Preparation and characterization of glyceryl monostearate-based oleofoams: a case application in low-fat chocolate

Abstract

Oleofoam fabricated using sunflower oil and glyceryl monostearate (GMS) was employed in the development of low-fat chocolate. The influence of GMS concentration on overrun, microstructure, rheological properties, and storage stability of oleofoams were determined, followed by whipping duration impacts on the overrun and microstructure. Then optimal GMS concentration and whipping parameter were selected to prepare stable oleofoams for chocolate formulations with 25 %, 50 % and 100 % replacement of cocoa butter (CB). The properties of the chocolates were evaluated by texture, rheological, thermal, crystal polymorph and sensory characteristics. Results showed that with the increasing substitution of CB, the texture properties, melting enthalpy value, and CB flavor intensity of chocolate reduced. Chocolates with partial replacement demonstrated melting temperature equivalent to CB chocolate, while 100 % substituted chocolate was higher. The 25 % oleofoam chocolate demonstrated superior overall acceptance versus CB chocolate. These results indicate the potential of GMS oleofoams in the development of low-fat chocolate.

Highlights

• •Oleofoam formulated at 12 % concentration showed desirable characteristics.
• •Chocolate with 100 % cocoa butter (CB) replacement exhibits inferior quality.
• •25 % CB substitution by oleofoam matches CB chocolate in sensory acceptance.
• •GMS-based oleofoam enables low-fat aerated chocolate with retained quality.

1. Introduction

Chocolate is deeply cherished by consumers worldwide for its unique texture and flavor profile, with global consumption continuing to rise (Sarıtaş et al., 2024). Chocolate primarily consists of cocoa butter, cocoa powder and sugar powder. Though CB plays a vital role in chocolate and other cocoa-based products due to its distinctive physicochemical properties (Joseph, Batra, Selvasekaran, & Chidambaram, 2021), it also faces significant challenges including supply shortages driven by rising demand (Parra-Paitan, Zu Ermgassen, Meyfroidt, & Verburg, 2023), temperature sensitivity during processing (Jin, Jin, Wang, & Akoh, 2019), and storage instability that frequently leads to fat bloom formation (Chen, Zhou, Song, Jin, & Wei, 2022). Traditional cocoa butter substitutes, such as cocoa butter equivalent, cocoa butter replacer and cocoa butter substitute, are widely used to partially replace CB to produce chocolates. However, these compounds present significant nutritional concerns due to their elevated content of saturated fatty acids and trans fatty acids. Therefore, the strategic development of next-generation cocoa butter alternatives with zero-trans-fatty-acids and low-saturated-fatty-acids has emerged as a critical imperative in food lipid science. Current advancements in edible structuring systems have yielded innovative CB alternatives, with oleogel technology emerging as a promising solution. And oleogels have been applied in the manufacture of chocolate products as reported in the previous studies (Espert, Salvador, & Sanz, 2020; Fu et al., 2025; Li & Liu, 2019; Sun et al., 2021). While oleogels offer a viable alternative to CB for chocolate manufacturing, their formulation demands high volumes of edible oil, maintaining a caloric density analogous to solid fats (Metilli et al., 2021).

Aerated food products demonstrate substantial global consumer acceptance, being widely perceived as novel offerings with reduced caloric density (Deotale, Dutta, Moses, Balasubramaniam, & Anandharamakrishnan, 2020). In food systems, foam formation occurs via gas dispersion within continuous liquid or semi-solid phases, yielding products such as aerated chocolates, cake batter, frozen aerated desserts, and different types of beverages (Pugh, Hamlett, & Fairhurst, 2023). Aerated chocolate represents a foam-type food system wherein gases (e.g., air, N₂) are dispersed within molten lipid phases, conferring distinctive textural and sensory characteristics. Its aeration mechanism parallels conventional foam formation processes. Concurrently, aerated chocolate exhibit lower caloric content due to partial fat displacement by bubble or foam.

Lipid-continuous foams can be used in aerating food matrices (Gunes et al., 2017). Recently, whipped oleogel, which called oleofoam, has been excessively discussed and investigated. Currently, oleogelators of crystalline particles type such as fatty acids, fatty alcohols, GMS, diacylglycerols, phytosterols, and waxes have been used to produce oleofoams (Alhasan, Tehrani, & Varidi, 2024; Binks, Garvey, & Vieira, 2016; Du et al., 2021; Fameau et al., 2015; Grossi, Fang, Rao, & Chen, 2023; Li, Ying Lee, Wang, & Qiu, 2023; Wettlaufer & Flöter, 2022). These crystalline particles developed by oleogelators adsorbed at the bubble interface and formed a dense layer, which stabilized the oleofoams via Pickering mechanism. Among these crystalline particles, GMS is extensively studied due to their safety and excellent structuring properties. Oleofoam utilization offers substantial benefits including reduced mass density and caloric reduction versus pure oils, facilitating saturated fat substitution (Fameau & Saint-Jalmes, 2020). Furthermore, as non-aqueous systems, oleofoams inherently inhibit microbial proliferation through water activity restriction, conferring significant food safety advantages.

It has been reported that oleofoams have been successfully applied in food products. (Han et al., 2024) developed an aerated mayonnaise using sunflower wax-based oleofoams, demonstrating similar brightness, sensory properties, and texture to commercially available low-fat mayonnaise products. (Saremnejad, Mohebbi, & Koocheki, 2020) developed a reduced-fat sauce using mono- and diglycerides-stabilized oleofoam that exhibited comparable rheological properties and stability to its full-fat products. What's more, Mohanan and colleagues (Mohanan, Harrison, Cooper, Nickerson, & Ghosh, 2022) applied oleofoams in cakes, achieving similar hardness and chewiness to traditional shortening-based cakes. Notably, cakes containing MAG-based oleofoams showed superior quality characteristics. While existing literature has documented applications of oleofoams in food, it remains in the nascent stage. Particularly, limited research focused on the application of oleofoams in chocolate.

Hence, in this study, we aimed to develop stable oleofoams and apply to aerated chocolate systems. GMS was utilized as a gelator to prepare sunflower oil- based oleofoams. And the overrun, microstructure and rheological properties of oleofoams were characterized. By substituting CB with oleofoams, we systematically investigate the effects of oleofoam on the texture, rheological properties, crystalline polymorphism, thermal behavior and sensory characteristics of chocolates. This work provided fundamental insights for developing oleofoam-based fat alternatives and quality control strategies for low-fat aerated chocolate products.

2. Materials and methods

2.1. Materials

Sunflower oil was bought from Kerry Food Industry Co., Ltd. (Shanghai, China). Glyceryl monostearate was purchased from Aladdin Biochemical Technology Co., Ltd. (Shanghai, China). Cocoa butter was the product of Huadong Cocoa Food Co., Ltd. (Taizhou, China). Soybean lecithin was provided by Oubo Xing Biotechnology Co., Ltd. (Beijing, China). Icing sugar and cocoa powder were obtained from the locol supermarket. All ingredients were used without further purification.

2.2. Methods

2.2.1. Preparation of oleofoams and chocolates

The oleogelators GMS were weighted and added to sunflower oil to obtain concentrations of 5 %, 8 %, 10 %,12 %, 15 % (w/w), respectively. Then, the mixtures were heated and stirred by a magnetic stirrer (RCT basic, IKA, Germany) at 80 °C until clear solutions were obtained. Immediately, the solutions were transferred into a refrigerator at 4 °C for 24 h to form oleogels. Then, at ambient temperature, a handheld electric mixer (DDQ-C02N1, Bear, Guangzhou, China) was used to whip the oleogels for certain time to obtain oleofoams. All samples were stored at 25 °C for subsequent analyses.

The formulations of cocoa butter chocolate (CB-C) and oleofoam-based chocolate (OF-C) were shown in Table 1. At first, cocoa butter was melted at 60 °C. Then lecithin, cocoa butter and icing sugar were added and stirred for 1 h. Subsequently, the mixtures were transferred to a laboratory planetary ball mill (QM-3SP4, Nanda, Nanjing, China) and grinded for 2 h at 300 rpm. After refining, the oleofoams and chocolate sauce were mixed and tempered in three stages (50 °C, 28 °C, and 32 °C). In the end, chocolate was placed in a mold and transferred to 4 °C refrigerator for 24 h.

Table 1.

Formulations of chocolate.

Samples		Cocoa butter chocolate	Oleofoam-based chocolate
Abbreviation		CB-C	25 % OF-C	50 % OF-C	100 % OF-C
Raw material (g/100 g)	CB	50	37.5	25	/
	Oleofoam	/	12.5	25	50
	Cocoa powder	15	15	15	15
	Icing sugar	34.5	34.5	34.5	34.5
	Lecithin	0.5	0.5	0.5	0.5

2.2.2. Overrun

The parameter overrun provides a measure of aeration extent within oleofoams, which can be calculated by the following equation:

$$\text{Overrun}\left(\%\right)=\frac{{\mathrm{V}}_{\mathrm{f}}-{\mathrm{V}}_{\mathrm{g}}}{{\mathrm{V}}_{\mathrm{g}}}\times 100$$

where V_f and V_g represent the volume of oleofoam and the initial oleogel, respectively.

2.2.3. Microstructure of oleofoam

The microstructure of oleofoam samples were observed under polarized light using polarized light microscope (PLM, DM2700P, Leica, Germany), which equipped with a digital camera (DMC4500, Leica, Germany). Freshly prepared oleofoams were placed on a glass slide, covered with a coverslip carefully. All samples were captured under 20 × 10 magnification. And bubble size analysis was conducted using ImageJ software (National Institutes of Health, USA).

2.2.4. Rheological properties

The rheological properties of oleofoams and chocolates were analyzed by using a HAAKE MARS60 rheometer (ThermoScientific, Waltham, USA), which equipped with a temperature control system and probe P35. The oleofoams were carried out on a parallel plate geometry with a diameter of 1 mm. In strain sweep experiments, the strain amplitude varied from 0.01 % to 100 % at a constant frequency of 1 Hz to obtained the linear viscoelastic range (LVR). Then, frequency sweep texts (0.1–100 Hz) were performed at a fixed strain of 0.1 %. The viscosities of all the samples were measured at shear rate from 0.1 to 100 s⁻¹. Cut the chocolates into pieces and placed them into an oven at 50 °C until completely melted, and then analyzed them at 40 °C. And oleofoams were measured at 25 °C.

2.2.5. Storage stability of oleofoams

Approximately 25 mL of oleofoam samples were transfered to glass sample bottles and stored at 25 °C. Besides, the visual appearances of oleofoams were recorded at 0, 7, 30 and 60 d, respectively.

2.2.6. X-ray diffraction (XRD) analysis

To remove the sugar, aerated chocolates were chopped into pieces and soaked in cold water for 48 h (with multiple water changes during this period). The polymorphic behaviors of chocolates were characterized by powder X-ray diffraction (Ultima IV, Rigaku, Tokyo, Japan), which equipped with Cu/Kα radiation (λ = 1.5406 Å). All samples were measured at 25 °C with a voltage of 40 kV and a current of 40 mA. The crystalline structure was scanned with a 2θ ranging from 15° to 30° at a scanning rate of 5° min⁻¹. Data was analyzed and processed using the Jade 6.5 Software. The d-value was calculated using the following formula:

$$2d=\frac{\lambda }{\sin 2\theta }$$

where λ is the wavelength of the X-ray beam and θ is the half of the scanning angle.

2.2.7. Differential scanning calorimetry (DSC) analysis

A differential scanning calorimeter (DSC 200F3, Netzsch, Germany) was used to measure the thermal properties of samples. Approximately 10 mg of sample was weighed in an aluminum pan and then sealed, while an empty aluminum pan as reference. Within a constant 20 mL/min nitrogen environment, the samples were heated from 0 °C to 80 °C at a rate of 5 °C/min to measure heat flow. The peak melting temperature (T_m) and enthalpy of melting (ΔH_m) were calculated.

2.2.8. Texture properties

Texture Profile Analysis (TPA) of samples were performed using a texture analyzer (TMS-PILOT, Food Technology Corporation, USA) equipped with a 250 N load cell. The cylindrical probe height (25 mm) was calibrated prior to the first test, followed by 1 s pause. The samples were compressed up to 30 % of the original height at a constant speed of 30 mm/min. And the trigger force was set of 0.375 N. The hardness of chocolate was measured, with three replicates per sample.

2.2.9. Electronic nose

Approximately 10 g of sample was weighed and chopped, and then placed into a sealed centrifuge tube for 30 min. Measurements were performed using a portable electronic nose (PEN3, Airsense Analytics GmbH, Schwerin, Germany), which has an array of 10 different metal oxide sensors positioned into a small chamber. The test parameters were setting as follows: flush time for 60 s, measurement time for 90 s and the flow rate of 400 mL/min.

2.2.10. Sensory evaluation

Ten panelists across different age groups conducted sensory evaluations of the aerated chocolate samples, scoring them based on preference. The panel evaluated samples based on these sensory attributes: appearance, texture, cocoa flavor, mouthfeel and total acceptance. Panelists were required to rinse their mouths with water after tasting each chocolate sample to eliminate residual flavors and ensure the accuracy of sensory evaluations.

2.2.11. Statistical analysis

All experiments were repeated more than three times using freshly prepared samples. The diagrams were created using Origin 2021 (Origin Inc., Northampton, USA). All data were reported as mean ± standard deviation (SD) by using IBM SPSS Statistics 27.0 (SPSS Inc., Chicago, USA), and one-way analysis of variance (ANOVA) was performed with Duncan's test. Statistical differences were considered significant at p < 0.05.

3. Result and discussion

3.1. Influencing factors of oleofoams

3.1.1. Concentration

As shown in Fig. 1A, the overrun of oleofoam initially increased and then decreased with rising GMS concentration. The oleogelator concentration had significant effect on overrun (p < 0.05). At 12 % GMS, the overrun reached its maximum (100 %). But when the concentration increased to 15 %, it dropped to 80 %. These results aligned with findings by (Grossi et al., 2023), who reported that increasing MAG concentration from 5 % to 10 % enhanced overrun from 202 % to 217 %, whereas further increasing it to 15 % reduced the overrun to 177 %. Higher concentrations promoted crystal formation, which stabilized air incorporation. However, exceeding a critical threshold increased the viscosity of the continuous phase, hindering effective air entrapment and thereby reducing the maximum overrun.

Fig. 1.

The overrun of oleofoams with different GMS concentrations (A). Bubble size distribution (B) and microstructure images of oleofoams (C). Scale bar = 50 μm.

The PLM images of oleofoams with varying GMS concentration were shown in Fig. 1C. At 5 % GMS concentration, the bubbles were unevenly distributed. Under low concentrations, the oil-air (O-A) interface was sparsely covered by crystals, resulting in poor foam stability. As the GMS concentration increased, more crystals adsorbed at the interfaces, effectively encapsulating the bubbles and improving uniformity and stability. Notably, the 12 % GMS oleofoam exhibited tightly packed crystals surrounding the bubbles, forming a denser structure. This aligned with findings by (Du et al., 2021), who observed that oleofoam with 11 % MAG developed smaller and more uniform bubbles, and enhanced stability compared to lower concentrations. MAG acted as Pickering stabilizer by adsorbing at bubble interface. However, excessive GMS (15 %) led to over-crystallization, hindering bubble dispersion. Similarly, (Metilli et al., 2021) reported that 30 % CB sample displayed fewer and larger bubbles, increased deformation, and larger crystalline aggregates compared to 15 % and 22 % CB formulations. As can be observed in Fig. 1B and Table 2, increasing GMS concentration shifted the bubble size distribution leftward and reduced bubble diameter. However, at 15 % concentration, the bubble diameter increased, which aligned with the overrun result.

Table 2.

The bubble size of oleofoam at different concentrations.

Sample	Average diameter
5 %	28 ± 14.58a
8 %	25 ± 12.07b
10 %	22 ± 12.34cd
12 %	20 ± 9.71d
15 %	23 ± 14.82bc

Different letters in same column indicate significant differences (p < 0.05).

3.1.2. Whipping time

The whipping time also exerted a significant influence on overrun of oleofoam (p < 0.05). As can be seen from Fig. 2A, with the increase of whipping time, the overrun of oleofoams rise rapidly. After reaching the maximum value, further whipping would lead to a decline of overrun. This result was in line with the results of (Saremnejad et al., 2020) and (Binks & Marinopoulos, 2017), who found the overrun significantly increased with prolonged whipping time, followed by a slight decline to a constant value.

Fig. 2.

The overrun of oleofoams with different whipping time (A), and microstructure images of oleofoams (B). Scale bar = 50 μm.

In addition, by combining PLM images (Fig. 2B) showing the microstructural changes of oleofoams, we could better elucidate the influence of whipping time on overrun. At the initial stage of whipping, air was rapidly incorporated into the system, forming large and irregular bubbles. Furthermore, it could be observed that GMS crystals were not only present in the bulk phase, but also partially adsorbed at the bubble interfaces. However, these interfacial crystals were relatively scarce, forming thin crystalline layers that result in weak bubble structures (Du et al., 2021). With further whipping, crystals gradually adsorbed at the bubble interfaces, while those in the continuous phase decreased, and the number of bubbles increased. The PLM images obtained after 5 min of whipping clearly showed well-defined crystalline layers surrounding the bubbles, with relatively uniform bubble size and shape. Nevertheless, prolonged whipping led to bubble coarsening, consequently resulting in the decrease of overrun and irregular bubble size. This coincided with a previous report by (Du et al., 2021), where they noticed excessive whipping led to crystal coalescence and induced bridging formation. This made bubbles irregular and tended to be larger. In summary, the optimal whipping time was determined to be 5 min, which served as the basis for subsequent experiments.

3.2. Rheological properties of oleofoams

The rheological properties of oleofoams were systematically characterized using a rheometer, encompassing strain sweep, frequency sweep and shear rate sweep measurements. As shown in Fig. 3A, all samples exhibited elastic modulus (G′) > viscous modulus (G″) within the LVR, demonstrating typical semi-solid gel characteristics with considerable structural strength. It could be attributed to the combined effects of lipid crystallization during cooling and stirring, as well as the incorporation of gas (Han et al., 2024). Notably, the 5 % GMS sample showed the lowest G′, while the 15 % GMS sample displayed the highest G′, confirming that the G′ value exhibited a positive correlation with concentration (Du et al., 2021). The crossover points of G′ and G″, called yield stress, decreased with increasing concentration. In other words, an enlargement of the LVR was observed with higher concentrations.

Fig. 3.

Strain sweep (A), frequency sweep (B) and shear rate sweep (C) of GMS oleofoams.

Frequency sweep analysis (Fig. 3B) demonstrated that the G′ uniformly dominates over the G″ across the specified frequency range for all concentrations, confirming the existence of a lipid crystal-driven viscoelastic architecture within oleofoams (Fameau & Saint-Jalmes, 2017). In addition, both G′ and G″ exhibited progressive enhancement with increasing frequency, signaling a reduction in flexibility and concomitant elevation of structural rigidity. This trend, however, showed minimal development in 15 % oleofoam system.

The relationship between viscosity and shear rate was displayed in Fig. 3C. All samples exhibited shear-thinning behaviors, evidenced by the decreasing apparent viscosity with increasing shear rate until reaching a plateau, confirming their pseudoplastic fluid characteristics across all tested concentrations. This was similar to the phenomenon observed by (Qiu, Lei, Lee, Zhang, & Wang, 2021). And the non-aqueous foam system typically demonstrated characteristic pseudoplastic flow behavior due to shear-induced crystal orientation ordering (Grossi, Fang, Rao, & Chen, 2024). Furthermore, the pseudoplastic behavior may help enhance process efficiency in industrial food systems (Hong, Fan, & Li, 2025), such as ice cream, spreads, and chocolate formulations.

3.3. Storage stability of oleofoams

The stability of oleofoams serves as an important reference for their application characteristics in food products. The storage stability changes of oleofoams during 60 days were shown in Fig. 4. It is obvious that the stability of oleofoams exhibited a strong correlation with GMS concentration. At low concentration, phase separation occured in oleofoams with accelerated liquid drainage. This phenomenon may be attributed to an insufficient quantity of GMS particles, which failed to form a robust crystalline network structure to encapsulate the oil phase effectively. The high rigidity of oleofoams likely contributes to their superior storage stability (Han et al., 2024). At the same time, samples with higher concentrations demonstrated relatively stable properties without noticeable oil leakage. This observation aligned with our previous discussion based on PLM analysis, where higher concentrations promoted greater crystal adsorption at the interfaces. In other words, the synergistic effects of Pickering stabilization and network stabilization in oleofoams effectively suppressed both bubble coalescence and Ostwald ripening (Gunes et al., 2017). The latter predominantly drove phase separation during storage (Heymans et al., 2018). After two months of storage, the volume of oleofoams decreased. Under prolonged storage conditions, bubble coalescence occurred, consequently resulting in volume reduction of the oleofoams. In summary, the robust storage stability exhibited by high-concentration oleofoams actively preserves structural integrity and textural properties in aerated food systems, thereby enhancing product quality retention.

Fig. 4.

Visual appearance changes of oleofoams after storage for 0 (A), 7 (B), 30 (C), and 60 (D) days. From left to right, the concentrations are 5 %, 8 %, 10 %, 12 %, and 15 % respectively.

The selection of 12 % GMS oleofoam as the optimal medium for low-fat chocolate manufacturing was determined through characterization of physicochemical properties and microstructural evaluation.

3.4. Appearance and texture properties of chocolates

Chocolate appearance (Fig. 5A) revealed that CB-C can be demolded completely, exhibiting a rigid and uniform shape. The 25 % OF-C and 50 % OF-C samples displayed minor edge breakage, whereas 100 % OF-C failed to demold intact due to structural collapse.

Fig. 5.

Appearance (A), hardness (B), and XRD profiles of chocolate (C).

Hardness, defined as the maximum force (N) of the first compression cycle, is a crucial quality attribute of chocolate. The maximum peak force was shown in Fig. 5B. Obviously, the hardness of the samples decreased rapidly as the replacement of oleofoam increased in chocolate, which may be attributed to eutectic softening effect. It means that chemical composition disparity between cocoa butter substitutes and cocoa butter leads to reduced hardness in formulated chocolate products (Zhang, Geng, Ma, & Liu, 2025). Replacement of CB with oleofoam introduced a controlled bubble structure in the chocolate. The bubbles acted as a discontinuous phase, which influenced the originally dense cocoa butter crystal network in chocolate. And this led to structural weakening and overall density reduction, thereby impacting hardness. As noted by (Haedelt, Beckett, & Niranjan, 2007), chocolate with lower aeration exhibited higher density and was consequently perceived as harder. Chocolate appearance serves as a visual indicator of textural quality, predicting demoulding success or failure. Additionally, when CB was completely replaced with oleofoam, the low hardness of chocolate prevented proper demolding. This could be attributed to the fact that the crystal structure of CB determined the characteristics of chocolate, while the crystals in oleofoam were insufficient to support a robust network structure. Weakened network strength and insufficient processing of the dispersed phase in CB led to excessive softness of chocolate (Roufegarinejad, Habibzadeh Khiabani, Konar, Toofighi, & Rasouli Pirouzian, 2023).

3.5. XRD analysis

For chocolate, the stable β_V polymorph is the most desirable crystal form because its crystalline network helps inhibit fat bloom and provides an optimal melting point to maintain the shape (Svanberg, Ahrné, Lorén, & Windhab, 2011). The βv polymorph was identified in the chocolate through characteristic diffraction peaks in the XRD pattern. The CB chocolate exhibited a particularly sharp diffraction peak at d = 4.65 Å, along with four additional peaks of varying intensities. The XRD pattern of 25 % OF-C closely resembles that of CB-C, attributable to CB-dominant crystallization governing the polymorphic structure. Despite maintaining βv crystal signatures at 4.6 Å, oleofoam chocolates, both partial and complete CB replacement, exhibited lower diffraction peak intensities to CB chocolate. The reduction in CB content served as the key determinant underlying this result (Li & Liu, 2019). And increasing oleofoam substitution elevated liquid vegetable oil content in chocolate. Consequently, chocolates with 50 % and 100 % substitution exhibit broadened, low-intensity peaks resulting from amorphous scattering of triglycerides in vegetable oil. The disordered molecular structure of triglycerides in vegetable oil prevented the formation of highly ordered crystalline arrangements characteristic of CB.

3.6. Rheological properties of chocolates

The yield stress was a crucial parameter for assessing the flow characteristics of molten chocolate. Thus, the LVR of the chocolates were confirmed at first. It can be observed that with increasing oscillatory strain, both G′ and G″ gradually decrease, indicating a transition from elastic to viscous behavior in the chocolate samples. And among the four types of chocolate, CB-C exhibited the lowest yield stress. This meant that the CB-C system was the least stable. (Zhu et al., 2023) reported similar findings, demonstrating that CB-C had the smallest yield stress, while partial replacement of CB with oleogels enhanced the mechanical resistance of the chocolates. The results in Fig. 6B suggested that CB-C had the lowest G′ and G″ values, while 100 % OF-C showed the highest G′ and G″ values. In addition, all chocolate samples exhibited higher G′ than G′′ throughout the frequency range without crossover, indicating their dominant elastic characteristics (Zhu et al., 2023). It can be observed that as the shear rate increased, the viscosity of all four types of chocolate decreased, exhibiting typical non-Newtonian fluid behavior. This was likely due to structural breakdown caused by shear force (Toker et al., 2018). At low shear rates, the 100 % substituted chocolate exhibited the highest initial viscosity. Finally, four types of chocolate all tended to stabilize at higher shear rates. The air bubbles contributed little to the nutritional value of chocolates, but they significantly affected the rheology and texture of chocolates (Haedelt et al., 2007).

Fig. 6.

Strain sweep (A), frequency sweep(B), viscosity curve (C) and thermodynamic properties (D) of chocolates.

3.7. Thermal behavior of chocolates

The melting profile of chocolate is essential to its performance and oral processing experience. Thus, the melting parameters of chocolate were determined by DSC analysis (Fig. 6D). In contrast to other components, CB-C displayed a single melting peak at 25.08 °C and the highest enthalpy of 43.16 J/g. Similar phenomena have been documented in prior studies (Li & Liu, 2019). The 100 % OF-C sample exhibitd a distinct melting transition differing from other chocolates, primarily due to its GMS-based oleofoam structure. (Shuai et al., 2023) documented analogous behavior in CB-replaced chocolates with high substitution levels of oleogel. The melting enthalpy of chocolate decreased with increasing oleofoam content. (Zhang et al., 2025) confirmed that the quantity and configuration of crystals were modified when CB content decreased, consequently affecting thermal dissolution behavior. The thermal behavior aligned with textural results, where chocolates with lower melting enthalpy exhibited softer texture.

3.8. Electronic nose

The flavor of chocolate is one of the most critical factors influencing consumer acceptance, and analytical tools can help better characterize aroma compound levels. As a novel analytical tool, the electronic nose can be applied for fast quality control applications in the food of aroma analysis. The characteristic values for radar chart plotting were obtained by extracting the stabilized sensor response values. Fig. 7A showed the radar plots of electronic nose responses for four chocolate samples, where similar profile contours can be observed across all specimens. And among the sensors used in this study, sensors W5S, W1S, W1W and W2W displayed strong responses to volatile compounds in all chocolates. With increasing CB substitution levels, the response values of these four sensors decreased significantly, particularly showing a substantial reduction in W1W and W2W sensor outputs. In other words, the cocoa flavor intensity was reduced. In addition, the other six sensors showed minimal response variation, indicating low sensitivity to volatile compounds in the chocolate's aroma profile.

Fig. 7.

Electronic nose response patterns visualized via radar charts (A) and PCA score (B) for different chocolate systems.

Principal component analysis (PCA) was subsequently performed. The contribution rates of the first principal component (PC1) and the second principal component (PC2) were 78.77 % and 18.47 %, respectively, with a cumulative contribution rate reaching 97.24 %. PCA result revealed distinct differences between the CB group and the other three experimental groups. And 25 % OF-C and 50 % OF-C chocolate samples showed little difference in flavor.

3.9. Sensory evaluation

Fig. 8 displayed the sensory evaluation results of the chocolate samples. Despite the electronic nose demonstrating superior flavor intensity of CB-C, specific alternative chocolates achieved near-parity with CB-C in sensory profiles. The introduction of oleofoam has proven effective in refining chocolate flavor dimensions. Cocoa butter-based chocolate system showed enhanced sensory performance metrics in both appearance and mouthfeel relative to oleofoam chocolate analogs. Given that the requirements for sensory evaluation in this study prioritized abundant cross-sectional bubbles and a loose honeycomb configuration, the 25 % and 50 % OF-C exhibited superior morphology compared to CB-C. In terms of overall acceptability, CB-C and 50 % OF-C demonstrated comparable preference, while the 25 % OF-C variant achieved higher acceptance scores. The 100 % OF-C exhibited inferior performance across all evaluated sensory parameters.

Fig. 8.

Sensory evaluation of chocolates.

4. Conclusion

This study successfully developed GMS-based oleofoams using sunflower oil and applied them as CB substitutes in aerated chocolate. Optimal oleofoam stability and structure were achieved at 12 % GMS concentration and 5 min whipping time, yielding maximal overrun and uniform bubble distribution via Pickering stabilization. And oleofoams demonstrated favorable shear-thinning behavior and long-term storage stability.

Partial CB replacement with oleofoams produced chocolates with acceptable texture, melting profiles, and β_V polymorphic stability, though hardness and melting enthalpy decreased proportionally with substitution levels. Notably, 25 % OF-C matched CB-C in sensory acceptance, excelling in mouthfeel and flavor. However, 100 % CB substitution failed to form solid chocolate due to critically low hardness and disrupted crystal networks. These findings demonstrated that GMS-based oleofoams enable significant fat reduction without compromising sensory quality at ≤50 % CB replacement, offering a viable strategy for low-fat aerated chocolate development.

CRediT authorship contribution statement

Lukai Ma: Software, Project administration, Methodology, Investigation, Data curation, Conceptualization. Linjing Li: Writing – original draft, Software, Data curation. Zijian Li: Methodology, Conceptualization. Xianhong Bi: Methodology, Conceptualization. Hui Chen: Writing – review & editing. Xintong Cai: Methodology, Investigation. Charles Brennan: Writing – review & editing. Weiwei Cheng: Writing – review & editing. Linlin Li: Writing – review & editing, Supervision, Resources, Methodology, Investigation.

Informed consent statement

Informed consent was obtioned from all subjects involved in this study.

Ethical statement

Ethical permission is not required.

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.

Data availability

Data will be made available on request.