Yeast protein has long been touted as a sustainable alternative to animal and plant proteins, but one stubborn flaw has kept it out of many food formulations: it barely dissolves in water. A new laboratory study reports that a carefully sequenced combination of alkaline treatment, high-pressure microfluidization and heat treatment can transform this poorly soluble ingredient into transparent, highly soluble particles, raising solubility from 12.7% to 88.5% at neutral pH.
The team worked with a commercial yeast protein preparation containing 82.4% protein, sourced from Angel Yeast Co., Ltd., and systematically compared single treatments with combined sequences to isolate what each step contributed.
The starting material was far from ideal. In distilled water, untreated yeast protein showed a solubility of just 12.7% and the highest turbidity of any sample tested, a sign of severe aggregation. The authors attribute this poor behavior to a dense, aggregated state of the proteins, which they describe as the main barrier preventing yeast protein from finding practical application in the food industry despite its otherwise favorable nutritional profile.
Yeast protein does have genuine advantages that motivated the work. It constitutes 35% to 60% of yeast dry weight, has a nutritional quality the authors describe as comparable to whey protein, offers a balanced amino acid profile, hypoallergenic properties and a low-cholesterol, low-fat composition, and can be produced sustainably without dependence on climate or land resources. It is also recognized as safe for consumption in many countries. The problem has always been functionality, not nutrition.
The researchers’ strategy rested on the observation that no single modification was sufficient on its own. Extreme alkaline pH can induce protein unfolding and increase electrostatic repulsion, but for a resilient, highly aggregated protein like yeast protein this effect alone was often insufficient. Heat treatment could enhance unfolding but lacked the mechanical force to efficiently disrupt large aggregates, while other mechanical methods such as ultrasound or conventional homogenization suffer from non-uniform energy distribution or insufficient shear intensity.
High-pressure microfluidization offered the missing ingredient. Its micro-channel interaction chamber forces fluid streams to collide at extreme velocities, generating ultra-high shear rates and violent impact forces. In the experimental protocol, yeast protein suspensions were adjusted to pH 12 with sodium hydroxide, then subjected to one pass through the microfluidizer at 100 megapascals, followed by heating at 60 or 90 °C for 30 minutes, rapid cooling, and finally neutralization to pH 7 with hydrochloric acid. The alkaline step was designed to unfold the protein and keep it soluble and reactive for the mechanical and thermal stages that followed.
The results were striking. Simple alkaline treatment alone raised solubility from 12.7% to 38.4%, a substantial improvement but still short of what the authors consider necessary for industrial applications. Heat treatment alone only slightly enhanced solubility. But when high-pressure microfluidization and heating at 90 °C were inserted into the alkaline sequence, solubility climbed to 88.5%, roughly seven times that of the untreated protein. The treated sample was visibly transparent, with an absorbance at 600 nanometers close to zero, while the untreated solution was the most turbid of all.
Supporting measurements told a consistent structural story. Untreated yeast protein formed micron-scale aggregates with an average diameter of 60.23 micrometers, and the combined alkaline-microfluidization-heat samples showed the smallest particle sizes of all. Scanning electron microscopy revealed that the irregular, blocky structures of the native protein were decomposed into small fragments of more uniform size. Free sulfhydryl content roughly doubled in the best-treated sample, indicating structural unfolding or disulfide bond breakage, and surface hydrophobicity rose by 662.70% in the leading sample, showing that hydrophobic residues previously buried inside the aggregates had been exposed to the solvent.
Spectroscopic analyses added further detail. Intrinsic fluorescence measurements showed a slight blue shift and a maximum intensity 201.16% higher than untreated protein in the leading sample, indicating that tryptophan residues ended up in a less polar microenvironment after modification. Fourier-transform infrared analysis showed that alkaline treatment reduced alpha-helix content while increasing beta-sheet and beta-turn content, consistent with structural unfolding and dissociation. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that untreated yeast protein displayed two main bands, above 180 kilodaltons and below 15 kilodaltons, while the modified samples showed five major molecular weight ranges, evidence that high-molecular-weight aggregates had dissociated into smaller constituent subunits and fragments.
The functional benefits extended beyond solubility. The best-treated sample showed the highest water holding capacity and oil holding capacity of all samples, representing a 180.9% increase in water holding capacity and an 84.1% increase in oil holding capacity relative to untreated yeast protein. The authors attribute the improved water retention primarily to the reduction in particle size, which increased the specific surface area and facilitated the retention and hydration of capillary water, while the improved oil binding resulted mainly from the exposure of hidden hydrophobic groups that provide sites for binding oil molecules.
The authors are candid about the limitations of their study. They note that the work omitted controls of non-alkaline high-pressure microfluidization, used empirical processing parameters of 100 megapascals and a single pass based on existing literature rather than comprehensive parametric screening, and examined only two representative temperatures, 60 and 90 °C, without systematic optimization. They call for future research to isolate the individual mechanical effects and systematically optimize the processing parameters to maximize the functionality of yeast protein.
Even with those caveats, the study offers a concrete recipe for converting a low-value, poorly soluble protein into a functional food ingredient. By combining the chemical unfolding power of extreme alkaline pH, the mechanical disruption of ultra-high shear microfluidization, and the thermal guidance of refolding at 90 °C, the process produces stable, uniform, submicron-sized particles that resist re-aggregation after neutralization. As the global demand for protein sources is projected to grow toward a population of approximately 10 billion by 2050, strategies that unlock the potential of sustainable microbial proteins may become increasingly valuable to food formulators seeking alternatives to conventional animal and plant sources.
Subject of Research: A combined alkaline, high-pressure microfluidization and heat treatment that improves yeast protein solubility and water and oil holding capacity in the laboratory.
Article Title: Sequential high-pressure microfluidization and heat treatment under alkaline treatment process transforms yeast protein into highly soluble particles
Article References: Du, J., Wan, X., Chen, Q., Wu, Y., Gong, A., Zhang, H., & Wang, X. (2026). Sequential high-pressure microfluidization and heat treatment under alkaline treatment process transforms yeast protein into highly soluble particles. Current Research in Food Science, Article 101612. https://doi.org/10.1016/j.crfs.2026.101612
Image Credits: AI Generated
DOI: 10.1016/j.crfs.2026.101612
Keywords: yeast protein, solubility, high-pressure microfluidization, alkaline treatment, heat treatment, pH-shift, food ingredients, protein functionality, water holding capacity, oil holding capacity, particle size, protein structure
News Source: Alan Morgan. (October 28, 2026). Alkaline Shear and Heat Turn Poorly Soluble Yeast Protein into Nanoparticles. Scienmag.
