yakult was inspired by the ideas of Mechnikov’s Lactobacillus-soured yogurt, Calpis was modeled after Mongolian airag and was fermented with Lactobacillus casei.
Recently, brands such as Activia (a subsidiary of Dannon) have invested heavily in microbiome research and have developed probiotic yogurts containing supplementary cultures of improved Lactobacillus lactis and Bifidobacterium lactis that are marketed as having superior probiotic properties. As a result of this commercialization, probiotic bacterial strains have become increasingly economically valuable and many are patented, meaning that their use by different companies and individuals is legally restricted by financial licensing agreements.
A world away from these regulated, commercialized yogurts is the diverse variety of small-scale and homemade sour mik products found in kitchens across the world. One of the most distinctive is airag (also called ayran or kumiss), a fermented horse milk drink popular across Central and Inner Asia. This bubbly and mildly alcoholic drink is the result of yeast and LAB which converts milk lactose into carbon dioxide, lactic acid, acetic acid, and alcohol. Airag was so important during the Mongolia Empire that Karakorum, the capital of the empire between AD 1235 and 1260, reportedly had at its center an elaborate silver fountain from which flowed airag instead of water (May 2016). Another distinctive fermented milk drink is kefir. Originally from the Caucasus, it is made through the action of kefir “grains” – complex clusters of symbiotic bacteria and yeasts that may contain up to 50 species . In northern China, a gelatinous milk custard called nai lao is consumed. Made by cooking milk with fermented rice wine, nai lao was originally introduced to China by the dairy-producing Manchus in the 1700s. Viili, a viscous fermented milk product consumed in Scandinavia, is the product of mesophilic fermentation, and, like airag and kefir, it is also made through the fermentation of both yeasts (specifically Geotrichum candidum) and LAB (Lactococcus lactis and Leuconostoc mesenteroides). The characteristic gluey, ropy texture of viili results from its abundance of exopolysaccharides – long chains of sugars excreted from the bacterial cells. Finally, quark, a kind of strained soured milk popular in German speaking countries, is produced by fermenting skim milk at ambient temperatures using mesophilic Lactococcus bacteria, followed by heating to form a curd, and then straining.
Yogurt and sour milk products have been produced by humans throughout large parts of the Near East, Europe, Asia, and Africa since prehistory. Souring milk extends the use life of milk, and it also enhances milk’s nutritional content and digestibility. Hundreds, if not thousands, of distinct sour milk products have been developed by dairying societies, and these traditions have been passed down across generations, a culinary partnership of people, livestock, bacteria, and yeasts that stretches back millennia. Although this microbial inheritance has been largely replaced with a few cultured laboratory strains in industrialized North American and European food systems, heirloom microbial communities can still be found in the sour milk products of traditional dairy producers around the world. In rural Mongolia, starter cultures of traditional microbes, affectionately called khöröngö (“wealth, inheritance”), continue to be passed down from generation to generation, propagating new batches of tarag yogurt again and again. For rural Mongolians – who consume nearly one third of their diet as dairy products despite being genetically lactose intolerant - microbial fermentation is more than just a means of preservation, it is the essential factor that supports their cuisine and enables their nomadic way of life on the steppe. The remarkable power of microbes to transform is what makes sour milk products such a surprising culinary feast. More than a simple food, sour milk products are living history, enlivened by their long parntership with us. So next time you are in the supermarket, skip the additives and flavorings and fillers, take in the full flavor of a simple cup of all-natural yogurt and contemplate the genealogy of the microbes you are consuming. In all likelihood, their predecessors were isolated from a Bulgarian peasant yogurt in Paris before a war refugee in Barcelona turned them into a starter culture that would conquer the world.
*Cover image by Peter Hershey peterhershey, CC0, via Wikimedia Commons