Physicochemical and structural properties of proteins extracted from dehulled industrial hempseeds: Role of defatting process and precipitation pH

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.

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.

Structural, functional properties, and in vitro digestibility of sunflower protein concentrate as affected by extraction method: Isoelectric precipitation vs ultrafiltration

This study was the first to compare the structural features, functional properties and in vitro digestibility of two protein concentrates produced from defatted sunflower meal via two different three-stage processes (chlorogenic acid removal-alkaline extraction-isoelectric precipitation versus chlorogenic acid removal-alkaline extraction-ultrafiltration; concentrates termed AI-SPC and AU-SPC, respectively). Compared with AI-SPC, AU-SPC with a darker brown color had much higher protein recovery yield and purity, much higher solubility at pH 4-7, higher oil-holding capacity, greater emulsifying and foaming capacities at pH 7 and 9, and slightly lower foaming capacity at pH 3. The bioavailability was higher for AU-SPC after oral-gastric-intestinal digestion. Moreover, AI-SPC occurred as clumps/lumps of particles, whilst AU-SPC appeared as flat blocks with continuous surfaces. AU-SPC was more negatively charged, and had a smaller particle size, less β-sheet, more β-turn, slightly more α-helix structure. These results confirmed the close relationship between protein production methods and its functional properties and digestibility.

Hemp (Cannabis sativa L.) protein: Impact of extraction method and cultivar on structure, function, and nutritional quality

Hemp (Cannabis sativa L.) is increasingly gaining traction as a novel and sustainable source of plant protein. Accordingly, the aim of this study was to investigate the effectiveness of two protein extraction methods, alkaline extraction coupled with isoelectric precipitation (AE-IEP) and salt extraction coupled with ultrafiltration (SE-UF) in producing hemp protein isolates (pH-HPI and salt-HPI) with high purity and yield. Structural characterization as impacted by extraction method and cultivar was performed and related to functional performance and nutritional quality. Both extraction methods, with carefully selected parameters, resulted in HPI with high purity (86.6-88.1% protein) and protein extraction yields (81.6-87.3%). All HPI samples had poor solubility (∼9-20%) at neutral pH compared to commercial soy protein and pea protein isolates (cSPI, cPPI). A relatively high surface hydrophobicity and low surface charge contributed to such poor solubility of HPI. However, HPI demonstrated similar solubility at acidic pH (50-67%) and comparable gel strength (up to 24 N) to cSPI. Comparing experimental amino acid composition to the theoretical amino acid distribution in hemp protein provided insights to the functional performance of the protein isolates. While pH-HPI demonstrated better functionality than salt-HPI, minimal structural, functional, and nutritional differences were noted among the pH-HPI samples extracted from four different cultivars. Overall, results from this work could be used to guide future attempts to further develop successful protein extraction processes, and to provide valuable insights to propel breeding efforts that target enhanced hemp protein characteristics for food applications.

Physicochemical Characterisation of Seeds, Oil and Defatted Cake of Three Hempseed Varieties Cultivated in Spain

The increasing use of hempseed in food products highlights the need for a comprehensive database for scientific research and industrial applications. In food development, information about the techno-functional properties of raw materials plays a crucial role in determining the suitability of each product for specific applications. Thus, this study aims to characterise three hempseed varieties (Ferimon, Henola and Uso-31), comparing their physicochemical and nutritional compositions. Moreover, the study investigates the impact of hempseed varieties on the techno-functional, physical and thermal properties of the partially defatted hempseed flours (PDHFs) obtained from single screw pressing (SSP) oil extraction. The fatty acid and tocopherol profiles of the dehulled seeds and oil were also analysed. Significant variations in yield and physical properties were observed among hempseed varieties, influenced by genetics, adaptation to agro-climatic conditions and cultivation systems. Despite its lower yield (kg/ha), Uso-31 exhibited superior 1000-seed weight, dehulling yield and larger mean seed size (1.79 ± 0.02 mm). Hempseed oil was rich in unsaturated fatty acids, particularly linoleic (51.2-53.4 g/100 g oil) and α-linolenic (14.88-18.97 g/100 oil) acids, showing variations in γ- and α-tocopherols depending on the variety. The variety also influenced the least gelation concentration (LGC) and techno-functional properties such as water absorption capacity (WAC), emulsifying activity (EA) and emulsion stability (ES). SDS-PAGE and DSC measurements indicated the presence of 11S and 7S globulin proteins with denaturation temperatures above 87.8 °C. These findings confirm that the studied hempseed flours are valuable techno-functional and nutritional ingredients suitable for sustainable food formulations.

Microfluidized hemp protein isolate: an effective stabilizer for high-internal-phase emulsions with improved oxidative stability

BACKGROUND

Hemp protein isolates (HPIs), which provide a well-balanced profile of essential amino acids comparable to other high-quality proteins, have recently garnered significant attention. However, the underutilized functional attributes of HPIs have constrained their potential commercial applications within the food and agriculture field. This study advocates the utilization of dynamic-high-pressure-microfluidization (DHPM) for the production of stable high-internal-phase emulsions (HIPEs), offering an efficient approach to fully exploit the potential of HPI resources.

RESULTS

The findings underscore the effectiveness of DHPM in producing HPI as a stabilizing agent for HIPEs with augmented antioxidant activity. Microfluidized HPI exhibited consistent adsorption and anchoring at the oil-water interface, resulting in the formation of a dense and compact layer. Concurrently, the compression of droplets within HIPEs gave rise to a polyhedral framework, conferring viscoelastic properties and a quasi-solid behavior to the emulsion. Remarkably, HIPEs stabilized by microfluidized HPI demonstrated superior oxidative and storage stability, attributable to the establishment of an antioxidative barrier by microfluidized HPI particles.

CONCLUSION

This study presents an appealing approach for transforming liquid oils into solid-like fats using HPI particles, all without the need for surfactants. HIPEs stabilized by microfluidized HPI particles hold promise as emerging food ingredients for the development of emulsion-based formulations with enhanced oxidative stability, thereby finding application in the food and agricultural industries. © 2023 Society of Chemical Industry.

The physicochemical properties, functionality, and digestibility of hempseed protein isolate as impacted by spray drying and freeze drying

Hempseed protein has gained increasing attention for its sustainability and nourishment. This study aimed to investigate the effects of spray drying and freeze drying on the physicochemical properties, functionality, and digestibility of hempseed protein isolate (HPI). Compared to undried-HPI, both drying techniques altered physicochemical and structural properties. Particularly, protein denaturation temperature increased in freeze-dried HPI (FD-HPI) and spray-dried HPI (SD-HPI) samples (∼90 °C) than in undried-HPI (82.5 °C). Lysine content decreased from 38.26 mg/g in undried-HPI to 35.03 and 33.18 mg/g in FD-HPI and SD-HPI, respectively. Results revealed the loss of 26 and 17 kDa bands after drying. Notably, FD-HPI exhibited higher emulsifying stability and oil-holding capacity than SD-HPI. While both FD-HPI and SD-HPI had higher digestibility than undried-HPI, a 50% reduction in the liberation of free α-amino groups after digestion was found. This study provided information regarding changes in HPI after drying, offering insights for HPI production and application in the food industry.

Proteomic Profiles of Whole Seeds, Hulls, and Dehulled Seeds of Two Industrial Hemp (Cannabis sativa L.) Cultivars

As a source of nutritionally important components, hemp seeds are often dehulled for consumption and food applications by removing the hard hulls, which increases their nutritional value. The hulls thus become waste, although they may contain valuable protein items, about which there is a lack of information. The present work is therefore aimed at evaluating the proteome of hemp (Cannabis sativa L.) at the whole-seed, dehulled seed, and hull levels. The evaluation was performed on two cultivars, Santhica 27 and Uso-31, using LC-MS/MS analysis. In total, 2833 protein groups (PGs) were identified, and their relative abundances were determined. A set of 88 PGs whose abundance exceeded 1000 ppm (MP88 set) was considered for further evaluation. The PGs of the MP88 set were divided into ten protein classes. Seed storage proteins were found to be the most abundant protein class: the averages of the cultivars were 65.5%, 71.3%, and 57.5% for whole seeds, dehulled seeds, and hulls, respectively. In particular, 11S globulins representing edestin (three PGs) were found, followed by 7S vicilin-like proteins (four PGs) and 2S albumins (two PGs). The storage 11S globulins in Santhica 27 and Uso-31 were found to have a higher relative abundance in the dehulled seed proteome (summing to 58.6 and 63.2%) than in the hull proteome (50.5 and 54%), respectively. The second most abundant class of proteins was oleosins, which are part of oil-body membranes. PGs belonging to metabolic proteins (e.g., energy metabolism, nucleic acid metabolism, and protein synthesis) and proteins related to the defence and stress responses were more abundant in the hulls than in the dehulled seeds. The hulls can, therefore, be an essential source of proteins, especially for medical and biotechnological applications. Proteomic analysis has proven to be a valuable tool for studying differences in the relative abundance of proteins between dehulled hemp seeds and their hulls among different cultivars.

Mechanistic insights into the improving effects of germination on physicochemical properties and antioxidant activity of protein isolate derived from black and white sesame

Germination is a natural green technology to improve the nutritional and techno-functional quality of plant-based proteins. In this study, the mechanism of improving the functional and antioxidant properties of black and white sesame protein isolates (SPI) through germination process was investigated. Results showed that the surface hydrophobicity and sulfhydryl content increased significantly after germination, which were supported by multispectral analysis suggesting the exposed and unfolded conformational transition of germinated SPI. Moreover, the increased particle size was observed by microscopy analysis and reducing electrophoresis, which indicated that depolymerized protein molecules were rearranged to form protein aggregates during germination. The structural modification induced by germination contributed to the superior solubility (increased to 3.15-fold and 2.36-fold at pH 8 for black and white SPI, respectively), foaming capacity (increased to 3.99-fold and 1.69-fold, respectively), emulsifying ability (increased to 2.84-fold and 2.71-fold, respectively), and diverse chemical antioxidant activities (increased up to 5.60-fold) of SPI in both varieties. This was the first comprehensive study to investigate germination as a promising technology for obtaining high-quality SPI.

Sensory profile of pulse-based high moisture meat analogs: A study on the complex effect of germination and extrusion processing

Germination and extrusion are two processes that could affect beany flavors in pulse-based high-moisture meat analogs (HMMAs). This research studied the sensory profile of HMMAs made by protein-rich flours from germinated/ungerminated pea and lentil. Air-classified pulse protein-rich fractions were processed into HMMAs with twin screw extrusion cooking, optimized at 140 °C (zone 5 temperature) and 800 rpm screw speed. Overall, 30 volatile compounds were identified by Gas Chromatography-Mass Spectrometry/Olfactory. Chemometric analysis exhibited that the extrusion markedly (p < 0.05) reduced beany flavor. A synergistic effect of germination and extrusion process was observed, decreasing some beany flavors such as 1-octen-3-ol and 2,4-decadienal, and the overall beany taste. Pea-based HMMAs are suitable for lighter, softer poultry meat, while lentil-based HMMAs are suited for darker, harder livestock meat. Those findings offer novel insights into the regulation of beany flavors, odor notes, color, and taste to improve the sensory quality of HMMAs.

Micronized cold-pressed hemp seed cake could potentially replace 50% of the phosphates in frankfurters

Present study aimed to investigate the concentration effect of micronized cold-pressed hemp seed cake (MCPHSC) on the quality profiles and sensorial attributes of 50% phosphates reduced frankfurters. The results showed that MCPHSC could be used as an ideal phosphates replacer for obviously decreasing the cooking loss and promoting textural and gel properties of reduced-phosphates frankfurters (P < 0.05), which was verified by scanning electron microscopy. Moreover, the incorporation of MCPHSC could significantly inhibit the occurrence of lipid oxidation of reduced-phosphates frankfurters during storage in a dose-dependent manner (P < 0.05). Additionally, replacing 50% phosphates with 2% (w/w) MCPHSC was found to possess the best optimal replacement effect to enhance the quality profiles of reduced-phosphates frankfurters (P < 0.05). However, a higher amount of MCPHSC had a negative effect on the sensorial evaluations of the reduced-phosphates frankfurters. Our results suggested that the addition of MCPHSC could be applied as a practical way for improving the quality defects of reduced-phosphates frankfurters.

The Impact of Dehulling and Germination on the Physiochemical, Protein Solubility and Water and Oil Holding Capacities of Yellow Eye Bean (Phaseolus vulgaris L.) Protein Concentrates

Pulse varieties including Yellow Eye (YE) beans (Phaseolus vulgaris L.) are a rich source of protein (~26.5%) that can be utilized to create value-added protein concentrates. Pre-treatments including dehulling and germination have been shown to be effective at improving the nutritional and functional properties of extracted protein concentrates. However, the composition and functionality of these protein concentrates can vary depending on the pre-treatments and the method of extraction used (salt vs. alkaline). Furthermore, little is known about the impact of combining these different processing methods on the properties of YE bean protein concentrates. The objective of this study was to evaluate how germination and dehulling pre-treatments individually and when combined influence protein extraction efficiency, physiochemical properties (surface hydrophobicity and intrinsic fluorescence), and the functionality (solubility, oil and water holding capacities) of salt and alkaline extracted protein concentrates. Compared to the salt extracted concentrates, the alkaline protein concentrates exhibited higher protein recovery yields (16–23% vs. 43–56%) respectively. Conversely, the salt extracted protein concentrates exhibited superior functional properties as observed by improved water holding capacities and less variation in their solubilities at different pH values (4 to 10). When the pre-treatments were combined, the salt extracted concentrates exhibited improved extraction efficiencies and improved hydrophobicity and intrinsic fluorescence, whereas the opposite trend was observed in the alkaline protein concentrates. These observations were attributed to differences in the protein content and composition of the salt vs. alkaline protein concentrates. Overall, these findings suggest that dehulling and germination are potential processing methods that may be used to improve the physiochemical characteristics of salt extracted protein concentrates from yellow eye beans. Future research may investigate the potential application of these ingredients in different food formulations.

Physicochemical and Functional Modifications of Hemp Protein Concentrate by the Application of Ultrasonication and pH Shifting Treatments

According to the Food and Agriculture Organization (FAO), protein demand is expected to increase globally by around 40% by 2030 as a response to the world's population growth. Due to their clean label, vegan or vegetarian based applications, nutritional value, and cost-efficient properties, plant-based proteins have been widely studied. However, most of the alternatives currently found in the market have some challenges because of their poor solubility, emulsifying, gelling, and foaming attributes. Hemp seed protein has gained increasing attention due to its unique amino acids and fatty acids profiles. In this study, commercial HPC mixtures were adjusted to pH 2, 4, 6, 8, 10, and 12 followed by ultrasonication (US) for 5 min (5 s on: 5 s off) and incubated for an hour before neutralizing to pH 7. Following the treatments, the samples were analyzed for their hydrodynamic diameter, conductivity, zeta potential, polydispersity index, surface hydrophobicity, solubility, electrophoresis (SDS-PAGE), free sulfhydryl group, and optical characteristics. The samples treated with ultrasound at pH 8 and 10 significantly (p < 0.05) enhanced the solubility of the hemp seed protein by 12.12% and 19.05%, respectively. Similarly, the samples treated with ultrasonication and pH shifting at pH 6, 8, and 10 also significantly increased the amount of free sulfhydryl content (p < 0.05) to 41.6, 58.72, and 46.54 mmol/g from 32.8 mmol/g, respectively. This study shows that the application of ultrasonication and pH shifting is a promising alternative method to modify the functional properties of HPC and widen their applications in the food, cosmetics, and pharmaceutical industries.

Effect of Extracts Derived from Brown Algae (Sargassum horneri) on the Gel Property and Moisture Distribution of Hairtail Surimi Gel (Trichiurus haumela)

The cross-linking degree between myosin affected the surimi gel properties in the hairtail. In this study, the effects of phlorotannin extracts (PE) derived from brown algae (Sargassum horneri) with different concentrations (0.05%, 0.3%, 1% w/w) on the hairtail surimi gel-forming properties were investigated in comparison with the commercial phloroglucinol (PG). The breaking forces of surimi gel with 1% PE and 0.05% PG were increased by 14.80% and 2.73%, respectively. The increase in deformation was 9.66% with 1% PE compared with the control added with water, but there was no increase in deformation of surimi gel with 0.05% PG. The improved surimi gel structure with PE as a bridge for the three-dimensional network forming of protein was observed in the microstructure. Moreover, PE could significantly shorten the water relaxation time (p < 0.05), reduce free water content (p < 0.05), and increase the hydrogen proton density of the hairtail surimi according to the results of NMR, dielectric properties, and MRI map, respectively. Our findings suggest that the extracts from the brown algae could be a potential economical gel structure enhancer to improve the myosin network.

Protein extraction from cold-pressed hempseed press cake: From laboratory to pilot scale

During the production of industrial hempseed oil, a press cake is formed as a byproduct, which is often used as animal feed although it contains a high amount of protein that could be used for human consumption. Extracting this valuable protein would reduce food waste and increase the availability of plant-based protein. A protein extraction process based on the pH-shift method was adapted to improve the protein extraction yield from industrial hempseed press cake (HPC). Parameters such as alkali extraction pH, time, and temperature, as well as isoelectric precipitation pH, were investigated in laboratory scale and were thereafter carried out in a pilot trial to explore the suitability for future scale up. The phytic acid content of the extracted protein isolate was also analyzed to investigate any potential inhibitory effect on mineral absorption. A final protein yield of 60.6%, with a precipitated protein content of 90.3% (dw), was obtained using a constant alkali extraction pH of 10.5 for 1 h at room temperature, followed by precipitation at pH 5.5. The pilot trial showed promising results for the future production of industrial hemp protein precipitate on a larger scale, showing a protein yield of 57.0% and protein content of 90.8% (dw). The amount of phytic acid in the protein isolate produced in the optimal laboratory experiment and in the pilot trial was 0.595 and 0.557 g phytic acid/100 g dw, respectively, which is 83%-88% less than in the HPC. This is in the range of other plant-based protein sources (tofu, kidney beans, peas, etc.). PRACTICAL APPLICATION: Industrial hempseed press cake is a byproduct in the production of industrial hempseed oil, which is mostly used as animal feed, but has the potential to become an additional source of plant-based protein for human consumption with a suitable protein extraction method. The extracted hemp protein could be used to develop new plant-based dairy or meat analog products.

Physicochemical property changes and aroma differences of fermented yellow pea flours: role of Lactobacilli and fermentation time

The aim of this study was to evaluate the physicochemical properties and aroma differences of yellow pea flours fermented by five lactic acid bacteria (LAB) strains including two Lactiplantibacillus, two Lactobacillus, and one Lacticaseibacillus with different fermentation time. The cell population and the pH of pea flour slurry, as well as the proximate chemical composition, amino acids, thermal and pasting properties, surface morphology, and aromatic differences of fermented flours were characterized. The cell population of all strains except for Lactobacillus helveticus was observed to reach above 107 CFU mL-1 after 24 h of fermentation. The fermentation with Lactobacilli resulted in the increase of amino acids and ash contents, and the reduction of fat content. Rapid viscosity analysis indicated that short time (18 h) fermentation with L. helveticus drastically improved the pasting properties of the flours by facilitating starch granule expansion. The aromatic compounds of the fermented yellow pea flours were highly reliant on the strains and fermentation time. The untargeted metabolomics analysis with the aid of multivariate data analysis can discriminate the aroma differences among the fermented yellow pea flours. L. acidophilus fermentation led to the production of three aromatic compounds which may contribute to an improved aromatic profile.