From Carrot Waste to Protein-Rich Food: How Fungal Fermentation Is Turning Side Streams into Sustainable Nutrition
- Gauri Khanna
- 3 days ago
- 3 min read
Too long to read? Go for the highlights below.
Researchers have successfully transformed liquid waste from carrot processing into high-protein fungal mycelium, achieving yields of up to 15 grammes per litre with protein content reaching 31%
The pink oyster mushroom mycelium outperformed soy protein in taste tests when used in burger patties, offering a promising alternative to conventional plant-based proteins
This fermentation approach addresses both food waste and protein scarcity, converting by-products from natural colour production into nutritious food ingredients in just six to ten days
The global food system generates enormous quantities of side streams: industry parlance for the liquid and solid by-products of processing. From carrot juice production alone, thousands of litres flow away daily, destined for disposal or low-value uses. Yet these nutrient-rich liquids harbour untapped potential. Recent research from Justus Liebig University demonstrates how fungal fermentation can transform such waste into valuable protein sources, offering a practical solution to dual challenges: food waste and the growing demand for sustainable protein alternatives.
Screening Fungal Candidates
The research team evaluated 106 fungal strains, testing their ability to grow on liquid side streams from black and orange carrot processing, materials left over from natural food colouring production. These substrates presented challenges: low pH values and high citric acid content inhibited many species. Yet certain fungi thrived. Pleurotus djamor, commonly known as the pink oyster mushroom, emerged as particularly promising across both substrates.
This wasn't arbitrary selection. Fungi, as nature's decomposers, possess remarkable enzymatic capabilities, breaking down complex plant materials including cellulose and hemicellulose: fibres indigestible to humans. By harnessing this ability, mycelium cultivation converts agricultural by-products into digestible protein whilst maintaining food-grade quality throughout the process.
Optimising Production Parameters
Initial screening provided baseline performance, but systematic optimisation proved crucial. Using Response Surface Methodology (a statistical technique for analysing how multiple factors interact) researchers adjusted carbohydrate concentration and pH levels across 34 experimental runs per fungus-substrate combination. The improvements were substantial: Pleurotus djamor's dry matter yield increased 2.6-fold on orange carrot medium, whilst crude protein content rose 30% on black carrot substrate.
The optimised mycelium achieved protein contents of 21.6% to 31%, comparable to conventional meat and exceeding most plant-based proteins. Beyond quantity, quality matters: amino acid analysis revealed a biological value of 83 for mycelium grown on black carrot medium: matching beef and approaching milk. This metric indicates how efficiently the body can utilise consumed protein.
Production speed presents another advantage. Whilst traditional mushroom cultivation requires weeks for fruiting bodies to develop, submerged fermentation produces protein-rich mycelium within six to ten days. This efficiency stems from cultivating the fungal network itself rather than waiting for reproductive structures.
From Laboratory to Plate
Nutritional metrics matter little if consumers reject the product. Sensory evaluation provided encouraging results. When incorporated into burger patties, the mycelium received significantly higher ratings than soy: protein isolate, scoring 3.5 versus 2.5 out of 5. Panellists appreciated the texture particularly, describing mycelium-based products as less dry and floury than soy alternatives.
In vegan sausages, mycelium exhibited umami characteristics and meat-like flavours whilst avoiding the bitter off-notes associated with chickpea-based products. The fungal ingredient required no flavour masking, presenting as nearly neutral in taste and colour: a valuable trait for food manufacturers seeking versatile ingredients.
This research demonstrates industrial feasibility: converting food processing side streams into protein sources addresses waste management whilst contributing to food security. As global population approaches 10 billion by 2050, such circular approaches to protein production may transition from laboratory curiosity to necessity. The technology exists; scaling remains the challenge.
