Properties Of Gels Research Articles

Enhanced Gelation Properties and Saltiness Perception of Low-Salt Surimi Gel with Psyllium Husk Powder.

Reducing salt intake is an effective strategy for preventing and managing hypertension and cardiovascular diseases. In this study, psyllium husk powder (PHP) was incorporated into surimi to address the challenges of diminished saltiness and texture in low-salt surimi products. PHP promoted the conversion of α-helix structures into β-sheet and strengthening intermolecular interactions, such as ionic bonds, hydrogen bonds, hydrophobic interactions, and disulfide bonds. The addition of PHP enhanced the connectivity and uniformity of the surimi gel network, resulting in an increase in gel strength from 11.35 to 13.88 N and a reduction in cooking loss from 6.33% to 2.27%. Additionally, the more compact gel network structure improved the fluidity of immobile water within the low-salt surimi gel. The surimi gel containing 1.5% PHP accelerated a 30% higher Na+ release rate compared to the low-salt surimi gel, enhancing the saltiness perception to levels comparable with high-salt surimi gel, as measured by an electronic tongue. These findings present a promising approach to improving the texture and saltiness perception of surimi gel products while reducing salt content.

Boosting Supramolecular Gelation Efficiency and Properties: Ionic Strength as a Key to Superior Hydrogels.

Controlling the minimum gelation concentration (MGC) of low molecular weight (LMW) hydrogelators is a key for modulating gel properties, such as mechanical strength, viscoelasticity, and stability, which are crucial for applications ranging from drug delivery to tissue engineering. However, tweaking the MGC under specific conditions, such as pH and/or temperature, poses a considerable challenge. Herein, we varied the ionic strength of buffer solutions using NaCl for several LMW hydrogelators, including Fmoc-Phe, Fmoc-Tyr, Fmoc-Trp, Fmoc-Met, and Fmoc-Cha, and assessed their gelation efficiency at pH 7.4 and ambient temperature. Interestingly, Fmoc-Phe demonstrated a ∼67% (3-fold) MGC reduction, from 0.24 to 0.08 wt %, at 500 mM NaCl, transforming it a "super hydrogelator" (MGC < 0.1 wt %), while Fmoc-Trp showed 60% MGC reduction. Higher ionic strength effectively shields the electrostatic repulsion between negatively charged (-COO-) groups on the Fmoc-Phe, promoting closer aggregation and more efficient self-assembly and allowing for gelation at lower concentrations. In contrast, Fmoc-Met, Fmoc-Cha, and Fmoc-Tyr precipitated in the presence of NaCl, suggesting that NaCl specifically modulates the MGC of Fmoc-amino acid gelators containing unsubstituted aromatic side chains. Furthermore, these results indicate that cation-π interactions likely play a role, alongside carboxylic acid neutralization. While Fmoc-Phe forms gels in the presence of other monovalent cations, it does not form a hydrogel in the presence of divalent (CaCl2) and trivalent (AlCl3), indicating that enhancement of hydrogelation is specific to monovalent cations. Although the fibrillar structure of Fmoc-Phe hydrogels remained consistent, addition of NaCl increased fibril stickiness, creating densely packed networks that modulate the mechanical strength. Unlike typical cases where increased ionic strength leads to precipitation, Fmoc-Phe gelation at high NaCl concentrations (150-500 mM) is significant, yielding a robust supramolecular hydrogel that remains stable in high ionic-strength environments. This outcome suggests that ionic strength could be a valuable factor to enhance the efficient gelation of LMW hydrogelators.

Improved textural properties of transglutaminase treated milk acid gel: Influence of citric acid

Keeping the stability of yogurt during the fermentation, storage and transportation process is necessary to reduce the syneresis. To achieve this goal, the combination of the acid treatment and transglutaminase (TG) was proposed to improve the textural properties of milk acid gels. We investigated the synergistic effect of acid treatment and TG on the water holding capacity (WHC) and physical stability of milk acid gels. As the pH of the skimmed milk decreased from 6.7 to 5.2, the casein micelles dissociated into smaller particles, exposing more site for the crosslinking of TG. The WHC and stability of the TG-treated acid gels were significantly enhanced as the particle size of casein micelles decreased. Our results suggested that the combination of the treatment of acid and TG could significantly improve the textural properties of milk acid gels by the dissociation of casein micelles induced and increase in the covalent-crosslinking. This study provided a simple and novel method to improve the stability of the milk gels, which showed enormous potential for dairy processing.

Structural and functional optimization of egg white protein hydrogels by succinylation: Gel properties and mineral enrichment

The development of novel gel-mineral supplements is important for improving the health of patients with dysphagia. In this study, we used natural egg white protein (NEWP) and phosphorylated egg white protein (STEWP) as controls. We modified NEWP with succinic anhydride to produce varying degrees of succinylated egg white protein (SAEWP). The addition of 20 % (w/v) succinic anhydride increased the β-sheet content of SAEWP from 11.97 % to 50.60 %, which stabilized the gel structure and formed a uniformly ordered three-dimensional network, resulting in the average pore size of SAEWP could reach >80 μm. Compared to NEWP, SAEWP hydrogel with 20 % succinic anhydride showed a 22.27 % increase in water holding capacity, a 56.13 % increase in hardness, and a 173.01 % increase in elasticity. Immersion in a calcium chloride solution resulted in a 220 % increase in calcium content. This study provides new insights into the development of innovative gel mineral supplements.

Ultrasonic treatment of emulsion gels with different soy protein-hemp protein composite ratios: Changes in structural and physicochemical properties

To improve the emulsion gel system of single soybean isolate protein (SPI) and to broaden the application field of hemp protein isolate (HPI), ultrasonic treatment and HPI were introduced to improve the properties of SPI emulsion gel and to explore the mechanism. The results showed that the gel strength (218.6 g) and water-holding capacity (86.24 %) of the emulsion gels were improved under ultrasonic treatments when the ratio of SPI:HPI was >6:4, and the reticulation structure of the gels was enhanced. When the ratio of SPI:HPI was <6:4, the gel structure was loose and formless. Ultrasonic treatment has a significant effect on the emulsion gel with the ratio of SPI:HPI was >6:4. Appropriate ultrasonic treatment (400 W) changed the protein structure, improved the rheological properties of emulsion gels to form the protein-oil-coated network structure. However, excessive ultrasonic treatment (600 W) will destroy the conformation of the protein, reducing the stability of the structure. The effect of ultrasonic treatment on emulsion gels with the ratio of SPI:HPI was <6:4 is low, but improved the gel protein digestibility. This study provides a theoretical basis for the application of ultrasonic in composite protein emulsion gels systems and the development and application of HPI.

A comparative study of different soybean oil forms on the physicochemical properties of surimi myofibrillar protein gel: The role of soybean protein isolate and κ-carrageenan

Natural soybean oil, Pickering emulsion, high-internal-phase emulsion (HIPE), and emulsion gel were prepared to investigate their effects on the physicochemical properties of surimi myofibrillar protein gels. Their effects on gel strength ranked as: emulsion gel > Pickering emulsion > HIPE > soybean oil. At the same oil content, the emulsion gel exhibited higher G' than the other forms whereas natural oil exhibited the lowest G', and T22 was smaller in the emulsion gel group, indicating that the emulsion gel enhanced the interaction between water molecules and protein macromolecules. FT-IR testified that 9 % natural oil reduced the β-sheet content to 26.34 %, whereas Pickering emulsion, HIPE, and emulsion gel recovered the β-sheet content to 31.30 %, 36.17 %, and 32.69 %, respectively. Emulsion gel led to fewer voids, and the oil droplets in emulsion gel were more regularly spherical and homogeneously dispersed in the gel matrix, which might be attributed to the filling effects as well as “bridging action” of soybean protein isolate and κ-carrageenan within surimi proteins. In conclusion, we demonstrated emulsion gel as a good replacer to mitigate the negative effect of oil on the texture and structure of surimi gels, which would be a promising approach for oil supplementation in surimi production.

Evaluating the efficacy of citrus fruit peel extract in preserving the quality of silver carp (Hypophthalmichthys molitrix) surimi during frozen storage

This research investigated the effects of mosambi peel extract (MPE) on the stability of proteins and textural characteristics of silver carp surimi during frozen storage at -20°C. The findings revealed that surimi fortified with 0.75% MPE displayed upgraded protein solubility (PS), water holding capacity (WHC), Ca2+-ATPase activity, and sulfhydryl (SH) content. It also exhibited reduced levels of total carbonyls and surface hydrophobicity, along with higher overall acceptability compared to surimi treated with synthetic cryoprotectants (control) throughout storage. Additionally, MPE slowed down the increase in total volatile basic nitrogen (TVBN) and protein degradation index (PI), as evidenced by SDS-PAGE showing higher intensities of myosin heavy chain (MHC) and actin over the storage period. Moreover, the incorporation of MPE effectively mitigated lipid oxidation as peroxide value (PV), and thiobarbituric acid (TBA) were lesser than control. Fourier-transform infrared spectroscopy (FTIR) peaks specified that the relative content of α-helix and β-sheet structures remained more stable in the MPE-treated group compared to the control, along with the improved gel and textural properties of surimi. Hence, this study suggests that 0.75% MPE could serve as a natural alternative to synthetic cryoprotectants, ensuring the oxidative stability of silver carp surimi during frozen storage while enriching it with beneficial bioactive compounds.

Emulsifying and ethanol-induced gelling properties of capsicum pectin: The impact of capsicum variety and deproteinization using the Sevag method.

This study investigated the emulsifying and ethanol-induced gelling properties of capsicum pectins from bell pepper and chili pepper, and also examined the effect of deproteinization (using the Sevag method). The research revealed that bell pepper pectin (BPP) formed smaller aggregates (337 nm at pH 2) with a higher hydrophobicity in solution due to its lower molecular weight (2.02 × 105 g/mol) and higher degree of esterification (82.15 %) compared to chili pepper pectin (CPP) (3.29 × 105 g/mol, 78.33 %). Consequently, BPP exhibited superior interfacial tension reduction ability, resulting in emulsion with smaller droplet size (483 nm at pH 2). Conversely, CPP showed superior ethanol-induced gelling property in comparison to BPP, as its lower degree of esterification and higher molecular weight facilitated hydrogen bonding interactions and crosslinking during gelation. Deproteinization with the Sevag method reduced protein content, molecular weight and esterification degree of BPP and CPP, but its impact on their emulsifying properties differed significantly. Interestingly, deproteinization notably improved the ethanol-induced gelling property of both pectins, since the increased carboxyl groups in the deproteinized products promoted hydrogen bonding during gelation. This study could facilitate the comprehensive utilization of capsicum and also advance our understanding of the impact of the Sevag method.

The Formation Mechanism of Zein Gel Induced by Amyloid-like Fibrils

The preparation of zein gels often leads to unstable product quality due to poor reproducibility, posing substantial challenges for the food industry and biomedical applications. Thus, it is essential to study the gelation mechanism and key factors responsible for gelation. Herein, we report four types of assembled structures from zein solutions in binary ethanol–water solvents with either a high concentration (30% w/v) and a low concentration (5% w/v), namely, spheres, spheres with tangential structures, amyloid-like fibrils, and sub-agglomerates with crystal structures. The tangential structure at the edges of the spheres was first observed by transmission electron microscopy (TEM) at the initial stage, offering a model for studying protein folding and aggregation mechanisms. By observing the gelation processes with TEM for morphology, cryo-TEM to confirm structure preservation, HR-TEM for fine details, and negatively stained TEM to reveal hidden features, along with small-angle X-ray scattering (SAXS), we identified two types of gels: one was mainly network structures formed by sphere–sphere fusion, which was thermoreversible, and the other one was irreversible gel due to the increase in the amount of amyloid-like fibrils. Results show that the existence of thermoreversible zein gels indicates potential effective regulation tools of zein gel properties. In addition, amyloid-like fibrils were first isolated from native zein. During amyloid-like fibril formation, the number of tangential structures increased considerably, which were composed of thinner fibrils. High-resolution TEM showed a substructure with a 0.35 nm interplanar spacing, providing evidence of β-sheet aggregates also as confirmed by SAXS. This unique substructure has not been reported in other edible proteins. Moreover, understanding the fibrillation mechanism of zein provides a basis for controlling and developing novel food structures for food protein function and offers insights into neurodegenerative diseases.

Gel properties of mung bean protein‑sodium caseinate hybrid yogurt: Physicochemical properties, microstructure, and intermolecular interactions

The study aimed to evaluate the gel properties of mung bean protein (MP)/sodium caseinate (NaCas) hybrid yogurt at various mixing ratios, such as rheology, texture, water holding capacity, microstructure, and formation mechanism. The gel hardness, storage modulus (G′) and water holding capacity of MP/NaCas yogurt increased and subsequently decreased as the NaCas level increased, maximum at a MP/NaCas ratio of 70:30. Meanwhile, as the MP/NaCas ratio was 70:30, the hybrid yogurt gel formed tighter and finer network structure. Moreover, the MP/NaCas hybrid yogurt slowed down the acidification rate with increasing NaCas ratio. Especially when NaCas was added at 50 %, the blend sample presented the longest fermentation time (280 min). Results showed that the optimal physicochemical characteristics of the yogurt gel were obtained when MP/NaCas ratio was mixed at 70:30. The results of the intermolecular forces indicated that hydrophobic interactions were the main factor causing yogurt gel formation.

Improving gel properties of silver carp (Hypophthalmichthys molitrix) myosin with flavonols: Unveiling the advantages of isorhamnetin

This study explores the impact of flavonols (kaempferol, quercetin, kaempferitrin, and isorhamnetin) on the gel properties of myosin derived from silver carp (Hypophthalmichthys molitrix). Before employing a two-stage heating process, myosin samples are pretreated with flavonols, which enhance the structural stability of myosin and aid in the dispersion of myosin molecules. These pretreatments prepare the samples for subsequent thermal processing, where flavonols facilitate myosin unfolding and enhance intermolecular aggregation, thereby improving gel strength. This process also transforms free water within the gel to bound water, significantly increasing the water-holding capacity. Both macroscopic and microscopic rheological analyses suggest that flavonols, particularly isorhamnetin, notably enhance the elasticity and viscosity of myosin during the gelation process. Further, microstructural examinations employing techniques such as small-angle X-ray scattering and micro-computed tomography demonstrate that samples treated with flavonols develop denser and more uniform gel networks. Analytical studies reveal that flavonols, especially methylated derivatives like isorhamnetin, effectively promote gelation through strengthening hydrophobic interactions, disulfide bonds, and ionic interactions among myosin molecules. This research underscores the potential of flavonols as natural additives to enhance the quality and functional properties of surimi products, thereby elevating the processing standards of aquatic products.

The Viscoelastic Behavior of Legume Protein Emulsion Gels—The Effect of Heating Temperature and Oil Content on Viscoelasticity, the Degree of Networking, and the Microstructure

Legume proteins are increasingly used in structuring various foods under the influence of heating and stirring energy. Based on available studies, this structuring potential is not yet fully understood. This raises the question of the suitability of legume isolates and concentrates for structuring in emulsion gels and the effect of heat and oil on the gel properties. In this study, soy- and pea-based suspensions and emulsions were prepared with the least gelling concentration using different oil concentrations (0%, 7.5%, 15%, 22.5%, and 30%). The viscoelastic properties were measured before and after heating cycles (65 °C and 95 °C). Scanning electron microscopy images complemented the results. All gels measured showed viscoelastic solid behavior. Thermal treatment showed a positive effect on the gel properties for most samples, especially for concentrates (reduction in the loss factor and networking factor &gt; 1). The concentrates showed much higher networking factors and tighter cross-linking than the isolates. The rheological and microstructural properties of the emulsion gels are influenced by a number of factors, such as carbohydrate content, protein chemistry, the protein purification method, and initial viscosity. Moreover, the influence of oil on the rheological properties depends on the material used and whether oil droplets act as an active or inactive filler.

Chemical composition, rheological properties and calcium-induced gelation mechanism of Premna microphylla Turcz polysaccharide

The aim of this study was to investigate the chemical composition, molecular weight (Mw), and monosaccharide composition of Premna microphylla Turcz polysaccharide (PMP) and revealed the effects of calcium ions (Ca2+) on the rheological properties, thermal stability, texture properties, and structural properties of PMP gels. Additionally, the gelation mechanism of PMP was proposed. The results revealed that PMP was a negative charge acidic polysaccharide primarily composed of glucose, galactose and rhamnose. The results of small and large amplitude oscillatory shear experiments illustrated that the storage modulus (G′), loss modulus (G″), relaxation modulus (G(t)) of PMP gels showed a positive correlation with Ca2+ concentration, indicating the addition of Ca2+ improved the viscoelasticity and shear thinning capacity of PMP gels. Furthermore, the gel strength, hardness, and thermal stability of PMP gels were enhanced with increase of Ca2+ concentration. The microstructure of PMP gel was changed obviously after adding Ca2+, generating the lamellar and lump-like structure due to the PMP aggregation. The results of Zeta potential, X-ray diffraction, and Fourier transform infrared spectroscopy (FT-IR) analysis indicated that electrostatic interactions played a crucial role in the formation of PMP gel and three-dimensional structure. These results suggested that PMP had great potential for application in the food industry due to their excellent gelation properties.

Scalable fabrication of freely shapable 3D hierarchical Cu-doped hydroxyapatite scaffolds via rapid gelation for enhanced bone repair

Critical-sized bone defects present a formidable challenge in tissue engineering, necessitating innovative approaches that integrate osteogenesis and angiogenesis for effective repair. Inspired by the hierarchical porous structure of natural bone, this study introduces a novel method for the scalable production of ultra-long, copper-doped hydroxyapatite (Cu-HAp) fibers, utilizing the rapid gelation properties of guar gum (GG) under controlled conditions. These fibers serve as foundational units to fabricate three-dimensional porous scaffolds with a biomimetic hierarchical architecture. The scaffolds exhibit a broad pore size distribution (1–500 μm) and abundant nanoporous features, mimicking the native bone extracellular matrix. Physicochemical characterization and in vitro assays demonstrated that the copper doping significantly enhanced osteogenic and angiogenic activities, with optimized concentrations (0.8 % and 1.2 % Cu) facilitating the upregulation of osteogenesis-related genes and proteins, as well as promoting endothelial cell proliferation. In vivo studies further confirmed the scaffolds' efficacy, with the 1.2Cu-HAp group showing a remarkable increase in bone regeneration (bone volume/total volume ratio: 35.7 ± 1.87 %) within the defect site. This research offers a promising strategy for the rapid fabrication of multifunctional scaffolds that not only support bone tissue repair but also actively accelerate the healing process through enhanced vascularization.

Hydrophobic association supramolecular gel suitable for oil and gas drilling in fractured formation

Supramolecular gel can be used to seal fractures and pores in the formation during oil and gas drilling and production. In this study, a supramolecular gel plugging agent based on hydrophobic association was prepared by free radical polymerization of acrylamide, octadecyl methacrylate, sodium dodecyl sulfate and other monomers by micellar copolymerization. The forming time, rheology, swelling, mechanical properties and plugging properties of supramolecular gels were studied. The experimental results show that the formation time of supramolecular gel plugging agent is controllable, and it has excellent viscoelastic recovery ability in a certain range of shear strain and scanning frequency. When the compression amount is close to 88.3%, the compressive stress reaches 3.82 MPa. Meanwhile, the swelling performance of supramolecular gel was good, and the equilibrium swelling degree reached 22.1% after 188 min swelling in 15% NaCl brine solution. In 1% NaCl solution, the equilibrium swelling degree of supramolecular gel reached 32.5%. In addition, supramolecular gel has strong formation bonding ability, good plugging performance, plugging rate is greater than 95%, can effectively reduce the leakage and improve the plugging effect of low permeability layer. It is of reference and guiding significance for the long-term plugging of heterogeneous and malignant leakage formations.

Insights into transglutaminase on structural and rheological properties of gels from adzuki bean protein pretreated by electric fields

The demand for protein is increasing as the global population continues to grow. The plant protein has been favored and plant-based food has become a research hotspot for healthy diet, environmental protection, animal ethics and other issues. Adzuki bean protein (ABP) is a quality source with complete amino acids, abundant essential amino acids and beanless flavour. ABP is rich in glutamine and lysine which are good substrates for transaminase (TGase) induced gelation. The pulsed electric field (PEF), alternating current EF (ACEF), direct current EF (DCEF) were applied to pretreat ABP aiming at improving the efficacy of TGase induced crosslinking. The results showed that the TGase decreased the free amino amount significantly and increased the molecular weight of ABP. The EF pretreatments significantly influenced the secondary and tertiary structures of ABP with a decrease in β-sheets, increase in random coils, β-turns, and α-helices, also decrease in fluorescence intensity with blueshift. The content of disulfide bond increased with the decrease of free sulfhydryl groups. The ionic bonds decreased and hydrophobic actions surpassed significantly hydrogen bonds. The hydrophobicity increased. The electric field intensity corresponded to variation of microstructure, texture and rheological behaviour of the ABP gel according to the type of the EF.

Rheological and Tribological Properties of Konjac Gum-Lecithin Composite System: Effect of Incorporation of Saliva and Friction Surface Properties.

This research explored the development of composite systems using konjac gum (KGM) and soy lecithin at concentrations of 1% KGM-0.01% lecithin and 1% KGM-0.2% lecithin. The study investigated the influence of both oral and artificial saliva on the rheological and tribological properties of these systems, as well as the lubrication on different friction surfaces with varying characteristics. It has been found that different friction surfaces exhibited distinct morphological features and roughness values, significantly impacting surface wettability when treated with saliva. The viscosity of KGM-lecithin composite systems increased slightly compared to KGM hydrogel. However, adding oral or artificial saliva led to a noticeable decrease in viscosity. Lecithin did not significantly alter the viscoelastic properties of KGM gel, but the incorporation of artificial and oral saliva introduced some changes. CLSM images showed that the stability and distribution of lecithin within the composite system varied with lecithin concentration and saliva type, with artificial saliva ensuring a stable and even distribution, while oral saliva caused aggregation and irregular distribution. Furthermore, the study found that the lubrication performance of the KGM-lecithin system was influenced by the properties of the friction surface, with hydrophilic rough surfaces providing superior lubrication compared to rough surfaces. The addition of lecithin enhanced lubrication across all tested surfaces, and artificial saliva surpassed oral saliva in reducing friction coefficients. These findings offer valuable insights into the potential use of KGM-lecithin composite systems as fat mimetics, particularly in enhancing lubrication for various applications.

Mechanism of CaCl2 modulation of the properties of acyl-modified ovalbumin–myofibrillar protein composite gel

Chicken breast products exhibit a rough texture and poor taste owing to the special fibrous tissue structure of chicken breast. Thus, adapting the taste of processed chicken breast products is pivotal to improving consumer satisfaction. Therefore, we used CaCl2 and acyl-modified ovalbumin (AOVA) in a concerted effort to improve the gelation properties of chicken breast myofibrillar protein (MP). The investigation of molecular interactions and microstructure revealed the mechanism behind the changes in the physicochemical properties of the prepared gel. Molecular docking showed that AOVA enhanced the gel structure of MP through hydrogen bonding and salt bridges. The investigation results indicated that 0.30 mol/L CaCl2 facilitated the unfolding of AOVA-MP molecules, increasing the number of disulphide bonds and hydrophobic interactions, as well as conferring better hardness, springiness, cohesiveness, and chewing properties to the AOVA-MP gel with a denser and more homogeneous gel network structure. This study provides new insights into the quality improvement in chicken breast mince products.

Microstructure of starch complexes coated with arabinoxylans and β-glucans: Effect on gelatinization and digestion properties

Research has shown that the presence of a complete cell wall structure in the grain endosperm reduces the digestibility of grains (starch) in the human body. In this study, composite structures of diverse contents of arabinoxylan (AX) and β-glucan (BG) in combination with wheat starch were constructed to simulate the grid structure formed by the combination of starch granules wrapped within cell walls in the starch endosperm. The gel properties following gelatinization and aging of the complexes were analyzed using rheology, differential scanning calorimetry, X-ray scanning, and infrared spectroscopy. Based on this, the differences in the in vitro digestion process of starch complexes were investigated, and the digestion mechanism was explored to offer a theoretical basis for the development of starch-based foods with a low glycemic index. The synergistic effect of AX and BG was found to promote the entanglement and aggregation of molecules, AX and BG inhibits the gelatinization of starch. AX/BG (10 % blend proportion) significantly inhibited starch digestion in the starch complexes, with the lowest hydrolysis rate (76.7 %), which may be because AX and BG wrap the starch particles effectively.

Evaluation of hydrogen peroxide diffusion in the pulp chamber, bleaching efficacy, and physicochemical properties of an experimental in-office bleaching gel containing a hydroxyapatite-capsaicin composite.

This study assessed the hydrogen peroxide (HP) diffusion into the pulp chamber, bleaching efficacy (BE), surface roughness (Ra), and Knoop microhardness (KHN) of an experimental bleaching gel containing a hydroxyapatite-capsaicin composite (HAp-CAP). Human premolars were randomly assigned to three groups (n = 9) based on the dental bleaching gel used (50min; one session): only 35% HP, 35% HP + HAp-CAP, and not exposed to bleaching (negative control; NC). HP diffusion (µg/mL) into the pulp chamber was assessed using UV-Vis spectrophotometry, and BE (ΔEab, ΔE00, and WID) was evaluated using a digital spectrophotometer. Human molars were used to determine Ra and KHN before and 7days after the bleaching procedure, and for Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analyses. A paired t-test or t-test was used for statistical analysis (α = 0.05). A higher amount of HP into the pulp chamber and significant BE (ΔEab, ΔE00, and WID) were observed for 35% HP and 35% HP + HAp-CAP compared to NC (p < 0.001), with no significant difference between them (p > 0.05). SEM and EDS demonstrated material deposition on the enamel surface after bleaching for 35% HP + HAp-CAP, which helped maintain the KHN (p > 0.05). Furthermore, Ra increased for both groups (p < 0.05). The 35% HP + HAp-CAP did not decrease HP diffusion into the pulp chamber, reduced KHN values, and increased Ra. Material deposition on the enamel surface was observed, and BE was effective.