Preparation of β-ionone microcapsules by gelatin/pectin complex coacervation

Advances in Microencapsulation of Flavor Substances: Preparation Techniques, Wall Material Selection, Characterization Methods, and Applications

This review systematically examines advances in flavor microencapsulation technology from 2014 to 2024, focusing on innovations in preparation techniques, trends in wall material selection, and characterization methods. Literature metrological analysis shows that spray drying is the predominant technology (25% of reports); its shortcomings in volatile flavor retention have driven improved strategies such as vacuum low-temperature drying, ultrasound assistance, and monodisperse atomization. Emerging technologies such as electrohydrodynamic methods (electrospinning/electrospraying) and supercritical fluid processing are favored due to their nonthermal advantages. Overall, traditional polysaccharides have been widely used due to their good emulsifying and stabilizing properties. In the meanwhile, plant-based polysaccharides (e.g., inulin, hemicellulose) and proteins (e.g., pea protein) are increasingly preferred as the wall materials driven by sustainability and clean-labeling requirements. Morphological analysis and particle size and distribution studies have highlighted the key role of microstructure in stability and release kinetics, with multicore and multishell structures optimizing controlled release performance. Despite progress, gaps remain in the standardized assessment of encapsulation efficacy, the cost-effectiveness of novel materials, and practical food applications. In the future, a combination of interdisciplinary approaches is needed to investigate low-energy preparation technologies, functionalized wall materials, and intelligent release mechanisms to achieve the better application of flavor microencapsulates in food.

Structures and compositions of the oil/wall interfaces and wall layers affected the properties of spray-dried fish oil powders

Herein, 12 types of fish oil emulsions were used to prepare 12 types of spray-dried fish oil powders with three gelatins (positive fish gelatin, positive porcine skin gelatin, and negative bovine skin gelatin), two negative pectins (high and low methoxy pectin), and negative sodium starch octenyl succinate (SSOS). The powders consisted of microscale capsules with bi- or monolayer oil/wall interfaces, and monolayer wall layers. SSOS significantly decreased the bulk and tapped densities of the powders. All powders had low water activities (0.14-0.26). Gelatin/pectin and gelatin/pectin/SSOS powders had encapsulation efficiencies of 45.1 %-75.9 % and 70.1 %-93.0 %, respectively. The oxidative stability depended on the compositions of the powder wall layers. FG+/LMP/SSOS wall layer induced the lowest PV peak value (325 ± 15 mmol/kg oil). BSG-/HMP/SSOS wall layer induced the highest PV peak value (1273 ± 49 mmol/kg oil). The free fatty acid release percentages in the in vitro digestion system depended on the structures and compositions of oil/wall interfaces. FG+@LMP/SSOS interface induced the lowest FFA release percentage (33.9 % ± 1.7 %) and BSG-/HMP interface induced the highest FFA release (79.3 % ± 8.1 %). The results suggested useful information on the effect of oil/wall interfaces and wall layers on the preparation and properties of fish oil powders.

Preparation of Cinnamomum camphora essential oil microcapsules using gelatin/gum arabic and evaluation of their antifungal effects on Fusarium spp

We developed a complex coacervation method of preparing Cinnamomum camphora essential oil (CEO) microcapsules using gelatin and gum arabic as wall materials. The microencapsulation process was optimized using Plackett-Burman and Box-Behnken designs with a maximum yield of 84.48 ± 3.15 % and encapsulation efficiency of 91.89 ± 2.71 %. The thermogravimetric analysis demonstrated that the microencapsulation process clearly enhanced the thermal stability of the CEO, and assessment of their controlled-release ability revealed that the release mechanism of the microcapsules resembled diffusion. The CEO microcapsules exhibited effective antifungal activity against Fusarium culmorum and Fusarium sporotrichioides, and the inhibitory effect was highly correlated with the fumigation concentration of the microcapsules. This study provides valuable information for utilizing microcapsule carriers to deliver CEO as well as improve its preservation stability, which will broaden the applications of the CEO in the agricultural and food preservation industries.

Vanillin strengthened complex coacervation behavior between gelatin and sodium carboxymethyl cellulose endowed improved mechanical properties of microcapsules

The inherent heterogeneous structure of biomass molecules usually makes the formed interfacial film prone to defects such as core material mass transfer loss, while chemical modification may be an effective means to improve the performance of biobased interfacial films. In this study, gelatin‑sodium carboxymethyl cellulose (CMC-Na) complex coacervation microcapsules were used as models and the typical aroma molecule vanillin as modifier to explore the differences in mechanical properties and other physicochemical properties of microcapsules before and after modification, as well as the potential mechanism of the differences. Results showed that the aldehyde group of vanillin formed covalent imine bond with the amino group on gelatin protein through Schiff base reaction, and the hydroxyl group on the benzene ring of vanillin formed hydrogen bonds with CMC-Na and gelatin simultaneously; these two effects were synergistically enhanced cross-linking between wall materials, thereby strengthening the mechanical properties of the microcapsules. The rupture force of microcapsules with 0.5 % vanillin was 36.60 % higher than that of blank microcapsules. In summary, this study used aroma compounds to modify biomass macromolecules, which provided a new idea for strengthening the physicochemical properties of bio-based microcapsules.

Microencapsulation of glutathione through water/oil emulsification and complex coacervation: Improved encapsulation efficiency, physicochemical stability, and sustained release effect

The feasibility of preparing microcapsules of water-soluble ingredient via complex coacervation was explored. Gelatin and gum arabic were used as wall materials to encapsulate glutathione (GSH) through water in oil (W/O) emulsion. Soy lecithin at a concentration of 3 % (w/w) was used as an emulsifier, and the aqueous phase containing 15 % GSH (w/w) was emulsified with soybean oil at a ratio of 5:5 (w/w), which resulted in a stable W/O emulsion. Furthermore, GSH microcapsules produced under optimal conditions, core/wall ratio 1:1, wall material content 1 % (gelatin: gum arabic = 1:1), stirring rate 400 r/min, added 0.25 g glutamine transaminase (TGases) per gram of gelatin, exhibited good morphology, high encapsulation efficiency and yield, which being 92.88 % and 92.10 %, respectively. After comparing the effects of four different oil emulsions on the microencapsulation of GSH, it was found that all had excellent encapsulation efficiency, indicating that no specific oil phase was required for emulsions preparation. GSH microencapsulation by complex coacervation significantly enhanced its stability, reduced the loss ratio of GSH by 23.5 % when capsules were heated at 150 °C for 2 h. Moreover, GSH microencapsulation increased its retention by 23.25 % and 43.88 % during capsules storage at 40 °C and under light exposure, respectively. In addition, GSH microcapsules effectively prevented its degradation during simulated gastrointestinal digestion induced by salivary amylase, pepsin and acidic environments, while rapidly released GSH under trypsin and alkaline environments. This study provided new insights into water-soluble ingredients microencapsulation and its efficient application in the food and nutraceutical industries.

The complex coacervation of gum Arabic and krill protein isolate and their application for Antarctic krill oil encapsulation

Antarctic krill oil (AKO) possesses potent bioactivities but has limited applications in the food industry due to its poor stability, strong off-flavor, and low bioavailability of contained astaxanthin. In this study, Antarctic krill protein isolate (AKPI) was separated from processing by-product of krill and utilized as a novel wall material via complexing it with gum Arabic (GA) to improve the limitations of AKO. The strong complex coacervation reaction between AKPI and GA was occurred at the pH of 3.8 and the ratioAKPI-to-GA of 3:1, while electrostatic interaction and hydrogen-bond interaction were determined to be the main driving forces of such reaction. The ratiowall-to-core was confirmed as 1:0.75 after comprehensively assessing the effect of AKO content on the various properties of AKPI-GA coacervated microcapsules, while the wall material concentration and pH were optimized at 1 % and 3.8, respectively. The obtained solid AKO microcapsules exhibited the encapsulation efficiency of 80.22 %. AKPI-GA coacervated microcapsules extremely masked the odor of AKO and achieved the controlled-release of AKO in the gastrointestinal tract. Meanwhile, the encapsulated AKO displayed higher astaxanthin retention and oxidative stability compared with non-encapsulated AKO during storage.

Thiamethoxam-Loaded Ethyl Cellulose Microspheres for Extending the Efficacy Duration and Reducing the Toxicity on the Growth of Maize (Zea mays L.)

Thiamethoxam has been widely used in agriculture due to its excellent insecticidal activity. However, thiamethoxam is prone to loss during practical applications, especially in soil application, which seriously reduces its performance. In this work, thiamethoxam is loaded in ethyl cellulose microspheres to solve this issue, and the thiamethoxam-loaded ethyl cellulose microspheres (thiamethoxam/EC) are facilely and effectively fabricated by emulsified solvent volatilization. The exceptional embedding capacity of thiamethoxam/EC was elucidated through a systematic investigation of its controlled release and antiphotolysis properties. The encapsulation efficiency of thiamethoxam/EC was found to be ∼70.36%. Even after 130 h in a phosphate-buffered saline solution, the release of thiamethoxam from the thiamethoxam/EC complex continued, with a cumulative release of ∼52.38%. In contrast, the cumulative release of thiamethoxam/EC in soil after being flushed with 580 mL of water was a mere 14.74%, significantly lower than the value of 42.73% observed for unencapsulated thiamethoxam at the same volume. Additionally, thiamethoxam/EC demonstrated benign biocompatibility with Escherichia coli and maize (Zea mays L.) seedlings. The ultraviolet resistance of thiamethoxam in the thiamethoxam/EC formulation was nearly 3 times greater than that of uncoated thiamethoxam, and the insecticidal efficacy against Mythimna separata improved by 11.46% at a low concentration of 1 mg/L after a 10 day incubation in a greenhouse. The microspheroidization process not only extended the efficacy duration of fluazinam on target crops but also contributed to the sustainable use of pesticides and environmental protection.

Influence of Solvent Dielectric Constant on the Complex Coacervation Phase Behavior of Polymerized Ionic Liquids

Complex coacervation is an associative phase separation process of oppositely charged polyelectrolyte solutions, resulting in a coacervate phase enriched with charged polymers and a polymer-lean phase. To date, studies on the phase behavior of complex coacervation have been largely restricted to aqueous systems with relatively high dielectric constants due to the limited solubility of most polyelectrolytes, hindering the exploration of the effects of electrostatic interactions from differences in solvent permittivity. Herein, we prepare two symmetric but oppositely charged polymerized ionic liquids (PILs), consisting of poly[1-[2-acryloyloxyethyl]-3-butylimidazolium bis(trifluoromethane)sulfonimide] (PAT) and poly[1-ethyl-3-methylimidazolium 3-[[[(trifluoromethyl)sulfonyl]amino]sulfonyl]propyl acrylate] (PEA). Due to the delocalized ionic charges and their chemical structure similarity, both PAT and PEA are soluble in various organic solvents with a wide range of dielectric constants, ranging from 16.7 (hexafluoro-2-propanol (HFIP)) to 66.1 (propylene carbonate (PC)). Notably, no significant correlation is observed between the solvent dielectric constant and the phase diagram of the complex coacervation of PILs. Most organic solvents lead to similar phase diagrams and salt resistances regardless of their dielectric constants, except two protic solvents (HFIP and 2,2,2-trifluoroethanol (TFE)) showing significantly low salt resistances compared to the others. The low salt resistance in these protic solvents primarily arises from strong hydrogen bonding between PILs and solvents as evidenced by 1H NMR and small-angle neutron scattering (SANS) experiments. Our finding suggests that for the coacervation of PILs, particularly those with delocalized and weak charge interactions, entropy from the counterion release and polymer-solvent interaction χ parameter play a more important role than the electrostatic interactions of charged molecules, rendered by the dielectric constant of the solvent medium.

Complex coacervation of low methoxy pectin with three types of gelatins for the encapsulation of fish oil

Herein, the complex coacervation of low methoxy pectin (LMP) with three types of gelatins was explored to encapsulate fish oil. The fish oil@gelatin-LMP complex coacervates with good precipitation separation could be obtained at low gelatin concentrations (Fish gelatin, FG: 10-80 mg/mL; porcine skin gelatin, PSG: 10-40 mg/mL; bovine skin gelatin, BSG: 10-80 mg/mL), high gelatin: fish oil mass ratios (4:1-1:1), appropriate gelatin: LMP mass ratios (3:1-12:1 for FG and PSG, 6:1 for BSG), and appropriate pH (FG: 4.90-5.50; PSG: 4.80-5.40; BSG: 4.10-4.50). FG induced similar loading ability, lower encapsulation ability, and comparable peroxide values to the mammalian gelatins. FG induced higher or similar free fatty acid released percentages to mammalian gelatins in the in vitro gastrointestinal model at low gelatin concentrations (10-40 mg/mL). These results provided useful information to understand the protein-polysaccharide complex coacervation to encapsulate oil-based bioactive substances.

Optimization and characterization of alginate/cinnamaldehyde electrosprayed microcapsule and its application to mongolian cheese preservation

alginate is a good candidate for encapsulating bioactive compounds because the Na+ on its carboxyl groups can take part in an ion exchange process with Ca2+ to generate a calcium alginate shell. Electrospraying technology was used to prepare cinnamaldehyde (CA)-loaded alginate microcapsules. The generation of microcapsules with a minimal diameter could improve the mass transfer of encapsulated materials. The electrospraying parameters were optimized using response surface methodology (RSM). The results indicated that lower alginate concentration led to microcapsules with smaller diameters. The interaction between the concentration of alginate and the needle size affecting the microcapsule diameter was more significant than other mutual interactions. The optimum conditions were an alginate concentration of 1.27 % (w/v), needle size of 24.62 G, flow rate of 2.29 mL/h, voltage of 12.98 kV, CaCl2 concentration of 0.30 M, and distance of 11.01 cm. With a minimal diameter (155.34 μm), the obtained microcapsules displayed good encapsulation efficiency (86.00 ± 1.7 %) and loading capacity (45.00 ± 2.6 %), which had better preserving effects for Mongolian cheese. The study provided a reference for the production of the microcapsules with high antimicrobial effectiveness, exploring the new technological developments and applications of alginate.

Structural and functional properties of lactoferrin modified with carboxymethyl chitosan: Physical mixing and transglutaminase glycosylation

Protein-polysaccharide combinations frequently demonstrate functional attributes that surpass those of the individual biopolymers. This study aimed to elucidate the physicochemical, structural, and functional properties of two types of lactoferrin (LF)-carboxymethyl chitosan (CMCS) complexes formed by physical mixing and enzymatic glycosylation. LF and CMCS interactions were characterized using phase behavior, particle size, and zeta-potential analysis. The results indicated the formation of an electrostatic complex with a size of <150 nm at pH 8. SDS-PAGE and Fourier transform infrared spectroscopy confirmed that TGase catalyzed the cross-linking and glycosylation of LF, with the extent of glycosylation dependent on the concentration of CMCS. The introduction of CMCS has been observed to result in alterations to the secondary, tertiary, and microstructure of LF, which impact the functional characteristics of LF. The incorporation of CMCS markedly enhances the thermal stability of LF, with a denaturation temperature of 126.66 °C. The addition of CMCS (0.5 wt%) to LF resulted in a significant (P < 0.05) improvement in the emulsifying activity of LF, but it did not improve its foaming properties. This study offers novel ideas and approaches for developing protein and polysaccharide complexes with improved functional properties, thereby expanding the potential applications of edible proteins.

Coenzyme Q10-loaded microcapsules stabilized by glyceryl monostearate and soy protein isolates-flaxseed gum: Characterization, in vitro release and digestive behavior

This study aimed to stabilize microcapsules with core materials of glyceryl monostearate (GMS) and octyl and decyl glycerate, and wall materials of soy protein isolates (SPI) and flaxseed gum (FG) by complex coacervation method to overcome the drawbacks of coenzyme Q10 (CoQ10). It was demonstrated by the study that the obtained microcapsules were irregular aggregates. Differential scanning calorimetry and x-ray diffraction patterns indicated that CoQ10 was entrapped inside the disordered semisolid cores of microcapsules. The CoQ10 loading and encapsulation efficiency analysis revealed that GMS and FG helped CoQ10 better encapsulated inside the microcapsules. The in vitro release curve showed a "burst" release of CoQ10 absorbed on the surface of microcapsules for the first 180 min, followed by a sustained release of the encapsulated CoQ10. GMS and FG contributed to the sustained release and the release mechanism of the microcapsules was Fickian diffusion. The in vitro simulated digestion demonstrated that the constructed microcapsules improved the bio-accessibility of CoQ10. Finally, due to the protection of GMS and FG, microcapsules had good storage stability. In conclusion, this study emphasized the potential of using new microcapsules to deliver and protect lipophilic ingredients, providing valuable information for developing functional foods with higher bioavailability.

A Review of Modified Gelatin: Physicochemical Properties, Modification Methods, and Applications in the Food Field

Gelatin is a significant multifunctional biopolymer that is widely utilized as a component in food, pharmaceuticals, and cosmetics. Numerous functional qualities are displayed by gelatin, such as its exceptional film-forming ability, gelling qualities, foaming and emulsifying qualities, biocompatibility and biodegradable qualities. Due to its unique structural, physicochemical, and biochemical characteristics, which enhance nutritional content and health benefits as well as the stability, consistency, and elasticity of food products, gelatin is utilized extensively in the food business. Additionally, gelatin has demonstrated excellent performance in encapsulating, delivering, and releasing active ingredients. Gelatin's various modifications, such as chemical, enzymatic, and physical processes, were analyzed to assess their impact on gelatin structures and characteristics. Hopefully, gelatin will be more widely used in various applications after modification using suitable methods.

Preparation and characterization of vitamin E microcapsules stabilized by Zein with different polysaccharides

Vitamin E (VE) microencapsulation using a green surfactant emulsifier not only protects the active substance and is also environmentally friendly. In this study, we used alcohol ether glycoside as an emulsifier to prepare VE microcapsules using the biological macromolecule Zein and various polysaccharides. The resulting nano microcapsules exhibited a spherical structure, stable morphology, uniform size, and a >90% encapsulation efficiency. They also had good thermal stability and slow-release properties. Of these, xanthan gum/Zein-VE microcapsules were superior, with antioxidant properties up to 3.05-fold higher than untreated VE. We successfully developed VE nano microcapsules that meet eco-friendly and sustainable requirements, which may have applications in the food and pharmaceutical industries.

Advances in protein-based microcapsules and their applications: A review

Due to their excellent emulsification, biocompatibility, and biological activity, proteins are widely used as microcapsule wall materials for encapsulating drugs, natural bioactive substances, essential oils, probiotics, etc. In this review, we summarize the protein-based microcapsules, discussing the types of proteins utilized in microcapsule wall materials, the preparation process, and the main factors that influence their properties. Additionally, we conclude with examples of the vital role of protein-based microcapsules in advancing the food industry from primary processing to deep processing and their potential applications in the biomedical, chemical, and textile industries. However, the low stability and controllability of protein wall materials lead to degraded performance and quality of microcapsules. Protein complexes with polysaccharides or modifications to proteins are often used to improve the thermal instability, pH sensitivity, encapsulation efficiency and antioxidant capacity of microcapsules. In addition, factors such as wall material composition, wall material ratio, the ratio of core to wall material, pH, and preparation method all play critical roles in the preparation and performance of microcapsules. The application area and scope of protein-based microcapsules can be further expanded by optimizing the preparation process and studying the microcapsule release mechanism and control strategy.

Preparation and characterization of active films based on oregano essential oil microcapsules/soybean protein isolate/sodium carboxymethyl cellulose

This study aimed to prepare oregano essential oil microcapsules (EOMs) by the active coalescence method using gelatin and sodium alginate as wall materials and oregano essential oil (OEO) as the core material. EOMs were added to the soybean protein isolate (SPI)/sodium carboxymethyl cellulose (CMC) matrix to prepare SPI-CMC-EOM active films, and the physical and chemical features of the active films and EOMs were characterized. The results showed that the microencapsulated OEO could protect its active ingredients. Scanning electron microscopy results showed that EOMs were highly compatible with the film matrix. The solubility of active films decreased upon adding EOMs, and their ultraviolet resistance and thermal stability also improved. When the added amount of EOMs was 5 %, the active films had the best mechanical properties and the lowest water vapor permeability. The active films prepared under this condition had excellent comprehensive performance. Also, adding EOMs considerably enhanced the antioxidant of the active films and endowed them with antibacterial properties. The application of the SPI-CMC-EOM films to A. bisporus effectively delayed senescence and maintained the freshness of the postharvest A. bisporus. This study provided a theoretical foundation for the incorporation of EOMs into active films based on biological materials.

Preparation, physicochemical characterization and swelling properties of composite hydrogel microparticles based on gelatin and pectins with different structure

Composite hydrogel microparticles based on pectins with different structures (callus culture pectin (SVC) and apple pectin (AU)) and gelatin were developed. Hydrogel microparticles were formed by the ionotropic gelation and electrostatic interaction of COO- groups of pectin and NH3+ groups of gelatin, which was confirmed by FTIR spectroscopy. The addition of gelatin to pectin-based gel formulations resulted in a decrease in gel strength, whereas increasing gelatin concentration enhanced this effect. The microparticle gel strength increased in proportion to the increase in the pectin concentration. The DSC and TGA analyzes showed that pectin-gelatin gels had the higher thermal stability than individual pectins. The gel strength, Ca2+ content and thermal stability of the microparticles based on gelatin and SVC pectin with a lower degree of methylesterification (DM) (14.8 %) were higher compared to that of microparticles based on gelatin and AU pectin with a higher DM (40 %). An increase in the SVC concentration, Ca2+ content and gel strength of SVC-gelatin microparticles led to a decrease in the swelling degree in simulated gastrointestinal fluids. The addition of 0.5 % gelatin to gels based on AU pectin resulted in increased stability of the microparticles in gastrointestinal fluids, while the microparticles from AU without gelatin were destroyed.