Effect of chitosan on the heat stability of whey protein solution as a function of pH

Physicochemical and Functional Properties of Thermal-Induced Polymerized Goat Milk Whey Protein

Goat milk whey protein products are a hard-to-source commodity. Whey protein concentrate was directly prepared from fresh goat milk. The effects of the heating temperature (69-78 °C), time (15-30 min), and pH (7.5-7.9) on the physicochemical and functional properties of the goat milk whey protein were investigated. The results showed that the particle size of the samples significantly increased (p < 0.05) after heat treatment. The zeta potential of polymerized goat milk whey protein (PGWP) was lower than that of native goat milk whey protein. The content of the free sulfhydryl groups of PGWP decreased with increasing heating temperature and time, while an increase in surface hydrophobicity and apparent viscosity of PGWP were observed after heat treatment. Fourier Transform Infrared Spectroscopy analysis indicated that heat treatment and pH had considerable impacts on the secondary structure of goat milk whey protein. Transmission electron microscope images revealed that heat induced the formation of a large and uniform protein network. Additionally, the changes in the physicochemical and structural properties contributed to the improvement of the emulsifying and foaming properties of goat milk whey protein after heat treatment. The results may provide a theoretical basis for the applications of polymerized goat milk whey protein in related products.

Effects of Heat Treatment Duration on the Electrical Properties, Texture and Color of Polymerized Whey Protein

In this research effects of heat treatment duration on the electrical properties (zeta potential and conductivity), texture and color of polymerized whey protein (PWP) were analyzed. Whey protein solutions were heated for 30 min to obtain single-heated polymerized whey protein (SPWP). After cooling to room temperature, the process was repeated to obtain double-heated polymerized whey protein (DPWP). The largest agglomeration was demonstrated after 10 min of single-heating (zeta potential recorded as -13.3 mV). Single-heating decreased conductivity by 68% and the next heating cycle by 54%. As the heating time increased, there was a significant increase in the firmness of the heated solutions. Zeta potential of the polymerized whey protein correlated with firmness, consistency, and index of viscosity, the latter of which was higher when the zeta potential (r = 0.544) and particle size (r = 0.567) increased. However, there was no correlation between zeta potential and color. This research has implications for future use of PWP in the dairy industry to improve the syneretic, textural, and sensory properties of dairy products.

Complexation of Anthocyanin-Bound Blackcurrant Pectin and Whey Protein: Effect of pH and Heat Treatment

A complexation study between blackcurrant pectin (BCP) and whey protein (WP) was carried out to investigate the impact of bound anthocyanins on pectin−protein interactions. The effects of pH (3.5 and 4.5), heating (85 °C, 15 min), and heating sequence (mixed-heated or heated-mixed) were studied. The pH influenced the color, turbidity, particle size, and zeta-potential of the mixtures, but its impact was mainly significant when heating was introduced. Heating increased the amount of BCP in the complexes—especially at pH 3.5, where 88% w/w of the initial pectin was found in the sedimented (insoluble) fraction. Based on phase-separation measurements, the mixed-heated system at pH 4.5 displayed greater stability than at pH 3.5. Heating sequence was essential in preventing destabilization of the systems; mixing of components before heating produced a more stable system with small complexes (<300 nm) and relatively low polydispersity. However, heating WP before mixing with BCP prompted protein aggregation—producing large complexes (>400 nm) and worsening the destabilization. Peak shifts and emergence (800−1200 cm−1) in infrared spectra confirmed that BCP and WP functional groups were altered after mixing and heating via electrostatic, hydrophobic, and hydrogen bonding interactions. This study demonstrated that appropriate processing conditions can positively impact anthocyanin-bound pectin−protein interactions.

Chitosan improves storage stability of wheat-embryo globulin

Wheat-embryo globulin (WEG) has been shown to confer health benefits, however, it often forms aggregates during industrial production, which decrease its quality and efficacy. In this study, electrostatic interaction between chitosan (CS) and the protein was used to stabilize WEG. Initially, it was observed that the solubility of WEG was lowest in the pH range of 4-5, and its isoelectric point was 4.70. Next, the optimal preparation conditions for CS-WEG complex were pH of 5.903, combination ratio of 1.05, and ionic strength of 77.070 mM. Finally, characterization of the zeta-potential, particle size, rheological properties and fluorescence microscopy of the composite, it was found that addition of CS significantly increased the zeta potential, reduced poly dispersity index, and reduced the particle size to a certain extent. Moreover, addition of CS caused shear thinning and increased viscosity of the complex, but decreased the dispersion stability over time. In summary, these results revealed that CS mainly increased the apparent viscosity and the electrostatic interaction of WEG to improve the dispersion stability when it slowly polymerized with WEG. This study provides important ideas for improving industrialized production of WEG.

Sustainable thermoresponsive whey protein- and chitosan-based oil-in-water emulsions for cosmetic applications

OBJECTIVE

In this study, the biopolymers whey protein and chitosan were used to create a thermoresponsive emulsion. The impact of the inclusion of chitosan and inclusion of specific oils on the rheological properties and response to temperature were investigated by a stepwise build-up from simple solutions to oil-in-water (O/W) emulsions. Whey protein (WP) concentration and chitosan concentration were varied. The results may help develop strategies for incorporating thermoresponsive materials in stable and high-performing formulations for use in cosmetics.

METHODS

Solutions of whey protein concentrate (WPC) by itself, chitosan by itself and the combination of the two at various concentrations were tested with flow sweeps, temperature sweeps and frequency sweeps. Then, three different oils of jojoba, avocado and silicone were included to form emulsions and the tests were repeated to determine flow behaviour, response to temperature and structure.

RESULTS

By comparing 15 wt. % and 20 wt. % WP solutions, it was found that 15 wt. % WP could provide good viscosities and modulus at a lower amount of material used. The solution composed of 15 wt. % WP, and 0.5 wt. % chitosan was found to have the greatest structural response to temperature compared to solutions with 1.0 wt. % and 1.5 wt. % chitosan. Compared to the addition of 10 wt. % silicone and 10 wt. % avocado oil to form emulsions, the addition of 10 wt. % jojoba oil further strengthened the gel network the most. The final emulsion with pigment added had improved viscosity and thermoresponsive behaviour. The WP and chitosan emulsions were shear thinning, elastically dominated and behaved as classical gels. The behaviour of the emulsions was dependent upon the hydrophobic interactions between the protein and the oil and the electrostatic interactions between the protein and the chitosan.

CONCLUSION

An emulsion composed of 15 wt. % WP, 10 wt. % jojoba oil and 0.5 wt. % chitosan solution was found to have the greatest structural response to temperature. This study of an O/W emulsion containing whey protein concentrate and chitosan demonstrated that different oils and conditions can be used to tune thermoresponsive and rheological behaviour.

Beneficial Effects of Tamarind Trypsin Inhibitor in Chitosan-Whey Protein Nanoparticles on Hepatic Injury Induced High Glycemic Index Diet: A Preclinical Study

Several studies have sought new therapies for obesity and liver diseases. This study investigated the effect of the trypsin inhibitor isolated from tamarind seeds (TTI), nanoencapsulated in chitosan and whey protein isolate (ECW), on the liver health status of the Wistar rats fed with a high glycemic index (HGLI) diet. The nanoformulations without TTI (CW) and ECW were obtained by nanoprecipitation technique, physically and chemically characterized, and then administered to the animals. The adult male Wistar rats (n = 20) were allocated to four groups: HGLI diet + water; standard diet + water; HGLI diet + ECW (12.5 mg/kg); and HGLI diet + CW (10.0 mg/kg), 1 mL per gagave, for ten days. They were evaluated using biochemical and hematological parameters, Fibrosis-4 Index for Liver Fibrosis (FIB-4), AST to Platelet Ratio Index (APRI) scores, and liver morphology. Both nanoparticles presented spherical shape, smooth surface, and nanometric size [120.7 nm (ECW) and 136.4 nm (CW)]. In animals, ECW reduced (p < 0.05) blood glucose (17%), glutamic oxalacetic transaminase (39%), and alkaline phosphatase (24%). Besides, ECW reduced (p < 0.05) APRI and FIB-4 scores and presented a better aspect of hepatic morphology. ECW promoted benefits over a liver injury caused by the HGLI diet.

Recent advances in microfluidic-aided chitosan-based multifunctional materials for biomedical applications

Chitosan-based biomaterials has shown great advantages in a broad range of applications, including drug delivery, clinical diagnosis, cell culture and tissue engineering. However, due to the lack of control over the fabrication processes by conventional techniques, the wide application of chitosan-based biomaterials has been hampered. Recently, microfluidics has been demonstrated as one of the most promising platforms to fabricate high-performance chitosan-based multifunctional materials with monodisperse size distribution and accurately controlled morphology and microstructures, which show great promising for biomedical applications. Here, we review recent progress of the fabrication of chitosan-based biomaterials with different structures and integrated functions by microfluidic technology. A comprehensive and in-depth depiction of critical microfluidic formation mechanism and process of various chitosan-based materials are first interpreted, with particular descriptions about the microfluidic-mediated control over the morphology and microstructures. Afterwards, recently emerging representative applications of chitosan-based multifunctional materials in various fields, are systematically summarized. Finally, the conclusions and perspectives on further advancing the microfluidic-aided chitosan-based multifunctional materials toward potential and versatile development for fundamental researches and biomedicine are proposed.

Proteins Derived from the Dairy Losses and By-Products as Raw Materials for Non-Food Applications

The disposal of a high volume of waste-containing proteins is becoming increasingly challenging in a society that is aware of what is happening in the environment. The dairy industry generates several by-products that contain vast amounts of compounds, including proteins that are of industrial importance and for which new uses are being sought. This article provides a comprehensive review of the potential of the valorisation of proteins that can be recovered by chemical and/or physical processes from protein-containing milk by-products or milk surplus, particularly whey proteins or caseins. Whey proteins and casein characteristics, and applications in non-food industries, with special emphasis on the textile industry, packaging and biomedical, are reported in this review, in order to provide knowledge and raise awareness of the sustainability of these proteins to potentiate new opportunities in a circular economy context.

Development and characterization of an edible chitosan-whey protein nano composite film for chestnut (Castanea mollissima Bl.) preservation

Chitosan (CHI) and whey protein are usually used to prepare edible films for food preservation. However, the composite film composed of the two components does not yield satisfactory properties for chestnut preservation. In this study, nano-cellulose and cinnamaldehyde (CMA) were added to CHI and whey protein, creating a new composite film with strong water retention, bacteriostatic, and mechanical properties. The water vapor permeability (WVP) of the film decreased by 21.61% with the addition of 0.5% (w/v) nano-cellulose, and 23.02% with the addition of 0.3% (w/v) CMA. Furthermore, water solubility (WS) decreased 22.05%, and the density of the film was significantly improved with the addition of 0.3% (w/v) CMA. The optimized formula of the film was CHI 2.5% (w/v), whey protein 3.0% (w/v), nano-cellulose 0.5% (w/v), CMA 0.3% (w/v), and pH 3.8, as determined by orthogonal testing L9(3⁴ ), with fuzzy comprehensive assessment, of WVP, WS, tensile strength, and elongation at break. The film clearly inhibited the growth of E. coli, S. aureus, and Chinese chestnut fungus, destroying the mycelial structure of the fungus. In addition, coating effectively reduced the weight loss, mildew rate, and calcification index during 16 days of storage of chestnuts at 25 °C.

Preparation of Chitosan Poly(methacrylate) Composites for Adsorption of Bromocresol Green

In the present study, chitosan poly(methacrylate) composites were prepared and applied for adsorption of bromocresol green from aqueous solutions. The synthesized composites were characterized with scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The bromocresol green removal by the developed adsorbent was investigated, and the effects of experimental parameters, including sample pH and adsorption time, were also examined. Furthermore, the adsorption characteristics of the synthesized adsorbent, including kinetics, adsorption isotherms, and thermodynamics, were comprehensively studied. The adsorption isotherm was well described by the Freundlich model, and the maximum adsorption capacity was 39.84 μg mg^-1 by shaking for 40 min at pH 2.0. Bromocresol green adsorption kinetics followed a pseudo-second-order kinetic model, indicating that adsorption was the rate-limiting step. Thermodynamic parameters and the negative values of Gibbs free energy change (ΔG°) showed that adsorption was a spontaneous process. The positive values of entropy change (ΔS°) implied that the adsorption of bromocresol green on chitosan poly(methacrylate) composites was an increasing random process. In addition, enthalpy change (ΔH°) values were positive, suggesting that the adsorption of bromocresol green was endothermic. The adsorption percentage of bromocresol green with chitosan poly(methacrylate) composites remained above 97% after three times of recycling test.

Systematical characterization of physiochemical and rheological properties of thermal-induced polymerized whey protein

BACKGROUND

Effects of pH (6-8), protein concentration (60-110, g kg^-1 ), heating temperature (70-95 °C) and time (5-30 min) on physiochemical and rheological properties of thermal-induced polymerized whey protein isolate (PWP) were systematically investigated. Degree of denaturation, particle size, zeta potential, free sulfhydryl group content, surface hydrophobicity and apparent viscosity were determined.

RESULTS

Heating whey protein above 75 °C at pH 7 or 8 resulted in denaturation of 80-90% whey protein. pH variation had a remarkable influence on particle size of samples (P < 0.05), whereas heating temperature and time did not generate significant changes. Zeta potential of PWP samples fell in the range of -30 to -40 mV. Free sulfhydryl group content of PWP samples decreased with increasing level regarding each factor. Surface hydrophobicity analysis showed that samples at higher pH or concentration became less hydrophobic, and increasing heating temperature or time resulted in higher hydrophobicity index. Time sweep test revealed that increasing protein concentration, heating temperature or time led to higher apparent viscosity. Flow behavior of PWP samples approached Newtonian character as protein concentration, heating temperature or time decreased.

CONCLUSION

Systematic data may provide helpful information in designing a heating process for dairy products and application of PWP in the food industry. © 2018 Society of Chemical Industry.

Characterization of the Structural and Colloidal Properties of α-Lactalbumin/Chitosan Complexes as a Function of Heating

This research investigated the interaction between α-lactalbumin (α-la) and chitosan at different temperatures. Chitosan was added to α-la solution (5 g L^-1) to achieve different α-la/chitosan ratios (8:1, 5:1, and 2:1), which were then subjected to different heating temperatures (20, 70, and 90 °C). The results indicated that a low amount of chitosan (8:1) precipitated α-la molecules. Increasing chitosan to a ratio of 5:1 resulted in exposure of the internal structure of α-la, and those formed complexes had high turbidity and average size, which were decreased by an increasing temperature. A further increase of chitosan to a ratio of 2:1 protected the internal structure of α-la molecules. All samples exhibited a similar adsorption behavior at the air/water interface, but the presence of chitosan significantly increased film elasticity. The produced complexes can be regarded as functional ingredients, which can be used as an emulsifying agent and a delivery material to control the release of bioactive compounds.