Protein isolate from Stauntonia brachyanthera seed: Chemical characterization, functional properties, and emulsifying performance after heat treatment

Isolation and characterization of nettle (Urtica dioica L.) seed proteins: Conversion of underutilized by-products of the edible oil industry into food emulsifiers

This study aimed to upcycle a byproduct of the edible oil industry, cold-pressed nettle seed meal (CPNSM), into a plant-based emulsifier, thereby increasing the sustainability of the food system. The protein content of the nettle seed protein (NSP) powder was 48.3% with glutamic acid (16.6%), asparagine (10.7%), and arginine (9.7%) being the major amino acids. NSPs had a denaturation temperature of 66.6 °C and an isoelectric point of pH 4.3. They could be used as emulsifiers to form highly viscous coarse corn oil-in-water emulsions (10% oil, 4% NSP). Nevertheless, 10-fold diluted emulsions exhibited rapid creaming under different pH (2-9), salt (0-500 mM NaCl) and temperature (>40 °C) conditions, but they were relatively stable to aggregation. Our findings suggest that NSPs could be used as emulsifiers in highly viscous or gelled foods, like dressings, sauces, egg, cheese, or meat analogs.

Sustainable proteins from wine industrial by-product: Ultrasound-assisted extraction, fractionation, and characterization

Plant proteins are increasingly being used in the food industry due to their sustainability. They can be isolated from food industry waste and converted into value-added ingredients, promoting a more circular economy. In this study, ultrasound-assisted alkaline extraction (UAAE) was optimized to maximize the extraction yield and purity of protein ingredients from grapeseeds. Grapeseed protein was extracted using UAAE under different pH (9-11), temperature (20-50 °C), sonication time (15-45 min), and solid/solvent ratio (10-20 mL/g) conditions. The structural and functional attributes of grapeseed protein and its major fractions (albumins and glutelins) were investigated and compared. The albumin fractions had higher solubilities, emulsifying properties, and in vitro digestibilities but lower fluid binding capacities and thermal stability than the UAAE and glutelin fraction. These findings have the potential to boost our understanding of the structural and functional characteristics of grapeseed proteins, thereby increasing their potential applications in the food and other industries.

Influence and mechanism of food matrices onto the TBBQ-eliminated performance during in-vitro digestion

Food matrices greatly impact TBBQ content during digestion, while lacking sufficient research and understanding. This study investigated the influence and mechanism of fried foods on the TBBQ-eliminated performance during in-vitro digestion. The results indicated that TBBQ content varied significantly among food matrices after in-vitro digestion, with the highest in peanuts (38.3%). The correlation analysis revealed that proteins remarkably facilitated TBBQ-eliminations while fats decreased the TBBQ-eliminated rate. The TBBQ-eliminated performance of proteins, protein digestive mixtures, and amino acids uncovered that sulfhydryl groups were crucial reactive groups to eliminate TBBQ, and TBBQ-eliminated rates under intestinal pH (8.0) were faster than gastric pH (1.5). Additionally, fats significantly reduced the protein-triggered TBBQ-eliminations, originating that the oil-water interface increased the interaction difficulty between lipophilic TBBQ and proteins. Thus, this work provided an in-depth understanding of food matrices (especially proteins and fats) in TBBQ eliminations to enlighten the promising TBBQ-risk-reduced strategies with high-protein and low-fat foods.

Effect of extraction pH on amino acids, nutritional, in-vitro protein digestibility, intermolecular interactions, and functional properties of guar germ proteins

The chemical compositions, intermolecular interactions, and functional properties of guar germ proteins (GGP) were investigated at different extraction pH (7 to 11). The protein efficiency ratio, essential amino acid index (46.53), predicted biological value (39.02), nutritional index (42.67), and protein purity (91.69 %) were found to be highest at pH 9. The in-vitro protein digestibility of GGP sample was highest at pH 11. From SDS-PAGE, the band intensity (<10 kDa) became thinner with an increase in extraction pH from 7 to 9 and then thicker. Meanwhile, smallest particle size and weaker ionic and hydrogen bonds were found at pH 11. The β-sheet content was more dominating in GGP samples. Moreover, higher denaturation temperatures of GGP samples indicated that protein molecules had a compact tertiary structure. Furthermore, the GGP extracted at pH 7 showed better functional properties. The principal component analysis suggested that pH 9 was more suitable for isolating GGP.

Functional properties of glutelin from Camellia oleifera seed cake: Improvement by alkali-assisted phosphorylation through changes in protein structure

To explore the effect and its mechanism of alkali-assisted phosphorylation on the functional properties of Camellia Oleifera seeds cake glutelin (CSCG), CSCG was treated with different concentration of sodium trimetaphosphate (STMP, 1.0, 2.0, 3.0, 4.0, and 5%, w/v) in different pH environment (3.0, 5.0, 7.0, 9.0, and 11.0). The results showed that alkali assist improved the phosphorylation degree of CSCG, and the optimum pH value is 9.0. FT-IR and XPS confirmed the successful modification of phosphate groups on CSCG through covalent interaction. Alkali-assisted phosphorylation decreased the particle size and increased electronegativity of CSCG, as well as changed in its surface hydrophobicity, crystallinity, and intrinsic fluorescence. All these changes of protein structure triggered by alkali-assisted phosphorylation led to the improvement of water solubility, water/oil absorption capacity, emulsifying ability, foamability, and in vitro digestibility of CSCG. This work could provide a theoretical basis for industrial production of CSCG with excellent functional properties.

Effect of Hydrothermal Treatment on the Structure and Functional Properties of Quinoa Protein Isolate

The aim of this study was to investigate the effects of hydrothermal treatment at different temperatures and times on the structure and functional properties of quinoa protein isolate (QPI). The structure of QPI was investigated by analyzing changes in the intrinsic fluorescence spectrum, ultra-violet (UV) spectrum, and Fourier transform infrared spectrum. The solubility, water/oil-holding capacity, emulsifying activity, and emulsion stability of QPI were studied, as were the particle size and the thermogravimetric properties of QPI. The results showed that the average particle size of QPI gradually increased with the increase in hydrothermal treatment time and temperature, and reached a maximum value of 121 °C for 30 min. The surface morphology also became rough and its thermal stability also increased. The endogenous fluorescence and UV spectral intensity at 280 nm decreased gradually with increasing hydrothermal treatment time and temperature, and reduced to the minimum values at 121 °C for 30 min, respectively. After hydrothermal treatment, the secondary structure of QPI tended to be disordered. The functional properties of QPI after treatment were all superior to those of the control. The results of this study might provide a basis for the processing and utilization of QPI.

Preparation of novel self-assembled albumin nanoparticles from Camellia seed cake waste for lutein delivery

The potential utilization value of Camellia seed cake was explored by extracting albumin (CSCA) to develop nanoparticles for lutein delivery. First, thermal property and amphiphilicity of CSCA were evaluated to guide nanoparticle preparation. Next, CSCA nanoparticles modified with chitosan (CS) were prepared through a thermally induced self-assembly method derived by electrostatic attraction and hydrophobic interaction. The optimized nanoparticles were prepared from CSCA:CS at a mass ratio of 2:1 with pH of 4.5, and an incubation temperature and time of 80 ℃ and 10 min, respectively. The nanoparticles had the highest effective loading capacity for lutein at 5.89 ± 0.78%, and the corresponding encapsulation efficiency was 43.82 ± 5.69%. The storage stability of lutein was improved by nanoparticle loading, and the bioaccessibility of lutein in simulated intestinal digestion increased from 26.8 ± 4.4% to 57.3 ± 9.6% after encapsulation into nanoparticles. These findings may facilitate the development of new and sustainable proteins from plant waste for delivery system applications.

Development of composite nanoparticles from gum Arabic and carboxymethylcellulose-modified Stauntonia brachyanthera seed albumin for lutein delivery

Lutein is a carotenoid with several beneficial functions, but its poor water solubility, chemical instability, and low bioavailability limits its application. To overcome these shortcomings, self-assembly composite nanoparticles from Stauntonia brachyanthera seed albumin (SBSA), gum Arabic (GA), and carboxymethylcellulose (CMC) were developed for lutein encapsulation. Firstly, SBSA was extracted from seeds and its physicochemical properties were evaluated. Followingly, the nanoparticles were prepared with SBSA through a heat induced self-assembly method which were modified by GA and CMC. The nanoparticles exhibited good storage, pH, and salt stability. Hydrogen bonds, hydrophobic interactions, and electrostatic interactions were proved to derive the formation of nanoparticles. The maximum effective loading capacity (LC) of the lutein in nanoparticles was 0.92 ± 0.01% with an encapsulation efficiency (EE) at 83.95 ± 0.98%. Heat stability and storage stability of lutein were significantly enhanced after encapsulation into nanoparticles. In addition, the bioaccessibility of lutein increased from 17.50 ± 2.60% to 46.80 ± 4.70% after encapsulation into nanoparticles.

Modulation of the structural and functional properties of perilla protein isolate from oilseed residues by dynamic high-pressure microfluidization

Dynamic high-pressure microfluidization (DHPM) is an alternative method to physically modify proteins to improve their functional properties. In this study, perilla protein isolate (PPI) was treated by DHPM at different pressures. Results showed that DHPM treatment reduced the particle size and absolute potential of PPI by 75.90% and 22.28%. The increased surface hydrophobicity and free sulfhydryl content were observed in DHPM-treated PPI, which may be caused by the comformation changes of PPI. Furthermore, DHPM treatment would not cause the degradation of the main subunits and the variation of crystalline regions in PPI, but enhancing the thermal stability of PPI at 90 MPa and 120 MPa. Functional properties analysis indicated that DHPM treatment at 120 MPa was more effective in improving the solubility, foaming and emulsifying capacities of PPI. The results suggested that DHPM can be used to enhance the functional properties of PPI and expand its application in food systems.