Functional Biopolymer Particles: Design, Fabrication, and Applications

Is nano safe in foods? Establishing the factors impacting the gastrointestinal fate and toxicity of organic and inorganic food-grade nanoparticles

Nanotechnology offers the food industry a number of new approaches for improving the quality, shelf life, safety, and healthiness of foods. Nevertheless, there is concern from consumers, regulatory agencies, and the food industry about potential adverse effects (toxicity) associated with the application of nanotechnology in foods. In particular, there is concern about the direct incorporation of engineered nanoparticles into foods, such as those used as delivery systems for colors, flavors, preservatives, nutrients, and nutraceuticals, or those used to modify the optical, rheological, or flow properties of foods or food packaging. This review article summarizes the application of both inorganic (silver, iron oxide, titanium dioxide, silicon dioxide, and zinc oxide) and organic (lipid, protein, and carbohydrate) nanoparticles in foods, highlights the most important nanoparticle characteristics that influence their behavior, discusses the importance of food matrix and gastrointestinal tract effects on nanoparticle properties, emphasizes potential toxicity mechanisms of different food-grade nanoparticles, and stresses important areas where research is still needed. The authors note that nanoparticles are already present in many natural and processed foods, and that new kinds of nanoparticles may be utilized as functional ingredients by the food industry in the future. Many of these nanoparticles are unlikely to have adverse affects on human health, but there is evidence that some of them could have harmful effects and that future studies are required.

Complex coacervation between lysozyme and pectin: Effect of pH, salt, and biopolymer ratio

The complexation between lysozyme and pectin was studied by acidification using zeta potential, turbidity measurements and calorimetry titration. The complexes were analyzed in various NaCl concentrations with different ratios. At ratio 1:1 with 0.01M NaCl, is worth mentioning that the insoluble complexes were formed between pH 2.0 and 7.0, which represents a great range to apply this complex to different food matrices. When the ratio was increased from 1:1 to 3:1, the pH range between the pH_φ1 and pH_φ2 increased even more. When the NaCl concentration was increased from 0.01M to 0.2M, a progressive reduction of turbidity was observed. At 0.4M NaCl, there was total suppression of complex formation at ratio ≤ 3:1. The process of complex coacervate formation occurred in two different steps, presenting favorable enthalpic as well as entropic contributions. The positive entropy change is a strong indication that water molecules have been released from the complex surface, however the positive sign of TΔS suggests that hydrophobic interactions were involved in the interaction between lysozyme and pectin. Microscopy images of the samples revealed that the complexes presented a spheroid-like appearance which may contribute to possible future applications.

Heteroprotein complex coacervates of ovalbumin and lysozyme: Formation and thermodynamic characterization

The formation of heteroprotein coacervates obtained by the interaction of ovalbumin (Ova) and lysozyme (Lys) was investigated using turbidimetric analysis and the zeta potential at different protein ratios, pH values and concentrations of NaCl. The complexes were formed over a wide pH range with a 1:1 (Ova:Lys) ratio and the highest turbidity was observed at pH 7.5, which optimal biopolymer interactions occurring. The addition of NaCl disfavored formation, even at low concentrations, and suppressed it at 300mM. The complex coacervate formation occurred in the region between the isoelectric points (pI) of the proteins, predominantly by electrostatic interactions but with participation of hydrogen bonds. The structures formed had an average size of ∼2μm, which was well above the isolated proteins, and microscopic analysis revealed that the complexes had a globular structure. The interaction was exothermic and spontaneous with a favorable entropic and unfavorable entropic contribution during interaction.

Relationship between processing history and functionality recovery after rehydration of dried cellulose-based suspensions: A critical review

Cellulose-based suspensions have raised more and more attention due to their broad range of properties that can be used in paper industry and material science but also in medicine, nanotechnology and food science. Their final functionality is largely dependent on their processing history and notably the structural modifications that occur during drying and rehydration. The purpose of this work is to make a state-of-the-art contribution to the mechanisms involved in the process-structure-function relationships of cellulose-based hydrogels. The different assumptions that exist in the literature are reviewed taking the key role of the initial sample characteristics as well as the processing conditions into consideration. The decrease in swelling ability after drying is clearly due to an overall shrinkage of the structure of the material. At microscale, pore closure and cellulosic fibril aggregation are mentioned as the main reasons. The origins of such irreversible structural modifications take place at molecular level and is mainly explained by the establishment of a new balance of interactions between all components. Nevertheless, the respective contribution of each interaction are still under investigation.

Effect of crosslinking on the physical and chemical properties of β-lactoglobulin (Blg) microgels

HYPOTHESIS

Microgels assembled from the protein β-lactoglobulin are colloidal structures with potential applications in food materials. Modifying the internal crosslinking within these microgels using enzymatic or chemical treatments should affect dissolution, swelling, and viscous attributes under strongly solvating conditions.

EXPERIMENTS

Microgels were treated with citric acid, glutaraldehyde and transglutaminase to induce cross-linking or with tris(2-carboxyethyl)phosphine to reduce disulfide linkages. Change in hydrodynamic particle size due to acidic pH, alkaline pH, ionic strength, osmolyte concentration, ethanol, urea, sodium dodecyl sulfate, and reducing agents was evaluated by light scattering measurements. Changes in microgel nanomechanical properties were evaluated via force spectroscopic measurements in water.

FINDINGS

Average microgel size increased ∼20% in alkaline pH and with ethanol contents above 10%, and decreased ∼20% with sucrose contents above 10%. Cross-linking by glutaraldehyde and transglutaminase prevented size increases in alkaline pH. Microgel plasticity and elastic modulus were unaffected by treatments. Microgels treated with glutaraldehyde were found to have much greater stability to urea, sodium dodecyl sulfate, and reducing agents when compared to other samples. Even without cross-linking, microgels remained stable against precipitation and dissolution over a wide range conditions, indicating their broad utility as colloidal stabilizers, texture modifiers or controlled release agents in food or other applications.

Impact of Chitosan Molecular Weight and Attached Non-Interactive Chains on the Formation of α-Lactalbumin Nanogel Particles

Thermal treatment of protein⁻polysaccharide complexes will form nanogel particles, wherein the polysaccharide controls nanogel formation by limiting protein aggregation. To determine the impact of the chitosan molecular weight and non-interactive chains on the formation of nanogels, mixtures of α-lactalbumin were prepared with selectively-hydrolyzed chitosan containing covalently-attached polyethylene glycol chains (PEG) and heated near the protein's isoelectric point to induce formation of nanogels. Turbidity of heated mixtures indicated the formation of suspended aggregates, with greater values observed at higher pH, without attached PEG, and among samples with 8.9 kDa chitosan. Mixtures containing 113 kDa chitosan-PEG formed precipitating aggregates above pH 5, coinciding with a low-magnitude colloidal charge and average hydrodynamic radii > 400 nm. All other tested mixtures were stable to precipitation and possessed average hydrodynamic radii ~100 nm, with atomic force microscopy showing homogeneous distributions of spherical nanogel aggregates. Over all of the tested conditions, attached PEG led to no additional significant changes in the size or morphology of nanogels formed from the protein and chitosan. While PEG may have interfered with the interactions between protein and the 113 kDa chitosan, prompting greater aggregation and precipitation, PEG did not indicate any such interference for shorter chitosan chains.

Nanotechnology Approaches for Increasing Nutrient Bioavailability

Health-promoting ingredients such as phenolic compounds, vitamins, and minerals are being increasingly introduced into foods and beverages to produce "functional foods" specifically designed to improve human health, well-being, and performance. However, it is often challenging to incorporate these nutraceuticals into foods because they have poor solubility characteristics, impart undesirable flavor profiles, are chemically unstable, or have low bioavailability. This problem can often be overcome by encapsulating the bioactive components in nanoparticle-based delivery systems. The bioavailability of encapsulated bioactive agents often increases when the size of the particles containing them decreases, due to their faster digestion, ability to penetrate the mucus layer, or direct uptake by cells. Nanoparticles can be formulated to survive passage through specific regions of the gastrointestinal tract and then release their payload at a specified point, thus maximizing their potential health benefits. Nutraceutical-loaded nanoparticles can be fabricated through lipid formulations, natural nanocarriers, specialized equipment, biopolymer nanoparticles, and miscellaneous techniques. Classification into these five groups is based on the main mechanism or ingredient used to fabricate the nanoparticles. This chapter focuses on the utilization of food-grade nanoparticles for improving the performance of nutraceuticals in functional foods and beverages.

Mixing behaviour of WPI–pectin-complexes in meat dispersions: impact of biopolymer ratios

Particulated complexes composed of oppositely charged biopolymers were incorporated into highly concentrated protein matrices as potential fat replacers and structuring agents.

Application of response surface methodology and spectroscopic approach for investigating of curcumin nanoencapsulation using natural biopolymers and nonionic surfactant

This study aimed at encapsulation of poor water-soluble curcumin so that it could be utilized in various food products as a functional ingredient. Biopolymer nanoparticles were assembled from sodium caseinate and gum arabic using electrostatic complexation in the presence of nonionic surfactant Tween 20. Fourier transform infrared spectroscopy was used to investigate the interactions of curcumin with protein, polysaccharide and surfactant. The effects of sodium caseinate (A), gum arabic (B), Tween 20 (C) and pH (D) on responses were studied using a three-level four-factor Box-Behnken design. For each response, a second-order polynomial model was developed. For optimum nanoencapsulation of curcumin, the variables concentration of sodium caseinate, concentration of gum arabic, pH and concentration of Tween 20 were 0.21, 0.5, 5 and 0.14 wt% respectively. The particles were characterized by ζ-potential measurement. Spectroscopic results and data modelling, showed interaction of curcumin with sodium caseinate, gum arabic and Tween 20. Also, the nonionic surfactant Tween 20, influenced the electrostatic interaction between sodium caseinate and gum arabic.

Organic Nanoparticles in Foods: Fabrication, Characterization, and Utilization

In the context of food systems, organic nanoparticles (ONPs) are fabricated from proteins, carbohydrates, lipids, and other organic compounds to a characteristic dimension, such as a radius smaller than 100 nm. ONPs can be fabricated with bottom-up and top-down approaches, or a combination of both, on the basis of the physicochemical properties of the source materials and the fundamental principles of physical chemistry, colloidal and polymer sciences, and materials science and engineering. ONPs are characterized for dimension, morphology, surface properties, internal structures, and biological properties to understand structure-function correlations and to explore their applications. These potential applications include modifying physical properties, improving sensory attributes and food quality, protecting labile compounds, and delivering encapsulated bioactive compounds for improved bioactivity and bioavailability. Because ONPs can have digestion and absorption properties different from conventional materials, the eventual applications of ONPs require in vitro and in vivo studies to guide the development of safe food products that utilize the unique functionalities of ONPs.

Nanoscale Nutrient Delivery Systems for Food Applications: Improving Bioactive Dispersibility, Stability, and Bioavailability

There has been a surge of interest in the development of nanoscale systems for the encapsulation, protection, and delivery of lipophilic nutrients, vitamins, and nutraceuticals. This review article highlights the challenges associated with incorporating these lipophilic bioactive components into foods, and then discusses potential nanoscale delivery systems that can be used to overcome these challenges. In particular, the desirable characteristics required for any nanoscale delivery system are presented, as well as methods of fabricating them and of characterizing them. An overview of different delivery systems is given, such as microemulsions, nanoemulsions, emulsions, microgels, and biopolymer nanoparticles, and their potential applications are discussed. Nanoscale delivery systems have considerable potential within the food industry, but they must be carefully formulated to ensure that they are safe, economically viable, and effective.

PRACTICAL APPLICATION

Nanoscale delivery systems have numerous potential applications in the food industry for encapsulating, protecting, and releasing bioactive agents, such as nutraceuticals and vitamins. This review article highlights methods for designing, fabricating, characterizing, and utilizing edible nanoparticles from a variety of different food-grade ingredients.

Reduced-fat foods: the complex science of developing diet-based strategies for tackling overweight and obesity

Fat plays multiple roles in determining the desirable physicochemical properties, sensory attributes, nutritional profile, and biologic response of food products. Overconsumption of fats is linked to chronic diseases, such as obesity, coronary heart disease, diabetes, and cancer. There is therefore a need to develop reduced-fat products with physicochemical properties and sensory profiles that match those of their full-fat counterparts. In addition, foods may be redesigned to increase the feelings of satiety and satiation, and thereby reduce overall food intake. The successful design of these types of functional foods requires a good understanding of the numerous roles that fat plays in determining food attributes and the development of effective strategies to replace these attributes. This article provides an overview of the current understanding of the influence of fat on the physicochemical and physiologic attributes of emulsion-based food products and highlights approaches to create high-quality foods with reduced-fat contents.

Encapsulation, protection, and release of hydrophilic active components: potential and limitations of colloidal delivery systems

There have been major advances in the development of edible colloidal delivery systems for hydrophobic bioactives in recent years. However, there are still many challenges associated with the development of effective delivery systems for hydrophilic bioactives. This review highlights the major challenges associated with developing colloidal delivery systems for hydrophilic bioactive components that can be utilized in foods, pharmaceuticals, and other products intended for oral ingestion. Special emphasis is given to the fundamental physicochemical phenomena associated with encapsulation, stabilization, and release of these bioactive components, such as solubility, partitioning, barriers, and mass transport processes. Delivery systems suitable for encapsulating hydrophilic bioactive components are then reviewed, including liposomes, multiple emulsions, solid fat particles, multiple emulsions, biopolymer particles, cubosomes, and biologically-derived systems. The advantages and limitations of each of these delivery systems are highlighted. This information should facilitate the rational selection of the most appropriate colloidal delivery systems for particular applications in the food and other industries.

Stable and pH-sensitive protein nanogels made by self-assembly of heat denatured soy protein

In this study, we examined the possibility of preparing stable soy protein nanogels by simply heating homogeneous soy protein dispersion. The protein nanogels formed were characterized by z-average hydrodynamic diameter, polydispersity index, turbidity, ζ-potential, morphology, and their stability to pH and ionic strength change. Soy protein dispersion (1% w/v) was homogeneous around pH 5.9 where it had the lowest polydispersity index (∼0.1). Stable and spherical nanogels were formed by heating soy protein dispersion at pH 5.9 under 95 °C. They sustained constantly low polydispersity index (∼0.1) in the investigated pH range of 6.06-7.0 and 2.6-3.0. The nanogels were pH-sensitive and would swell with pH change. They were stable at 0-200 mM NaCl concentration. Denaturation of soy glycinin was the prerequisite for the formation of stable nanogels. Soy protein nanogels had a core-shell structure with basic polypeptides and β subunits interacting together as the hydrophobic core; and acid polypeptides, α', and α subunits locating outside the core as hydrophilic shell. The inner structure of soy protein nanogels was mainly stabilized by disulfide bonds cross-linked network and hydrophobic interaction. Soy protein nanogels made in this study would be useful as functional ingredients in biotechnological, pharmaceutical, and food industries.

Changes in protein conformation and surface hydrophobicity upon peroxidase-catalyzed cross-linking of apo-α-lactalbumin

In this study, we explore the effect of peroxidase-catalyzed cross-linking on the molecular conformation of apo-α-lactalbumin (apo-α-LA) and the resulting changes in protein surface hydrophobicity. In studying conformational changes, we distinguish between early stages of the reaction ("partial cross-linking"), in which only protein oligomers (10(6) Da > Mw ≥ 10(4) Da) are formed, and a later stage ("full cross-linking"), in which larger protein particles (Mw ≥ 10(6) Da) are formed. Partial cross-linking induces a moderate loss of α-helical content. Surprisingly, further cross-linking leads to a partial return of α-helices that are lost upon early cross-linking. At the same time, for partially and fully cross-linked apo-α-LA, almost all tertiary structure is lost. The protein surface hydrophobicity first increases for partial cross-linking, but then decreases again at full cross-linking. Our results highlight the subtle changes in protein conformation and surface hydrophobicity of apo-α-LA upon peroxidase-catalyzed cross-linking.