Conformational states of sunflower (Helianthus annuus) Helianthinin: effect of heat and pH

Properties and Characterization of Sunflower Seeds from Different Varieties of Edible and Oil Sunflower Seeds

Sunflower seeds, oil, and protein powder are rich in nutritional value, but the quality of different varieties of sunflower seeds is quite different, and the comprehensive comparative analysis characteristics of edible and oil sunflower seeds are still unclear. The comprehensive analysis and comparison of the raw material indicators, physicochemical properties, and processing characteristics of four edible and four oil sunflower seed varieties were investigated. The results showed that the engineering properties, texture characteristics, single-cell structure, and oil, protein, and starch granule distribution were different between edible and oil sunflower seeds. The composition of fatty acids and amino acids was different among edible, oil sunflower seeds and different varieties. The oleic acid (18.72~79.30%) and linoleic acid (10.11~51.72%) were the main fatty acids in sunflower seed oil, and in amino acid composition, the highest content was glutamic acid (8.88~11.86 g/100 g), followed by aspartic acid (3.92~4.86 g/100 g) and arginine (4.03~4.80 g/100 g). Sunflower meal proteins were dominated by 11S globulin and 2S albumin, and the secondary structure was dominated by β-folding, with -SH and S-S varying greatly among different varieties. Sunflower meal proteins vary widely in terms of functional properties among different varieties, and specialized quality screening was necessary. This study provided a reference and theoretical support for understanding sunflower seeds to further promote the processing and utilization of sunflower seeds.

An efficient co-delivery system based on multilayer structural nanoparticles for programmed sequential release of resveratrol and vitamin D3 to combat dextran sodium sulfate-induced colitis in mice

Multilayer structural nanoparticles (MSNPs) fabricated by layer-by-layer self-assembly were used for the co-encapsulation of resveratrol (Res) and vitamin D3 (Vd). Res and Vd co-encapsulated MSNPs (Res-Vd-MSNPs) were evaluated by appearance, morphology, particle size, ζ potential and encapsulation efficiency (EE). The results showed that Res-Vd-MSNPs were spherical in shape with a particle size of 625.4 nm and a surface charge of +26.1 mV. The EE of Res and Vd was as high as 93.6 % and 90.8 %, respectively. Res-Vd-MSNPs exhibited better stability and lower degradation rate in simulated gastric fluid, allowing the programmed sequential release of Vd and Res in simulated intestinal fluid and simulated colonic fluid, which was also confirmed by in vivo fluorescence imaging of mice. In addition, Res-Vd-MSNPs effectively alleviated the clinical symptoms of dextran sulfate sodium salt (DSS)-induced colitis in mice, including weight loss, diarrhea and fecal bleeding, and it especially exerted a preventive effect on DSS-induced colon tissue damage and colon shortening. Furthermore, Res-Vd-MSNPs suppressed the expression of anti-inflammatory cytokines such as TNF-α, IL-1β and IL-6 and ameliorated DSS-induced oxidative damage, decreased colonic myeloperoxidase (MPO) and nitric oxide (NO) activities and elevated glutathione (GSH) level in DSS-treated mice. This study illustrated that MSNPs were potential carriers for developing the co-delivery system for the synergistic prevention and treatment of ulcerative colitis.

Plant Protein versus Dairy Proteins: A pH-Dependency Investigation on Their Structure and Functional Properties

Plant proteins are constantly gaining attention as potential substitutes for dairy proteins, due to their suitable functionality and nutritional value. This study was designed to compare the structural and functional responses of different plant protein isolates (soy, pea, lentil, and chickpea) with two commonly used dairy protein (whey protein isolates and sodium caseinate) under different pH treatments (pH 3.0, 5.0, 7.0, and 9.0). The results showed that pH had a different alteration on the structural, surface properties and functional properties of plant and dairy proteins. Plant protein generally possessed a darker color, lower solubility, emulsifying properties, and foaming capacity, whereas their foaming stability and water holding capacity were higher than those of dairy proteins. Soy protein isolates were characterized by its comparable proportion of β-turn and random coils, zeta-potential, emulsifying (30.37 m²/g), and water-holding capacity (9.03 g/g) at alkaline conditions and chickpea protein isolates showed good oil-holding capacity (3.33 g/g at pH 9) among plant proteins. Further analysis confirmed that pH had a greater influence on the structural and functional properties of proteins as compared to protein sources, particularly at acidic conditions. Overall, this study might help processors select the appropriate plant protein as dairy alternatives for their target application in plant-based food products.

Combined Effect of Extraction and Purification Conditions on Yield, Composition and Functional and Structural Properties of Lupin Proteins

Lupin meal presents great potential as an alternative plant-based source of proteins for human nutrition. In the present work, different conditions of extraction and purification were evaluated for production of lupin protein isolates. The results showed that the protein extraction yield was comparable at acidic and conventionally used alkaline extraction pH (37% vs. 40–45%, respectively). Proteins extracted were principally composed of globulins. The ionic strength negatively impacted the protein extractability at pH 2, whereas no significant differences were observed between extractions at 20 to 50 °C. The selected extraction conditions (pH 2 and 7) combined with purification by isoelectric precipitation or ultrafiltration process generated the isolate-grade products. Interestingly, further characterization revealed a partial denaturation of proteins extracted at pH 2 resulting in loss of protein solubility at pH 6 and 7 (10–50%), modifications in secondary structure, lower thermal stability, and formation of protein aggregates. However, foaming and emulsifying properties were generally similar for almost all lupin isolates. Further investigation might be of interest with regard to the extraction behaviours and structural and functional properties of specific lupin protein fractions.

Color and structural modifications of alkaline extracted sunflower protein concentrates and isolates using L-cysteine and glutathione

Alkaline sunflower protein extraction can be performed along with de-phenolization of sunflower seed proteins if greening is unwanted. This greening is promoted at alkaline pH when chlorogenic acid (CGA) oxidizes and reacts with amino acids such as lysine. Thiol-containing dough conditioners: L-cysteine hydrochloride and glutathione (GSH) were investigated as an alternative de-greening strategy to acidification and de-phenolization. Greening and browning inhibition of thiols (GSH and Cysteine) were modeled by a combination of additive and interaction effects of extraction pH (7.0 to 11.0) and thiol concentration (0.00 to 5.60 mM) randomly assigned by Response Surface Methodology (RSM). The powders with the highest greening were the controls (pH 8.9-9.3 and no added thiols) and powders at pH 10.41 with 0.82 mM thiols. From RSM, the maximum greening inhibition was achieved at pH 8.71 and 4.23 mM cysteine, and pH 8.51 and 3.78 mM GSH. However, cysteine caused more browning at alkaline pH than GSH. Furthermore, fluorescence spectroscopy showed that cysteine had a protective effect against alkaline unfolding, whereas GSH quenched fluorescence in a concentration-dependent manner. Overall, de-greening of alkaline extracted sunflower protein was achieved by adding cysteine or glutathione, but the thiols differed in their contribution to the browning and unfolding effect.

Enhancing stability and anti-inflammatory properties of curcumin in ulcerative colitis therapy using liposomes mediated colon-specific drug delivery system

Curcumin liposomes (CUR-LPs) was identified by evaluating morphology, appearance, zeta potential, particle diameter, and drug encapsulation efficiency. The results indicated that particle diameter, surface charge and polydispersity index (PDI) of curcumin (CUR)-loaded anionic liposomes were 167 nm, -34 mV and 0.09, respectively. CUR-LPs is high stable pseudo-pH-sensitive nanoparticles system which has a favorable stability in simulated gastric fluid and slower degradation rate allowing CUR sustained release for prolonged times in simulated intestinal fluid. Within 1 h, the CUR consumption was 21.82% in simulated gastric fluid (SGF) and 27.32% in simulated intestinal fluid (SIF), respectively. CUR-LPs could attenuate clinical symptoms including weight loss, diarrhea and fecal bleeding. Especially, it could also prevent dextran sulfate sodium salt (DSS)-inducedcolon tissue damage and colon shortening, and reduce the production of malondialdehyde (MDA), colonic myeloperoxidase (MPO), Interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in animal model. Our study illustrated that liposomes (LPs) was a potential carrier to develop the colon-specific drug delivery system incorporating CUR for treating ulcerative colitis.

A Rational Approach for the Production of Highly Soluble and Functional Sunflower Protein Hydrolysates

Exploitation of plant proteins as an alternative to animal proteins currently presents an important challenge for food industries. In this contribution, total sunflower protein isolate from cold press meal was used as a starting material for the generation of highly soluble and functional hydrolysates that could be used in various food formulations. To do this, a rational and complete approach of controlled hydrolysis was implemented using the individual Alcalase and Prolyve enzymes. The method of stopping the hydrolysis reaction was also evaluated. The influence of operating conditions on hydrolysis kinetics and enzymatic mechanism was studied to identify the appropriate hydrolysis conditions. The gain of the solubility was then analyzed and compared to that of the initial proteins. Finally, the emulsifying and foaming properties (capacities and stabilities) of the resulting hydrolysates were also assessed. As a result, controlled enzymatic proteolysis significantly improved the sunflower protein solubility at neutral pH (twofold increase) and generated highly soluble hydrolysates. The limited proteolysis also maintained the good foam capacities and allowed an improvement in the initial foam stabilities and emulsifying capacities and stabilities of sunflower proteins. This contribution can greatly increase the value of sunflower meal and help in the development of sunflower protein products in the future.

Sunflower Proteins at Air-Water and Oil-Water Interfaces

The adsorption of a sunflower protein extract at two air-water and oil-water interfaces is investigated using tensiometry, dilational viscoelasticity, and ellipsometry. For both interfaces, a three step mechanism was evidenced thanks to master curve representations of the data taken at different aging times and protein concentrations. At short times, a diffusion limited adsorption of proteins at interfaces is demonstrated. First, a two-dimensional protein film is formed with a partition of the polypeptide chains in the two phases that depends strongly on the nature of the hydrophobic phase: most of the film is in the aqueous phase at the air-water interface, while it is mostly in the organic phase at the oil-water interface. Then a three-dimensional saturated monolayer of proteins is formed. At short times, adsorption mechanisms are analogous to those found with typical globular proteins, while strong divergences are observed at longer adsorption times. Following the saturation step, a thick layer expands in the aqueous phase and appears associated with the release of large objects in the bulk. The kinetic evolution of this second layer is compatible with a diffusion limited adsorption of the minor population of polymeric complexes with hydrodynamic radius R_H ∼ 80 nm, evidenced in equilibrium with hexameric globulins (R_H ∼ 6 nm) in solution. These complexes could result from the presence of residual polyphenols in the extract and raise the question of the role of these compounds in the interfacial properties of plant protein extracts.

Multi-objective optimization of solid/liquid extraction of total sunflower proteins from cold press meal

The impact of pH (6-9) and NaCl concentration (0-0.5 mol.L^-1) on sunflower protein extraction was studied through design of experiments. The considered criteria were protein extraction yield (total proteins, helianthinin and albumins), chlorogenic acids covalently bound to proteins, and free chlorogenic acid concentration in the aqueous extract. Statistical analysis showed that the obtained by design of experiments the polynomial models of each extraction criteria were reliable for predicting the responses. They were employed in an original multi-objective optimization methodology. The optimal conditions revealed to be pH 7.3/0.3 mol.L^-1 NaCl yielded 46.83% and 59.16% of total protein and albumin extraction yield, 1.730 and 1.998 mg.g^-1 of chlorogenic acids covalently bound to helianthinin and albumins in aqueous extract, respectively. The sunflower protein isolate obtained after extraction in this condition had good solubility (40-80% at pH 5-8), functional properties (foaming and emulsifying) and a satisfying color.

Fabrication and Characterization of Curcumin-Loaded Liposomes Formed from Sunflower Lecithin: Impact of Composition and Environmental Stress

There is significant interest in the formulation of liposome-based delivery systems using cheap plant-based commercial sources of lecithin. This study evaluated the impact of phospholipid type on the formation, stability, and curcumin-loading of sunflower liposomes. Four kinds of sunflower lecithin (Sunlipon 50, 65, 75, and 90) with different phosphatidylcholine (PC) levels were used to prepare the liposomes using microfluidization. The particle size, surface charge, microstructure, and stability of the liposomes were determined. All four kinds of lecithin were suitable for fabricating stable liposomes regardless of the PC content. Curcumin was loaded into the liposomes using a newly developed pH-driven method. The loading capacity and heat stability of curcumin increased as the PC content of the lecithin increased. These results showed that commercial plant-based lecithins may be suitable for overcoming some of the hurdles normally associated with using liposomes in the food industry, such as high cost and poor stability.

Comparison of Protein Extracts from Various Unicellular Green Sources

Photosynthetic unicellular organisms are considered as promising alternative protein sources. The aim of this study is to understand the extent to which these green sources differ with respect to their gross composition and how these differences affect the final protein isolate. Using mild isolation techniques, proteins were extracted and isolated from four different unicellular sources (Arthrospira (spirulina) maxima, Nannochloropsis gaditana, Tetraselmis impellucida, and Scenedesmus dimorphus). Despite differences in protein contents of the sources (27-62% w/w) and in protein extractability (17-74% w/w), final protein isolates were obtained that had similar protein contents (62-77% w/w) and protein yields (3-9% w/w). Protein solubility as a function of pH was different between the sources and in ionic strength dependency, especially at pH < 4.0. Overall, the characterization and extraction protocol used allows a relatively fast and well-described isolation of purified proteins from novel protein sources.

Pepsin-Assisted Transglutaminase Modification of Functional Properties of a Protein Isolate Obtained from Industrial Sunflower Meal

The utilization of industrial sunflower meal to produce protein-rich products for the food industry is an alternative approach for better and more efficient use of this agricultural by-product. Sunflower meal proteins possess specific functional properties, which however need improvement to broaden their potential as supplements for delivering high--quality products for human nutrition. The aim of the study is to evaluate the combined influence of low-degree pepsin hydrolysis and transglutaminase (TG) modification on industrial sunflower meal protein isolate functionality at pH=2 to 10. Three TG-modified pepsin hydrolysates with the degree of hydrolysis of 0.48, 0.71 and 1.72% were produced and named TG-PH1, TG-PH2 and TG-PH3, respectively. All three TG-modified pepsin hydrolysates exhibited improved solubility at pH between 3.5 and 5.5 as the highest was observed of TG-PH3 at protein isoelectric point (pI=4.5). Sunflower meal protein isolate and TG-modified sunflower meal protein isolate had greater solubility than the three TG-modified hydrolysates at pH<3 and >7. Significant improvement of foam making capacity (p<0.05) was achieved with all three TG-modified pepsin hydrolysates in the entire pH area studied. Pepsin hydrolysis of the protein isolate with the three degrees of hydrolysis did not improve foam stability. Improved thermal stability was observed with TG-PH3 up to 80 °C compared to the protein isolate (pH=7). At 90 °C, TG modification of the protein isolate alone resulted in the highest thermal stability. Pepsin hydrolysis followed by a treatment with TG could be used to produce sunflower protein isolates with improved solubility, foam making capacity and thermal stability for use in the food industry.

Purification and biochemical characterization of 11S globulin from chan (Hyptis suaveolens L. Poit) seeds

Chan (Hyptis suaveolens) is a Mesoamerican crop highly appreciated since the pre-Hispanic cultures. Its proteins are a good source of essential amino acids; however, there are no reports on the properties of its individual proteins. In this study, the 11S globulin (Hs11S) was purified and biochemically characterized. The molecular weight of native Hs11S was about 150-300 kDa with isoelectric points of 5.0-5.3, composed by four monomers of 53.5, 52, 51.1 and 49.5 kDa, each formed by one acidic subunit and one basic subunit linked by a disulfide bond. Dynamic light scattering, size exclusion chromatography and native PAGE show that Hs11S is assembled in different oligomeric forms. LC-MS/MS analysis confirmed its identity. Hs11S presents antigenic determinants in common with lupin 11S globulin. Carbohydrate moieties or phosphate groups linked to Hs11S were not detected. This information is very useful in order to exploit and utilize rationally chan 11S globulin in food systems.

Isolation and characterization of soluble protein from the green microalgae Tetraselmis sp

Extraction of high-value protein fractions for techno-functional applications in foods can considerably increase the commercial value of microalgae biomass. Proteins from Tetraselmis sp. were extracted and purified after cell disintegration by bead milling, centrifugation, ion exchange chromatography using the absorbent Streamline DEAE, and final decolorization by precipitation at pH 3.5. The algae soluble isolate was free from the intense color typical for algae products and contained 64% (w/w) proteins and 24% (w/w) carbohydrates. The final isolate showed solubility independent of ionic strength and 100% solubility at and above pH 5.5. Since most plant proteins used in foods show poor solubility in the pH range 5.5-6.5, the algae soluble protein isolate could be useful for techno-functional applications in this pH range.

Formation and stability of foams made with sunflower (Helianthus annuus) proteins

Foam properties of a sunflower isolate (SI), as well as those of helianthinin and sunflower albumins (SFAs), were studied at various pH values and ionic strengths and after heat treatment. Less foam could be formed from helianthinin than from SFAs, but foam prepared with helianthinin was more stable against Ostwald ripening and drainage than foam prepared with SFAs. Foams made with SFAs suffered from extensive coalescence. The formation and stability of foams made from reconstituted mixtures of both proteins and from SI showed the deteriorating effect of SFAs on foam stability. Foam stability against Ostwald ripening increased after acid and heat treatment of helianthinin. Partial unfolding of sunflower proteins, resulting in increased structural flexibility, improved protein performance at the air/water interface. Furthermore, it was observed that the protein available is used inefficiently and that typically only approximately 20% of the protein present is incorporated in the foam.

Emulsion properties of sunflower (Helianthus annuus) proteins

Emulsions were made with sunflower protein isolate (SI), helianthinin, and sunflower albumins (SFAs). Emulsion formation and stabilization were studied as a function of pH and ionic strength and after heat treatment of the proteins. The emulsions were characterized with respect to average droplet size, surface excess, and the occurrence of coalescence and/or droplet aggregation. Sunflower proteins were shown to form stable emulsions, with the exception of SFAs at neutral and alkaline pH values. Droplet aggregation occurred in emulsions made with SI, helianthinin, and SFAs. Droplet aggregation and subsequent coalescence of emulsions made with SFAs could be prevented at pH 3. Calcium was found to cause droplet aggregation of emulsions made with helianthinin, at neutral and alkaline pH values. Treatments that increase conformational flexibility of the protein molecule improved the emulsion properties of sunflower proteins.