The team focused on a leavening combination of glucono-delta-lactone, commonly abbreviated GDL, and sodium bicarbonate. When these two food-grade compounds meet in water, GDL gradually hydrolyzes into gluconic acid, which then reacts with the bicarbonate to release carbon dioxide and produce sodium gluconate as a byproduct. This slow hydrolysis is precisely what makes GDL attractive compared with fast-acting acids such as citric acid, which floods dough with gas almost instantly and risks losing much of it before the gluten network can develop. Conventional formulation practice has always treated the stoichiometric ratio, the exact chemical balance between acid and base, as the gold standard for optimizing recipes. The researchers set out to test a provocative question: does the stoichiometric ratio actually represent the optimal functional balance, or are the two reaction products doing fundamentally different jobs that need to be tuned separately?

To answer this, the team designed an elegant experimental strategy. They prepared doughs at three sodium bicarbonate levels, 1.0, 1.5, and 2.0 percent of flour weight, each paired with the corresponding amount of GDL according to its neutralization value. Then, in a crucial second step, they decoupled the salt from the gas. By completely reacting GDL with sodium bicarbonate in water at 60 degrees Celsius for 24 hours, they generated a solution of pure sodium gluconate with all the carbon dioxide already released. This pre-formed salt was then added to dough formulations on top of the normal reaction, allowing the researchers to observe what the salt alone contributes, independent of any additional gas production. A yeast-leavened dough served as the commercial benchmark throughout.

The molecular story begins with the gluten proteins themselves. Using measurements of free sulfhydryl groups, disulfide bonds, intrinsic fluorescence, and surface hydrophobicity, the researchers tracked how protein structure shifted across the reaction levels. Moving from the low to the intermediate level, disulfide bond content rose while free sulfhydryl groups declined, a signature of the sulfhydryl-disulfide exchange reactions that knit gluten chains into a three-dimensional network. Fluorescence intensity and surface hydrophobicity also increased, indicating that hydrophobic amino acid residues such as tryptophan, tyrosine, and phenylalanine were being progressively exposed as protein chains unfolded in an ordered fashion. This moderate unfolding, driven by the gradual acidification of GDL hydrolysis, appears to be the sweet spot where proteins are flexible enough to interact but not so disrupted that the network collapses.

The high reaction level told a cautionary tale. At 2.0 percent sodium bicarbonate, disulfide bonding dropped to its lowest while free sulfhydryl groups peaked, and surface hydrophobicity climbed even higher. The researchers interpret this as evidence that the intense ionic environment generated by abundant sodium gluconate intensified electrostatic shielding between gluten chains, promoting irregular and excessive re-aggregation rather than orderly network construction. Zeta potential measurements reinforced this picture: the absolute value fell steadily from 32 millivolts at the low level to 26 millivolts at the high level, eroding the electrostatic energy barrier that normally keeps protein particles from clumping. Particle size distributions shifted correspondingly toward larger aggregates, with the 2.0 percent samples showing the broadest peaks and the strongest signals around 10,000 nanometers, hallmarks of runaway protein aggregation.

Because expanding dough is essentially a foam, the behavior of proteins at the air-water interface matters enormously. Proteins must diffuse to bubble surfaces, penetrate the interface, unfold, and rearrange into a cohesive film that resists deformation as bubbles grow. The researchers measured all of these stages using dynamic interfacial tension, adsorption kinetics modeling, and dilatational rheology. The intermediate reaction level proved optimal at every step: it produced the fastest penetration and rearrangement rate constants, and the highest elastic and viscous moduli of the interfacial films. Lissajous plots, which visualize how interfacial films respond to cyclic stretching and compression, showed that the 1.5 percent films retained a regular, resilient response even at large deformations, while the 2.0 percent films became increasingly distorted and heterogeneous. In short, moderate salt formation built the toughest bubble armor.

Microscopy and rheology translated these molecular findings into dough-level reality. Scanning electron microscopy and confocal laser scanning microscopy revealed that at the intermediate level, starch granules were uniformly embedded in a continuous, well-stretched protein network, and adding extra sodium gluconate made the network even more homogeneous. Dynamic rheology confirmed that the 1.5 percent plus salt dough had the highest storage and loss moduli of all formulations, meaning it was the most elastic and resistant to deformation. Rheo-fermentation measurements then delivered the most striking numbers: at the intermediate level, dough height reached 28 centimeters, already exceeding the yeast control at 22 centimeters, and salt supplementation pushed it to 32 centimeters. At the high reaction level, despite abundant gas production, the gap between gas release profiles with and without added salt revealed that much of the carbon dioxide was simply escaping from a weakened, poorly structured dough.

The final proof arrived in the steamer. Steamed bread made at the intermediate level with salt supplementation achieved the highest specific volume of the entire study, 2.63 milliliters per gram, with a fuller appearance, finer and more uniform crumb cells, and improved texture. The high reaction level produced larger but coarser and less evenly distributed gas cells, the result of bubble coalescence in a dough that could not hold what it had generated. The authors conclude that optimal steamed bread quality depends on a balance between adequate carbon dioxide generation and a sufficiently strong viscoelastic network to retain that gas, with moderate sodium gluconate formation providing the gas-holding capacity that gas alone cannot supply. Neither factor working alone can produce a superior product.

The implications extend well beyond steamed bread. The principle that in situ generated salts actively shape protein interactions, interfacial films, and dough mechanics, rather than serving as inert byproducts, could reshape how formulators approach any chemically leavened cereal product, from cakes to tortillas to biscuits. It suggests that acid and bicarbonate selection should account not only for gas release kinetics but also for the structural properties of the salt each pairing produces. The study does carry limitations the authors acknowledge: carbon dioxide could not be introduced independently into the dough, and pH was not treated as an explicit variable, so future work with controlled gas supplementation and pH monitoring will be needed to fully separate the contributions. Still, for a food industry actively seeking yeast-free alternatives driven by consumer interest and intolerance concerns, this research provides something rare: a mechanistic roadmap showing that the secret to great chemically leavened bread lies not just in making gas, but in making the right salt at the right time to keep it.

Subject of Research: Chemical leavening of wheat dough and steamed bread quality through coordinated carbon dioxide evolution and in situ sodium gluconate formation

Article Title: Insights into the Coordinated roles of CO 2 Evolution and in situ Generated Sodium Salts across Gluten Protein, Dough Development, and Steamed Bread Quality, in a Chemically Leavened System.

Article References: Wang, A., Mohammadi, N., Tong, L.-T., & Scannell, A. G. (2026). Insights into the Coordinated roles of CO2 Evolution and in situ Generated Sodium Salts across Gluten Protein, Dough Development, and Steamed Bread Quality, in a Chemically Leavened System.. Current Research in Food Science, Article 101585. https://doi.org/10.1016/j.crfs.2026.101585

Image Credits: AI Generated

DOI: 10.1016/j.crfs.2026.101585

Keywords: chemical leavening, steamed bread, gluten protein, sodium gluconate, glucono-delta-lactone, carbon dioxide, dough rheology, air-water interface, disulfide bonds, gas retention, yeast-free, food science

Phosphogypsum is the bulky, problematic by-product of phosphoric acid production for fertilizer manufacturing. Global stockpiles have now exceeded six billion tonnes, with another 200 to 250 million tonnes added every year, while utilization rates remain stubbornly low. Chemically, the material is dominated by gypsum, calcium sulfate dihydrate, with calcium oxide content commonly around 30 percent by weight. That makes it an tantalizingly abundant calcium reservoir for mineral carbonation, the process in which CO2 reacts with calcium- or magnesium-bearing phases to form stable carbonate minerals such as calcite. Unlike steel slag or carbide slag, however, phosphogypsum holds its calcium in sparingly soluble gypsum rather than in readily reactive lime or calcium silicates, so its carbonation depends entirely on whether that bound calcium can first be coaxed into solution.

Researchers led by Ying Shi and colleagues at Central South University in China tackled this problem with a comparative experiment of unusual rigor. They tested four activators, ammonium chloride, sodium acetate, ammonium acetate, and sodium gluconate, against plain deionized water, to dissolve calcium out of washed phosphogypsum from Guizhou Province. The resulting calcium-rich leachates were then carbonated under an identical protocol: pH was raised above 12 with sodium hydroxide, and each leachate was exposed to a CO2 atmosphere in sealed gas-tight bags for fourteen days, with the gas renewed daily. By measuring dissolved calcium at every stage and characterizing every solid that emerged, the team could link three successive steps that most studies treat in isolation: calcium release, calcium consumption, and carbonate product formation.

The leaching results were dramatic. Water alone extracted only modest amounts of calcium, leaving dissolved concentrations between roughly 726 and 833 milligrams per liter. Ammonium chloride nearly tripled that, sodium acetate and ammonium acetate pushed higher still, and sodium gluconate was in a class of its own, sustaining dissolved calcium concentrations around 15,300 milligrams per liter, roughly twenty times the blank system. Under optimized conditions, sodium gluconate released up to 98.5 percent of the available calcium from the solid, dissolving so much gypsum that only 5.4 grams of residue remained from an initial 240 grams of phosphogypsum. Electron microscopy showed the characteristic plate-like gypsum particles almost completely dismantled, while X-ray diffraction confirmed the near-total removal of gypsum and a relative enrichment of insoluble quartz. The gluconate anion, the study notes, forms stable soluble complexes with calcium ions, shifting the gypsum dissolution equilibrium and driving continued release.

Then came the twist. When the leachates were carbonated, the leachate with the most dissolved calcium performed the worst at consuming it. The ammonium chloride system, starting from a moderate 2,376 milligrams per liter of dissolved calcium, plummeted below 50 milligrams per liter within a single day. Sodium acetate and ammonium acetate followed similar trajectories, and after fourteen days all three had achieved calcium consumption efficiencies of 98.7 to 99.0 percent. The sodium gluconate leachate, despite beginning with 15,315 milligrams per liter, crawled down slowly, still holding 2,177 milligrams per liter after two weeks, for a final consumption efficiency of just 85.8 percent. Its pH also stayed persistently high, remaining near 11.8 at the end of the experiment while the other systems settled around neutral.

The authors attribute this behavior to lingering calcium-gluconate complexation. Even though the total dissolved calcium was enormous, much of it was locked in soluble complexes rather than existing as free calcium ions, reducing the ion activity product needed to trigger calcium carbonate precipitation and delaying supersaturation and nucleation. In other words, a high calcium concentration on paper does not guarantee that the calcium is chemically available to react with carbonate. The study is careful to note that carbon dioxide was supplied from a static gas phase without stirring or sparging, so gas-liquid mass-transfer resistance may also have shaped the apparent kinetics, but all leachates faced the same conditions, making the comparison fair.

The solid products told the same story from a different angle. Every leachate produced calcite, the crystalline form of calcium carbonate, confirmed by X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis. But the quality of the products diverged sharply. The water, ammonium chloride, sodium acetate, and ammonium acetate systems yielded solids that were overwhelmingly carbonate, with apparent calcium carbonate equivalents of 93.56 to 96.90 percent by weight. The sodium gluconate product was a different beast entirely: quantitative X-ray diffraction showed crystalline calcite made up only about 20 percent of the recovered solid, with the remainder predominantly X-ray amorphous, accompanied by an unusual silicon-oxygen signature and a distinct thermal profile featuring substantial low-temperature mass loss.

Translated into climate terms, the differences are meaningful. Normalized to the initial phosphogypsum mass, the water, ammonium chloride, sodium acetate, and ammonium acetate routes mineralized an estimated 3.96, 14.36, 15.87, and 20.00 kilograms of CO2 per tonne of phosphogypsum, respectively. The sodium gluconate route, judged only by its quantified crystalline calcite, incorporated 72.51 kilograms of CO2 per tonne into calcite, a far higher figure that reflects its extraordinary calcium supply. Yet the authors caution that this headline number masks the complexity of the product and the substantial calcium left stranded in solution, which matters enormously if the goal is clean, well-defined carbonate for construction fillers or cementitious applications.

The broader lesson is a methodological one that could ripple through the field. Most phosphogypsum carbonation studies optimize a single leaching-carbonation system and report calcium recovery or carbonate yield, without asking whether more calcium release actually translates into better carbonation. By systematically decoupling the two stages, this study shows they can even be inversely related. Ammonium chloride emerges as the balanced performer, offering moderate calcium release, near-complete consumption, and clean calcite-dominated products, while sodium gluconate demonstrates that powerful complexing agents can extract calcium superbly yet sabotage its subsequent use. For engineers designing carbonation-based materials from industrial waste, the criterion for a good recycled calcium source must therefore expand from how much calcium a leachate contains to how much of that calcium can actually be consumed and converted into well-defined carbonate solids.

There remain open questions. The authors acknowledge that a complete calcium-sulfur-carbon material balance was not established, and they call for future work with phase-resolved elemental accounting to track where every element ends up. Impurities in phosphogypsum, including soluble phosphorus, fluoride, organic matter, and heavy metals, may also interact with calcium phases and carbonate nucleation in ways not yet fully resolved, and the sample from a single Guizhou source may not represent phosphogypsum from other phosphate ores. Still, the core message stands: in the race to turn a six-billion-tonne waste mountain into a carbon sink, chemistry that looks strongest at the extraction stage may quietly undermine the storage stage, and only a full-chain view, from dissolution to precipitation, can identify the leachates truly fit for locking CO2 into stone.

Subject of Research: Activator-assisted calcium release from phosphogypsum and its aqueous carbonation for CO2 mineralization

Article Title: Comparative study of phosphogypsum-derived leachates as recycled calcium sources for carbonation: Linking Ca release, consumption and carbonate product formation

Article References: Shi, Y., Guo, Q., Li, S., Zhou, X., Yan, K., & Liu, P. (2026). Comparative study of phosphogypsum-derived leachates as recycled calcium sources for carbonation: Linking Ca release, consumption and carbonate product formation. Case Studies in Construction Materials, 25, Article e06557. https://doi.org/10.1016/j.cscm.2026.e06557

Image Credits: AI Generated

DOI: 10.1016/j.cscm.2026.e06557

Keywords: phosphogypsum, mineral carbonation, CO2 sequestration, calcium leaching, calcite, sodium gluconate, ammonium chloride, industrial waste valorization, gypsum dissolution, carbonate precipitation, low-carbon construction materials, recycled calcium sources

The study, published in the journal Environmental Geochemistry and Health by a team led by Hongyang Wang of Liaoning University together with colleagues from Northeastern University and Inner Mongolia Yitai Guanglian Coal Chemical, addresses a stubborn technical bottleneck. Coal seam water injection, in which water is pumped into a seam ahead of mining to pre-wet the coal, has long been a frontline dust control strategy. But conventional water struggles to infiltrate the pore and fracture networks of deep coal, especially when mixed metallic substances within the coal matrix block penetration. The result is uneven wetting, dry zones that shatter into inhalable dust during extraction, and suppression rates that fall far short of what occupational health standards demand.

The researchers’ solution is a composite formulation built from three widely available components: sodium gluconate, abbreviated SG, fatty alcohol polyoxyethylene ether known as AEO-3, and sodium fatty alcohol polyoxyethylene ether sulfate, or AES. Each ingredient plays a distinct role. Sodium gluconate, a chelating agent, is capable of binding the metallic substances dispersed in the coal, thereby clearing obstacles that would otherwise impede water movement through the coal’s internal pore structure. AEO-3, a nonionic surfactant, and AES, an anionic surfactant, work in combination to lower the surface tension of the injection solution and reduce the contact angle at the water-coal interface, two of the most important physical parameters governing how readily a liquid spreads across and soaks into a hydrophobic solid surface.

Coal is notoriously water-repellent. Its surface is dominated by hydrophobic carbon structures with relatively few oxygen-containing functional groups, the chemical handles to which water molecules can attach. The SAA formulation changes this chemistry. According to the team’s laboratory characterization, treatment with the agent increased the number of oxygen-containing functional groups on the coal surface, giving water more anchoring points and improving wettability at the molecular scale. At the same time, the surfactants promoted agglomeration of micron-sized coal dust particles, causing individual fine grains to clump into larger, heavier particles that settle out of the air more readily. The effect on particle size distribution was quantifiable: the median particle size, known as the D50 value, increased by 22.58 percent compared with untreated dust.

To test how these microscopic changes translate into real dust control performance, the team constructed a custom dust-suppression simulation system in the laboratory. The apparatus allowed them to generate airborne coal dust under controlled conditions and measure how effectively different spray solutions captured it. When SAA-treated water was used, the effective dust-suppression rate reached 71.50 percent. That figure is 2.17 times the performance of traditional water-mist dust suppression, meaning the formulated agent more than doubled the capture efficiency achievable with plain water alone. For an industrial process where even marginal gains in suppression translate into measurably lower respirable dust exposures for miners, a performance margin of this size is significant.

The most consequential part of the study, however, took place underground. The researchers carried out on-site dust suppression tests at the 3-802 working face of a production coal mine, injecting SAA-treated water into the seam using standard water injection equipment. Before injection, dust sampling established baseline conditions. After treatment, the average coal dust particle size at the face had risen to 2.53 times its pre-injection value, confirming that the agglomeration effect observed in the laboratory survived the journey from bench to bordeline. Larger particles mean less respirable dust, faster settling and cleaner air at the point where miners actually work.

Monitoring across multiple underground measurement points showed total dust suppression rates ranging from 60 to 84 percent, a broad but consistently strong performance envelope that reflects the natural variability of ventilation, mining activity and seam conditions across a working face. Beyond improving air quality, the treatment appeared to influence the mechanical behavior of the coal itself. The team reports that SAA water injection reduced the tendency of the coal to fracture and generate dust, a property linked in earlier research to burst liability, the dangerous propensity of some deep coal seams to fail suddenly and violently. By softening this tendency, the agent may offer a secondary safety benefit against rock bursts and coal bursts, phenomena that remain among the most feared hazards in deep mining.

What distinguishes this work from many prior surfactant studies, the authors argue, is the full chain of evidence it assembles. Laboratory mechanism analysis, surface chemistry characterization, particle size measurement, simulation chamber testing and underground field trials are all presented in a single integrated study, closing the gap that so often separates promising bench chemistry from deployable engineering practice. The funding came from the National Natural Science Foundation of China under grant 52427805, and the work involved authors from Liaoning University’s School of Environmental Sciences, Northeastern University’s School of Resources and Civil Engineering, and Inner Mongolia Yitai Guanglian Coal Chemical, a collaboration that pairs academic environmental science with direct industrial access.

The implications extend beyond a single mine. Deep coal mining is expanding in major producing nations, and occupational dust exposure remains a leading cause of preventable disease among miners, including coal workers’ pneumoconiosis, an incurable and often fatal lung condition. The health burden of coal dust has been documented extensively in the occupational health literature, and regulators continue to tighten permissible exposure limits. Technologies that make existing controls, such as water injection and water sprays, substantially more effective without requiring wholesale redesign of mining equipment are therefore valuable. The SAA formulation uses relatively inexpensive, commercially available chemicals, which the authors suggest positions it for practical engineering application.

Challenges remain before widespread adoption. Field performance will need to be validated across seams of different rank, metamorphic grade and mineralogy, since the wetting behavior of coal varies considerably with its chemical composition. Long-term dosing, environmental discharge and cost at scale will also require scrutiny. Nevertheless, the reported numbers give the approach credibility: a doubling of mist suppression efficiency in the lab, suppression rates of up to 84 percent underground, and a measurable reduction in fracturing tendency all point toward a wetting agent that does more than tweak surface tension. By combining chelation, nonionic and anionic surfactant synergy, and verified field performance, the SAA study offers deep coal mines a concrete new tool in the long-running fight against dust, and offers miners something even more precious: cleaner air at the coal face.

Subject of Research: A composite SAA wetting agent for enhancing coal seam water injection and dust suppression in deep coal mining

Article Title: High-efficiency ‘SAA’ wetting agent for coal mine dust control: from preparation and mechanism to field application

Article References: Wang, H., Zhao, T., Wang, H., Wang, H., Leng, Y., Pan, Y., Xu, L., & Zhu, Y. (2026). High-efficiency ‘SAA’ wetting agent for coal mine dust control: from preparation and mechanism to field application. Environmental Geochemistry and Health, 48(15), Article 600. https://doi.org/10.1007/s10653-026-03491-3

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03491-3

Keywords: coal mining, dust suppression, wetting agent, coal seam water injection, surfactants, deep mining, occupational health, coal dust, sodium gluconate, wettability, Environmental Geochemistry and Health, rock burst