Functional and molecular properties of calcium precipitated soy glycinin and the effect of glycation with κ-carrageenan

Na+/K+ enhanced the stability of the air/water interface of soy hull polysaccharide and intestinal mucus

The stable energy barrier of mucin and soy hull polysaccharide (SHP) is established at the air/water interface in the intestinal fluid and is conducive to the absorption and transportation of nutrients. This study aimed to investigate the effect of different concentrations (0.5 % and 1.5 %) of Na+ and K+ on the energy barrier through the digestive system model in vitro. The interaction between ions and microwave-assisted ammonium oxalate-extracted SP (MASP)/mucus was characterized by particle size, zeta potential, interfacial tension, surface hydrophobicity, Fourier transform infrared spectroscopy, endogenous fluorescence spectroscopy, microstructure, and shear rheology. The results showed that the interactions between ions and MASP/mucus included electrostatic interaction, hydrophobic interaction, and hydrogen bond. The MASP/mucus miscible system was destabilized after 12 h, and the ions could improve the system stability to some extent. MASP aggregated continuously with the increase in the ion concentration, and large MASP aggregates were trapped above the mucus layer. Furthermore, the adsorption of MASP/mucus at the interface increased and then decreased. These findings provided a theoretical basis for an in-depth understanding of the mechanism of action of MASP in the intestine.

Glycation Improved the Interfacial Adsorption and Emulsifying Performance of β-Conglycinin to Stabilize the High Internal Phase Emulsions

This study investigated the interfacial adsorption and emulsifying performance of glycated β-conglycinin (7S) with D-galactose (Gal) at various times. Results indicated that glycation increased the particle sizes and zeta potentials of glycated 7S by inducing subunit dissociation. Glycation destroyed the tertiary structures and transformed secondary structures from an ordered one to a disordered one, leading to the more flexible structures of glycated 7S compared with untreated 7S. All these results affected the structural unfolding and rearrangement of glycated 7S at the oil/water interface. Therefore, glycated 7S improved interfacial adsorption and formed an interfacial viscoelasticity layer, increasing emulsifying performance to stabilize high internal phase emulsions (HIPE) with self-supportive structures. Furthermore, the solid gel-like network of HIPE stabilized by glycated 7S led to emulsification stability. This result provided new ideas to improve the functional properties of plant proteins by changing the interfacial structure.

Health Beneficial Bioactivities of Faba Bean Gastrointestinal (In Vitro) Digestate in Comparison to Soybean and Pea

Faba beans are a promising emerging plant-based protein source to be used as a quality alternative to peas and soy. In this study, the potential health beneficial activities of three Canadian faba bean varieties (Fabelle, Malik and Snowbird) were investigated after in vitro gastrointestinal digestion and compared to two commonly used legumes (peas and soy). The results revealed that the faba beans had a higher antioxidant activity than peas when assessed with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays, except for the Fabelle variety. In the oxygen radical absorbance capacity (ORAC) and the iron chelating assays, the faba beans had a lower antioxidant activity than soy. Interestingly, Fabelle and Snowbird showed a higher antioxidant effect than the peas and soy at the cellular level. The antihypertensive properties of Fabelle and Malik varieties were significantly higher than peas but lower than soy. The in vitro antidiabetic activity was higher for soy, but no differences were found at the cellular level. The faba bean peptides were further fractionated and sequenced by mass spectrometry. Eleven peptides with in silico predicted bioactivities were successfully identified in the faba bean digestate and support validating the health-promoting properties of peptides. The results demonstrate the bioactive potential of faba beans as a health-promoting food ingredient against non-communicable diseases.

Effect of chitosan oligosaccharide glycosylation on the emulsifying property of lactoferrin

There is fast increasing interest in the development of alimentary protein stabilized emulsions due to their potential applications in functional food fields. This work studied the effect of glycation degree with chitosan oligosaccharide (COS) on the emulsifying properties of lactoferrin (LF) through Maillard reaction. In the present study, SDS-PAGE and FT-IR were used to confirm LF and COS covalently binding together successfully. Intrinsic fluorescence showed that glycation with COS led more hydrophobic groups exposed to the surface of the structure and particle size increase of LF. Emulsions with 50% (v/v) oil phase and protein concentration of 2% (w/v) was fabricated through one-step shear method. Compared with native LF, emulsions stabilized by LF-COS conjugates showed smaller droplet size and lower creaming index (CI). Among these samples, LF-COS conjugates under 4 h had the best emulsifying efficiency and stability, the emulsion droplet size and the CI of which decreased 39.66% and 28.55% compared with LF, respectively. Furthermore, glycation with COS enhanced the interfacial activity of LF leading to more adsorbing amount and forming thicker layer on the droplets and gel network in the emulsions. This finding would make sense to further understand the modification of emulsifying properties of alimentary proteins through glycosylation with saccharides and develop novel protein-based emulsifiers.

Molecular structure and functional properties of glycinin conjugated to κ-carrageenan and guar gum: A comparative study

Molecular structure and functional properties of glycinin conjugated to κ-carrageenan and guar gum using a dry-heating method were comparatively analyzed. Glycosylation was confirmed by analyzing the degree of grafting, protein subunit composition, infrared absorption profile, and changes in contents of protein secondary structures. K-carrageenan was proven to possess a greater susceptibility to be grafted to glycinin than guar gum due to its relatively low molecular weight and negatively charged characteristics. The improvement of solubility by glycosylation with guar gum near the isoelectric point of glycinin was better than that by glycosylation with κ-carrageenan. Glycinin glycosylated with both polysaccharides exhibited enhanced emulsifying activity and stability. The enhanced apparent viscosity, elastic modulus, and viscous modulus also demonstrated that glycosylation promoted the appearance of stable elastic network structure. In summary, glycosylation with these two polysaccharides conferred glycinin superior emulsifying and rheological properties, and κ-carrageenan exhibited a better performance compared to guar gum.

Hermetia illucens Protein Conjugated with Glucose via Maillard Reaction: Antioxidant and Techno-Functional Properties

The food industry is considering novel sources of proteins with enhanced functionalities to meet the increasing demand and population growth. Edible insect proteins have emerged as an alternative that is environmentally friendly and economically viable and thus could make a significant contribution to global food security. This study was aimed to establish the effect of conjugation via the Maillard reaction on the antioxidant and techno-functional properties of black soldier fly larvae protein concentrate. Reaction mixtures containing black soldier fly larvae protein concentrate and glucose (2 : 1 weight ratio) were wet-heated at 50, 70, and 90°C for 2, 4, 6, 8, and 10 h, respectively, with an initial pH of 9. The results showed that the browning indices of the black soldier fly larvae-glucose (BSFL-Glu) model system increased with an increase in reaction time and temperature, with conjugates formed at 90°C exhibiting the highest browning intensity at 420 nm. At 50°C, the DPPH-RS of the conjugates ranged from 15.47 to 32.37%. The ABTS⁺ radical scavenging activity of BSFL-Glu conjugates produced at 90°C exhibited significantly (p < 0.05) higher scavenging activity as a function of reaction time. The foaming capacity of BSFL-Glu conjugates produced at 70°C showed a significant increase (p < 0.05) as a function of reaction time. Principal component analysis was applied to browning and antioxidant indices. Component 1 of the score plot accounted for 89%, while component 2 accounted for 8% of the observed variability and allowed discrimination/differentiation of the samples based on the heating temperature. These findings provide a practical means to improve the functionality of novel edible insect proteins for food application.

Health Promoting Bioactive Properties of Novel Hairless Canary Seed Flour after In Vitro Gastrointestinal Digestion

The bioactive properties and health-promoting effects of two novel yellow (C09052, C05041) and two brown (Calvi, Bastia) hairless canary seed (Phalaris canariensis L.) cultivars were investigated in comparison to two common cereal grains (wheat and oat). The cereal flours were digested using the standardized INFOGEST in vitro human gastrointestinal digestion model. The three-kilo dalton molecular weight cutoff (3 kDa MWCO) permeate of the generated digestates was assessed in vitro for their antioxidant, chelating, antihypertensive and antidiabetic activities. The results showed no significant differences in studied bioactivities between yellow and brown canary seed cultivars, except for antioxidant activity by the DPPH and chelating Fe2+ assays, where brown cultivars had higher activities. Canary seeds had superior or equivalent antioxidant activity than those from oat and wheat. The anti-hypertensive activity (Angiotensin-converting enzyme (ACE) inhibition) in yellow canary seed cultivars was significantly higher than that of oat and wheat, particularly for C09052 and Calvi varieties. Peptides exhibiting the highest antihypertensive activity from the permeate of the C09052 canary seed variety were further fractionated and identified by mass spectrometry. Forty-six peptides were identified belonging to 18 proteins from the Pooideae subfamily. Fourteen of the parent proteins were homologous to barley proteins. Peptides were analyzed in silico to determine potential bioactivity based on their amino acid composition. All 46 peptides had potential anti-hypertensive and anti-diabetic activities and 20 had potential antioxidant activity, thereby validating the in vitro assay data. Canary seed peptides also exhibited potential antiamnestic, antithrombotic, immunostimulating, opioid and neuro-activity, demonstrating important potential for health promoting effects, particularly against cardiovascular disease.

Effect of Soybean Soluble Polysaccharide on the Formation of Glucono-δ-Lactone-Induced Soybean Protein Isolate Gel

The effect of soybean soluble polysaccharide (SSPS) on the formation of glucono-δ-lactone (GDL)-induced soybean protein isolate (SPI) gel was investigated. Electrophoretic analysis showed the SSPS did not change the electrophoretic behavior of SPI during the formation of SPI gel. However, infrared analysis indicated the β-sheet content increased, and the contents of random coil and α-helix decreased in both cooked SPI and SPI gel. The SSPS and SPI might conjugate via the Maillard reaction according to the results of grafting degree, color change, and infrared analyses. The main interactions during the formation of SPI gel changed from non-covalent to electrostatic interaction after adding SSPS. Sulfhydryl group content also increased in both cooked SPI and SPI gel. The water-holding capacity and gel strength of SPI gel decreased as the SSPS concentration increased. Larger aggregate holes were observed in the microstructure of SPI gel at higher SSPS concentration. Thus, SSPS could covalently conjugate with SPI and influence the formation of hydrogen bonds, disulfide bonds, and electrostatic interaction among SPI molecules to eventually form a loose gel network.

Molecular Mechanism for Improving Emulsification Efficiency of Soy Glycinin by Glycation with Soy Soluble Polysaccharide

Glycation with carbohydrates has been considered to be an effective strategy to improve the emulsifying properties of plant storage globulins, but the knowledge is inconsistent and even contradictory. This work reported that the glycation with soy soluble polysaccharide (SSPS) progressively improved the emulsification efficiency of soy glycinin (SG) in a degree-of-glycation (DG)-dependent manner. The glycation occurred in both the acidic (A) and basic (B) polypeptides to a similar extent. The physicochemical and structural properties of glycated SG samples with different DG values of 0-35% were characterized. The emulsifying properties of unglycated and glycated SG were performed on the emulsions at an oil fraction of 0.3 and a protein concentration in the aqueous phase, produced using microfluidization as the emusification process. The glycation with increasing the DG led to a progressive decrease in solubility and surface hydrophobicity but remarkably increased the magnitude of ζ-potential. Dynamic latter scattering and spectroscopic results showed that the glycation resulted in a gradual dissociation of the 11S-form SG at the quaternary level (into different [AB] subunits), in a DG-dependent way, while their tertiary ([AB] subunits) and secondary structure were slightly affected. Besides the emulsification efficiency, the glycation progressively accelerated the droplet flocculation and facilitated the adsorption of the proteins at the interface and formation of bridged emulsions. The results demonstrated that the improvement of the emulsification efficiency of SG by the glycation with SSPS was largely attributed to the enhanced conformation flexibility at the [AB] subunit level as well as facilitated formation of bridged emulsions. It was also confirmed that once the glycated SG adsorbed at the interface, it would readily dissociated into subunits; the dissociated [AB] subunits exhibited an outstanding Pickering stabilization. The findings would be of importance for providing new knowledge about the molecular mechanism for the modification of emulsifying properties of oligomeric globulins by the glycation with polysaccharides.

HPMC (hydroxypropyl methylcellulose) as a fat replacer improves the physical properties of low-fat tofu

BACKGROUND

The effect of the addition of hydroxypropyl methylcellulose (HPMC) on the textural properties of low-fat tofu was investigated. Three fat levels (240, 100 and 30 g kg^-1 ) were used to make tofu, which were identified as C (full-fat tofu), L1 and L2. HPMC (5 g kg^-1 ) was added to soymilk to prepare control and low-fat tofu, designated as CH, L1H and L2H.

RESULTS

Soymilk with a lower fat level had a lower viscosity: 143 (C), 100 (L1) and 42 (L2) cP. The addition of HPMC increased the viscosity of all types of soymilk, particularly in L2H (107 cP). With fat reduction, tofu syneresis increased from 19% (C) to 29% (L2), although syneresis of L2H recovered to 19%, which is similar to high-fat control tofu. Decreased fat resulted in a lower firmness in L2 (0.67 N) compared to control (0.78 N). Firmness increased to 1.08 N in L2H tofu, whereas the firmness of CH tofu was 0.63 N. All types of tofu showed a denser, well-connected and cross-linking structure when HPMC was added, especially in L2H tofu.

CONCLUSION

HPMC improved the texture of the low-fat tofu by creating a harder texture and reducing syneresis. HPMC is an effective fat replacer for lower fat soymilk. © 2017 Society of Chemical Industry.