Structural, physicochemical and interfacial stabilisation properties of ultrafiltered African yam bean (Sphenostylis stenocarpa) protein isolate compared with those of isoelectric protein isolate

Green fractionation and hydrolysis of fish meal to improve their techno-functional properties

A green strategy employing water as solvent has been adopted to obtain protein hydrolysates from fish meal (FM), its water-soluble fraction (WSP), and its non-water-soluble fraction (NSP). The techno-functional properties of the hydrolysates have been investigated and compared to hydrolysates obtained with Alcalase®. In general, SWH hydrolysates presented higher content of free amino acids and higher degree of hydrolysis, which reflected on the molecular size distribution. However, Alcalase® hydrolysates presented better solubility (from 74 ± 4% for NSP at pH = 2 up to 99 ± 1% for WSP at pH = 4-7). According to fluorescence experiments, FM and NSP hydrolysates showed the highest surface hydrophobicity, which has been related to better emulsifying properties and higher emulsion stability. The emulsions stabilized with 2%wt. of SWH-treated NSP showed the smallest particle sizes, with D[4,3] = 155 nm at day 0, and good stability, with D[4,3] = 220 nm at day 7, proving that water fractionation followed by SWH treatment is a good method to improve the techno-functional properties of the hydrolysates.

Synthesis, characterization, biological activity, and in vitro digestion of selenium nanoparticles stabilized by Antarctic ice microalgae polypeptide

A new type of uniformly dispersed selenium nanoparticles (SeNPs) was prepared using Antarctic ice microalgae polypeptides (AIMP) as the stabilizer and dispersant. Different characterization techniques and tests show that the SeNPs are effectively combined with AIMP through physical adsorption and hydrogen bonding to form a more stable structure. Orange-red, zero-valence, amorphous, and spherical AIMP-SeNPs with a diameter of 52.07 ± 1.011 nm and a zeta potential of -41.41 ± 0.882 mV were successfully prepared under the optimal conditions. The AIMP-SeNPs had significantly higher DPPH, ABTS and hydroxyl radicals scavenging abilities compared with AIMP and Na2SeO3, and prevented the growth of both Gram-negative and Gram-positive bacteria by disrupting the integrity of cell walls, cell membranes and mitochondrial membranes. The AIMP-SeNPs had higher gastrointestinal stability compared with SeNPs. Thus, this research highlights the crucial role of AIMP as a biopolymer framework in the dispersion, stabilization, and size management of SeNPs and concludes that AIMP-SeNPs can be exploited as a potent antioxidant supplement and antibacterial substance in foods and medicine.

Nutritional, functional, and bioactive properties of african underutilized legumes

Globally, legumes are vital constituents of diet and perform critical roles in maintaining well-being owing to the dense nutritional contents and functional properties of their seeds. While much emphasis has been placed on the major grain legumes over the years, the neglected and underutilized legumes (NULs) are gaining significant recognition as probable crops to alleviate malnutrition and give a boost to food security in Africa. Consumption of these underutilized legumes has been associated with several health-promoting benefits and can be utilized as functional foods due to their rich dietary fibers, vitamins, polyunsaturated fatty acids (PUFAs), proteins/essential amino acids, micro-nutrients, and bioactive compounds. Despite the plethora of nutritional benefits, the underutilized legumes have not received much research attention compared to common mainstream grain legumes, thus hindering their adoption and utilization. Consequently, research efforts geared toward improvement, utilization, and incorporation into mainstream agriculture in Africa are more convincing than ever. This work reviews some selected NULs of Africa (Adzuki beans (Vigna angularis), African yam bean (Sphenostylis stenocarpa), Bambara groundnut (Vigna subterranea), Jack bean (Canavalia ensiformis), Kidney bean (Phaseolus vulgaris), Lima bean (Phaseolus lunatus), Marama bean (Tylosema esculentum), Mung bean, (Vigna radiata), Rice bean (Vigna Umbellata), and Winged bean (Psophocarpus tetragonolobus)), and their nutritional, and functional properties. Furthermore, we highlight the prospects and current challenges associated with the utilization of the NULs and discusses the strategies to facilitate their exploitation as not only sources of vital nutrients, but also their integration for the development of cheap and accessible functional foods.

Osteogenic activities of four calcium-chelating microalgae peptides

BACKGROUND

Adequate calcium intake is necessary to prevent osteoporosis, which poses significant public health challenges. The natural bioactive peptide calcium chelates have been regarded as superior calcium supplements. Microalgae peptides are regarded as potential candidates for protection from bone loss in osteoporosis. This study aimed to prepare microalgae calcium-chelating peptides from four microalgae proteins and assess their osteogenic activities in osteoporosis-like zebrafish.

RESULTS

After in vitro gastrointestinal digestion, 4.42% Chlorella pyrenoidosa protein, 2.74% Nannochloropsis oceanica protein, 6.07% Arthospira platensis protein and 10.47% Dunaliella salina protein were retained. The calcium-chelating capacities of four microalgae protein hydrolysates (MPHs) ranged from 14.10 ± 7.16% to 34.11 ± 9.34%. CaCl₂ addition increased the maximum absorption peaks, absorption intensities and particle sizes of MPHs. Calcium-chelating MPHs showed stronger osteogenic activities than MPHs in the osteoporosis-like zebrafish model, with significantly increased mineralized tissue area and integrated optical density.

CONCLUSION

Microalgae proteins have favorable digestibilities. Among the four MPHs, Nannochloropsis oceanica protein hydrolysates showed the highest calcium-chelating capacity, which might be due to its high degree of hydrolysis after in vitro digestion and high content of Ser, Tyr, Thr, Asp and Glu. The absorption intensities and particle sizes of MPHs both increased after calcium addition. MPH treatment could reverse dexamethasone-induced osteoporosis of zebrafish, and MPHs-Ca chelates showed higher osteogenic activities in osteoporosis-like phenotype zebrafish. © 2022 Society of Chemical Industry.

Comparative Study of the Structural and Functional Properties of Membrane-Isolated and Isoelectric pH Precipitated Green Lentil Seed Protein Isolates

The demand for isolated seed proteins continues to increase but functionality in food systems can be greatly dependent on the extraction method. In this work, we report the physicochemical and functional properties of lentil seed proteins isolated using various protocols. Lentil flour was defatted followed by protein extraction using isoelectric pH precipitation (ISO) as well as NaOH (MEM_NaOH) and NaCl (MEM_NaCl) extractions coupled with membrane ultrafiltration. The MEM_NaCl had significantly (p < 0.05) higher protein content (90.28%) than the ISO (86.13%) and MEM_NaOH (82.55%). At pH 3-5, the ISO was less soluble (2.26-11.84%) when compared to the MEM_NaOH (25.74-27.22%) and MEM_NaCl (27.78-40.98%). However, the ISO had higher yield and protein digestibility (48.45% and 89.82%) than MEM_NaOH (35.05% and 77.87%) and MEM_NaCl (13.35% and 77.61%), respectively. Near-UV circular dichroism spectra showed that the MEM_NaOH had loose tertiary conformation at pH 3, 5, 7 and 9 while ISO and MEM_NaCl had more compact structures at pH 7 and 9. The three protein isolates formed better emulsions (lower oil droplet sizes) at pH 7 and 9 when compared to pH 3 and 5. In contrast, foaming capacity was better at pH 5 than pH 3, 7, and 9.

Physicochemical, functional and structural properties of the major protein fractions extracted from Cordyceps militaris fruit body

The physicochemical and functional as well as structural properties of major protein fractions (albumin, globulin, glutelin) sequentially extracted in water, salt, alkaline solution respectively from Cordyceps militaris Minfu20 fruit body were investigated. The glutelin (43.11%, w/w) was the predominant protein component of C. militaris fruit body followed by albumin (36.47%) and globulin (17.94%). The three proteins extracted from different solvents showed different characteristics, which were related to the alternation of amino acid composition, surface hydrophobicity, and structural feature. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the albumin and globulin mainly consisted of polypeptides with size < 20 kDa. The glutelin showed serious staining on the lane which may have a relatively bigger molecular weight. Intrinsic fluorescence intensity (FI) suggested glutelin contained more unfolding conformations (highest FI) which were probably resulted in a better foaming capacity of 151% and emulsion formation with the smallest size oil droplets (10.410 µm). The protein fractions showed great nutritional quality since they satisfied all recommended essential amino acid allowances for adults of Food & Agriculture Organization (FAO)/World Health Organization (WHO). Therefore, Cordyceps militaris Minfu20 fruit body proteins have potential alternative renewable edible fungi (mushroom) protein and could be used effectively as a food ingredient to improve food nutrition and product diversification compared with plant proteins.

Heat treatment of sunflower protein isolates near isoelectric point: Effect on rheological and structural properties

In the present study sunflower protein isolates were subjected to heat treatment (80 °C for 5 min, 15 min and 25 min) at three pH values (3.5, 4.5 and 5.5). The strength of gel prepared from treated protein isolates was lower than the gels from native protein isolates and gel strength increased with increase in temperature treatment. Higher denaturation temperatures were observed in treated protein isolates than native protein isolates and increased with increase in thermal treatment time. Treated protein isolates showed more resistance against thermal degradation than native protein isolates as was evident from thermal gravimetric analysis. Secondary and tertiary structure determined by circular dichroism and intrinsic fluorescence respectively were significantly altered after thermal treatment. Lower crystal size along with reduced crystallinity was observed in treated protein isolates than native protein isolates and was further reduced with increase in heating time as was determined by X-ray diffraction.

Physicochemical and functional properties of protein isolate obtained from cottonseed meal

To investigate the effect of preparation methods of cottonseed meals on protein properties, the physicochemical and functional properties of proteins isolated from hot-pressed solvent extraction cottonseed meal (HCM), cold-pressed solvent extraction cottonseed meal (CCM) and subcritical fluid extraction cottonseed meal (SCM) were investigated. Cottonseed proteins had two major bands (at about 45 and 50kD), two X-ray diffraction peaks (8.5° and 19.5°) and one endothermic peak (94.31°C-97.72°C). Proteins of HCM showed relatively more β-sheet (38.3%-40.5%), and less β-turn (22.2%-25.8%) and α-helix (15.8%-19.5%), indicating the presence of highly denatured protein molecules. Proteins of CCM and SCM exhibited high water/oil absorption capacity, emulsifying abilities, surface hydrophobicity and fluorescence intensity, suggesting that the proteins have potential as functional ingredients in the food industry.