Extrusion-modified Lentinula edodes stems enhance dough properties: Dependence on dietary fiber composition

TL;DR

Extrusion-modified Lentinula edodes stems improve dough properties by altering dietary fiber composition and reducing digestibility.

Contribution

The study reveals how extrusion processing of Lentinula edodes stems affects dough structure and digestibility.

Findings

Extruded L. edodes stems (≤15%) helped form a hydrated gel network and slowed starch retrogradation.

Untreated L. edodes stems disrupted starch interactions and hindered crystalline structure development.

Extrusion increased soluble fiber, enhancing starch crystallization and lowering dough digestibility.

Abstract

Dietary fiber-rich edible fungi are increasingly recognized for their potential to enhance the textural, sensory, and nutritional qualities of dough-based products. In this work, the effects of extrusion-modified Lentinula edodes stems (LESs) on the structural characteristics, physicochemical properties, and in vitro digestibility of wheat dough were investigated. The results showed that an appropriate addition level of extruded LESs (≤15%) facilitated the formation of a hydrated gel network, thereby retarding starch retrogradation in the dough matrix. In contrast, the incorporation of untreated LESs disrupted starch-involved interactions, impeding molecular assembly and the development of an ordered crystalline structure. Furthermore, low-moisture extrusion induced a substantial soluble fraction from LESs materials, which enhanced starch crystallization in the dough and reduced its digestibility. These findings reveal the potential of dietary fiber-rich edible fungi to enhance dough-based products and facilitate the development of innovative prebiotic functional foods.

•L. edodes stems modulated dough properties via their dietary fiber composition.•Non-extruded L. edodes stems reduced dough elasticity and viscosity.•Extruded L. edodes stems promoted dough with low digestibility.

L. edodes stems modulated dough properties via their dietary fiber composition.

Non-extruded L. edodes stems reduced dough elasticity and viscosity.

Extruded L. edodes stems promoted dough with low digestibility.

Figures

Schematic design of low-moisture extrusion system, including the twin screw extruder, feeder and extrusion (EXT) die.Fig. 1

SEM images of the dough samples (scale bar = 2 μm). WD sample represents the wheat dough without untreated LESs addition, while the LW-10, LW-15, and LW-20 samples denotes the wheat dough added with 10%, 15%, and 20% untreated LESs, respectively. EW-10, EW-15, and EW-20 samples represent the wheat dough added with 10%, 15%, and 20% extruded LESs, respectively.Fig. 3

Rapid viscosity analysis. WD sample represents the wheat dough without untreated LESs addition, while the LW-10, LW-15, and LW-20 samples denotes the wheat dough added with 10%, 15%, and 20% untreated LESs, respectively. EW-10, EW-15, and EW-20 samples represent the wheat dough added with 10%, 15%, and 20% extruded LESs, respectively.Fig. 6Table 1Gelatinization properties of the dough samples supplemented with untreated LESs and extruded LESs (10%, 15%, 20%).Table 1SamplesPeak Viscosity (cp)Trough Viscosity (cp)Breakdown Viscosity (cp)Final Viscosity (cp)Setback Viscosity (cp)Pasting Temperatu

Rheological properties: (a) Storage modulus (G', solid square) and loss modulus (G", hollow circle) as a function of frequency; (b) Apparent viscosity as a function of shear rate; (c) Steady flow curves. WD sample represents the wheat dough without untreated LESs addition, while the LW-10, LW-15, and LW-20 samples denotes the wheat dough added with 10%, 15%, and 20% untreated LESs, respectively. EW-10, EW-15, and EW-20 samples represent the wheat dough added with 10%, 15%, and 20% extruded LESs, respectively.Fig. 7

Textural properties: (a) Hardness; (b) Chewiness; (c) Springiness. WD sample represents the wheat dough without untreated LESs addition, while the LW-10, LW-15, and LW-20 samples denotes the wheat dough added with 10%, 15%, and 20% untreated LESs, respectively. EW-10, EW-15, and EW-20 samples represent the wheat dough added with 10%, 15%, and 20% extruded LESs, respectively.Fig. 8

Full text

Introduction

1

As a primary raw material in food production, the functional properties of wheat flour largely govern product quality, particularly in shaping the unique texture of baked goods and pasta, including bread, noodles, and cakes (Ferreira et al., 2025; Xu et al., 2019). However, conventional wheat flour products still have room for improvement in terms of textural performance, sensory quality, and nutritional composition (Kong et al., 2020). In response to this concern, the strategic incorporation of polysaccharide-based texture improvers into wheat flour has gained prominence as an effective strategy to enhance the dough quality.

Dietary fiber, a distinctive category of polysaccharides, plays a crucial functional role in modulating the hydration capacity and viscoelastic properties of dough-based products (Tang et al., 2024). Based on their aqueous solubility characteristics, dietary fiber constituents were fundamentally classified into the two discrete fractions (Feng et al., 2025). During dough processing, soluble dietary fiber enhances the hydration capacity of food systems through its pronounced water-binding properties, which not only foster molecular interactions but also contribute to the development of an intricate gel network matrix (Wang et al., 2024). Such hydrated network may improve dough chewiness and springiness, thereby enabling dough-based products to exhibit better textural and sensory attributes (Bu et al., 2025). Although insoluble dietary fiber addition may compromise dough texture, its incorporation at optimal levels could promote favorable modifications in gut microbiota composition (Ma et al., 2025). The interplay between these two components in the dietary system affects both the technological quality and consumer acceptability of dough-based products. Consequently, physical modification technologies have been widely explored to tailor the structural and functional properties of dietary fiber. Among these approaches, extrusion processing has attracted considerable attention owing to its high efficiency and controllability. Extrusion combines high temperature, mechanical shear, and pressure, inducing molecular degradation and reorganization of dietary fiber (Wu et al., 2025). A previous study indicated that extrusion treatment reduces psize and promotes the conversion of insoluble into soluble fractions, thereby enhancing hydration capacity (Guan et al., 2025). This structural transformation represents a promising strategy for enhancing the functional performance of fiber-rich fungi in dough applications. From a sustainability perspective, agricultural by-products (such as bran, fruit pomace, and legume residues) are increasingly recognized as cost-effective sources of dietary fiber. Their valorization transforms former processing waste into a resource that advances both efficiency and circular bioeconomy principles.

Therefore, the study utilized Lentinula edodes stems by-products as raw materials and subjected to extrusion modification. Based on the composition of dietary fiber, the effects of extrusion-modified Lentinula edodes stems on the structural characteristics, physicochemical properties, and in vitro digestibility of wheat dough were investigated. These findings would provide valuable insights for expanding the utilization of dietary fiber-rich edible fungi in food processing, which holds significant potential for the development of innovative prebiotic products.

Materials and methods

2

Materials

2.1

Lentinula edodes stems (LESs) were purchased from Fujian Kangwang Food Co., Ltd. (Fujian, China). According to compositional analysis, LESs consisted of (w/w): insoluble dietary fiber (43.2% ± 0.2%), soluble dietary fiber (1.4% ± 0.1%), carbohydrates (20.4% ± 0.1%), moisture (13.1% ± 0.1%), protein (16.7% ± 0.1%), ash (4.2% ± 0.1%), and fat (0.1% ± 0.03%).

Commercial wheat flour was purchased from Wonder Farm Co. Ltd. (Shandong, China), with the following composition (w/w): starch (67.9% ± 0.1%), protein (12.1% ± 0.1%), lipid (1.4% ± 0.1%), and ash (0.5% ± 0.1%). α-Amylase (derived from porcine pancreatic, ≥5000 U/g) and 3,5-dinitrosalicylic acid assay kit were obtained from Yuanye Bio-Technology Co., Ltd. (Shanghai, China). Bile salt was purchased from Solarbio Co., Ltd. (Beijing, China). Yeast powder was supplied by Angel Yeast Co., Ltd. (Hubei, China). All other reagents used in this study were analytical grade.

Low-moisture extrusion (LME) pretreatment

2.2

The LME system consists of a parallel co-rotating twin-screw extruder equipped with a 10 mm diameter at the extrusion end (HM30-IV, Jinan Hengmai Machinery Co., Ltd., China). In the heating sections, the twin-screw with a length-to-diameter ratio of 30 was horizontally positioned in the extrusion barrel (Fig. 1). The LME system was segmented into three temperature zones, each controlled by electric heating and water-cooling modules. The temperatures in the three zones were set to 60 °C, 80 °C, and 100 °C, respectively. Prior to LME trials, the moisture content of the LESs materials was adjusted to 30% (w/w) by gradually adding deionized water. The mixture was homogenized using a high-speed homogenizer (T25 digital Ultra-Turrax, IKA, Staufen, Germany) at 5000 rpm for 3 min to ensure moisture uniformity. Then, the hydrated samples were sealed in polyethylene bags and equilibrated at 4 °C for 24 h before LME processing. Based on preliminary experiments, the feed rate (solid) was set to 35 g/min, and the screw speed was set to 180 rpm. Subsequently, the collected extrudates were freeze-dried, ground, and passed through an 80-mesh sieve for further analysis.Fig. 1. Schematic design of low-moisture extrusion system, including the twin screw extruder, feeder and extrusion (EXT) die.Fig. 1

Preparation of the dough

2.3

Based on the prior experimental optimization, wheat flour was blended with 10%, 15%, and 20% (w/w) of untreated and extruded LESs, followed by pre-mixing with a mixer (HM770 Hauswirt, Germany). The resulting doughs were transferred to a fermentation cabinet (FJK-SK-02, Fujian Electronics Co., Ltd., Fuzhou, China) and incubated at 37 °C for 30 min. After fermentation, the dough samples were divided into 50 g portions and manually shaped into round forms. The shaped dough was then steamed at 100 °C for 30 min. Subsequently, the steamed samples were freeze-dried to a constant weight, ground into fine powder, and passed through an 80-mesh sieve to obtain samples for further analysis. Wheat dough samples containing 10%, 15%, and 20% extruded LESs were designated as EW-10, EW-15, and EW-20, respectively. The control samples containing untreated LESs at the same levels were labeled LW-10, LW-15, and LW-20, and the wheat dough without LESs addition was designated as WD sample.

Particle size distribution analysis

2.4

The particle size distribution of the dough samples was determined using a laser diffraction psize analyzer (Mastersizer 3000, Malvern Panalytical, UK). Prior to measurement, approximately 0.2 g of each sample was dispersed in deionized water used as the dispersion medium under continuous stirring. Measurements were performed in wet dispersion mode, with the obscuration level controlled at approximately 10%. The refractive indices of starch and water were set to 1.53 and 1.33, respectively.

Scanning electron microscopy (SEM)

2.5

The dough samples were affixed to the SEM stubs using conductive adhesive and coated with a thin gold layer under vacuum. Microstructural characterization was carried out using a field-emission SEM (Gemini SEM 300, Carl Zeiss AG Co., Ltd., Germany) operated at an accelerating voltage of 10 kV and a magnification of 5000 × .

X-ray diffraction (XRD)

2.6

The crystalline structure of the dough samples was analyzed using an X-ray diffractometer (Ultima IV, Rigaku Crop., Tokyo, Japan) equipped with Cu Kα radiation (λ = 1.5418 Å) operated at 40 kV and 40 mA. The diffraction patterns were recorded over a 2θ range of 5° to 70° with a scanning rate of 5°/min (Zheng et al., 2024). The crystalline patterns of the samples were subsequently identified using MDI Jade v.6.5 and Origin 2023 software. The relative crystallinity of the dough samples was calculated using the following formula:

$$[eqn]$$

where Ac is the crystalline area and Aa is the amorphous area.

Fourier transform infrared (FTIR) spectroscopy

2.7

The dough samples and KBr powder (1:100, w/w) were mixed and ground under an infrared lamp. Briefly, the mixture was compressed into transparent disks using a hydraulic press. Each sample was measured using an infrared spectrometer (Nicolet iS20, Thermo Fisher Scientific, Madison, U.S.A.). The measurements were collected with 64 times at a spectral resolution of 4 cm^−1^ over the wavenumber range of 500–4000 cm^−1^. The fingerprint region of the dough samples (900–1200 cm^−1^) was deconvoluted using Peakfit v.4.0 (Systat Software Inc., Palo Alto, U.S.A.) with Gaussian-Lorentzian peak profiles. The ratio of R_1047/1022_ and R_995/1022_ represents the peak area ratios of 1047 cm^−1^ to 1022 cm^−1^ and 995 cm^−1^ to 1022 cm^−1^, respectively.

Rapid viscosity analysis (RVA)

2.8

The pasting properties of dough suspension (8%, w/v) were determined using a rapid viscosity analyzer (TecMaster, Perten Instruments, Sydney, Australia), according to the procedure described by Su et al. (2024). The temperature program was initially increased from 30 °C to 95 °C at a rate of 10 °C/min, maintained at 95 °C for 2 min, and cooled to 50 °C at the rate of 10 °C/min. The peak viscosity (PV), trough viscosity (TV), breakdown viscosity (BV), final viscosity (FV), setback viscosity (SV), and pasting temperature (PT) were recorded by the RVA supporting software. After gelatinization, the samples were cooled to 25 °C and stored at 4 °C prior to rheological analysis.

Rheological properties

2.9

The rheological parameters of the dough samples (obtained from the RVA experiment) were measured on a rheometer (HR20, TA Instruments Ltd., U.S.A.) equipped with parallel plates of 40 mm diameter. Approximately 1 g of the samples was placed between parallel plates with a gap (1 mm) and equilibrated at 25 °C for 30 s. Excess sample was carefully trimmed from the edges, and silicone oil was applied to the rim of the solvent trap to prevent moisture evaporation during the measurement.

Frequency sweep

2.9.1

The dough samples (obtained from the RVA experiment) were determined within the linear viscoelastic region (1% strain) at a frequency range from 0.1 to 100 Hz. The storage modulus (G') and loss modulus (G") were recorded as functions of frequency.

Steady-shear flow behavior

2.9.2

The steady-shear flow behavior of the dough samples was investigated over a shear rate range of 0.1 to 100 s^−1^. The relationship between shear stress and shear rate was analyzed and fitted using the power law equation:

τ = K(γ)^n^.

where τ represents the shear stress (Pa), γ denotes the shear rate (s^−1^), K is the consistency coefficient (Pa·sⁿ), and n is the flow behavior index.

Texture profile analysis (TPA)

2.10

According to the method described by Zheng et al. (2024), the dough samples were cut into 1 × 1 × 1 cm cubes and subjected to texture properties using a TMS-Pilot texture analyzer (TMS-Pilot, Food Technology Corp., Virginia, U.S.A.). The dough samples were compressed to 50% of original height using a cylindrical probe with a diameter of 75 mm. This experiment was conducted under a constant force of 75 N at a deformation rate of 1 mm/s. The hardness, springiness and chewiness of the dough samples were calculated using TL-Pro texture analysis software.

In vitro digestion

2.11

The in vitro digestion of the dough samples was conducted with the methods reported by Liu et al. (2023). Briefly, porcine pancreatic α-amylase (290 U/mL) was dissolved in acetate buffer (0.1 M, pH = 5.2) to prepare the digestive solution. To simulate oral mastication, the dough samples were subjected to compression treatment using a texture analyzer equipped with a flat cylindrical probe (75 mm in diameter). Approximately 0.2 g of dough was compressed to 50% strain at 1.0 mm/s, held for 5 s, and then released. This compression–release cycle was repeated five times to simulate the mechanical deformation occurring during human mastication. After compression treatment, the dough sample (0.2 g) was dispersed in a mixture containing 5 mL of digestive juice, 20 μL of 0.3 M CaCl_2_ and 1.25 mL of 0.01 M bile salt solution. The mixture was then transferred to centrifuge tubes and incubated in a shaking water bath at 160 rpm and 37 °C for 3 h. At the designated time point (0, 20, 40, 60, 90, 120, 180 min), the centrifuge tubes were removed and subjected to heat treatment at 100 °C for 5 min. After centrifugation (6570 ×g, 10 min), the glucose content was determined by 3,5-dinitrosalicylic acid (DNS) kit. According to the methods proposed by Englyst et al. (1992), the total hydrolysis and the proportions of rapidly digested starch (RDS), slowly digested starch (SDS), and resistant starch (RS) were calculated as follows:

$$[eqn]$$ $$[eqn]$$ $$[eqn]$$ $$[eqn]$$

where W indicates the weight of the dough samples, and G_t_ denotes the concentration of glucose produced at the t time. G_0_, G_20_, and G_120_ indicate the concentrations of glucose at 0, 20, and 120 min, respectively. RDS (%), SDS (%), and RS (%) represent the proportions of rapidly digestible starch, slowly digestible starch and resistant starch, respectively.

Statistical analyses

2.12

All experiments were conducted with at least three independent replicates. Statistical analyses were performed using SPSS v.26.0 (IBM Corp., U.S.A.). Significant differences between groups were analyzed by one-way analysis of variance (ANOVA) followed by Duncan's multiple range test (P < 0.05). The relationship between variables were evaluated using Pearson's correlation coefficient. Graphs were drawn using Origin 2022 (OriginLab Corp., Northampton, MA, U.S.A.).

Results and discussion

3

Particle size analysis

3.1

The particle size distributions of the dough samples are presented in Fig. 2. As the level of extruded LESs increased, the particle size distribution of the EW samples exhibited broader. At an addition level of 15%, the EW-15 samples displayed a 35.07% increase in particle size compared to the WD samples. This increase is likely due to extrusion-induced rises in the soluble fraction, which enhance interactions between LESs and starch. Such interactions may promote starch hydration and swelling, thereby contributing to the observed enlargement of particle size. In contrast, the LW samples showed a reduction in particle size relative to the WD sample. Among them, the LW-15 samples exhibited the smallest psize (Fig. 2b). This decrease is attributed to the insoluble dietary fiber in LESs, which impeded starch swelling by restricting aggregation and water penetration. The effect was particularly evident in flours with larger granule sizes, as reported by previous studies (Zhuang et al., 2024; Donmez et al., 2021; Korompokis et al., 2019). These results suggest that fiber-rich edible fungi could modulate the particle-size distribution of dough by altering starch hydration and swelling.Fig. 2(a) Psize distribution; (b) Histogram of the average psize distribution. WD sample represents the wheat dough without untreated LESs addition, while the LW-10, LW-15, and LW-20 samples denotes the wheat dough added with 10%, 15%, and 20% untreated LESs, respectively. EW-10, EW-15, and EW-20 samples represent the wheat dough added with 10%, 15%, and 20% extruded LESs, respectively.Fig. 2

Microstructure analysis

3.2

Fig. 3 presents the microstructure of the dough samples at varying addition levels of LESs and extruded LESs. It can be found that the incorporation of LESs induced structural fractures, likely because insoluble fibers impeded water penetration and disrupted the continuity of the dough matrix. In contrast, extruded LESs facilitated the formation of a honeycomb-like network in the dough. These irregular pores were likely formed by water evaporation during the lyophilization process. Moreover, soluble dietary fiber preserved additional moisture within the dough matrix and thus promoted pore formation. Similar honeycomb-like porous structures have been observed in rice starch containing guar gum (Dangi et al., 2019) and in maize starch supplemented with the soluble dietary fiber (Liu et al., 2019). These results indicate that incorporating LESs significantly altered the dough microstructure, which may enhance the processing characteristics (e.g., flavor and texture).Fig. 3SEM images of the dough samples (scale bar = 2 μm). WD sample represents the wheat dough without untreated LESs addition, while the LW-10, LW-15, and LW-20 samples denotes the wheat dough added with 10%, 15%, and 20% untreated LESs, respectively. EW-10, EW-15, and EW-20 samples represent the wheat dough added with 10%, 15%, and 20% extruded LESs, respectively.Fig. 3

Crystalline structure analysis

3.3

To distinguish the crystalline pattern of the dough samples, all peaks in the 5–35° (2θ) range were deconvoluted using Gaussian fitting (Fig. 4a). All samples exhibited diffraction peaks at 13°, 17°, 20° and 24° (2θ), which indicates the crystalline diffraction of B-type and V-type allomorphs. As shown in Fig. 4c, the relative crystallinity of the LW-15 sample (1.92% ± 0.02%) was 0.49% lower than that of the WD sample (2.41% ± 0.02%), indicating that the incorporation of untreated LESs suppressed starch recrystallization during dough formation. This reduction in crystallinity is consistent with previous findings (Wu et al., 2021), which demonstrated that insoluble dietary fiber can interfere with amylose rearrangement and double-helical structure formation, thereby inhibiting starch retrogradation. In contrast, the addition of extruded LESs significantly altered the crystalline organization of starch. This enhancement suggests that extrusion-induced modifications in dietary fiber composition and structure may promote starch chain reassociation and crystalline domain development. These results highlight the dominant role of the dietary fiber composition from LESs in regulating starch crystallinity.Fig. 4(a) X-ray diffractograms and peak-fitted profiles; (b) Relative crystallinity. WD sample represents the wheat dough without untreated LESs addition, while the LW-10, LW-15, and LW-20 samples denotes the wheat dough added with 10%, 15%, and 20% untreated LESs, respectively. EW-10, EW-15, and EW-20 samples represent the wheat dough added with 10%, 15%, and 20% extruded LESs, respectively.Fig. 4

Molecular structure

3.4

Fig. 5 displays the FTIR spectra of the dough samples within the range of 500–4000 cm^−1^. Characteristic absorption bands corresponding to the O—H stretching (3000–3700 cm^−1^), asymmetric stretching of –COO^−^ (2930 cm^−1^), and carbohydrate-related vibrations (900–1200 cm^−1^) were identified. The infrared fingerprint region within 900–1200 cm^−1^ is primarily associated with the characteristic vibrations of starch molecules, and the signal bands in this region were further deconvoluted using Gaussian fitting (Fig. 5c&5d). An enhancement of the peak at 951 cm^−1^ accompanied by the reduction in intensity at 1037 cm^−1^ suggests a higher degree of short-range order in starch, reflecting strengthened hydrogen bonding and the formation of more ordered double-helical structures. Additionally, the relative crystalline of dough samples was evaluated using the peak area ratios of 1047 cm^−1^ to 1022 cm^−1^, while the double helical structures was assessed based on the peak area ratios of 995 cm^−1^ to 1022 cm^−1^ (He et al., 2020). After incorporating LESs, both the R_1047/1022_ and R_995/1022_ values of the LW samples decreased (Fig. 5b). This trend suggested that the addition of LESs may prevent the starch chain rearrangement and inhibit the formation of short-range ordered structure. This inhibitory effect is likely attributed to the presence of insoluble dietary fiber, which may interfere with the establishment of hydrogen bonding networks through steric hindrance. The observed decreases in R_1047/1022_ and R_995/1022_ values were consistent with the XRD results, confirming a reduction in crystallinity. The R_1047/1022_ and R_995/1022_ values of the EW-15 samples reached the maximum at 0.37 ± 0.02 and 1.16 ± 0.03, respectively. This effect may be attributed to the incorporation of the extruded LESs into the dough matrix, which facilitated the rearrangement of starch chains and promoted the formation of an ordered helical structure. Collectively, this result indicates that an appropriate level of extruded LESs could effectively modulate starch molecular and enhance short-range structural order in dough systems.Fig. 5(a) FTIR spectra; (b) Peak area ratios of 1047 cm^−1^ to 1022 cm^−1^ (R_1047/1022_, blue line) and 995 cm^−1^ to 1022 cm^−1^ (R_995/1022_, red line); (c)-(d) Deconvoluted spectra (900–1200 cm^−1^). WD sample represents the wheat dough without untreated LESs addition, while the LW-10, LW-15, and LW-20 samples denotes the wheat dough added with 10%, 15%, and 20% untreated LESs, respectively. EW-10, EW-15, and EW-20 samples represent the wheat dough added with 10%, 15%, and 20% extruded LESs, respectively. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)Fig. 5

Rapid viscosity analysis (RVA)

3.5

The gelatinization profiles of the dough samples with varying addition levels of untreated LESs and extruded LESs are presented in Fig. 6. The LW samples exhibited higher peak viscosity, trough viscosity, and final viscosity than the WD samples. In contrast, the incorporation of extruded LESs resulted in a pronounced reduction in viscosity of the EW samples (Table 1). These changes in viscosity were closely associated with the swelling capacity of starch granules during the heating. The decrease in peak viscosity was primarily attributed to the entanglement between soluble dietary fiber and starch molecules, which restricted granule swelling and limited starch pasting. The breakdown viscosity (BV) is regarded as an indicator of the thermal stability and retrogradation tendency of starch granules during gelatinization (Wang et al., 2020). The addition of LESs increased BV of the dough samples, suggesting that LESs reduced the thermal stability and accelerated retrogradation of the dough system. The setback viscosity (SV) represents the degree of starch recrystallization, mainly associated with amylose rearrangement during short-term retrogradation (Tu et al., 2021). Relative to the WD samples, the EW samples exhibited significantly lower SV values (P < 0.05), indicating delayed starch retrogradation. Moreover, the EW-20 samples showed a higher SV value than the EW-15 samples, implying that excessive addition of extruded LESs may promote starch degradation. These findings indicate that adding extruded LESs at levels below 15% facilitates the formation of a stable gel network in the dough while retarding starch retrogradation.Fig. 6. Rapid viscosity analysis. WD sample represents the wheat dough without untreated LESs addition, while the LW-10, LW-15, and LW-20 samples denotes the wheat dough added with 10%, 15%, and 20% untreated LESs, respectively. EW-10, EW-15, and EW-20 samples represent the wheat dough added with 10%, 15%, and 20% extruded LESs, respectively.Fig. 6. Table 1Gelatinization properties of the dough samples supplemented with untreated LESs and extruded LESs (10%, 15%, 20%).Table 1. SamplesPeak Viscosity (cp)Trough Viscosity (cp)Breakdown Viscosity (cp)Final Viscosity (cp)Setback Viscosity (cp)Pasting Temperature (°C)WD55.07 ± 1.01^c^50.67 ± 1.53^d^4.40 ± 1.04139.33 ± 2.52^b^88.67 ± 3.21^ab^59.73 ± 1.62^b^LW-1063.10 ± 1.85^b^64.03 ± 1.05^b^/145.67 ± 2.08^b^81.63 ± 1.10^b^66.67 ± 1.53^a^LW-1586.00 ± 3.61^a^65.83 ± 3.25^b^/159.33 ± 6.43^a^93.50 ± 3.50^a^64.70 ± 0.56^a^LW-2088.33 ± 4.51^a^74.67 ± 1.53^a^/161.33 ± 3.51^a^86.67 ± 4.16^ab^65.60 ± 2.48^a^EW-1055.33 ± 1.53^c^65.07 ± 1.90^b^/109.00 ± 4.58^c^43.93 ± 3.69^c^65.35 ± 0.56^a^EW-1546.83 ± 1.76^d^56.67 ± 3.51^c^/85.33 ± 4.04^d^28.67 ± 6.66^d^64.02 ± 1.75^a^EW-2033.33 ± 1.53^e^45.17 ± 0.76^e^/79.07 ± 2.90^d^33.90 ± 3.44^d^58.03 ± 0.98^b^WD sample represents the wheat dough without LESs addition, while the LW-10, LW-15, and LW-20 samples denotes the wheat dough added with 10%, 15%, and 20% untreated LESs, respectively. EW-10, EW-15, and EW-20 samples represent the wheat dough added with 10%, 15%, and 20% extruded LESs, respectively. Values with different letters in the same column indicate significant differences (P < 0.05).

Rheological properties

3.6

Dynamic rheological analysis

3.6.1

The storage modulus (G') and loss modulus (G") curves measured within the linear viscoelastic range. All samples exhibited the G' values higher than G" values, indicating that the system was predominantly elastic (Fig. 7a). With increasing levels of LESs, the G′ values of the LW samples decreased. This is likely because LESs competed with starch for water, limiting water available for gelatinization (Xu et al., 2021). Moreover, the insoluble dietary fiber may hinder the formation of a continuous gel network, thereby weakening the elasticity of starch gel in the dough. As the levels of extruded LESs increased, both G' and G" values progressively declined, suggesting a weakening of the dough gel network. This behavior may be attributed to the tendency of amylose to undergo recrystallization rather than to form a compact gel network. Consistent with this interpretation, previous research (Zhuang et al., 2024) reported that ordered helical structures exhibit limited interactions with water molecules, which may hinder the development of elastic-dominated gel networks. These findings indicate that extruded LESs modulates dough rheology primarily by altering water availability and gel network connectivity.Fig. 7. Rheological properties: (a) Storage modulus (G', solid square) and loss modulus (G", hollow circle) as a function of frequency; (b) Apparent viscosity as a function of shear rate; (c) Steady flow curves. WD sample represents the wheat dough without untreated LESs addition, while the LW-10, LW-15, and LW-20 samples denotes the wheat dough added with 10%, 15%, and 20% untreated LESs, respectively. EW-10, EW-15, and EW-20 samples represent the wheat dough added with 10%, 15%, and 20% extruded LESs, respectively.Fig. 7

Static rheological analysis

3.6.2

The steady-state shear flow properties of dough samples containing different levels of untreated and extruded LESs are shown in Fig. 7b&7c. The corresponding fitting parameters obtained from the power-law model are summarized in Table 2. The R^2^ values ranged from 0.9289 to 0.9798, indicating an excellent fit between the experimental data and the model predictions. The shear stress of the dough samples increased with shear rate, demonstrating typical non-Newtonian flow behavior. Meanwhile the apparent viscosity decreased with increasing shear rate, confirming shear-thinning behavior in the system (Fig. 7b). The reduction in the consistency index (K) after adding LESs or extruded LESs may be due to the shear-induced alignment of insoluble dietary fiber, which weakened gel stability. Moreover, the flow behavior index (n) of all dough samples was less than 1, confirming their pseudoplastic characteristics (Ji et al., 2021). In the LW samples, the n value rose from 0.24 ± 0.02 to 0.27 ± 0.01 with 20% LESs addition, suggesting a weakening of pseudoplasticity in the gel system. These results indicate that the modulation of flow behavior by LESs incorporating may provide opportunities to optimize the textural and rheological properties of fiber-enriched bakery products.Table 2. Rheological parameters of the dough samples.Table 2. SamplesK (*10^−6^)nR^2^WD22.33 ± 0.70^a^0.23 ± 0.01^c^0.9798LW-1012.06 ± 0.66^b^0.24 ± 0.02^bc^0.9499LW-159.20 ± 0.57^c^0.25 ± 0.02^bc^0.9454LW-208.28 ± 0.42^c^0.27 ± 0.01^b^0.9690EW-106.92 ± 0.68^d^0.31 ± 0.03^a^0.9289EW-153.76 ± 0.29^e^0.32 ± 0.02^a^0.9576EW-202.59 ± 0.18^f^0.34 ± 0.02^a^0.9707Values with different letters in the same column indicate significant differences (P < 0.05). K is the consistency coefficient (Pa·sⁿ), and n is the flow behavior index. The R^2^ represents the fitting accuracy of the model. WD sample represents the wheat dough without untreated LESs addition, while the LW-10, LW-15, and LW-20 samples denotes the wheat dough added with 10%, 15%, and 20% untreated LESs, respectively. EW-10, EW-15, and EW-20 samples represent the wheat dough added with 10%, 15%, and 20% extruded LESs, respectively.

Textural analysis

3.7

Fig. 8 presents the textural properties (e.g., hardness, chewiness and springiness) of the dough samples. As shown in Fig. 8a, the LW samples exhibited lower hardness compared with the WD samples. This reduction in dough hardness may be attributed to the insoluble dietary fiber in LESs, which could penetrate the dough matrix and disrupt its dense structure. In contrast, the EW samples exhibited significantly higher hardness, chewiness and springiness (Fig. 8b). This was attributed to the fact that the extruded LESs could induce cross-linking among protein, starch and dietary fiber, thereby forming an intricate gel network. Properly incorporating extruded LESs (∼15%) is beneficial to produce dough with excellent chewiness and springiness (Fig. 8c). These results indicate that the balance between disruptive and reinforcing effects of dietary fiber plays a key role in determining the final textural properties of the dough.Fig. 8. Textural properties: (a) Hardness; (b) Chewiness; (c) Springiness. WD sample represents the wheat dough without untreated LESs addition, while the LW-10, LW-15, and LW-20 samples denotes the wheat dough added with 10%, 15%, and 20% untreated LESs, respectively. EW-10, EW-15, and EW-20 samples represent the wheat dough added with 10%, 15%, and 20% extruded LESs, respectively.Fig. 8

In vitro digestion

3.8

The digestibility and starch composition of the dough samples are illustrated in Fig. 9. As displayed in Fig. 9a, the incorporation of LESs accelerated starch hydrolysis compared with the WD sample. It can be observed that the LW-15 samples exhibited higher total hydrolysis than the WD samples. This phenomenon could be explained by the disruptive effect of untreated LESs in the dough matrix, thereby exposing the enzyme binding sites. Interestingly, the addition of 15% extruded LESs reduced the total hydrolysis of the dough from 49.62% to 46.23%. This reduction can be explained by the increased proportion of soluble dietary fiber generated during extrusion, which interacts with starch molecules and restricts enzyme accessibility. Regarding starch fractions, the EW-15 samples exhibited the highest proportion of RS, reaching 55.17% ± 1.11%. This observation is in accordance with a previous study (Zhou et al., 2022), which reported that the soluble dietary fiber contributed to an intricate gel network structure with starch via hydrogen bonding, thereby impeding enzymatic hydrolysis. These results demonstrate that dietary fiber-rich materials have potential to modulate starch digestibility and the postprandial glucose response, which provides an innovation strategy for developing starchy foods with a low glycemic index.Fig. 9(a) In vitro starch digestibility; (b) Proportions of rapidly digested starch (RDS), slowly digested starch (SDS) and resistant starch (RS) in the dough samples. WD sample represents the wheat dough without LESs addition, while the LW-10, LW-15, and LW-20 samples denotes the wheat dough added with 10%, 15%, and 20% untreated LESs, respectively. EW-10, EW-15, and EW-20 samples represent the wheat dough added with 10%, 15%, and 20% extruded LESs, respectively.Fig. 9

Correlational analysis and potential mechanism

3.9

To explore the mechanistic interplay between LESs and dough, Pearson correlation analysis was conducted to assess the relationship between the addition level of LESs and the properties of dough. As illustrated in Fig. 10a, the incorporation level of LESs exhibited a positive correlation with the total hydrolysis (r = 0.80), while a negative correlation with the relative crystallinity (r = −0.37), 1047/1022 ratio (r = −0.21), hardness, chewiness (r = −0.72), and springiness (r = −0.84). Additionally, extruded LESs were positively correlated with the hardness (r = 0.48,), chewiness (r = 0.48), and springiness (r = 0.92), while negatively correlated with the relative crystallinity (r = −0.39), 1047/1022 ratio (r = −0.74), and total hydrolysis (r = −0.38). Based on the above results, the potential mechanism by which LESs regulated the structure and physicochemical properties of wheat flour was proposed (Fig. 10b&10c). This mechanism involves the application of low-moisture extrusion as a modification technique, which combines high-temperature extrusion and expansion effects (Babatunde et al., 2023; Xiao et al., 2023). This approach effectively modulates the dietary fiber composition and enhances its functional properties. Specifically, the process promotes the conversion of insoluble fiber into soluble fiber primarily by disrupting intermolecular hydrogen bonds under the synergistic effect of high pressure and shear stress (Zhang et al., 2024). The dietary fiber fractions regulate the molecular conformation and crystalline structure of wheat dough, thereby influencing the formation of the gel network and systematically modulating its physicochemical properties. The soluble fraction in extruded LESs facilitates gelation owing to its strong hydrophilicity, resulting in the development of a continuous and dense gel network structure within the dough. Consequently, this network limited the accessibility of digestive enzymes and delayed the starch hydrolysis process. In contrast, insoluble fiber in LESs may disrupt the continuity of the dough matrix and compromise the integrity of the network, thereby enhancing starch hydrolysis. The connection between the microstructural evolution and functional properties highlights the key role of extrusion-modified LESs in shaping dough structure and modulating digestibility. These findings provide a theoretical basis for designing functional starchy products with low glycemic index and high dietary fiber content.Fig. 10(a) Pearson correlation heatmap between the addition levels of untreated LESs and extruded LESs with the structural parameters, textural properties, and total hydrolysis of dough. The colour scale indicates the sign and magnitude of Pearson's correlation coefficients (yellow for positive, blue for negative). Statistical significance is denoted by asterisks (* P < 0.05, ** P < 0.01, *** P < 0.001); (b) Schematic illustration of the effects of untreated LESs and extruded LESs on the dough gelation behavior. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)Fig. 10

Conclusion

4

In this work, the impact of LESs on the structural parameters, rheological behavior, and in vitro digestibility of dough was evident, and exhibited a dependence on dietary fiber composition and incorporation level. The LESs dominated by insoluble fiber primarily disrupted the continuity of the starch matrix, leading to weakened elasticity and viscosity of the dough. By comparison, the extruded LESs could interacted with the leached amylose via hydrogen bonding to reduce the viscosity of dough. Moreover, a higher proportion of soluble dietary fiber facilitated the formation of a dense gel network, which restricted enzymatic accessibility and reduced the starch hydrolysis. Collectively, achieving an appropriate balance between soluble and insoluble dietary fiber is essential for fine-tuning dough structure and texture, while suitable processing conditions can further maximize both functional and nutritional benefits. These results support the development of fiber-enriched bakery products that combine desirable quality with substantial health benefits.

CRediT authorship contribution statement

Lihua Wen: Writing – review & editing, Formal analysis, Conceptualization. Jingfeng Qin: Formal analysis, Data curation. Jinhao Zheng: Methodology. Zebin Guo: Supervision, Conceptualization. Baodong Zheng: Supervision, Conceptualization. Yixin Zheng: Writing – review & editing, Visualization, Funding acquisition, Conceptualization.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.