Researchers Turn Mushroom Stems Into a Low-Salt Bread Ingredient

Gauri Khanna
6 minutes ago
3 min read

Flour made from oyster and button mushroom stems can slash sodium in bread by up to 97%, without compromising protein digestibility.
The approach valorises agricultural waste that would otherwise be discarded, supporting circular economy goals in the food industry.
Bread enriched with mushroom stem flour showed a lower predicted glycemic index, offering potential benefits for blood sugar management.

Bread is one of the largest contributors to dietary sodium in Western countries, accounting for a significant share of the 9 to 12 grams of salt most people consume daily, roughly double the World Health Organization's recommended maximum of 5 grams.

The Problem With Salt in Bread

Reformulating bread to contain less sodium is straightforward in principle but technically demanding in practice. Salt does far more than season: it regulates yeast fermentation, strengthens the gluten network, extends shelf life, and shapes the flavour profile of the final loaf. Simply removing it tends to produce flat, dense, and unpalatable results.

Researchers at Miguel Hernández University and the Mushroom Technological Research Center of La Rioja, Spain, have proposed an unconventional fix. Their study, published in Food Chemistry in 2026, tested whether dried, milled flour from the discarded stems of Agaricus bisporus (the common button mushroom) and Pleurotus ostreatus (oyster mushroom) could partially or fully replace sodium chloride in standard wheat bread, while preserving, or even improving, its nutritional value.

From Waste Stream to Functional Ingredient

Mushroom stems are a significant co-product of commercial cultivation. Stems alone can represent up to 20% of total mushroom yield, yet they retain the same bioactive compounds found in the fruiting body, including beta-glucans (soluble fibres that can form gels), chitin (a structural fibre), umami-related free amino acids such as L-glutamate, and a range of minerals. Rather than discarding this material, the research team dried and ground the stems into fine flours, then incorporated them into bread formulations at concentrations ranging from 0.5% to 6% by weight, replacing between 50% and 100% of the salt. The approach aligns with a broader movement to convert fungal fermentation and cultivation by-products into functional food ingredients.

Miguel Hernández University Researchers Turn Mushroom Stems Into a Salt-Fighting Bread Ingredient

The umami compounds present in mushroom stems are central to the salt-replacement strategy. L-glutamate and 5'-nucleotides act synergistically to enhance saltiness perception, meaning the brain registers a more intense savoury sensation even when less sodium is actually present. Button mushroom stems showed a notably higher umami equivalence index than oyster mushroom stems, suggesting a stronger capacity to compensate for the absence of salt at the sensory level.

What the Bread Actually Delivered

Across eight formulations, the results were broadly promising, though not without caveats. Sodium content fell from 2,164 mg per 100 g in the control loaf to as low as 59.7 mg per 100 g in a fully salt-free formulation using 1% oyster mushroom stem flour, a reduction of approximately 97%. Potassium, calcium, iron, and magnesium all increased with higher mushroom stem flour concentrations, with the button mushroom flour performing particularly well for calcium and iron enrichment. The highest formulation tested, 6% button mushroom stem flour, provided iron levels exceeding daily reference values set by the Codex Alimentarius.

Dietary fibre content also rose meaningfully, with oyster mushroom stem flour at 6% qualifying bread for a high-fibre designation under European Union nutritional guidelines. This fibre enrichment contributed to a lower predicted glycemic index in the oyster mushroom formulation containing 3% flour, dropping from 94.6 in the control to 89.2. The dietary fibre appeared to slow starch digestion by forming physical barriers that restricted enzyme access, a mechanism also observed in other fibre-rich food reformulation research. Protein digestibility remained near 85% across all tested formulations by the end of simulated intestinal digestion, suggesting that mushroom stem flour inclusion did not compromise the body's ability to absorb protein from bread.

The picture was less favourable on texture and volume. Oyster mushroom stem flour, which is richer in beta-glucans, competed more aggressively for water during dough mixing, weakening the gluten network and reducing loaf volume. At the 6% oyster mushroom level, sensory panellists rated overall acceptability significantly lower than the control. Button mushroom stem flour, with its higher chitin and lower beta-glucan content, had a less disruptive effect and maintained acceptable sensory scores across all concentrations tested. Mineral bioaccessibility, the proportion of minerals actually released during digestion and available for absorption, declined with mushroom stem flour addition, a finding the authors attributed in part to mineral-chitin interactions. This represents an important caveat when interpreting the raw mineral content figures.

Conclusions and the Path Forward

The research demonstrates that mushroom co-products carry real functional potential as sodium replacers in staple foods. Button mushroom stem flour, in particular, combined a meaningful sodium reduction with acceptable texture, enhanced mineral content, and maintained consumer acceptance. Further work on fermentation optimisation and processing techniques to improve mineral release will be needed before these formulations could be considered ready for industrial adoption.