Browsing the shelves of perfumeries, it immediately becomes apparent, even for less experienced consumers, that cosmetic products often display claims related to naturalness and sustainability. Marketing strategies are carefully designed to evoke the “bio” world and reassure consumers, giving the impression that these products are safer for both the skin and the environment.
Whether this trend is driven by growing consumer awareness of environmental impact or by stringent European regulations regarding ingredients, packaging and safety, the result is a rapidly expanding “green” beauty sector. According to Global Market Insights, the global natural cosmetics market was valued at $39.5 billion in 2024 and reached $41.3 billion in 2025. The market is expected to grow substantially in the coming decades, reaching $70.8 billion by 2035 with a compound annual growth rate of 5.6%1.
Brands are continuously seeking innovation and new market opportunities, turning to research laboratories to meet demand while simultaneously staying ahead of competitors. Therefore, researchers face a significant challenge: to investigate new natural and naturally derived substances that can replace traditional synthetic agents, while still ensuring pleasant textures and product stability under extreme temperatures and over time.
One important category in this context is rheology modifiers: substances that, when added to a material or a mixture of materials, alter its rheological behavior. Among these, several ingredients have been used for a long time; examples include xanthan gum, carrageenan and cellulose derivatives. Despite being well-known, these natural modifiers often require support from additional synthetic rheology modifiers, such as PEGs and acrylates, to achieve specific product characteristics2. These synthetic agents are included in “green” formulations to enhance stability or to produce the desired gel-like appearance without stringiness. Their exceptional performance allows their use even at low concentrations.
Consequently the viscosifying power, rheological profile and sensory properties of many natural rheology modifiers are often not comparable to synthetic alternatives. Another limitation is their higher formulation sensitivity to environmental conditions (typically unstable at high temperatures, under humidity variations, at extreme pH values, or in high-salt systems). This can lead to stability issues and less appealing textures, such as the stringy effect characteristic of xanthan gum, which is often undesirable for the end user.
For these reasons, the search for natural or naturally derived substances with increasingly competitive properties has become a priority, aiming to bridge the gap with the synthetic raw materials currently available on the market.
Throughout this search, three key principles remain central: efficacy, sensory performance and safety.
Materials and Experimental Approach
Four rheology modifiers were evaluated: glucomannan, Sphingomonas ferment extract, hydroxypropyl starch phosphate and sclerotium gum. These materials were selected for their promising functional properties and established safety profiles.
A comprehensive evaluation of the viscosity characteristics, sensory properties and interactions with ingredients commonly used in cosmetic formulations was carried out for each modifier.
Structural Features, Recommended Concentration Ranges and Rheological Characterization
Two of the selected polymers, Sphingomonas ferment extract and sclerotium gum, are fermentation-derived materials: the former is produced by the bacterium Sphingomonas, while the latter is obtained from the fungus Sclerotium rolfsii. Both polymers feature a polysaccharide multi-helix structure (See Figure 1), which confers high viscosity and strong resistance to chemical and physical stresses.
Figure 1 - a) Double helix structure of Sphingomonas ferment extract, b) triple helix structure of sclerotium gum.Courtesy of LabAnalysis
Glucomannan is extracted from the tuber of Amorphophallus muelleri (Porang) and is characterized by a single-helical structure enriched with hydroxyl and acetyl groups enhancing its water solubility. Hydroxypropyl starch phosphate is a chemically modified starch with a crosslinked network structure.
When these powders are dispersed in water, they form gels with different viscosity levels and sensory characteristics depending on the concentration used. An optimal concentration range between 0.5 and 1.0% was identified for all polymers, with the exception of hydroxypropyl starch phosphate, which exhibited a weak gelling ability and therefore required higher concentrations (4–6%) to reach viscosity values comparable to the other systems. This specific case may represent a formulation limitation, both due to increased raw material costs in the finished product and to reduced formulation space for other ingredients.
Viscosity measurements at different rotational speed (rpm) were performed using a Brookfield DV-I+ digital viscometer. The data indicated that all gels obtained from aqueous dispersions of these rheology modifiers exhibited pseudoplastic behavior, with viscosity decreasing as shear stress increased.
Figure 2 - Variation in viscosity of dispersions of glucomannan, Sphingomonas ferment extract and sclerotium gum at concentrations of 1%, and hydroxypropyl starch phosphate at a concentration of 5%, as a function of rotation speed.Courtesy of LabAnalysis
A detailed analysis of the viscosity curves, as presented in Figure 2, revealed that Sphingomonas ferment extract, sclerotium gum and hydroxypropyl starch phosphate maintain high viscosity values at low rpm (low shear stress); however, once a critical rpm threshold is reached the viscosity decreases sharply. Therefore these systems exhibit a yield stress behavior.
This behavior is attributed to the formation of supramolecular structures among polymer chains3, generating molecular complexes held together by weak interactions. Once the structure is disrupted (at high rpm beyond the yield point) viscosity rapidly decreases. From an application standpoint, this behavior translates into a high suspending power, useful for maintaining insoluble particles such as pigments, UV filters or decorative beads in suspension. During application, these gels exhibit high spreadability and a low perception of thickness, with the sensation that the gel fragments easily under mechanical action4.
Sensory Characterization of Gels and Polymer-based Emulsions
The gel system based on glucomannan exhibited a pronounced film-forming effect upon application, without the typical stringiness observed in many natural polymer dispersions. After drying, it left a pleasant velvety and silky residue. A similar residual sensation was noted following the application of gels based on hydroxypropyl starch phosphate and sclerotium gum. These two systems differ in their drying behavior: starch phosphate dries rapidly, whereas sclerotium gum shows longer drying times. Another distinctive feature of sclerotium-based gels is their low thickness during application and their tendency to fragment easily under mechanical stress. Gels obtained from Sphingomonas ferment extract display similar behavior and, after rapid drying, leave no perceptible residue.
When incorporated into oil-in-water (O/W) emulsions, the polymers confirmed the sensory impressions observed in the corresponding aqueous gels. The cream containing glucomannan was particularly film-forming and thick, with a slightly longer drying time allowing more playtime during application. No stringiness was observed and the final residue was extremely pleasant and silky.
Emulsions containing Sphingomonas ferment extract and hydroxypropyl starch phosphate were characterized by rapid drying, with Sphingomonas-based systems leaving no residual feel. Sclerotium gum, on the other hand, imparted a pronounced film-forming effect to the emulsion.
Stability and Compatibility Studies in Complex Cosmetic Systems
Aqueous dispersions of rheological modifiers were prepared at the following concentrations: glucomannan and Sphingomonas at 0.75%, starch phosphate at 5% and sclerotium gum at 1.2%. The study then focused on the interaction between the polymers and various classes of ingredients typically used in cosmetic products: solutions of 80% lactic acid or 10 % NaOH were added to adjust pH, as well as salts, ethanol, and other polymers. This investigation showed the good compatibility and versatility of these polymers under extreme pH conditions (pH 3–4 and 11–12) and in the presence of salts.
Effect of pH and Ionic Strength
Stability studies conducted at extreme pH values demonstrated that glucomannan and sclerotium gum, both characterized by non-ionic structures, respond to alkaline pH with a slight increase in viscosity, while sclerotium gum shows a similar behavior under acidic conditions. As the aqueous dispersion of glucomannan initially exhibited an acidic pH, an increase in viscosity was observed as the pH of the solution increased.
Figure 3 - Increase in viscosity of glucomannan, Sphingomonas ferment extract, hydroxypropyl starch phosphate and sclerotium gum dispersions at 10 rpm, at acidic and basic pH compared to neutral pH. Courtesy of LabAnalysis
Hydroxypropyl starch phosphate exhibits an anionic structure, similar to Sphingomonas ferment extract, although the latter displays a lower charge density. In alkaline environments (pH 11–12), both polymers showed a doubling of viscosity, due to dissociation of carboxyl and hydroxyl groups along the polymer chains, leading to maximum electrostatic repulsion. Under acidic conditions (pH 3–4), hydroxypropyl starch phosphate remained stable with no viscosity increase, while an increase was observed for Sphingomonas-based systems. The viscosity variations are shown in Figure 3.
The presence of mono- and divalent salts (NaCl and MgSO₄) led to up to a twofold increase in viscosity for most gel systems, promoting polymer chain solvation in water, even at salt concentrations as high as 2%. An exceptional case was observed for Sphingomonas ferment extract, whose viscosity increased up to fourfold.
The crosslinked structure of hydroxypropyl starch phosphate remained stable in the presence of salts, showing no significant viscosity variation. The viscosity increases are presented in Figure 4.
Figure 4 - Increase in viscosity of glucomannan, Sphingomonas ferment extract, hydroxypropyl starch phosphate and sclerotium gum dispersions at 10 rpm, upon addition of NaCl or MgSO4Courtesy of LabAnalysis
Ethanol Tolerance
Particularly noteworthy part of the study involved ethanol, an ingredient commonly used as a stabilizer, preservative and sensory modifier. Ethanol is often incompatible with polymeric systems, as it solvates hydrophobic groups, reducing interchain association and leading to viscosity loss.
For some polymers (glucomannan and hydroxypropyl starch phosphate) ethanol concentrations above 5% led to coacervation phenomena, characterized by the formation of aggregates composed of hydrophilic sols held together by electrostatic forces.
In contrast, Sphingomonas ferment extract maintained stable viscosity values at ethanol concentrations up to 40%, despite a more granular or “jelly-like” appearance. Sclerotium gum also showed no significant viscosity changes with increasing ethanol content; however, at 40% ethanol, the system became markedly tacky.
Overall, the lower compatibility of glucomannan and hydroxypropyl starch phosphate with ethanol appears to be related to their stronger dependence on water solvation. Conversely, Sphingomonas ferment extract and sclerotium gum, characterized by double- and triple-helix structures, tolerate higher ethanol concentrations, up to 40%.
Interaction with Other Natural Polymers
The compatibility of the rheology modifiers with commonly used natural viscosifying polymers was then evaluated, specifically xanthan gum (0.15%), microcrystalline cellulose and cellulose gum (1%). For this phase of the study, the following concentrations of the polymers under investigation were used: glucomannan and Sphingomonas at 0.25%, starch phosphate at 3% and sclerotium gum at 0.3%.
The association of glucomannan with xanthan gum resulted in the formation of a gel highly sensitive to elevated temperatures (See Figure 5), suggesting a possible instability of glucomannan at approximately 45 °C. In all tested combinations, synergistic effects between polymers were observed, leading to increased system viscosity without evidence of incompatibility. In particular, a remarkably significant viscosity increase was recorded for the aqueous dispersion of hydroxypropyl starch phosphate and microcrystalline cellulose and cellulose gum.
Figure 5 - Dispersion glucomannan 0.25% + xanthan gum 0.15%Courtesy of LabAnalysis
Behavior in Surfactant-Containing Systems
In this study, the same polymer concentrations reported in the previous interaction with other viscosity-enhancing polymers were used. Experiments conducted in the presence of surfactants highlighted an overall reduced compatibility, confirming the delicate nature of these systems. Various anionic (SLES, sodium methyl cocoyl taurate, sodium lauroyl methyl isethionate), non-ionic (lauryl glucoside) and amphoteric (cocamidopropyl betaine, disodium coco-amphodiacetate) surfactants were tested in combination with the natural polymers, with a total active surfactant matter (ASM) of 10%.
The most promising results were observed for dispersions based on Sphingomonas ferment extract and sclerotium gum, which showed greater compatibility compared to the other two polymers for which precipitation and flocculation phenomena were observed. For example, Sphingomonas was compatible with several of the tested surfactants and always tripled the system viscosity. Sclerotium gum was compatible with almost all tested surfactants; however a significant viscosity increase was observed only in the presence of lauryl glucoside, rising from 0.52 Pa·s to 3.64 Pa·s at 10 rpm.
On the other hand, glucomannan was stable only in the presence of SLES and doubled the gel viscosity; in the other systems, gel precipitation or flocculation was observed at t0 or after 24 h (t24). Starch phosphate was also stable only with a single surfactant (lauryl glucoside), showing behavior similar to glucomannan.
Role of the Polymers in Emulsion Stabilization
Finally, the polymers were tested in O/W emulsions to assess their stabilizing ability. Table 1 reports the base emulsion formulation in the absence of the polymers under investigation.
PHASE | INGREDIENTS (INCI names) | % w/w |
|---|---|---|
| A | AQUA | q.s. to 100 |
| DISODIUM EDTA | <1 | |
| DIAZOLIDINYL UREA | <1 | |
| GLYCERIN | 1-5 | |
| AMMONIUM ACRYLOYL-DIMETHYLTAURATE/VP COPOLYMER | <1 | |
| B | HYDROGENATED POLYDECENE | 5-10 |
| ISOPROPYL PALMITATE | 8-14 | |
| TOCOPHERYL ACETATE | <1 | |
| PHENOXYETHANOL | <1 | |
| C | PARFUM | q.s. |
100,000 |
Rheology modifiers were added after the copolymer and homogenized using a turboemulsifier at the following concentrations: glucomannan, Sphingomonas ferment extract and sclerotium gum at 0.5%, and hydroxypropyl starch phosphate at 1%. An improvement in emulsion stability was observed, particularly in terms of reduced average droplet size of the internal phase, suggesting a degree of emulsifying contribution.
Glucomannan showed a strong ability to improve the homogeneity of the internal phase; Sphingomonas ferment extract and sclerotium gum led to a thinning of the oil phase while maintaining some degree of heterogeneity. In the case of hydroxypropyl starch phosphate, incompatibility with the formulation system was observed, likely due to an excessively high polymer concentration. This analysis was made possible by evaluating the size of the internal-phase droplets through optical microscopy (Model No. 710278, Swift Instruments International s.a., USA) as shown in Figure 6.
Stability results were confirmed by centrifugation tests, which showed a clear reduction of surface separation phenomena compared to the base emulsion (particularly in the case of glucomannan), a marked increase for hydroxypropyl starch phosphate, and a slight decrease for Sphingomonas ferment extract and sclerotium gum.
Figure 6 - O/A cream dispersions, a) with 0.5% glucomannan, b) with 0.5% Sphingomonas ferment extract, c) 1% hydroxypropyl starch phosphate, d) 0.5% sclerotium gum, e) at time of preparation (t=0). Courtesy of LabAnalysis
Formulation Examples
In the following section, several example formulations are presented, developed using the gelling agents under investigation as rheological modifiers. The formulations were designed based on the compatibilities highlighted in the previous tests, with the aim of enhancing the functional properties of the polymers and their synergistic interactions with the other cosmetic ingredients previously analyzed. During the formulation design, priority was given to the use of as many naturally-derived ingredients as possible, in line with both the objectives of the present study and the current cosmetic market demand for “green” formulations.
Within this framework, an eye contour cream was developed using glucomannan as the rheological modifier (see Table 2). This polysaccharide gives an immediate sensation of freshness upon application, combined with a pleasant softness to the touch. The formulation is characterized by rapid drying, the absence of stickiness, and a velvety finish typical of glucomannan. At the selected use levels, a lightweight cream with a consistency suitable for tube packaging was obtained, exhibiting a viscosity ranging from 42 to 54 Pa·s (Brookfield DV-I+, S06, 25 °C).
PHASE | INGREDIENTS (INCI names) | % w/w |
|---|---|---|
A
| AQUA | q.s. to 100 |
| GLYCERIN | 1-4 | |
| PENTYLENE GLYCOL | 1-5 | |
| CAFFEIN | <1 | |
| TRISODIUM ETHYLENEDIAMINE DISUCCINATE, AQUA | <1 | |
| HYDROXYACETOPHENONE | <1 | |
A1 | GLUCOMANNAN | <0,5 |
B
| DICAPRYLYL ETHER | 2-5 |
| CETYL ALCOHOL | 1-4 | |
| CAPRYLIC/CAPRIC TRIGLYCERIDE | 5-8 | |
| SQUALANE | 1-3 | |
| OCTYLDODECYL MYRISTATE, HIPPOPHAE RHAMNOIDES EXTRACT | 1-4 | |
| HYDROGENATED COCO-GLYCERIDES | 1-3 | |
| POLYGLYCERYL-6 DISTEARATE, CANDELILLA/JOJOBA/RICE BRAN POLYGLYCERYL-3 ESTERS | 4-7 | |
B1 | POTASSIUM CETYL PHOSPHATE | <1 |
C
| 1,2-HEXANEDIOL, CAPRYLYL GLYCOL | 1-2 |
| TOCOPHEROL | <1 | |
D
| AQUA | 2-4 |
| CENTELLA ASIATICA EXTRACT | <1 | |
E | CI 77891, MICA, TIN OXIDE | 1-2 |
100,000 |
As reported in the study, the synergy between glucomannan and xanthan gum enables the formation of a gel-like structure using low concentrations of both gelling agents, allowing the development of a formulation suitable for eye contour patches in hydrogel (see Table 3). The gel maintains a compact structure at room temperature during application without crumbling and provides a lifting and refreshing effect, leaving a delicate silky residue on the skin.
PHASE | INGREDIENTS (INCI names) | % w/w |
|---|---|---|
A
| AQUA | q.s. to 100 |
| GLUCOMANNAN | <1 | |
| XANTHAN GUM | <1 | |
B
| AQUA | 20-40 |
| SODIUM HYALURONATE | <1 | |
| CAFFEINE | <1 | |
| ALLANTOIN | <1 | |
| NIACINAMIDE | 1-3 | |
| GLYCERIN | 1-4 | |
| SODIUM BENZOATE | <1 | |
C | AQUA, LACTIC ACID | q.s. to pH=5,3 |
D | AQUA, CI 42090 | <1 |
100,000 |
In addition, a leave-in detangling spray was formulated (see Table 4), which can be evenly nebulized onto damp hair, providing good nourishing and anti-frizz properties without leaving residues. After drying, the hair appears soft, voluminous and not weighed down. The polymer Sphingomonas ferment extract, due to its conditioning and protective properties, contributes to restructuring and strengthening damaged hair, enhancing the resistance and body of the hair fiber.
PHASE | INGREDIENTS (INCI names) | % w/w |
|---|---|---|
A
| AQUA | q.s. to 100 |
| POLYQUARTENIUM-10 | <1 | |
| SPHINGOMONAS FERMENT EXTRACT | <1 | |
| SODIUM CHLORIDE | <1 | |
| ETHANOL | 7-13 | |
| SODIUM BENZOATE | <1 | |
| GUAR HYDROXYPROPYLTRIMONIUM CHLORIDE | 1-4 | |
| AQUA, HYDROLYZED VEGETABLE PROTEIN | 1-3 | |
B
| PEG-40 HYDROGENATED CASTOR OIL | <1 |
| PARFUM | <1 | |
C | AQUA, LACTIC ACID | q.s. to pH= 5,3 |
100,000 |
Conclusion
In cosmetic formulations rheology modifiers represent a class of ingredients of fundamental importance, not only for their viscosifying and stabilizing properties but also for their contribution to the sensory profile of the product, a key factor in consumer perception.
The results obtained in this study therefore allow us to define the conditions of use of the individual natural polymers investigated, highlighting their compatibility, potential synergies with other raw materials, optimal application conditions and the functional and sensory properties they can impart to the final formulation. This information provides a valuable basis for the design and testing of new cosmetic formulations, with the aim of enhancing the performance of natural polymers and meeting the growing demands of the cosmetic market.
The polymers studied demonstrated high stability under extreme pH conditions, in the presence of salts, and in combination with other polymers such as xanthan gum, microcrystalline cellulose and cellulose gum.
When incorporated into the continuous phase of O/W emulsions they contribute to improved dispersion of the oil phase and to the overall stability of the system, with a particularly pronounced effect observed for glucomannan.
Overall, the polymers analyzed exhibited good stability in the presence of low concentrations of ethanol (5%), while sclerotium gum and Sphingomonas ferment extract retained their structural and rheological stability even at higher ethanol concentrations. These two polymers also showed the most promising performance in surfactant-containing systems, which are known to be particularly challenging for the incorporation of natural polymers.
Finally, a marked similarity in behavior was observed between sclerotium gum and Sphingomonas ferment extract, both of fermentative origin and characterized by a multi-helix structure, a feature that may account for the similarities observed in terms of compatibility and formulation performance.
References
- Global Market Insights. (2026). Natural cosmetics market size: By product type, by packaging type, by price range, by consumer group, by distribution channel & forecast 2024–2035 (Report ID: GMI7626). Global Market Insights, Inc.
- Matteo Franceschini, Fabio Pizzetti, Filippo Rossi. On the Key Role of Polymeric Rheology Modifiers in Emulsion-Based Cosmetics. Cosmetics 2025, 12(2), 76; https://doi.org/10.3390/cosmetics12020076
- Xin Gao, Lixin Huang, Jianlong Xiu, Lina Yi, Yongheng Zhao. Evaluation of Viscosity Changes and Rheological Properties of Diutan Gum, Xanthan Gum, and Scleroglucan in Extreme Reservoirs. Polymers (Basel). 2023 Nov 6;15(21):4338. doi: 10.3390/polym15214338
- Long Xu, Houjian Gong, Mingzhe Dong, Yajun Li. Rheological properties and thickening mechanism of aqueous diutan gum solution: Effects of temperature and salts. Carbohydr Polym. 2015 Nov 5;132:620-9. doi: 10.1016/j.carbpol.2015.06.083. Epub 2015 Jul 8
