Conjugates of α-lactalbumin, β-lactoglobulin, and lysozyme with polysaccharides: Characterization and techno-functional properties

Self-assembled α-lactalbumin nanostructures: encapsulation and controlled release of bioactive molecules in gastrointestinal in vitro model

BACKGROUND

Implementing encapsulation techniques is pivotal in safeguarding bioactive molecules against environmental conditions for drug delivery systems. Moreover, the food-grade nanocarrier is a delivery system and food ingredient crucial in creating nutraceutical foods. Nano α-lactalbumin has been shown to be a promissory nanocarrier for hydrophobic molecules. Furthermore, the nanoprotein can enhance the tecno-functional properties of food such as foam and emulsion. The present study investigated the nanostructured α-lactalbumin protein (nano α-la) as a delivery and controlled release system for bioactive molecules in a gastric-intestinal in vitro mimic system.

RESULTS

The nano α-la was synthesized by a low self-assembly technique, changing the solution ionic strength by NaCl and obtaining nano α-la 191.10 ± 21.33 nm and a spherical shape. The nano α-la showed higher encapsulation efficiency and loading capacity for quercetin than riboflavin, a potential carrier for hydrophobic compounds. Thermal analysis of nano α-la resulted in a ΔH of -1480 J g-1 for denaturation at 57.44 °C. The nanostructure formed by self-assembly modifies the foam volume increment and stability. Also, differences between nano and native proteins in emulsion activity and stability were noticed. The release profile in vitro showed that the nano α-la could not hold the molecules in gastric fluid. The Weibull and Korsmeyer-Peppas model better fits the release profile behavior in the studied fluids.

CONCLUSION

The present study shows the possibility of nano α-la as an alternative to molecule delivery systems and nutraceutical foods' formulation because of the high capacity to encapsulate hydrophobic molecules and the improvement of techno-functional properties. However, the nanocarrier is not perfectly suitable for the sustainable delivery of molecules in the gastrointestinal fluid, demanding improvements in the nanocarrier. © 2024 Society of Chemical Industry.

Characteristics and Functional Properties of Maillard Reaction Products from α-Lactalbumin and Polydextrose

The characteristics and the functions of Maillard reaction products (MRPs) produced by polydextrose (PD), a new type of prebiotic, and α-lactalbumin (α-LA) were valued. PD and α-LA were incubated at 60 °C and 79% relative humidity for up to 72 h to prepare MRPs. The results showed that the absorbance and fluorescence intensity of heated α-LA-PD increased, and the amount of free amino groups reduced as the reaction progressed, which confirmed the formation of different stages of MRPs. Electrophoresis revealed an increase in molecular mass and the degree of covalent cross-linking. The secondary structure of MRPs experienced no significant changes with the measurement of circular dichroism (CD), while the tertiary structure gradually unfolded, exposing hydrophobic groups. Furthermore, a significant increase was detected in the radical-scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and the ferric reducing/antioxidant power (FRAP) of MRPs. The findings offer a foundation for understanding the structural and functional features of MRPs in formula milk powder.

Physical treatment synergized with natural surfactant for improving gas-water interfacial behavior and foam characteristics of α-lactalbumin

The purpose of this study was to investigate effect of physical treatment (ultrasound, U/high pressure homogenization, H/combined treatment, UH or HU) and surfactant (Mogroside V, Mog) on air/water interface adsorption and foaming properties of α-lactalbumin (ALa). Firstly, the binding of Mog and all physical-treated ALa was a static quenching process. Mog had the greatest binding affinity for HU-ALa among all treated samples. U or H treatment could change surface hydrophobicity of ALa/Mog complex. Secondly, at the molar ratio (ALa:Mog) of 1:50, foaming ability (FA) of all ALa samples got the maximum. The sequence of FA in ALa and ALa/Mog complex was listed as follow: HU > U > H > UH. Moreover, foaming stability (FS) of HU-ALa was the highest, followed by H-ALa, U-ALa and UH-ALa. Meanwhile, low concentration Mog increased FS of ALa or UH-ALa, but it reduced FS of H-ALa, U-ALa and HU-ALa. Quartz crystal microbalance with dissipation monitoring (QCM-D) experiment indicated that ALa/Mog complex after U or H treatment was quickly absorbed at air/water interface, compared with the treated ALa, and HU-ALa/Mog had the largest frequency shift. In addition, HU-ALa had the thickest bubble membrane and the highest dissipation shift in all samples, indicating that the absorbed membrane thickness and viscoelasticity of samples was correlated with foam stability. Therefore, U and H treatment synergism with Mog was an effective approach to enhance foam properties of ALa, which indicated that HU-treated ALa/Mog complex could be viewed as the safe and efficient foaming agent applied in food processing.

Pulse Globulins 11S and 7S: Origins, Purification Methods, and Techno-functional Properties

A growing interest in pulse proteins in recent years results from their crucial role in the transition toward sustainable food systems. Consequently, current research is mainly focused on the production of protein ingredients and the evaluation of their nutritional and techno-functional properties for the development of animal product analogues. However, the individual impacts of the major proteins 11S legumin and 7S vicilin on pulse techno-functionalities remains unclear. Thus, this review aims to represent current knowledge on pulse 11S and 7S globulin origins, extraction, separation, and purification methods as well as their techno-functionalities. This paper also discusses the principal challenges related to pulse vicilin and legumin purification methods, such as efficiency and environmental concerns, as well as 11S/7S ratio variability. This review highlights the fact that 11S and 7S fractions serve different purposes in pulse functionality and that more efficient and eco-friendly purification techniques are required to properly assess their respective functional attributes. Such research would allow the determination of optimal 11S/7S ratios for the integration of pulse protein ingredients in various food formulations. Hence, food industries would be able to select species/varieties, agronomical methods, and processing methods to produce ingredients with suitable 11S/7S ratios, catering to consumers' ethical, environmental, and nutritional concerns.

Effects of the molecular weight of hyaluronan on the conformation and release kinetics of self-assembled 5-fluorouracil-loaded lysozyme-hyaluronan colloidal nanoparticles

Lysozyme (LYS) and hyaluronan with low (HA1: 3 kDa), medium (HA2: 120 kDa), and high (HA3: 1200 kDa) molecular weights were used to fabricate lysozyme-hyaluronan colloidal nanoparticles using a green self-assembly method. Fourier transform infrared spectroscopy indicated that hydrogen bonding, hydrophobic and electrostatic interactions promoted the formation of the colloidal nanoparticles. The hydrophobic area of prepared colloidal nanoparticles was quantified using a pyrene fluorescent probe, and the results showed that the LYS-HA3 nanoparticles had the strongest hydrophobic capacity. Furthermore, 5-fluorouracil (5-Fu) was used to evaluate encapsulation performance, demonstrating that the LYS-HA3 nanoparticles had the highest encapsulation ability (>90 %). All prepared 5-Fu-loaded lysozyme-hyaluronan (5-Fu@LYS-HA) colloidal nanoparticles exhibited excellent long-term storage stability at 4 °C for 60 days. Cellular uptake and in vitro release results indicated that the LYS-HA2 nanoparticles exhibited the highest cellular uptake efficiency, and the LYS-HA3 nanoparticles had the best slow-release effect, while the release process was mainly controlled by the combination of Fickian diffusion and structural relaxation, respectively. This study demonstrates the influence of molecular weight on the conformational and structural properties of colloidal nanoparticles, which has implications for the design of insoluble drug self-assembly systems.

Improving the emulsifying properties of sodium caseinate through conjugation with soybean soluble polysaccharides

This study was conducted to investigate the impact on the techno-functionality over sodium caseinate (NaCS) when are conjugated with soluble soybean polysaccharides (SSPS). NaCS/SSPS conjugates were prepared through the Maillard reaction using dry heating. The formation of covalent binding between NaCS and SSPS and structural changes of NaCS during glycation were confirmed via SDS-PAGE and ATR-FTIR. A positive correlation was observed between the increase in the browning index of samples and Amadori compounds formation over time, based on the colorimetric results. Emulsions stabilization using conjugates with a higher NaCS/SSPS ratio led to a decreasing trend in the droplets' size and creaming index. Meanwhile, higher viscosity and shear-thinning behavior were observed in conjugate-based emulsions. Finally, conjugates prepared with the NaCS/SSPS ratio of 9/1 at an incubation time of 24 h presented a higher pH and thermal stability and better performance in emulsion stabilization in comparison with each of the biopolymers alone.

Characterization of Conjugates between α-Lactalbumin and Benzyl Isothiocyanate-Effects on Molecular Structure and Proteolytic Stability

In complex foods, bioactive secondary plant metabolites (SPM) can bind to food proteins. Especially when being covalently bound, such modifications can alter the structure and, thus, the functional and biological properties of the proteins. Additionally, the bioactivity of the SPM can be affected as well. Consequently, knowledge of the influence of chemical modifications on these properties is particularly important for food processing, food safety, and nutritional physiology. As a model, the molecular structure of conjugates between the bioactive metabolite benzyl isothiocyanate (BITC, a hydrolysis product of the glucosinolate glucotropaeolin) and the whey protein α-lactalbumin (α-LA) was investigated using circular dichroism spectroscopy, anilino-1-naphthalenesulfonic acid fluorescence, and dynamic light scattering. Free amino groups were determined before and after the BITC conjugation. Finally, mass spectrometric analysis of the BITC-α-LA protein hydrolysates was performed. As a result of the chemical modifications, a change in the secondary structure of α-LA and an increase in surface hydrophobicity and hydrodynamic radii were documented. BITC modification at the ε-amino group of certain lysine side chains inhibited tryptic hydrolysis. Furthermore, two BITC-modified amino acids were identified, located at two lysine side chains (K32 and K113) in the amino acid sequence of α-LA.

Impacts of Ca2+ cation and temperature on bovine α-lactalbumin secondary structures and foamability - Insights from computational molecular dynamics

We used computational molecular dynamics (MD) to assess molecular conformations of apo- and holo-forms (respectively without and with Ca²⁺) of bovine α-lactalbumin (α-La) at different temperatures, and to correlate them with the protein's foaming properties. At 4 °C and 25 °C no major protein conformation changes occurred. At 75 °C, lots of changes were evidenced: the Ca²⁺ depletion triggered the complete loss of h2b, h3c helices and S1, S2 and S3 β-sheets, and partial losses of H1, H2 and H3 α-helices. The absence of Ca²⁺ in apo-α-La and its leaving from holo-α-La triggered electrostatic repulsion among Asp82, Asp84 and Asp87, leading to the formation of a hydrophobic cluster involving Phe9, Phe31, Ile1, Va42, Ile55, Phe80 and Leu81. These conformational changes were related to an interfacial tension decrease and to a foaming capacity increase, for both apo-α-La and holo-α-La. This study exemplifies how powerful MD is as a tool to provide a better understanding of the molecular origins of food proteins' techno-functionalities.

Characterization, techno-functional properties, and encapsulation efficiency of self-assembled β-lactoglobulin nanostructures

Whey is a cheese co-product with high protein content used in the food industry due to its techno-functional properties and nutritive value. This study aims to optimize the production of β-lactoglobulin (β-lg) nanostructures, to characterize their techno-functional properties and stability, and to apply them as a carrier of bioactive molecules. Box-Behnken planning was applied to determine the best conditions to obtain the β-lg nanostructure, which consists in treatment at 100 °C in NaCl 50 mmol·L^-1 for 60 min. TEM analysis showed a fibril structure in the observed nanostructures. The nanostructured systems formed foam and emulsion with higher stability than the systems composed of the native protein. The results for encapsulation efficiency of bioactive compounds were 96.50%, 89.04%, 67.78%, and 36.39% for quercetin, rutin, naringin, and vitamin B_2, respectively. Thus, β-lg nanostructure's great capacity to encapsulate hydrophobic molecules was verified.

Effect of sodium tripolyphosphate on the interaction and aggregation behavior of ovalbumin-lysozyme complex

The mechanism by which sodium tripolyphosphate affected the aggregation behavior of ovalbumin-lysozyme complexes was investigated in this work. The highest stability coefficients were detected for natural ovalbumin and lysozyme at pH 9.0 and pH 5.0, with values of 0.981 and 0.931, respectively. The turbidity of the phosphorylated ovalbumin-lysozyme complexes was 1.71-fold to the natural complexes at pH 7.0. This result was related to the fact that the phosphorylated sample had a lower isoelectric point. Besides, both intermolecular forces and SDS-PAGE analysis indicated that the disulfide bond was the most important interaction in the complex. Circular dichroism analysis showed that phosphorylation weakened the unfolding and stretching of the structure caused by heat treatment. Moreover, transmission electron microscopy pictures confirmed that the network structure of phosphorylated ovalbumin-lysozyme complex was broader than natural protein. This study provides information for further understanding the effect of phosphorylation on protein aggregation behavior.