To make a tasty yogurt, just add ants (and their microbes)

In various regions of Eurasia, an unusual component for a zesty yogurt delicacy scurries across the forest floor.

Red wood ants alongside their symbiotic microbes play a crucial role in acidifying and thickening milk, effectively fermenting it into a rich yogurt, according to research published on October 3 in iScience. For optimal results, utilizing live ants rather than frozen or dehydrated ones is essential for fostering the appropriate microbial and chemical environment.

The origins of yogurt-making trace back approximately 7,000 years. The advent of modern industrial techniques has simplified the process, predominantly relying on a limited number of acid-producing microbes. In contrast, traditional methods are characterized by their diversity, introducing a wide array of bacterial species. For example, in parts of Turkey, yogurt cultures have been initiated using pinecones or chamomile flowers.

Commercial yogurt production guarantees food safety and allows for greater volume, with factories achieving consistency in flavor. “We’ve found a balance that satisfies everyone’s palate,” notes Veronica Sinotte, a microbial ecologist at the University of Copenhagen. Homemade yogurt, however, reflects the individual skills of its maker, leading to variable tastes. For instance, community members in the Bulgarian homeland of anthropologist Sevgi Mutlu Sirakova claim they can identify the source of yogurt just by tasting it.

Sirakova’s ancestral village is situated within the area where the traditional practice of utilizing red wood ants (Formica rufa and F. polyctena) to produce yogurt was historically prevalent. In this locale, Sinotte, Sirakova, alongside their team from Ludwig-Maximilians-Universität München in Germany, introduced four live ants into a jar filled with warm raw cow’s milk. The jar was then buried within an ant mound, allowing the nest’s warmth to facilitate fermentation overnight. Upon retrieval, the milk had transformed into an early yogurt-like substance with a tangy and herbal flavor profile.

Investigations at the molecular level revealed that the F. polyctena ants house lactic and acetic acid bacteria that are crucial for milk thickening, including Fructilactobacillus sanfranciscensis, a species commonly found in sourdough. Additionally, the ants contribute formic acid, acting as a chemical deterrent against predators, to the fermenting mix. Milk-digesting enzymes from both the ants and the bacteria work collaboratively to transform the milk into a creamy yogurt.