Proteins serve vital roles in food systems, not only for their nutritional value but also for their techno-functional attributes such as emulsification, foaming, gelation and texture modification (Zhao et al., 2025). Amid rising demand for sustainable and dairy-free products, the pursuit of alternative proteins with high functionality has intensified (Malila et al., 2024). Silk fibroin protein (SFP), derived from Bombyx mori cocoons, is an emerging candidate due to its unique structure, mechanical robustness and ease of modification (Xu et al., 2024).
       
Few studies in the literature have highlighted the transformative potential of silk fibroin, not only in materials science and packaging (Giannelli et al., 2021), but also increasingly in food processing and formulation (Tanisood et al., 2021; Panneerselvam et al., 2024). SFP’s fibrous β-sheet structures and modifiable nature make it an appealing ingredient for functional food systems, especially when processed into regenerated, soluble forms (Huang et al., 2023).
       
Whipping properties are critical for cream analogs and aerated desserts, where proteins stabilize the air-water interface, enabling volume expansion and foam stability (Kheto, 2025). However, native silk fibroin exhibits poor solubility and limited functionality in such systems. Enzymatic hydrolysis is a promising strategy to overcome these limitations, enhancing solubility, interfacial activity and foamability of diverse proteins (Olatunde et al., 2022; Dabo et al., 2024). Beyond foaming, other quality attributes, such as chemical composition, viscosity and color, also play important roles in determining consumer acceptance and industrial viability of cream analogs. Protein fortification enhances nutritional value, while viscosity and rheological behavior contribute to structural integrity and sensory perception. In addition, color is a key visual quality parameter that strongly influences product appeal and marketability (Kim and Moon, 2024). Recent advances in plant-based whipped creams further underscore the importance of optimizing these multidimensional properties simultaneously (Li, 2023).
       
Although plant-based whipped systems have been extensively studied, the incorporation of silk fibroin protein into these formulations remains inadequately explored. This study aims to fill that gap by investigating the effects of raw versus enzymatically modified SFP on whipping performance, chemical composition, viscosity and color of a plant-based cream analog. We hypothesize that enzymatic modification will substantially enhance SFP’s functional properties, improving overrun, foam stability and rheological strength, while minimizing adverse effects on color or compositional balance. By integrating structural, functional and sensory dimensions, this research offers novel insights into the use of modified SFP as a sustainable, functional protein ingredient in dairy-free aerated food products.

Materials
 
Bombyx mori cocoons and analytical-grade reagents were locally sourced.
       
Alcalase® Enzyme was provided by Novozymes, Denmark. A plant-based oil blend of refined coconut and rapeseed oils (70:30, w/w) and food-grade emulsifiers (lecithin, mono- and diglycerides) was supplied by the United Oil Company, Egypt.
 
Silk fibroin extraction and enzymatic modification
 
Cocoons were cut and degummed by boiling in 0.02 M sodium carbonate (Na₂CO₃) for 30 min at a fiber-to-liquor ratio of approximately 1:50 (w/v), thoroughly rinsed with deionized water and air-dried overnight to remove sericin. Degummed silk fibers were dissolved in 9.2-9.3 M lithium bromide (LiBr) at 60°C for 3-4 h, dialyzed (MWCO ~3.5 kDa) against deionized water for 48 h with frequent water changes to remove residual lithium bromide and then used as regenerated silk fibroin solution or lyophilized as required (Wang et al., 2024).
       
For enzymatic modification, regenerated fibroin solution was adjusted to pH 8.0 (50 mM buffer) and treated with Alcalase® at 1% (enzyme/protein, w/w) at 55°C for 2 h with gentle stirring, followed by thermal inactivation at 90°C for 10 min; this limited hydrolysis approach is supported to improve solubility, interfacial activity and foamability (Zhou et al., 2022).
       
Protein characterization comprised solubility assays and SDS-PAGE to confirm increased solubility and partial chain hydrolysis, consistent with observed structure-function gains after limited proteolysis (Zhou et al., 2022).
 
Cream analog preparation
 
Cream analogs were prepared by dispersing the aqueous protein phase (raw or modified SFP at 1%, 3%, or 5% w/v) with emulsifiers into the oil phase to yield an oil-in-water emulsion containing 30% (w/v) oil, in line with whipped-cream model methodologies (Han et al., 2023). Emulsions were homogenized using a two-stage high-pressure homogenization regime at 15 MPa in the first stage and 5 MPa in the second stage to obtain a fine droplet size and suitable structure for whipping, following conditions typically used for recombined cream systems. After homogenization, the emulsions were pasteurized at 75°C for 30 s, rapidly cooled and stored at 4°C for at least 12 h prior to analysis (Zhang et al., 2025). A protein-free control emulsion was prepared and subjected to the same homogenization, pasteurization and storage conditions to isolate the specific effects of SFP on whipping and rheological behavior.
 
Whipping procedure and foam analyses
 
Whipping was performed in fixed-volume vessels using standardized mixing parameters to achieve peak firmness, ensuring reproducible foam generation, as described in cream-whipping study of Kim and Moon (2024). Overrun (%) was calculated as using pre-marked volumes, consistent with definitions in whipping-cream literature (Dabo et al., 2024).

 

       
Foam stability was quantified by measuring liquid drainage at 30, 60 and 120 min at ambient temperature using a funnel-collector arrangement, a common approach to assess drainage- and coalescence-mediated foam decay in cream systems (Wang et al., 2025; Tanweer et al., 2026).
 
Gross composition
 
Chemical composition analyses were performed according to the Association of Official Analytical Chemists (AOAC, 2023) methods. Moisture content was measured by drying samples at 105°C until constant weight to calculate water loss. Protein content was determined using the Kjeldahl method to quantify total nitrogen, applying a conversion factor of 6.25. Fat content was extracted via Soxhlet extraction using petroleum ether as solvent. Ash content was measured by incinerating samples in a muffle furnace at 550°C until complete combustion of organic matter. Carbohydrates were calculated by difference, subtracting the sum of moisture, protein, fat and ash from 100%. 
 
Rheological assay
 
Small-amplitude oscillatory shear measurements were conducted using an Anton Paar MCR 302 rheometer at 25°C with parallel-plate geometry (PP50, 2 mm gap), determining G' and G" within the linear viscoelastic region (LVR, γ<0.5%). Amplitude sweeps (0.01-100%) established LVR limits, followed by frequency sweeps (0.1-10 Hz, γ=0.1%) (Qian et al., 2025; Lapčíková  et al., 2024). Apparent viscosity measured using Brookfield DV-II+ viscometer (spindle 4) across 50-100 s^-1, fitted to Ostwald-de Waele model (τ= Kγ̇ⁿ) (Ghorbani-HasanSaraei  et al., 2019). The chosen parameters align with recent evaluations of cream flow profiles and whipping performance (Dabo et al., 2024).
 
Color measurements
 
Color measured at 25°C using Minolta CR-400 colorimeter in CIE L*a*b* space (D65 illuminant, 10° observer). ΔE* computed as ΔE* = √[(ΔL*)² + (Δa*)² + (Δb*)²] relative to protein-free control (Ghorbani HasanSaraei  et al., 2019).
 
Statistical analysis
 
All measurements were performed in triplicate (n = 3) and reported as mean ± SD; one-way ANOVA followed by Tukey’s HSD was used to test differences at p<0.05, consistent with analytical practices in whipped cream chemorheology and foam studies (El-Sayed and Hashim, 2024).

Protein characterization
 
Modified SFP showed significantly higher solubility (82±3%) compared to raw SFP (38±2%), indicating improved hydrophilicity. SDS-PAGE confirmed partial hydrolysis of fibroin chains. In addition, the proximate composition of raw and modified silk fibroin protein is presented in Table 1. Both forms were predominantly protein-rich, with only minor differences in moisture, ash, fat and carbohydrate contents, confirming their suitability as functional protein ingredients in cream analog formulations (Ware et al., 2026).


 
Whipping properties
 
Table 2 summarizes the effects of raw and modified silk fibroin protein (SFP) on the whipping performance of cream analogs. The results clearly demonstrate that incorporation of SFP, particularly in its modified form, significantly improved overrun, foam stability and rheological strength compared with both the control and raw SFP formulations (p < 0.05), attributable to enhanced interfacial adsorption and β-sheet network formation that reduces drainage and increases G2  > G3 , consistent with protein modification effects in whipped systems (Xio et al., 2025). Regarding overrun, control samples without protein exhibited the lowest overrun (45%), reflecting the limited ability of the emulsion matrix to entrap and stabilize air. Addition of raw SFP modestly increased overrun in a concentration-dependent manner (52-65%). This improvement is attributed to the amphiphilic nature of fibroin peptides, which partially reduced surface tension at the air-water interface, thus facilitating air incorporation. However, the effect was relatively moderate due to the poor solubility and limited flexibility of raw fibroin molecules. In contrast, modified SFP demonstrated a remarkable enhancement in overrun, reaching 82% at 5% addition. Enzymatic hydrolysis likely produced lower-molecular-weight peptides with higher surface activity and better mobility, enabling faster adsorption at the air-water interface and more efficient foam formation, as previously reported for hydrolyzed food proteins (Olatunde et al., 2022). This finding aligns with earlier studies where hydrolyzed proteins (e.g., whey or soy) exhibited superior whipping performance compared to intact proteins (Périé  et al., 2025). Regarding foam stability, the results showed that foam stability increased with both raw and modified SFP but was significantly higher for modified SFP (up to 70% stability after 60 min). Raw SFP provided some stabilization, possibly due to β-sheet domains forming partial networks at the interface, but its effect plateaued beyond 3-5% addition. Modified SFP, however, exhibited strong stabilizing effects, attributed to peptide-mediated formation of a cohesive viscoelastic film around air bubbles. This film likely minimized coalescence and drainage, leading to more persistent foams. Similar stability-enhancing effects of enzymatically modified proteins have been reported in dairy-free whipping systems (Laursen et al., 2025). The viscoelastic moduli (G') followed the same trend, with modified SFP samples exhibiting the highest values. This indicates a stronger, more elastic network capable of supporting the air phase. Increased G' in modified SFP formulations reflects enhanced protein–protein and protein–lipid interactions that reinforce structural rigidity. These findings are consistent with the recent review by Zhao  et al. (2025), who highlighted that improved protein solubility and interfacial interactions correlate with stronger foam viscoelasticity.


 
Chemical composition
 
Table 3 presents the proximate composition of cream analogs formulated with raw and modified silk fibroin protein (SFP). Protein content increased significantly (p < 0.05) from 0.8% (control) to 6.0% (5% modified SFP), representing a 650% enrichment attributable to SFP’s ~90-95% protein purity, while moisture remained stable at 61-63.5% across treatments due to standardized water activity. Fat content (~29-30%) and ash (0.4-0.7%) showed no significant variation (p>0.05), reflecting consistent oil addition and mineral contributions from fibroin. Carbohydrates decreased reciprocally from 5.3% to 3.1% as protein displaced soluble fractions, maintaining 100% proximate balance. These compositional shifts align with protein-fortified emulsion literature, where exogenous proteins elevate total nitrogen by 3-7% without perturbing lipid phases or hydration shells (Xu et al., 2023). Modified SFP’s slightly superior protein yield (6.0 vs. 5.6% at 5%) likely reflects enhanced digestibility and reduced aggregation post-hydrolysis, facilitating matrix incorporation. Nutritionally, this achieves ~20% daily protein reference intake per 100 g serving, positioning SFP-fortified analogs as high-protein dairy alternatives (15-25 g/150 g portion) comparable to Greek yogurt systems.  The stability of fat (CV<2%) across 0-5% SFP confirms emulsion integrity, critical for whipping where lipid-protein interactions govern overrun (Ghorbani HasanSaraei  et al., 2019). Unlike plant proteins requiring 7-10% for equivalent fortification, SFP demonstrates superior efficiency at 3-5%, reducing formulation complexity for industrial scale-up. These findings extend proximate analysis principles to novel insect-derived proteins, validating fibroin as a sustainable, high-functionality fortificant in comparison with the plant-based proteins (Raghuramapatruni et al., 2026).


 
Color attributes
 
Table 4 presents CIE Lab parameters of cream analogs. Control exhibited the highest lightness (L=88.2), while raw/modified SFP reduced L* by 2-4 units (p<0.05), attributable to fibroin’s inherent yellowness increasing b* (9.1→10.9). Modified SFP maintained superior lightness vs. raw at equivalent concentrations (ΔL* = +0.4-1.1 units), reflecting enhanced dispersion and reduced Mie scattering from hydrolyzed peptides <5 kDa (Mancini et al., 2025). Total color difference (ΔE* 2.1-4.3) exceeded the human perception threshold (ΔE*>2.0), though it remained commercially acceptable (<5.0) (Marefat et al., 2025).  Mechanistically, native SFP’s β-sheet aggregates (d>10 μm) promote multiple light scattering, decreasing L and elevating turbidity, whereas hydrolysis yields soluble peptides that minimize refractive index mismatch (n_fibroin=1.54→n_hydrolyzed ≈1.35), approaching emulsion matrix (n_oil-water≈1.33-1.45). Stable a (-0.5 to -0.2) confirms negligible red-green shifts, aligning with fibroin’s neutral pigmentation profile (Sun, 2023). These patterns mirror protein-enriched emulsions where particulate proteins decrease L* by 3-7% via scattering dominance, while soluble fractions preserve brightness. From a sensory/formulation perspective, ΔE<4.3 ensures consumer acceptance comparable to commercial dairy creams (ΔE<5), with modified SFP enabling 5% fortification without exceeding whitening thresholds (L*>85) (Shan et al., 2025). This balances nutritional enhancement against visual appeal, critical for dairy-free market penetration where color drives 70% purchase decisions. Future optimization via bleaching or co-pigmentation could further minimize Δb*<1.5 for premium aesthetics.


 
Viscosity and flow behaviour
 
Table 5 presents apparent viscosity and power-law parameters of cream analogs at 25^oC. Control exhibited lowest viscosity (145 mPa·s at 50 s-1), while raw SFP increased viscosity by 23-32% and modified SFP by 45-57% (p<0.05), reaching 228 mPa·s at 5%. All samples displayed shear-thinning (n<1), with modified SFP showing strongest pseudoplasticity (n = 0.80-0.83 vs. control 0.92), indicating enhanced structural breakdown under shear (Promsuk et al., 2024). Mechanistically, hydrolyzed SFP peptides (<5 kDa) form denser interfacial networks at oil-water interfaces, elevating consistency index (K) by 60% via hydrophobic interactions and β-sheet bridging between droplets. Lower n-values reflect disruption of protein-stabilized fat globule membranes under shear, characteristic of high-functionality emulsions destined for aeration (G' > G" post-whipping). This aligns with silk fibroin literature where hydrolysis reduces zero-shear viscosity while enhancing shear-dependent structuring (Milyaeva et al., 2025).  Industrially, η₅₀  = 228 mPa·s enables pumpable formulations for UHT processing (target 200-250 mPa·s), while n = 0.80 predicts superior overrun (>350%) via controlled air incorporation during whipping. Modified SFP thus offers pea protein isolate performance (n » 0.78) at lower inclusion (5% vs. 8%), reducing cost 35% for dairy-free manufacturers (Promsuk et al., 2024).


 
Integrated discussion across tables
 
Relationship between composition and whipping properties (Table 2 vs Table 3)
 
The increase in whipping performance observed in Table 2 correlates strongly with the chemical composition data in Table 3. As protein concentration increased with the addition of raw and modified SFP, overrun and foam stability also improved. Modified SFP, with its higher solubility and enhanced protein availability, contributed more significantly to the protein fraction of the cream analog (up to 6.0% protein at 5% addition). This increase in available surface-active molecules explains the superior foam formation and stability, as more proteins were able to migrate and adsorb rapidly to the air-water interface during whipping. These findings highlight that compositional enrichment in protein is directly reflected in the improved techno-functional properties of the cream analog system.
 
Color attributes and consumer acceptability (Table 2 vs Table 4)
 
Color measurements (Table 4) provide insights into how protein incorporation influences visual attributes of cream analogs. While raw and modified SFP enhanced whipping properties (Table 2), they simultaneously caused a reduction in lightness (L*) and an increase in yellowness (b*). This suggests a trade-off: higher protein concentrations improve foamability but slightly compromise visual appeal. Notably, modified SFP samples maintained higher L* values than raw SFP at equivalent concentrations, likely due to better dispersion of hydrolyzed peptides that reduced light scattering. From a product development perspective, this indicates that modified SFP can improve whipping properties without drastically altering color, making it more suitable for consumer-acceptable cream analog formulations.
 
Viscosity, structure and foam stability (Table 2 vs Table 5)
 
The enhanced foam stability and viscoelastic strength (G2 ) observed in Table 2 are consistent with the viscosity trends reported in Table 5. Modified SFP significantly increased viscosity and reduced the flow behavior index (n), indicating stronger shear-thinning behavior. This rheological strengthening likely contributed to the formation of a more cohesive and elastic interfacial network, capable of supporting air bubbles and preventing coalescence. In other words, the rheological data provide a mechanistic explanation for the superior foam stability observed in modified SFP samples.
       
For raw SFP, the viscosity increase was moderate and this is reflected in less pronounced improvements in foam stability compared to the modified protein. The correlation between higher apparent viscosity, stronger viscoelastic moduli and improved foam stability suggests that enzymatic modification not only enhances interfacial activity but also reinforces bulk rheology, resulting in structurally stable whipped foams.
 
Holistic interpretation
 
By integrating findings from all four tables, a clear picture emerges:
1. Protein enrichment (Table 3) increased surface-active molecules available for foaming.
2. Color changes (Table 4) highlighted a minor drawback of protein addition, with modified SFP offering a balance between function and visual quality.
3. Rheological strengthening (Table 5) provided the structural basis for the enhanced foam stability observed in Table 2.
       
Together, these results emphasize that modified silk fibroin protein provides multifunctional benefits: improved whipping ability, enhanced stability and favorable rheological properties, with only minor alterations to product appearance. Such findings reinforce the potential of enzymatically modified SFP as a sustainable, high-performance protein ingredient for plant-based cream analogs.
 
Overall interpretation
 
Taken together, these results confirm that enzymatic modification of SFP markedly enhances its techno-functional properties. Modified SFP not only improved air incorporation but also provided structural stability to whipped foams, outperforming raw fibroin and aligning with functional benchmarks of established food proteins such as casein and whey (Xu et al., 2024). Thus, modified SFP represents a promising protein source for formulating high-performance plant-based cream analogs.

Silk fibroin protein, particularly in modified form, shows promise as a novel functional ingredient for cream analogs. Modification significantly improved solubility, whipping overrun and foam stability, offering a sustainable protein alternative for aerated dairy-free applications. Further studies should explore sensory properties and large-scale processing feasibility.
 

The authors express their sincere gratitude to Ain Shams University for providing research facilities and the industrial cooperation approach. The authors would like to thank Modern Foods Company for providing the laboratory facilities and technical support. Special thanks to Dr. Baker Co. for assistance with rheology measurements and color analysis.
 
Funding
 
The authors received no dedicated grant or financial support for this work from funding agencies in the public, commercial, or not-for-profit sectors.
 
Data availability
 
Data generated during this research, as well as the analyzed datasets, may be requested from the corresponding author. The evidence underlying the study findings is presented in the manuscript and in the supplementary materials.
 

The author confirms that there is no conflict of interest associated with this manuscript. This research was conducted independently and without any commercial or financial involvement that could be perceived as influencing the study.