The research, led by Haoran Wang and colleagues, compared superheated steam treatment at 140, 160, and 180 degrees Celsius against two conventional pretreatments, steaming and stir-frying, using kernels of the Zangqing 320 cultivar from Tibet. Before treatment, the kernels were tempered to 20 percent moisture and equilibrated for six hours, then exposed to the steam for just six minutes. Conventional steaming required thirty minutes, and stir-frying involved twelve hours of soaking followed by thirty minutes of roasting at 160 degrees Celsius. The treated kernels were milled into whole flour, and gels were prepared from a 15 percent flour suspension heated at 95 degrees Celsius and cooled overnight.

The centerpiece of the investigation was beta-glucan, the soluble fiber responsible for many of barley’s health benefits. Using high-performance size-exclusion chromatography coupled with multi-angle laser light scattering, the team measured the weight-average molecular weight of beta-glucan isolated from both flour and gel. Native flour beta-glucan came in at 1.61 by ten to the fifth grams per mole. Every thermal treatment raised that figure, but superheated steam did so most dramatically: at 180 degrees Celsius the molecular weight climbed to 2.23 by ten to the fifth, the highest of any treatment. This finding runs counter to several earlier studies in which roasting, microwave heating, and oven baking depolymerized barley beta-glucan. The authors attribute the difference to moisture conditions and heating intensity. Tempering the kernels before treatment appears to shield the fiber from thermal degradation, while the rapid heat transfer and short exposure time of superheated steam limit chain scission.

The structural consequences extended well beyond beta-glucan. Fourier transform infrared spectroscopy revealed that gels made from steam-treated flour at 160 and 180 degrees Celsius showed increased short-range order in starch, reflected in a higher ratio of absorbance at 1047 to 1022 wavenumbers. Interestingly, this contrasts with the team’s own previous work on isolated starch, where the harshest steam treatment disrupted crystalline order most severely. In the whole-flour gel matrix, the researchers conclude, amylose and amylopectin chains released during gelatinization apparently reassociate into more ordered local domains upon cooling. Protein conformation shifted in parallel: as steam temperature rose, alpha-helix and beta-turn contents increased while beta-sheet and random coil proportions declined, signaling a partial rearrangement of the protein network.

Microscopy told a visually striking story. Scanning electron micrographs of the native gel revealed large, irregular pores, whereas gels from kernels treated at 160 degrees Celsius displayed a markedly more uniform morphology with smaller apparent pores. Confocal laser scanning microscopy, with starch stained green and protein red, showed that the numerous large dark voids of the native gel nearly vanished after treatment, with 160 degrees Celsius producing the most homogeneous starch-protein distribution. Push the temperature to 180 degrees Celsius, however, and the benefit reverses: larger, more irregular voids reappear alongside pronounced protein aggregation, indicating that excessive treatment intensity introduces new heterogeneity into the matrix.

Water behavior tracked these structural changes closely. Low-field nuclear magnetic resonance resolved three water populations in the gels, corresponding to bound, immobilized, and free water, with free water dominating at more than 95 percent of the total. Treatment at 160 and 180 degrees Celsius significantly increased the bound-water fraction, and all treatments raised the immobilized fraction, indicating a shift toward water populations with lower mobility. The effect was stronger for superheated steam than for conventional steaming or stir-frying. The authors suggest that higher molecular weight beta-glucan can retain water through hydrogen bonding, contributing to this immobilization, although at 180 degrees Celsius the bound and immobilized fractions dipped slightly, possibly because severe treatment depolymerizes starch chains that would otherwise hold water.

Texture analysis translated these molecular shifts into measurable mechanical differences. Springiness, the ability of a gel to recover after compression, responded most strongly to treatment: every thermal pretreatment increased it significantly, and the 160-degree steam sample achieved the highest value at 2.73 millimeters, up from 2.18 millimeters in the native gel. That peak springiness coincided with the most uniform pore structure and the lowest water mobility, painting a coherent picture of a gel whose architecture resists deformation and rebounds efficiently. Hardness, cohesiveness, and gumminess, by contrast, changed little across treatments, and only stir-frying produced a hardness significantly different from the control.

Rheology added nuance to the texture story. During temperature sweeps, all treated samples showed higher storage and loss moduli than the native gel, with the 140-degree sample exhibiting the strongest small-deformation viscoelastic response. In frequency sweeps, all gels behaved as elastic-dominant materials, with the storage modulus exceeding the loss modulus and the loss factor remaining below one across the tested range. The apparent tension between the highest springiness at 160 degrees and the highest modulus at 140 degrees reflects the different deformation regimes of the two measurements: the modulus was recorded at 1 percent strain within the linear viscoelastic region, while springiness measures recovery after 30 percent compression. Different regimes, the authors note, probe different aspects of the same heterogeneous network.

Perhaps the most consequential result concerns digestion. In vitro hydrolysis with pepsin, pancreatic alpha-amylase, and amyloglucosidase showed that superheated steam treatment reduced both rapidly and slowly digestible starch while boosting resistant starch, with the effect strengthening as temperature rose. At 180 degrees Celsius, resistant starch reached 15.87 percent, up from 8.78 percent in the native gel, while the estimated maximum digestibility fell from 93.40 percent to 87.59 percent. A logarithm-of-slope analysis split digestion into fast and slow phases and showed that treatment mainly suppressed hydrolysis during the first thirty minutes, consistent with the drop in rapidly digestible starch. Stir-frying, by contrast, barely moved the needle, leaving resistant starch essentially unchanged.

The authors propose that three concurrent changes explain the slowed digestion: greater starch short-range order, which produces compact hydrogen-bonded structures with reduced enzyme accessibility; elevated beta-glucan molecular weight, which increases viscosity and hinders enzyme diffusion; and protein aggregation, which adds a further physical barrier. Notably, the whole-flour gel digested more slowly than the isolated starch examined in the team’s earlier work, underscoring that non-starch components matter enormously in real foods. The practical upshot is a kind of dial: processors seeking better gel uniformity and elastic recovery could choose steam at 160 degrees Celsius, while those prioritizing slower starch digestion might opt for 180 degrees. For a gluten-free grain struggling to enter modern staple foods, a six-minute steam treatment that simultaneously improves texture and nutritional profile is a compelling proposition, and one that could reshape how ancient plateau cereals reach contemporary tables.

Subject of Research: Effect of superheated steam treatment on beta-glucan, gel structure, and starch digestibility in highland barley whole flour

Article Title: Effect of superheated steam treatment on endogenous β-glucan and gel properties of highland barley whole flour: Changes in gel structure and starch digestibility

Article References: Wang, H., Ma, T., Wang, L., Wang, L., Li, Y., & Qiu, J. (2026). Effect of superheated steam treatment on endogenous β-glucan and gel properties of highland barley whole flour: Changes in gel structure and starch digestibility. Food Chemistry: X, 39, Article 104557. https://doi.org/10.1016/j.fochx.2026.104557

Image Credits: AI Generated

DOI: 10.1016/j.fochx.2026.104557

Keywords: highland barley, superheated steam, beta-glucan, starch digestibility, resistant starch, gel properties, food processing, whole flour, rheology, molecular weight, Qinghai-Tibet Plateau, functional foods

The core challenge the researchers set out to solve is a molecular conflict of interest. Egg white is packed with high-quality proteins — ovalbumin, ovotransferrin, ovomucin and others — that gel, foam and emulsify beautifully, making it an attractive textural modifier for dairy products. But egg white also contains lysozyme, a potent antibacterial enzyme that cleaves the β-1,4 glycosidic bonds in bacterial cell wall peptidoglycan. That is excellent news for food preservation and terrible news for yogurt starters, which rely on Gram-positive lactic acid bacteria — Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus — to ferment lactose into lactic acid. Adding raw egg white to yogurt milk risks sabotaging the very organisms the fermentation depends on.

The team, led by Yunxiao Xie and Fang Geng, applied a pretreatment strategy they had developed in earlier work, abbreviated UHSD: liquid egg white is first blasted with 20 kHz ultrasound in pulsed mode for ten minutes while kept cold, then heated in a water bath at 72 °C for ten minutes, and only then spray-dried into a powder. The ultrasound cavitation and mechanical shear unfold protein aggregates, and the subsequent moderate heating promotes controlled aggregation and disulfide exchange between lysozyme and other egg white proteins. When the researchers measured apparent lysozyme activity using Micrococcus lysodeikticus cells as a substrate, the results were striking. Fresh egg white showed an apparent activity of 5660 U/mg. Conventional spray drying alone cut that by 54.6 percent, but the full ultrasound–heat–spray-drying sequence reduced it by 90.3 percent — a dramatic taming of the antibacterial enzyme while keeping the functional proteins largely intact.

With the pretreated powder in hand, the researchers formulated yogurts in which the powder partially replaced milk at 0, 1, 2 and 4 percent by mass, heat-treated the mixes at 72 °C for 30 minutes, inoculated them with a commercial two-strain starter, and fermented for ten hours. Every batch set into a stable gel with no visible whey separation, and all samples met the Chinese national standard minimum titratable acidity of 60 °T for fermented milk. Color measurements showed the supplemented yogurts became progressively lighter, with reduced red and yellow components — a subtle whitening effect that could be commercially appealing. Texture analysis, however, revealed a dose-dependent trade-off: hardness was unchanged at 1 and 2 percent addition but dropped significantly at 4 percent, and springiness peaked at the 1 percent level before falling at the highest dose.

The structural story behind those numbers emerged from microscopy and rheology. Scanning electron micrographs of freeze-dried yogurt showed that the control gel was relatively loose, with large pores, while the egg white-supplemented samples displayed progressively smaller gel particles and a more uniform, compact three-dimensional network — most pronounced at 4 percent. Rheological testing showed all samples were shear-thinning pseudoplastic fluids, but apparent viscosity shifted upward with increasing powder addition, and both the storage modulus G′ and loss modulus G″ rose across the frequency range, with G′ consistently exceeding G″, confirming elastic, weak-gel behavior throughout. In short, the egg white proteins were genuinely participating in the acid-induced casein network, cross-linking the gel and stiffening its response to deformation.

Yet a denser microstructure did not translate into proportionally better macroscopic performance. The 1 percent group achieved the highest water-holding capacity, significantly above all other groups, while the 4 percent group showed no advantage over the control, which held 64.3 percent of its water. The explanation lies in acidification. At 4 percent addition, the final pH rose by 2.3 percent relative to the control’s 4.38, and titratable acidity fell by 4.4 percent to 93.8 °T. Because yogurt gelation depends on acid gradually neutralizing the electrostatic repulsion between casein micelles as pH approaches their isoelectric point, a weaker fermentation slows and shallows that aggregation. The powder partially replaced milk, so the higher pH also reflects altered buffering and substrate availability — and the authors are careful to note that their design cannot separate the effect of added protein and solids from the specific contribution of the ultrasound–heat pretreatment itself, since a conventional spray-dried powder control was not included.

The most novel part of the study is its use of metatranscriptomics — sequencing the expressed RNA of the entire microbial community — to see how the starter cultures actually responded. From nine samples across the control, 1 percent and 4 percent groups, the team generated over 608 million raw reads, averaging roughly 7.77 gigabases per sample with Q30 quality scores above 95.7 percent. After removing ribosomal RNA, assembling transcripts de novo and annotating predicted proteins against the NR, KEGG, eggNOG and CAZy databases, they found that Bacillota transcripts dominated at over 98 percent in every group, with Streptococcus thermophilus and Lactobacillus delbrueckii as the core expressed species — exactly the signature of a healthy yogurt ferment. Ordination analyses showed the control clearly separated from both supplemented groups in transcriptional space.

The functional annotations told a coherent story. In the 4 percent group, transcript abundance assigned to glycolysis/gluconeogenesis, pyruvate metabolism and carbon metabolism all declined, consistent with the observed higher pH and lower acidity — the bacteria were transcribing fewer genes for lactose breakdown and lactic acid production. Carbohydrate-active enzyme genes showed the same pattern: glycoside hydrolase transcript abundance in the 4 percent group fell to about 48.7 percent of control levels, and glycosyltransferases to about 41.1 percent. Meanwhile, LEfSe analysis flagged lactic acid bacteria taxa such as Lactobacillaceae as differential in the 1 percent group, whereas the 4 percent group showed relatively higher representation of low-abundance, non-core taxa — possibly because the weakened acidification relaxed the selective pressure that normally suppresses non-yogurt microbes, and possibly because residual lysozyme, to which Gram-negative bacteria are more tolerant, subtly shifted the competitive balance. The authors stress that transcript abundance is not direct evidence of altered enzyme activity or metabolite concentrations, and that enzyme assays and metabolomics would be needed for confirmation.

The practical takeaway is a dose window rather than a free pass. At around 1 percent, the pretreated egg white powder delivered the best overall package: the highest springiness, the best water retention, a more compact gel network and a microbial community whose transcriptional profile remained firmly lactic-acid-bacteria dominated. At 4 percent, the same powder produced a visually denser network but softer texture, weaker acidification and a transcriptional drift toward non-core taxa. For an industry eager to boost protein content and improve texture with clean-label ingredients, that distinction matters enormously. The study also demonstrates the power of metatranscriptomics as a quality-control lens for fermented foods: instead of merely counting microbes, it reveals which metabolic programs are actively running, catching functional shifts that pH and texture measurements alone could only hint at. Future work with composition-matched controls will need to isolate what the ultrasound–heat pretreatment itself contributes, but the concept — defusing egg white’s antibacterial arsenal while enlisting its gelling proteins — now has both a physical and a molecular evidence base.

Subject of Research: Effects of ultrasound–heat pretreated egg white powder on yogurt quality, gel properties and microbial metatranscriptomic profiles

Article Title: Effects of ultrasound–heat pretreated egg white powder addition on the quality, gel properties, and metatranscriptomic profiles of yogurt

Article References: Xie, Y., Wang, X., Shui, Y., Hu, G., He, H., Wang, J., & Geng, F. (2026). Effects of ultrasound–heat pretreated egg white powder addition on the quality, gel properties, and metatranscriptomic profiles of yogurt. Food Chemistry: X, 39, Article 104550. https://doi.org/10.1016/j.fochx.2026.104550

Image Credits: AI Generated

DOI: 10.1016/j.fochx.2026.104550

Keywords: yogurt, egg white powder, ultrasound, lysozyme, gel properties, metatranscriptomics, lactic acid bacteria, food texture, spray drying, water-holding capacity, rheology, fermented dairy