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Chitosan (CH) is a biopolymer derived from chitin, which is the second most abundant polysaccharide in nature, after cellulose. Their functional groups -NH(2) and -OH can form intermolecular interactions with water and other molecules, enabling a variety of applications for CH. -NH(2) groups become protonated in acidic solutions, causing an increase in electrostatic repulsion between CH chains, which facilitates their dispersion in aqueous media. Aqueous solutions of acetic acid and/or acetates buffers have been used to disperse CH, but may not be adequate for technological applications, espeacially because of the strong flavor this acid confers to formulations. In this study, 0.125; 0.250; 0.500; 0.750 and 1.000 g (100 g)(−1) CH dispersions were prepared in acidic aqueous media (50 mmol L(−1)), not only with acetic (AA), but also with glycolic (GA), propionic (PA), or lactic (LA), acid aiming to evaluate the effects of biopolymer concentration and type of organic acid on: electrical conductivity, pH, density and rheological characteristics of dispersions. Moreover, ζ potential values of CH chains dispersed in these acidic aqueous media were assessed. pH, density and consistency index were influenced by the biopolymer concentration, but not by the acid type. At a given biopolymer concentration, ζ potential signs (+) and values suggested that electrostatic interactions between CH chains and counter-anions occurred, regardless of the type of the organic acid. Thus, at least from a physicochemical point of view, GA, PA or LA showed to be suitable to replace AA when preparing dispersions containing from 0.125 to 1.000 g (100 g)(−1) CH for technological purposes, such as thickening or stabilizer in formulated food products. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13197-020-04691-0) contains supplementary material, which is available to authorized users.

Combined effects of trisodium citrate (TSC), transglutaminase (Tgase) and heating were studied with relation to the mechanical properties of acid milk gels. Acidification of skimmed microfiltered milk samples was performed at 30 °C by addition of glucono – δ lactone to achieve final pH of 4.6 in 4 h. Increasing levels of TSC (0, 10 and 20 mM) were added to the samples, followed by addition of a constant level of Tgase (3 U/g of protein), and subsequent heating to 85 °C for 30 min. Prior to acidification, suspensions were analyzed in terms of amount of sedimentable material, hydration, hydrodynamic diameter (Dh) and ζ-potential (ζ) of the particles. Acid-induced gelation was studied using small deformation rheology followed by large deformation test. The water holding capacity of the gels (WHC) was performed at pH 4.6. Gels microstructure were investigated by confocal laser scanning microscopy at pH 4.6 and determination of mean pore size was performed by 2D-correlation analysis. Results showed that combined Tgase and TSC treatments had significant effect on rheological properties, WHC and gel microstructure. Higher stiffness of the gels was observed with Tgase and TSC at 10 mM, whereas a homogenous network distribution with smaller pore size was observed in the presence of Tgase and TSC at 20 mM.

Summary This study addressed the correlation between physical characteristics of double emulsions and sensory perception, as the microstructure of these systems may provide the mechanism to understanding the initial cause of the altered salty taste. Thus, double emulsions (W/O/W) were prepared using different volumes of the internal aqueous phase while maintaining the same fat and sodium contents in the evaluated systems. Polyglycerol polyricinoleate (PGPR) and tween 80 were used as hydrophobic and hydrophilic emulsifiers, respectively. After preparation, the samples were stored at 25 °C for 4 days and submitted to analysis of optical microscopy, distribution and polydispersity of the oil droplets size, electrical conductivity, rheological behaviour and sensorial analysis. It was found that the use of different emulsifier concentrations (PGPR) did not influence the physical characteristics of the emulsions with the same formulation, but emulsions with different internal aqueous phase concentrations presented different results. These distinct characteristics may have influenced sensorial perception, as the emulsion with higher internal phase concentration was considered saltier. Thus, it can be concluded that structural differences of the double emulsions can be used to decrease the sodium contents without perceivable changes in salty taste.

Combination of β-lactoglobulin (β-Lg) and lactoferrin (Lf), biomacromolecules derived from bovine whey, was used in the formation of supramolecular structures by thermal gelation technique to adjust the pH. Furthermore, the influence of the molar ratio, temperature, pH, and heating time in the formation of supramolecular structures were also studied. The characterization of the protein supramolecular structures was performed using dynamic light scattering, zeta potential measurements, molecular spectrofluorimetry, and circular dichroism spectroscopy. The thermal behavior of the pure proteins was investigated by differential scanning calorimetry. The protein denaturation temperatures were of around 85 °C for the β-Lg and around 52 °C and 85 °C (a small portion) for the Lf. The protein molar ratio of 2:1 Lf/β-Lg was used to form the structures, whose characterization showed that the best conditions of supramolecular structure formation occurred at pH 6.5 and at temperatures of 62.5 °C. In those conditions, more stable systems with reduced hydrophobic surface and average sizes between 30 and 100 nm were generated. The correlation between pH and temperature suggests that the method of preparation of the supramolecular structure affects its size during storage.

This research uses a computational fluid dynamic model to simulate motion and deformation of a dielectric drop in electrolyte solution in a microchannel. Wall charge density, the Debye-Hückel parameter and the Weber number are varied for uncharged, positively and negatively charged drop interfaces. Drop flow and deformation were analysed and the effects of charge distribution, electric field and permittivity jump were discussed. For a positively charged channel wall, negatively charged drops moved faster and positively charged drops moved slower than an uncharged drop. This effect increased for a higher We. Vortex flow was observed inside the drop. For a low surface tension, the drops were elongated due to electric forces acting on its surface with the charged drops deforming more than the uncharged one. When the permittivity component of the force was removed, the drop had a horizontal deformation that was sufficiently high to cause the negatively charged drop to break up.

Casein-based hydrogels are biocompatible, biodegradable, renewable, easy to obtain, inexpensive, and non-toxic. They exist in different physicochemical states, e.g. particle hydrogels, which can be dived in suspensions or emulsions and macro hydrogels that are gel colloid type. These biomaterials have drawn increasing attention in recent years due to their abilities to form networks of different tensile strengths and to encapsulate, protect and release biomolecules. This mini-review outlines the recent advances in casein-based hydrogel research and the uses of casein-based hydrogels as drug delivery system for both hydrophobic and hydrophilic molecules. The food and biomedical potential along with possible future uses of the casein-based hydrogels are discussed throughout the document.

Chitosan is a polysaccharide well-known for its applicability as a biocompatible, biodegradable, and non-toxic material to produce drugs excipients and food coatings. Acidic media are required to disperse chitosan, and aqueous solutions of acetic acid have been typically used for this purpose. However, this acid has several sensory drawbacks. In this study, chitosan was dispersed [0.1 g·(100 mL)−1] in aqueous media containing acetic (AA), glycolic (GA), propionic (PA), or lactic (LA) acid, at 10, 20, 30, 40, or 50 mmol·L−1. The increase of acid concentration reduced pH and viscosity of the dispersions, and |ζ potential| of dispersed particles. Conversely, it increased electrical conductivity and density of the dispersions, and hydrodynamic diameter of dispersed particles. At a given concentration, these effects were slightly more pronounced for dispersions formed with GA or LA, compared to AA or PA. FT-IR data suggested more intense attractive interactions of chitosan chains with glycolate and lactate anions, than with acetate and propionate. Chitosan chains interacted more strongly with hydroxylated acids counter-anions than with their non-hydroxylated counterparts, leading to slight quantitative changes of physicochemical properties of these systems. Then, in physicochemical terms, GA, LA or PA are suitable to replace AA when preparing aqueous chitosan dispersions for technological applications.

Herein, we used an electrospinning process to develop highly efficacious and hydrophobic coaxial nanofibers based on poly-cyclodextrin (polyCD) associated with poly(methacrylic acid) (PMAA) that combines polymeric and supramolecular features for modulating the release of the hydrophilic drug, propranolol hydrochloride (PROP). For this purpose, polyCD was synthesized and characterized, and its biocompatibility was assessed using fibroblast cytotoxicity tests. Moreover, the interactions between the guest PROP molecule and both polyCD and $\beta$CD were found to be spontaneous. Subsequently, PROP was encapsulated in uniaxial and coaxial polyCD/ PMAA nanofibers. A lower PROP burst effect (reduction of approximately 50%) and higher modulation were observed from the coaxial than from the uniaxial fibers. Thus, the coaxial nanofibers could potentially be a useful strategy for developing a controlled release system for hydrophilic molecules., Comment: 10 pages, 8 figures + Supplementary Data (4 pages, 6 figures)

Investigou-se, utilizando a técnica de espalhamento dinâmico de luz depolarizado, a relação das propriedades dinâmicas de suspensões de nanocristais de celulose (NCC) com a força G de centrifugação aplicada no processo de purificação das mesmas. Amostras contendo NCC foram preparadas por meio de hidrólise com ácido sulfúrico e centrifugadas nas intensidades de 1840, 4140, 7370, 11510 e 16580 de força G. Determinou-se os coeficientes de difusão translacionais e rotacionais e, a partir destes, calculou-se as larguras (d) e os comprimentos (L) dos NCC. Os valores de L e de d encontraram-se nas faixas de 213 ± 10 a 294 ± 14nm e de 4,4 ± 1,2 a 9,5 ± 2,0nm, respectivamente. Os resultados concordaram com os disponíveis na literatura, confirmando a aplicabilidade da técnica no estudo da dinâmica dos NCC em suspensões aquosas. Não observou-se variação significativa de L com o aumento da força G na faixa estudada. Por outro lado, houve redução de d para valores de força G acima de 7370.

Chitosan is a natural polycationic polysaccharide with several known biotechnological functionalities, but its application in food products as ingredient or additive remains nowadays unusual. Additionally, ultrasonic production of food-grade emulsions is still an open research field, so ultrasound applicability for such purpose must be evaluated case by case. In this study, chitosan was dispersed in acid aqueous media containing acetic, glycolic, propionic or lactic acid (50 mmol·L−1), then added of the emulsifier Tween 20, and finally mixed to sunflower oil, through ultrasonic homogenization (20 kHz, 500 W, 4 min), in order to prepare O/W emulsions (oil fraction = 0.25). In all studied systems, oil droplets with average hydrodynamic diameter

Chitosan, a natural, cationic polysaccharide, may be a hydrocolloid strategic to formulate acidic food products, as it can act as both bio-functional and technofunctional constituent. Typically, acetic acid is used to disperse chitosan in aqueous media, but the use of this acid is limited in food formulations due to its flavor. In this study, chitosan was firstly dispersed (0.1% m/V) in lactic acid aqueous solutions (pH 3.0, 3.5 or 4.0), and then evaluated regarding its thickener and emulsion stabilizer properties. O/W emulsions were prepared and characterized in terms of rheological properties, droplets average diameters and droplets $\zeta$-potential. Emulsions containing chitosan were 3 times more viscous than controls without chitosan, and presented storage modulus ($G'$) higher than loss modulus ($G''$). Furthermore, they displayed two different populations of droplets (average diameters of 44 and 365 nm) and positive $\zeta$-potential values (+50 mV). Droplets average diameters and $\zeta$-potential did not present significant changes ($p$ > 0.05) after storage at 25 $^{\circ}$C during 7 days. This study showed that i) food organic acids other than acetic acid can be used to disperse chitosan for technological purposes, and ii) chitosan dispersed at very low concentrations (0.1% m/V) had relevant effects on rheological and physicochemical aspects of food-grade emulsions., Comment: 10 pages (paper) + 8 pages (supplementary information). 4 figures (paper) + 2 figures (supplementary information)

Chemical or enzymatic cross-linking of casein micelles (CMs) increases their stability against dissociating agents. In this paper, a comparative study of stability between native CMs and CMs cross-linked with genipin (CMs-GP) as a function of pH is described. Stability to temperature and ethanol were investigated in the pH range 2.0-7.0. The size and the charge ($\zeta$-potential) of the particles were determined by dynamic light scattering. Native CMs precipitated below pH 5.5, CMs-GP precipitated from pH 3.5 to 4.5, whereas no precipitation was observed at pH 2.0-3.0 or pH 4.5-7.0. The isoelectric point of CMs-GP was determined to be pH 3.7. Highest stability against heat and ethanol was observed for CMs-GP at pH 2, where visible coagulation was determined only after 800 s at 140 $^\circ$C or 87.5% (v/v) of ethanol. These results confirmed the hypothesis that cross-linking by GP increased the stability of CMs., Comment: 5 pages, 2 figures, International Dairy Journal, 2016

The indiscriminate use of antibiotics and the emergence of resistant microorganisms have become a major challenge for the food industry. The purpose of this work was to microencapsulate the bacteriophage UFV-AREG1 in a calcium alginate matrix using microfluidic devices and to study the viability and efficiency of retention. The microcapsules were added to gel of propylene glycol for use as an antimicrobial in the food industry. The technique showed the number of the phage encapsulation, yielding drops with an average 100-250 $\mu$m of diameter, 82.1 $\pm$ 2% retention efficiency and stability in the gel matrix for 21 days. The gel added to the microencapsulated phage showed efficiency (not detectable on the surface) in reducing bacterial contamination on the surface at a similar level to antimicrobial chemicals (alcohol 70%). Therefore, it was possible to microencapsulate bacteriophages in alginate-Ca and apply the microcapsules in gels for use as sanitizers in the food industry., Comment: 8 pages, 5 figures

Bovine α-lactalbumin (α-La) and lysozyme (Lys), two globular proteins with highly homologous tertiary structures and opposite isoelectric points, were used to produce bio-based supramolecular structures under various pH values (3, 7 and 11), temperatures (25, 50 and 75 °C) and times (15, 25 and 35 min) of heating. Isothermal titration calorimetry experiments showed protein interactions and demonstrated that structures were obtained from the mixture of α-La/Lys in molar ratio of 0.546. Structures were characterized in terms of morphology by transmission electron microscopy (TEM) and dynamic light scattering (DLS), conformational structure by circular dichroism and intrinsic fluorescence spectroscopy and stability by DLS. Results have shown that protein conformational structure and intermolecular interactions are controlled by the physicochemical conditions applied. The increase of heating temperature led to a significant decrease in size and polydispersity (PDI) of α-La–Lys supramolecular structures, while the increase of heating time, particularly at temperatures above 50 °C, promoted a significant increase in size and PDI. At pH 7 supramolecular structures were obtained at microscale – confirmed by optical microscopy – displaying also a high PDI (i.e. > 0.4). The minimum size and PDI (61 ± 2.3 nm and 0.14 ± 0.03, respectively) were produced at pH 11 for a heating treatment of 75 °C for 15 min, thus suggesting that these conditions could be considered as critical for supramolecular structure formation. Its size and morphology were confirmed by TEM showing a well-defined spherical form. Structures at these conditions showed to be stable at least for 30 or 90 days, when stored at 25 or 4 °C, respectively. Hence, α-La–Lys supramolecular structures showed properties that indicate that they are a promising delivery system for food and pharmaceutical applications., CNPq and CAPES, and their support to FAPEMIG and CNPEM-LNBio (Centro Nacional de Pesquisa em Energia e Materiais-Laboratório Nacional de Biociências) both from Brazil. Fundação para a Ciência e a Tecnologia. The authors thank the FCT Strategic Project of UID/BIO/04469/2013 unit, COMPETE 2020 (POCI-01-0145-FEDER-006684), the project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462), and the project “BioInd - Biotechnology and Bioengineering for improved Industrial and Agro-Food processes”, REF. NORTE-07-0124-FEDER-000028 Co-funded by the Programa Operacional Regional do Norte (ON.2 – O Novo Norte), QREN, FEDER.

A new analytical expression for the size-dependent bandgap of colloidal semiconductor nanocrystals is proposed within the framework of the finite-depth square-well effective mass approximation in order to provide a quantitative description of the quantum confinement effect. This allows one to convert optical spectroscopic data (photoluminescence spectrum and absorbance edge) into accurate estimates for the particle size distributions of colloidal systems even if the traditional effective mass model is expected to fail, which occurs typically for very small particles belonging to the so-called strong confinement limit. By applying the reported theoretical methodologies to CdTe nanocrystals synthesized through wet chemical routes, size distributions are inferred and compared directly to those obtained from atomic force microscopy and transmission electron microscopy. This analysis can be used as a complementary tool for the characterization of nanocrystal samples of many other systems such as the II-VI and III-V semiconductor materials., Comment: 9 pages, 5 figures

The dynamics of swollen fractal networks (Rouse model) has been studied through computer simulations. The fluctuation-relaxation theorem was used instead of the usual Langevin approach to Brownian dynamics. We measured the equivalent of the mean square displacement $\langle \vec r^{\,2} \rangle$ and the coefficient of self-diffusion $D$ of two-and three-dimensional Sierpinski networks and of the two-dimensional percolation network. The results showed an anomalous diffusion, i. e., a power law for $D$, decreasing with time with an exponent proportional to the spectral dimension of the network.

The study of protein interactions has generated great interest in the food industry. Therefore, research on new supramolecular structures shows promise. Supramolecular structures of the whey proteins {\alpha}-lactalbumin and glycomacropeptide were produced under varying heat treatments (25 to 75 {\deg}C) and acidic conditions (pH 3.5 to 6.5). Isothermal titration calorimetry experiments showed protein interactions and demonstrated that this is an enthalpically driven process. Supramolecular protein structures in aqueous solutions were characterized by circular dichroism and intrinsic fluorescence spectroscopy. Additional photon correlation spectroscopy experiments showed that the size distribution of the structures ranged from 4 to 3545 nm among the different conditions. At higher temperatures, lower pH increased particle size. The foamability of the supramolecular protein structures was evaluated. Analysis of variance and analysis of regression for foaming properties indicated that the two-factor interactions between pH and temperature exhibited a significant effect on the volume and stability of the foam., Comment: 9 pages, 5 figures

Given ; the increasing number of antibiotic-resistant bacteria and the need to synthesize new antimicrobials, silver has attracted interest in the scientific < community because of its recognized antimicrobial activity. This study aimed to evaluate the antimicrobial effects of silver = nanoparticles obtained by a new method and tested at concentrations of 6 mg/ml and 60 mg/ml against the species Staphylococcus aureus, Listeria innocua, Salmonella Choleraesuis, Pseudomonas aeruginosa, Escherichia coli, and Bacillus cereus. The ability of these nanoparticles to remove or kill vegetative cells adhered to stainless steel surfaces was also evaluated. We observed that the silver nanoparticles (NP) obtained with the new method, concentrated nanoparticles (CNP), and silver nanoparticles with added sodium chloride (NPNaCl) had high antimicrobial activities (P , 0.05). We also verified that the most effective condition for the removal of P. aeruginosa cells on stainless steel coupons (10 by 10 mm) was immersion of the surfaces in CNP. The CNP treatment produced a 5-log reduction of the microbial population after 30 to 60 min of immersion. The CNP treatment also performed better than water and sodium carbonate, a compound commonly applied in clean-in-place procedures in the food industry, in removing adherent B. cereus cells from stainless steel cylinders. Therefore, these results suggest that silver nanoparticles synthesized by a new procedure may be used as antimicrobials in the food industry, for example, for the sanitization of utensils that come into contact with foods.

The effect of different ionic cosolutes (NaCl, Na$_2$SO$_4$, Li$_2$SO$_4$, NaSCN, Na$_2$[Fe(CN)5NO], and Na$_3$[Co(NO)$_6$]) on the interaction between sodium dodecyl sulfate (SDS) and poly(ethylene oxide) (PEO) was examined by small-angle X-ray scattering (SAXS) and isothermal titration calorimetric techniques. The critical aggregation concentration values (cac), the saturation concentration ($C_2$), the integral enthalpy change for aggregate formation ($\Delta H_{\mbox{agg}}$(int)) and the standard free energy change of micelle adsorption on the macromolecule chain ( $\Delta\Delta G_{\mbox{agg}}$) were derived from the calorimetric titration curves. In the presence of 1.00 mmol L$^{-1}$ cosolute, no changes in the parameters were observed when compared with those obtained for SDS-PEO interactions in pure water. For NaCl, Na$_2$SO$_4$, Li$_2$SO$_4$, and NaSCN at 10.0 and 100 mmol L$^{-1}$, the cosolute presence lowered cac, increased $C_2$, and the PEO-SDS aggregate became more stable. In the presence of Na$_2$[Fe(CN)5NO], the calorimetric titration curves changed drastically, showing a possible reduction in the PEO-SDS degree of interaction, possibility disrupting the formed nanostructure; however, the SAXS data confirmed, independent of the small energy observed, the presence of aggregates adsorbed on the polymer chain., Comment: 8 pages, 8 figures

We present dynamic light scattering (DLS) measurements of soft poly(methyl-methacrylate) (PMMA) and polyacrylamide (PA) polymer gels prepared with trapped bodies (latex spheres or magnetic nanoparticles). We show that the anomalous diffusivity of the trapped particles can be analyzed in terms of a fractal Gaussian network gel model for the entire time range probed by DLS technique. This model is a generalization of the Rouse model for linear chains extended for structures with power law network connectivity scaling, which includes both percolating and uniform bulk gel limits. For a dilute dispersion of strongly scattering particles trapped in a gel, the scattered electric field correlation function at small wavevector ideally probes self-diffusion of gel portions imprisoning the particles. Our results show that the time-dependent diffusion coefficients calculated from the correlation functions change from a free diffusion regime at short times to an anomalous subdiffusive regime at long times (increasingly arrested displacement). The characteristic time of transition between these regimes depends on scattering vector as approximately q(-2), while the time decay power exponent tends to the value expected for a bulk network at small q. The diffusion curves for all scattering vectors and all samples were scaled to a single master curve.