Fungi fusion: Turning food waste into culinary delights

Chef-turned-chemist Vayu Hill-Maini has a unique passion: transforming food waste into culinary delights using fungi.

One of his notable collaborators is Rasmus Munk, head chef and co-owner of the Michelin two-star restaurant Alchemist in Copenhagen. Inspired by Hill-Maini, Munk serves a dessert featuring orange-colored Neurospora mold grown on rice.

Flavored foods created with fungi

For the past two years, Hill-Maini has been working with a team of chefs at Blue Hill at Stone Barns, a Michelin two-star restaurant in Pocantico Hills, New York, to create flavorful dishes from Neurospora mold cultivated on grains and pulses, including the pulp left over from making oat milk. 

At Blue Hill, diners may soon enjoy a patty of grain topped with orange Neurospora, accompanied by a side of moldy bread – orange Neurospora grown on rice bread that, when fried, tastes and smells like a toasted cheese sandwich.

Bringing a common fungus to Western plates

But this is just the beginning for Hill-Maini, a Miller postdoctoral fellow at the University of California, Berkeley. 

In the lab of Jay Keasling, a UC Berkeley professor of chemical and biomolecular engineering, Hill-Maini has dedicated himself to understanding everything about Neurospora intermedia – a common fungus traditionally used in Indonesia to make a food called oncom from soy pulp. His goal is to adapt this fungus more broadly to Western food waste and palates.

“Our food system is very inefficient. A third or so of all food that’s produced in the U.S. alone is wasted, and it isn’t just eggshells in your trash. It’s on an industrial scale,” Hill-Maini explained. 

“What happens to all the grain that was involved in the brewing process, all the oats that didn’t make it into the oat milk, the soybeans that didn’t make it into the soy milk? It’s thrown out.”

Tackling the challenge of food waste

When a fellow chef from Indonesia introduced him to fermented oncom, Hill-Maini realized it was “a beautiful example of how we can take waste, ferment it, and make human food from it.” 

“So let’s learn from this example, study this process in detail, and maybe there’s broader lessons we can draw about how to tackle the general challenge of food waste.”

Exploration of fungal foods 

Hill-Maini’s enthusiasm for Neurospora inspired Blue Hill to install an incubator and tissue culture hood in its test kitchen this summer, allowing the restaurant to further explore fungal foods. 

Before this, Blue Hill’s chef in charge of special projects, Luzmore, would FedEx various substrates to Hill-Maini’s lab at the Joint BioEnergy Institute (JBEI) in Emeryville, California, where Neurospora would transform them for study. Luzmore has tasted many Neurospora experiments, but his favorite remains the one made from stale rice bread.

“It’s incredibly delicious. It looks and tastes like you grated cheddar onto bread and toasted it,” Luzmore said. “It’s a very clear window into what can be done with this.”

Transforming food with fungi

Cultures around the world have long consumed foods transformed by fungi – yeast turns grain into alcohol, Penicillium mold turns milk curds into blue cheese, and koji mold (Aspergillus oryzae) ferments soybeans into soy sauce and miso. 

However, oncom is unique in being made from waste food. Developed by native Javanese long ago, it seems to be the only human food fermented solely by Neurospora mold – at least, for now.

A paper by Hill-Maini on the genetics of Neurospora intermedia strains that transform soy milk waste into oncom, and how the fungi chemically alter 30 different types of plant waste, was published online on August 29 in the journal Nature Microbiology.

Potential of fungi for planetary health

“In the last few years, fungi and molds have caught the public eye for their health and environmental benefits, but a lot less is known about the molecular processes that these fungi carry out to transform ingredients into food,” Hill-Maini said. 

“Our discovery opens our eyes to these possibilities and further unlocks the potential of these fungi for planetary health and sustainability.”

In West Java, oncom comes in two varieties: red oncom, made by fermenting soy pulp left over from tofu production, and black oncom, grown on the leftover pressings from peanut oil extraction. Both are used in stir-fries, as fried snacks, and as fillings for dumplings.

Indigestible plant material 

One remarkable aspect of these moldy foods, Hill-Maini discovered, is that the fungi transform indigestible plant material – polysaccharides like pectin and cellulose from plant cell walls – into digestible, nutritious, and tasty food in just about 36 hours.

“The fungus readily consumes these materials and, in doing so, creates food and more of itself, which increases the protein content,” he said. “You actually see a transformation in nutritional value. The flavor profile changes – some off-flavors associated with soybeans disappear. And beneficial metabolites are produced in high amounts.”

Filamentous fungi and bland food

While yeast – a single-celled fungus – is well-known for fermenting grain and fruit into alcohol, the fungus that makes oncom is different. It’s a filamentous fungus, growing in thread-like filaments similar to those in the mycorrhizae of fungi in forest soil that produce mushrooms. 

However, the oncom fungus does not produce mushrooms; it resembles the mold that grows on spoiled food. Penicillium mold (which produces blue cheese) and koji mold (used for soy sauce, miso, and sake) are examples of filamentous fungi that elevate bland food to new levels.

Oncom, however, is one of the few fungal foods grown on food byproducts. In his paper, Hill-Maini demonstrated that N. intermedia can grow on 30 different types of agricultural waste, from sugar cane bagasse and tomato pomace to almond hulls and banana peels, without producing toxins that sometimes accumulate in other mushrooms and molds.

Genetic analysis of fungi 

Hill-Maini also analyzed the genetics of the fungi that produce oncom. Surprisingly, he found that the fungus responsible for red oncom is primarily N. intermedia – it was the dominant fungus in all 10 samples from West Java.

“What was very clear is, wow, this fungus is probably dominant and maybe sufficient for making this food possible, growing on the cellulose-rich soy milk waste and making the food in 36 hours.”

The fungi in black oncom, however, were dominated by various Rhizopus species, with their composition varying by location. Tempeh, another ancient and popular Javanese source of protein, is also produced by Rhizopus mold fermenting fresh soybeans.

Further genetic analysis revealed that there are essentially two types of Neurospora: wild strains found worldwide and strains specifically adapted to agricultural waste produced by humans.

“What we think has happened is that there’s been a domestication process as humans started generating waste or by-products, creating a new niche for Neurospora intermedia,” Hill-Maini said. “And through that, the practice of making oncom likely emerged. We found that these strains are better at degrading cellulose, essentially turning trash into treasure.”

Turning waste into tasty food 

Since the domesticated Neurospora strain effectively degrades cellulose in soy and peanut waste into a tasty food, Hill-Maini wondered if it could make other waste products edible.

“The most important thing, especially for me as a chef, is, ‘Is it tasty?’ Sure, we can grow it on all these different things, but if it doesn’t have sensory appeal, if people don’t perceive it positively outside of a very specific cultural context, then it might be a dead end,” he said.

In collaboration with Munk at Alchemist, Hill-Maini presented red oncom to 60 people who had never encountered it before and asked for their feedback.

“We found that people who had never tried this food before assigned it positive attributes – it was more earthy, nutty, mushroomy,” Hill-Maini said. “It consistently rated above six out of nine.”

Adding desert to the menu

The chefs at Alchemist also grew Neurospora on peanuts, cashews, and pine nuts, which were well-received.

“Its flavor is not polarizing and intense like blue cheese. It’s a milder, savory kind of umami earthiness,” Hill-Maini explained. Different substrates impart their own flavors, with fruity notes emerging when grown on rice hulls or apple pomace.

This led Munk to add a Neurospora dessert to Alchemist’s menu: a bed of jellied plum wine topped with unsweetened rice custard inoculated with Neurospora, left to ferment for 60 hours, and served cold with a drop of lime syrup made from roasted leftover lime peel.

“We experienced that the process changed the aromas and flavors in quite a dramatic way – adding sweet, fruity aromas,” Munk said. “I found it mind-blowing to suddenly discover flavors like banana and pickled fruit without adding anything besides the fungi itself. Initially, we were thinking of creating a savory dish, but the results made us decide to instead serve it as a dessert.”

This dessert was among other edible Neurospora fermentations discussed in a paper published last December in the International Journal of Gastronomy and Food Science, where Hill-Maini, Munk, and their colleagues reported on taste tests of oncom and oncom-like foods grown on substrates other than soy.

Extending the research to other culinary applications 

“I think it is amazing that we as a restaurant can contribute something like this to the scientific community,” Munk added.

“We have said from the start that Alchemist’s ambition is to change the world through gastronomy, and this project has that kind of potential. I am very excited to see what other culinary applications this research can lead to in the future, using other waste products from the food industry.”

Munk recently launched a food innovation center, Spora, initially focused on upcycling side-streams from the food industry and developing delicious and diverse protein sources.

Hill-Maini and his passion for cooking

Hill-Maini’s culinary journey began at home, where cooking was central to family life. His mother, of Indian descent from Kenya, held cooking classes in their Stockholm apartment in the 1990s, introducing Swedes to the spices and cooking styles of India. His father has Cuban and Norwegian roots.

“Growing up, I connected with cooking early on as a way to understand my cultural heritage and where I came from,” he said.

After high school, Hill-Maini took his passion for cooking to New York City, working in various low-level food-prep jobs before impressing one employer with the sandwiches he brought for lunch. 

By age 18, he was chosen to redesign the menu of a well-known Manhattan sandwich shop, where one of his creations was voted among the city’s top veggie sandwiches by The New York Times.

Eventually, he returned to school, supporting himself as a chef while pursuing his interest in the science behind the chemical transformations in cooking. After earning his bachelor’s degree from Carleton College in Northfield, Minnesota, he was accepted into the graduate program at Harvard University, where he studied biochemistry and conducted Ph.D. research on the gut microbiome.

Bringing biochemistry to the culinary world

“Then, you know, I wanted to come back to the kitchen,” he said. “The Miller Fellowship was an opportunity to say, ‘I have training in the culinary world. I have training in biochemistry and microbiology. How do I bring them together, especially considering the sustainability challenges we’re facing and how wasteful and devastating our food system is on the planet?’”

With fellowship support, Hill-Maini visited restaurants – including Blue Hill, Alchemist, and the Basque Culinary Center in Spain – to give workshops on fermentation.

“That inspired me to go back to Berkeley and think about my research differently,” he said.

A hub of innovation

Blue Hill has hosted him five times over the past two years, most recently in late June, to help inaugurate the restaurant’s microbiology lab, where Luzmore hopes Hill-Maini and other chef-scientists will visit and experiment.

“The reason why we have loved working with Vayu so much is because I think he really embodies a lot of where we are going,” Luzmore said. 

Now 20 years old, the for-profit Blue Hill restaurant and the nonprofit Stone Hill Farm are transitioning from being champions of farm-to-table dining to “endeavoring to make research a bigger part of what we do here – not just having a farm and a restaurant, but really, hopefully, being a hub of innovation – a sandbox where we can bring in people like Vayu to do this research.”

New tool in the toolbox

In addition to working at Blue Hill’s “sandbox,” Hill-Maini will soon have his own: a kitchen-equipped lab at Stanford University, where he has been appointed an assistant professor of bioengineering.

As he sautéed an oat milk waste burger he made in his Berkeley apartment last June, Hill-Maini enthusiastically discussed the opportunities Neurospora presents and the debt he owes to the Javanese, who long ago co-opted the fungus to make oncom. 

He sees Neurospora as offering a new type of fermentation that complements the widely used koji mold, which has become so prevalent among chefs that it’s almost overused. “This is a new tool in the chef’s toolbox.” 

A new way of looking at food 

Hill-Maini plated the perfectly seared burger – indistinguishable from a small beef patty – on a bed of cashew-avocado sauce, pairing it with roasted sweet potatoes and a fresh cucumber-cherry tomato salad with herbs and lemon. He cut the burger with a fork, swirled it through the sauce, and took a bite.

“Mmm, look at that – waste to food,” he said. “It has good bite, it’s savory, with a note of mushrooms and some fun, fruity aromas.”

In future research, Hill-Maini hopes to uncover how Neurospora produces these flavors and aromas, while also making a dent in the food waste stream.

“The science that I do – it’s a new way of cooking, a new way of looking at food that hopefully leads to solutions that could be relevant for the world,” he concluded.

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