Fibrillization of whey proteins improves foaming capacity and foam stability at low protein concentrations

Fabrication of bovine serum albumin nanofibrils: Physicochemical characteristics, emulsifying and foaming activities

Bovine serum albumin nanofibrils (BSNs) were fabricated under thermal treatment (85 °C) at acidic condition (pH 2.0) and the incubation time on the structural, and physicochemical characteristics were probed. The formation and development of BSNs have been detected and confirmed by Thioflavin T (ThT) fluorescence and circular dichroism (CD) measurements. The structural alterations of bovine serum albumin (BSA) have also been investigated using intrinsic fluorescence and Congo red (CGR) UV-vis spectroscopy. Atomic force microscopy (AFM) outcomes displayed the morphologies of BSNs at varied time, with a diameter of about 3 nm and a contour length of about 200 nm at 24 h. The apparent viscosities of BSNs at three different pH were in the following order: pH 3.0 > pH 5.0 > pH 7.0. Emulsifying and foaming properties of BSA were pronouncedly enhanced through fibrillation, which was highly correlated with the interfacial properties and structural characteristics. Highest EAI 54.2 m2/g was attained at 48 h and no pronounced alterations were observed for EAI at 24 h and 48 h. Maximum value of FC was obtained at 48 h for BSA. This study will provide some useful information in understanding the formation of BSNs and broaden their application in food systems as functional food ingredients.

Process optimization and characterization of hydrolysate from underutilized brown macroalgae (Padina tetrastromatica) after fucoidan extraction through subcritical water hydrolysis

The growing demand for macroalgal biomass as a source of proteins, peptides, and amino acids is garnering attention for their biological and functional properties. This study depicts the use of emerging green techniques, i.e. subcritical water, to hydrolyze protein from Padina tetrastromatica. The biomass was treated with subcritical water at varying temperatures between 100 and 220 °C for 10-40 min at a biomass to water proportion of 1:50 (w/v) and pressure of 4.0 MPa. The optimum conditions for recovering the maximum protein (127.2 ± 1.1 mg g-1), free amino acids (58.4 ± 1.0 mg g-1), highest degree of hydrolysis (58.8 ± 1.2 %) and low molecular weight peptides (<650 Da) were found to be 220 °C for 10 min. The amino acid profiling of the hydrolysate revealed that it contains 45 % essential amino acids, with the highest concentration of methionine (0.18 %), isoleucine (0.12 %) and leucine (0.10 %). It was found that the hydrolysate contains phenolics (23.9 ± 1.4 mg GAE g-1) and flavonoids (1.23 ± 0.1 mg QE g-1), which are largely responsible for antioxidant activity. The hydrolysate effectively inhibits acetylcholinesterase and α-amylase in vitro, with IC50 values of 17.9 ± 0.1 mg mL-1 and 16.0 ± 0.5 %, respectively, which can help prevent Alzheimer's disease and diabetes mellitus. Consequently, this study reveals that utilizing eco-friendly subcritical water hydrolysis method, 79 % of the protein was recovered from P. tetrastromatica, which might be an effective source of bioactive peptides in various nutraceutical, pharmaceutical and cosmeceutical applications.

An overview of edible foams in food and modern cuisine: Destabilization and stabilization mechanisms and applications

Foam, as a structured multi-scale colloidal system, is becoming increasingly popular in food because it gives a series of unique textures, structures, and appearances to foods while maintaining clean labels. Recently, developing green and healthy food-grade foaming agents, improving the stability of edible foams, and exploring the application of foam structures and new foaming agents have been the focus of foam systems. This review comprehensively introduces the destabilization mechanisms of foam and summarizes the main mechanisms controlling the foam stability and progress of different food-grade materials (small-molecular surfactants, biopolymers, and edible Pickering particles). Furthermore, the classic foam systems in food and modern cuisine, their applications, developments, and challenges are also underlined. Natural small-molecular surfactants, novel plant/microalgae proteins, and edible colloidal particles are the research hotspots of high-efficiency food-grade foam stabilizers. They have apparent differences in foam stability mechanisms, and each exerts its advantages. However, the development of foam stabilizers remains to be enriched compared with emulsions. Food foams are diverse and widely used, bringing unique enjoyment and benefit to consumers regarding sense, innovation, and health attributes. In addition to industrial inflatable foods, the foam foods in molecular gastronomy are also worthy of exploration. Moreover, edible foams may have greater potential in structured food design, 3D/4D printing, and controlled flavor release in the future. This review will provide a reference for the efficient development of functional inflatable foods and the advancement of foam technologies in modern cuisine.

Production and functional evaluation of nonfat dry milk with whey proteins as fibrils

Commercial manufacturing of dairy products involves the addition of dairy ingredients (such as nonfat dry milk and milk protein concentrates), as well as nondairy additives (such as gums, stabilizers, emulsifiers, and texture modifiers) to get the best product appearance, maintain the product quality, and extend shelf life. Though these nondairy additives are not harmful, consumers do not prefer them in dairy food formulations. Therefore, the dairy industry is working on improving the inherent functionality of dairy ingredients using different processes. Recently, fibrillation emerged as a new technique to convert globular proteins such as whey proteins into fibrils, which provide enhanced viscosity, foaming, and emulsification capacity. Therefore, skim milk was subjected to microfiltration followed by ultrafiltration of microfiltration permeate to fractionate whey proteins. Then, whey proteins were selectively fibrillated and mixed back with other streams of microfiltration and ultrafiltration to get fibrillated skim milk. Fibrillated skim milk was spray-dried to get fibrillated nonfat dry milk (NDM). Visible whey protein fibrils were observed in reconstituted fibrillated NDM, which showed survival of fibrils in fibrillated NDM. Fibrillated NDM showed significantly higher viscosity than control NDM. Fibrillated NDM also showed higher emulsification capacity, foaming capacity, and stability than the control NDM but lower gel strength. Considering the improved functionality of fibrillated NDM, they can be used in product formulations such as ice cream mix, where the thickening of a solution, good emulsification, and foaming properties are required.

Fabrication mechanism and functional properties of ovalbumin fibrils prepared by acidic heat treatment

BACKGROUND

Ovalbumin (OVA), accounting for 50% of proteins in egg white, is a kind of high-quality protein with excellent nutritional and processing functions. Acid heat treatment will induce the deformation and filtration of OVA, endowing it with improved functionality. However, the molecular kinetic process during the fibrillation of OVA and the application of the fabricated OVA fibrils (OVAFs) have not been thoroughly studied and revealed.

RESULTS

In this study, the fabrication mechanism and the application OVAFs as an interfacial stabilizer and polyphenol protector were investigated. Acidic (pH 3.0) heat treatment was used to induce the fibrillation of OVA, and thioflavin T fluorescence intensity, molecular weight distribution, and the tertiary and secondary structures of OVAF samples were recorded to determine the fibrillation efficiency and the molecular mechanism. The results showed that, in the initial stage of fibrillation, OVA first hydrolyzed to oligopeptides, accompanied by the exposure of hydrophobic domains. Then, oligopeptides were connected by disulfide bonds to form primary fibril monomers. Hydrophobic interaction and hydrogen bonding may participate in the further polymerization of the fibrils. The fabricated OVAFs were characterized by a β-sheet-rich structure and possessed improved emulsifying, foaming, and polyphenol protection ability.

CONCLUSION

The research work was meaningful for exploring the application of globular water-soluble OVA in an emerging nutritious food with novel texture and sensory properties. © 2023 Society of Chemical Industry.

Dynamic Surface Properties of α-Lactalbumin Fibril Dispersions

The dynamic surface properties of aqueous dispersions of α-lactalbumin (ALA) amyloid fibrils differ noticeably from the properties of the fibril dispersions of other globular proteins. As a result, the protocol of the application of ALA fibrils to form stable foams and emulsions has to be deviate from that of other protein fibrils. Unlike the fibrils of β-lactoglobulin and lysozyme, ALA fibrils can be easily purified from hydrolyzed peptides and native protein molecules. The application of the oscillating barrier method shows that the dynamic surface elasticity of ALA fibril dispersions exceeds the surface elasticity of native protein solutions at pH 2. ALA fibrils proved to be stable at this pH, but the stability breaks at higher pH levels when the fibrils start to release small peptides of high surface activity. As a result, the dynamic surface properties of ALA coincide with those of native protein solutions. The ionic strength strongly influences the adsorption kinetics of both fibril dispersions and native protein solutions but have almost no impact on the structure of the adsorption layers.

Nordic Crops as Alternatives to Soy-An Overview of Nutritional, Sensory, and Functional Properties

Soy (Glycine max) is used in a wide range of products and plays a major role in replacing animal-based products. Since the cultivation of soy is limited by cold climates, this review assessed the nutritional, sensory, and functional properties of three alternative cold-tolerant crops (faba bean (Vicia faba), yellow pea (Pisum sativum), and oat (Avena sativa)). Lower protein quality compared with soy and the presence of anti-nutrients are nutritional problems with all three crops, but different methods to adjust for these problems are available. Off-flavors in all pulses, including soy, and in cereals impair the sensory properties of the resulting food products, and few mitigation methods are successful. The functional properties of faba bean, pea, and oat are comparable to those of soy, which makes them usable for 3D printing, gelation, emulsification, and extrusion. Enzymatic treatment, fermentation, and fibrillation can be applied to improve the nutritional value, sensory attributes, and functional properties of all the three crops assessed, making them suitable for replacing soy in a broad range of products, although more research is needed on all attributes.

Fibrillation modification to improve the viscosity, emulsifying, and foaming properties of rice protein

Fibrillation of food proteins has attracted considerable attention as it can improve and broaden the functionality of proteins. In this study, we prepared three kinds of rice protein (RP) fibrils with different structural characteristics by the regulation of NaCl and explored the effect of protein structure on viscosity, emulsifying, and foaming properties. AFM results showed fibrils formed at 0 and 100 mM NaCl were mainly in the range of 50-150 nm and 150-250 nm, respectively. Fibrils formed at 200 mM NaCl were in the range of 50-500 nm and protein fibrils longer than 500 nm increased. There was no significant difference between their height and periodicity. Fibrils formed at 0 and 100 mM NaCl were more flexible and unordered than those formed at 200 mM NaCl. The viscosity consistency index K of native RP and fibrils formed at 0, 100, and 200 mM NaCl were determined. The K value of fibrils was higher than that of native RP. The emulsifying activity index, foam capacity and foam stability were enhanced by fibrillation, while longer fibrils exhibited lower emulsifying stability index, which may be because long fibrils resulted in difficulty of cover of emulsion droplets. In summary, our work provided a valuable reference for improving the functionality of rice protein and facilitated the development of protein-based foaming agents, thickeners, and emulsifiers.

Protein Nanofibrils from Fava Bean and Its Major Storage Proteins: Formation and Ability to Generate and Stabilise Foams

Protein nanofibrils (PNFs) have potential for use in food applications as texture inducers. This study investigated the formation of PNFs from protein extracted from whole fava bean and from its two major storage proteins, globulin fractions 11S and 7S. PNFs were formed by heating (85 °C) the proteins under acidic conditions (pH 2) for 24 h. Thioflavin T fluorescence and atomic force microscopy techniques were used to investigate PNF formation. The foaming properties (capacity, stability, and half-life) were explored for non-fibrillated and fibrillated protein from fava bean, 11S, and 7S to investigate the texturing ability of PNFs at concentrations of 1 and 10 mg/mL and pH 7. The results showed that all three heat-incubated proteins (fava bean, 11S, and 7S) formed straight semi-flexible PNFs. Some differences in the capacity to form PNFs were observed between the two globulin fractions, with the smaller 7S protein being superior to 11S. The fibrillated protein from fava bean, 11S, and 7S generated more voluminous and more stable foams at 10 mg/mL than the corresponding non-fibrillated protein. However, this ability for fibrillated proteins to improve the foam properties seemed to be concentration-dependent, as at 1 mg/mL, the foams were less stable than those made from the non-fibrillated protein.

Effects of ultrasound pretreatment on functional property, antioxidant activity, and digestibility of soy protein isolate nanofibrils

Nanofibrils, an effective method to modulate the functional properties of proteins, can be promoted by ultrasound pretreatment. This study investigated the effect of ultrasound pretreatment on the structure, functional property, antioxidant activity and digestibility of soy protein isolate (SPI) nanofibrils. The results showed that high amplitude ultrasound had a significant effect on structure of SPI nanofibrils. SPI nanofibrils pretreated by 80% amplitude ultrasound showed a blueshift of the amide II band in Fourier transform infrared spectroscopy (FTIR), resulted in more tryptophan residues being buried and increased the crystallinity. Low amplitude ultrasound (20%) pretreatment significantly improved the solubility, emulsifying activity index (EAI) and water absorption capacity (WAC) of SPI nanofibrils, but 80% amplitude ultrasound pretreatment of SPI nanofibrils reduced emulsifying stability index (ESI). High amplitude ultrasound (60% and 80%) pretreatment of SPI nanofibrils improved the foaming capacity and foaming stability and decreased denaturation temperature. DPPH radical scavenging activity of SPI nanofibrils were significantly improved by ultrasound pretreatment. 20% amplitude ultrasound pretreatment improved DPPH, ABTS radical scavenging activity and ferric reducing antioxidant power of SPI nanofibrils. The digestion rate of 80% amplitude ultrasound-pretreated nanofibrils were consistently higher, and SPI nanofibrils pretreated by ultrasound were more fragmented and shorter after simulating gastrointestinal digestion. This study would expand the application of food-grade protein nanofibrils in the food industry.

Spread Layers of Lysozyme Microgel at Liquid Surface

The spread layers of lysozyme (LYS) microgel particles were studied by surface dilational rheology, infrared reflection–absorption spectra, Brewster angle microscopy, atomic force microscopy, and scanning electron microscopy. It is shown that the properties of LYS microgel layers differ significantly from those of ß-lactoglobulin (BLG) microgel layers. In the latter case, the spread protein layer is mainly a monolayer, and the interactions between particles lead to the increase in the dynamic surface elasticity by up to 140 mN/m. In contrast, the dynamic elasticity of the LYS microgel layer does not exceed the values for pure protein layers. The compression isotherms also do not exhibit specific features of the layer collapse that are characteristic for the layers of BLG aggregates. LYS aggregates form trough three-dimensional clusters directly during the spreading process, and protein spherulites do not spread further along the interface. As a result, the liquid surface contains large, almost empty regions and some patches of high local concentration of the microgel particles.

Effect of Fibril Entanglement on Pickering Emulsions Stabilized by Whey Protein Fibrils for Nobiletin Delivery

The aim of the study was to investigate the effects of whey protein isolate (WPI) fibrils entanglement on the stability and loading capacity of WPI fibrils-stabilized Pickering emulsion. The results of rheology and small-angle X-ray scattering (SAXS) showed the overlap concentration (C*) of WPI fibrils was around 0.5 wt.%. When the concentration was higher than C*, the fibrils became compact and entangled in solution due to a small cross-sectional radius of gyration value (1.18 nm). The interfacial behavior was evaluated by interfacial adsorption and confocal laser scanning microscopy (CLSM). As the fibril concentration increased from 0.1 wt.% to 1.25 wt.%, faster adsorption kinetics (from 0.13 to 0.21) and lower interfacial tension (from 11.85 mN/m to 10.34 mN/m) were achieved. CLSM results showed that WPI fibrils can effectively absorb on the surface of oil droplets. Finally, the microstructure and in vitro lipolysis were used to evaluate the effect of fibrils entanglement on the stability of emulsion and bioaccessibility of nobiletin. At C* concentration, WPI fibrils-stabilized Pickering emulsions exhibited excellent long-term stability and were also stable at various pHs (2.0–7.0) and ionic strengths (0–200 mM). WPI fibrils-stabilized Pickering emulsions after loading nobiletin remained stable, and in vitro digestion showed that these Pickering emulsions could significantly improve the extent of lipolysis (from 36% to 49%) and nobiletin bioaccessibility (21.9% to 62.5%). This study could provide new insight into the fabrication of food-grade Pickering emulsion with good nutraceutical protection.

Plant protein-based fibers: Fabrication, characterization, and potential food applications

Proteins from plants have been considered as safer, healthier, and more sustainable resources than their animal counterparts. However, incomplete amino acid composition and relatively poor functionality limit their applications in foods. Structuring plant proteins to fibrous architectures enhances their physicochemical properties, which can favor various food applications. This review primarily focuses on fabrication of fibers from plant proteins via self-assembly, electrospinning, solution blow spinning, wet spinning, and high-temperature shear, as well as on several applications where such fibrous proteins assemble in quality foods. The changes of protein structure and protein-protein interactions during fiber production are discussed in detail, along with the effects of fabrication conditions and protein sources on the morphology and function of the fibers. Self-assembly requires proteolysis and subsequent peptide aggregation under specific conditions, which can be influenced by pH, salt and protein type. The spinning strategy is more scalable and produces uniformed fibers with larger length scales suitable for encapsulation, food packaging and sensor substrates. Significant progress has been made on high-temperature shear (including extrusion)-induced fibers responsible for desirable texture in meat analogues. Structuring plant proteins adds values for broadened food applications, but it remains challenging to keep processes cost-effective and environmentally friendly using food grade solvents.

Effect of selected monovalent salts on surfactant stabilized foams

Surfactant-stabilized foams have been at the centre of scientific research for over a century due to their ubiquitous applications in different industries. Many of these applications involve inorganic salts either due to their natural presence (e.g. use of seawater in froth floatation) or their addition (e.g. in cosmetics) to manipulate foam characteristics for the best outcomes. This paper provides a clear understanding of the effect of salts on surfactant-stabilized foams through a critical literature survey of this topic. Available literature shows a double effect of salts (LiCl, NaCl and KCl) on foam characteristics in the presence of surfactants. To elucidate the underlying mechanisms of the stabilizing effect of salts on foams, the effect of salts on surfactant-free thin liquid films is first discussed, followed by a discussion on the effect of salts on surfactant-stabilized foams with the focus on anionic surfactants. We discuss two distinctive salt concentrations, salt transition concentration in surfactant-free solutions and salt critical concentration in surfactant-laden systems to explain their effects. Using the available data in literature supported by dedicated experiments, we demonstrate the destabilizing effect of salts on foams at and above their critical concentrations in the presence of anionic surfactants. This effect is attributed to retarding the adsorption of the surfactant molecules at the interface due to the formation of nano and micro-scale aggregates.

Adsorption and foaming properties of edible egg yolk peptide nanoparticles: Effect of particle aggregation

The adsorption and foaming properties of an edible colloidal nanoparticle (EYPNs), self-assembled from the food-derived, amphiphilic egg yolk peptides, were investigated, with the aim of evaluating their potential as efficient particulate stabilizers for development of aqueous food foams. The influence of particle aggregation induced by the changes of environmental conditions (mainly the pH) on these properties of EYPN systems was determined. Our results showed that the EYPNs are a highly pH-responsive system, showing the pH-dependent particle aggregation behavior, which is found to strongly affect the interfacial adsorption and macroscopic foaming behaviors of systems. Compared to high pH (6.0–9.0), the EYPNs at low pH (2.0–5.0) showed higher surface activity with a lower equilibrated surface tension as well as a higher packing density of particles and particle aggregates at the interface, probably due to the reduced electrostatic adsorption barrier. Accordingly, the EYPNs at these low pH values exhibited significantly higher foamability and foam stability. The presence of large particle clusters and/or aggregates formed at low pH in the continuous phase may contribute to the foam stability of EYPNs. These results indicate that our edible peptide-based nanoparticle EYPNs can be used as a new class of Pickering-type foam stabilizer for the design of food foams with controlled material properties, which may have sustainable applications in foods, cosmetics, and personal care products.

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Edible nanoparticle EYPNs are efficient particulate stabilizers for making food foams.

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EYPNs have a pH-dependent particle aggregation behavior in aqueous solutions.

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The particle aggregation strongly affects the adsorption and foaming properties.

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The presence of particle aggregates contributes to the foam stability of EYPNs.

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The particle aggregates show higher surface activity and interfacial packing density.

Process development for a novel milk protein concentrate with whey proteins as fibrils

Milk protein concentrate (MPC) is a preferred ingredient to provide nutritional and functional benefits in various dairy and food products. Altering the protein configuration and protein-protein interactions in MPC can provide a novel functionality and may open doors for new applications. The fibrilization process converts the globular structure of whey proteins to fibrils and consequently increases viscosity and water holding capacity compared with the native protein structure. The objective of the current work was to selectively convert the whey proteins in MPC as fibrils. For this purpose, simulated control model MPC was prepared by combining solutions of micellar casein concentrate (MCC) and milk whey protein isolate (mWPI) to give casein and whey protein in an 80:20 ratio. The mWPI solution was converted to fibrils by heating at low pH, neutralized, and combined with MCC solution similar to control model MPC and termed "fibrillated model MPC." Thioflavin T fluorescence value, transmission electron microscopy, and gel electrophoresis confirmed the fibril formation and their survival after neutralization and mixing with MCC. Further, the fibrillated mWPI showed significantly higher viscosity and consistency coefficient than nonfibrillated mWPI. Similarly, fibrillated model MPC showed significantly higher viscosity and consistency coefficient compared with control model MPC. Hence, the fibrillated model MPC can be used as ingredient to increase viscosity. Heat coagulation time was found to be significantly higher for control model MPC compared with fibrillated model MPC.

Fabrication of Composite Structures of Lysozyme Fibril-Zein using Antisolvent Precipitation: Effects of Blending and pH Adjustment Sequences

Antisolvent precipitation is a widely used method to fabricate prolamin-based composites. In the present study, composite structures of lysozyme amyloid fibrils with zein proteins were fabricated using the antisolvent precipitation method by applying different blending and pH adjustment sequences. Globular prolamins were bound to the amyloid fibrils to combine their respective advantages. The dynamic light scattering showed that the composites with a characteristic stabilized behavior (43.60 ± 1.75 mV ∼ 35.20 ± 0.65 mV) were formed at pH 4.0-5.0, in which noncovalent interactions between fibril and particles occurred. Two different structures: fruit tree-like structure and beaded-like structure, were presented in AFM and TEM images due to the different pH adjustment sequences, while blending sequences had negligible effect on the morphology of the composites. A fruit tree-like entity was detected for lysozyme fibril-zein composites, where its "branches" bear zein globular particles. A beaded-like structure was observed for lysozyme fibril-zein composites, where lysozyme fibril was the thread and zein aggregates were the beads. The potential mechanism of this phenomenon can be explained as the fruit tree-like structure being primarily formed through electrostatic interactions while the beaded-like structure is mainly caused by hydrophobic interactions. The composites of fruit tree-like structures hold a more promising stability than those with beaded-like structures. The results of this research would give constructive information for the fabrication of amyloid fibril-prolamin protein composites, which may exhibit the combined advantages of each components and have potential applications in encapsulation and protection of bioactive substances and stabilizing emulsions.

Adsorption layer formation in dispersions of protein aggregates

The review discusses recent results on the adsorption of amyloid fibrils and protein microgels at liquid/fluid interfaces. The application of the shear and dilational surface rheology, atomic force microscopy and passive particle probe tracking allowed for elucidating characteristic features of the protein aggregate adsorption while some proposed hypothesis still must be examined by special methods for structural characterization. Although the distinctions of the shear surface properties of dispersions of protein aggregates from the properties of native protein solutions are higher than the corresponding distinctions of the dilational surface properties, the latter ones give a possibility to obtain new information on the formation of fibril aggregates at the water/air interface. Only the adsorption of BLG microgels and fibrils was studied in some details. The kinetic dependencies of the dynamic surface tension and dilational surface elasticity for aqueous dispersions of protein globules, protein microgels and purified fibrils are similar if the system does not contain flexible macromolecules or flexible protein fragments. In the opposite case the kinetic dependencies of the dynamic surface elasticity can be non-monotonic. The solution pH influences strongly the dynamic surface properties of the dispersions of protein aggregates indicating that the adsorption kinetics is controlled by an electrostatic adsorption barrier if the pH deviates from the isoelectric point. A special section of the review considers the possibility to apply kinetic models of nanoparticle adsorption to the adsorption of protein aggregates.

A Modern Technology Applied in Traditional Chinese Medicine: Progress and Future of the Nanotechnology in TCM

The application of nanotechnology to traditional Chinese medicine (TCM) enabled the development of Chinese medicine in the international society. The pharmacodynamics of TCM is not only depending on its chemical constituents but also related to its physical state such as particle size. Indeed, there is some new pesticide effect that appeared when the medicine was being made into nanophase. The application of nanotechnology to TCM can expand the use of a range of Chinese medicinal materials. In this review, we introduce the concept of nanometer TCM. We also review the preparation methods, advantages, and development tendency of Nano-TCM; furthermore, we analyze the problems in the process of development of Nano-TCM and put forward varies possible solutions to solve this problems, thereby providing new thought for the development of Nano-TCM.