Aberystwyth University study shows how fungal fermentation can improve aroma in alternative protein foods

Researchers at Aberystwyth University have developed a fungal fermentation process that improved the aroma and nutritional quality of alternative protein foods made from surplus bread crusts and perennial ryegrass protein.

• The study used solid-state fungal fermentation to transform surplus bread crusts and ryegrass protein into a protein-rich food ingredient.
• Researchers identified more than 150 aroma compounds during fermentation and found different fungi produced distinct smell profiles.
• The work formed part of a four-year collaborative project involving Aberystwyth University, the University of Reading and industrial partners.

The work, led by scientists at the university’s Institute of Biological, Environmental and Rural Sciences, explored how natural fungal fermentation could be used to make unconventional ingredients more appealing to consumers. The researchers fermented a mixture of leftover bread crusts and protein from perennial ryegrass for up to 72 hours, then analyzed the aroma compounds produced during the process.

The study, published in npj Science of Food, identified more than 150 aroma compounds created through solid-state fermentation, a method widely used in Asia to produce plant-based protein foods such as tempeh from legumes, beans and cereals.

The researchers reported that different fungal strains produced different aromas, ranging from alcoholic notes to cheesy and earthy profiles. The findings suggested that aroma could be adjusted during processing, potentially helping manufacturers develop more acceptable foods from food industry byproducts and agricultural crops not usually consumed directly by people.

“Smell is essential to our enjoyment of food. By understanding how aroma compounds develop during fungal fermentation, we can turn unconventional ingredients into novel food products that are more sustainable and more appealing to consumers,” said Juan Felipe Sandoval Rueda, lead author of the study. “We found that fermenting the bread crusts with different types of fungi produces different odors – some can be very alcoholic, others more cheesy or earthy.”

After fermentation, the material was dried and processed into a protein-rich powder. According to Sandoval Rueda, the powder could be added to other ingredients, including wheat flour, to make protein-enriched bread.

“Our study also discovered a new mathematical method of predicting the odor of new food products at an early stage in the process, with potential time and cost savings for industrial food manufacturers,” he said.

The project also involved the University of Reading and was funded by the UKRI Biotechnology and Biological Sciences Research Council and industrial partners including Samworth Brothers, a UK food manufacturer that employs more than 12,000 people across 15 bakeries. The company produces sandwiches for supermarkets as well as pork pies, Cornish pasties and other products.

Dr David Bryant, Senior Research Fellow at IBERS, said the work formed part of a wider four-year collaborative project to develop microbial foods in a more sustainable way.

“IBERS scientists are part of a wider, four-year collaborative project to develop microbial foods in a sustainable way and help feed a world where the population is continually increasing,” Bryant said. “One of the main base ingredients we have been using are surplus bread crusts from the baking and sandwich-making industry and we ferment these with protein from perennial ryegrass, which is traditionally fed to livestock.”

Because ryegrass is typically used for animal feed rather than human food, the researchers focused on aroma as a key factor in consumer acceptance.

“As people are not used to eating grass, we carried out this study to show how different types of fungal fermentation can be used to affect and enhance the aroma of the final product,” Bryant said. “The result is a more fragrant alternative protein that enhances the nutritional value of surplus bread while being environmentally friendly.”

The research also examined how the process could fit into a circular economy model. Professor Joe Gallagher, project co-supervisor at IBERS, said the approach used only the juice from pressed grass, leaving the remaining fiber available for other uses, including animal feed.

“In this process, only the juice from pressed grass is used, leaving the remaining fiber available, for example, as an animal feed,” Gallagher said. “Work at IBERS has shown that this fiber is easily ensiled (made into sileage) and having been through a screw press, is made highly digestible. This process could therefore create a new potential market for grasses and contribute further to the development of a circular economy.”

The fermentation processing was carried out at the pilot-scale biorefining facility at AberInnovation, located alongside IBERS on Aberystwyth University’s Gogerddan Campus. Further work is continuing at the site to refine taste and texture and to scale the process for potential commercial use.