A traditional food from Indonesia holds a microbial secret that researchers believe could help dispatch piles of food waste—from fruit peels, to rice husks, and coffee grounds—and turn it into something delicious.
Indonesians have been doing this for centuries with oncom, a staple food made from leftover soybean waste. After soybeans are processed to make tofu, the leftover pulp is infused with a fungus that ferments the mixture, covering it in a vivid orange skin. The resulting flavors are said to vary from mushrooms to the cheesy richness of brie, and even pork chops when fried. In fact, oncom is widely used as an affordable meat substitute in the country.
Intrigued, the researchers on the study, who collaborated with chefs, were curious to learn more about the fungus, and how else it might be applied. Outside of Indonesia, oncom’s unfamiliarity may make it off-putting to some people—but could that change?
Writing in Nature Microbiology, they decided to delve into this question by exploring the genetics of oncom fungus. They genetically-sequenced samples of soy-based oncom (it can also be produced from the byproducts of making peanut oil), and this revealed that across all samples one type of fungus was dominant, a species called Neurospora intermedia.
This led to the next fascinating discovery, when they compared N. intermedia isolated from oncom, with N. intermedia taken from sources in the wild. The oncom-derived fungus was genetically distinct from its wild cousins, and had formed a unique strain. This suggests that these fungus strains have become specially adapted to the food waste substrates, almost as if they’ve been domesticated. In particular, the fungus seemed to be well-adapted to feed on cellulose, which typically makes up a lot of the leftovers of industrial food processing.
This strengthened the researchers’ hunch that the fungus would be well-adapted to transform other waste into palatable food.
To find out, they decided to test the fungus strain on 30 types of food waste, mainly representing the kinds of byproducts you’d get from industrial food processing. These included the pomace left behind after pressing fruits and vegetables for their juice; the oat, hemp, and coconut mash leftover from making plant-based milk; and rice husks, spent grain, and wheat bran.
While the fungi refused to grow on a handful of waste foods—only olive pomace, grape pomace, and buckwheat husks—it thrived on almost everything else. Interestingly, on waste foods where the fungus grew most happily, the researchers found increased protein levels. Meanwhile, they detected none of the toxins that are sometimes associated with fungal foods.
The final hurdle was a taste test. When the research team cooked oncom for 61 Danish panelists who had never tried it before, the reviews were roundly positive. Most participants scored the food above 6 out of 9 for several attributes. They ranked it highly for its texture and flavor, which they described as earthy, mushroomy, and nutty.
Since working on the study, the researchers have worked with chefs to develop oncom-inspired foods such as a fermented patty made from oat milk waste, and a cheese-like delicacy made from old rice bread.
Food waste is often framed as a problem driven by unsustainable consumers. But a huge share originates in industrial food processing and production before it reaches any plate. Rescuing some byproducts from this wastestream could offset a chunk of food system emissions.
“This study serves as another reminder that traditional foods may hold clues to addressing global challenges in sustainability,” the researchers write.
Keasling et. al. “Neurospora intermedia from a traditional fermented food enables waste-to-food conversion.” Nature Microbiology. 2024.
Image: A sauteed patty composed of soy pulp inoculated with Neurospora mold and left to ferment for several days. UC Berkeley postdoctoral fellow Vayu Hill-Maini prepared and cooked the patty, plating it with a cashew cream sauce, baked yams and a fresh cherry tomato and cucumber salad. Patrick Farrell, UC Berkeley
