Effect of ultrasound assisted H2O2/Vc treatment on the hyperbranched Lignosus rhinocerotis polysaccharide: Structures, hydrophobic microdomains, and antitumor activity.

The effect of ultrasonic intensity (28.14, 70.35, and 112.56 W/cm2) on Lignosus rhinocerotis polysaccharide (LRP) degraded by ultrasound assisted H2O2/Vc system (U-H/V) was investigated. U-H/V broke the molecular chain of LRP and improved the conformational flexibility, decreasing the molecular weight, intrinsic viscosity ([η]) and particle size. The functional groups and hyperbranched structure of LRP were almost stable after U-H/V treatment, however, the triple helix structure of LRP was partially disrupted. With increasing ultrasonic intensity, the critical aggregation concentration increased from 0.59 mg/mL to 1.57 mg/mL, and the hydrophobic microdomains reduced. Furthermore, the LRP treated with U-H/V significantly inhibited HepG2 cell proliferation by inducing apoptosis. The increase in antitumor activity of LRP was closely associated with the reduction of molecular weight, [η], particle size and hydrophobic microdomains. These results revealed that U-H/V treatment facilitates the degradation of LRP and provides a better insight into the structure-antitumor activity relationship of LRP.

Emulsified sausages with yeast protein as an animal fat replacer: Effects on nutritional composition, spatial structure, gel performance, and sensory quality.

This paper investigated the effect of yeast protein (YP)-fat replacement on the nutritional composition, spatial structure, gel performance, and sensory quality of emulsified sausages. YP is enriched with essential amino acids (36.49 g/100 g), which improved the nutritional quality of sausages whereas reducing its fat content. Moreover, YP could absorb water and fat, thus the YP-added sausages exhibiting an amount-dependent increase in emulsion stability and water migration. The microstructure illustrated that YP acted as a filler to improve structural homogeneity and compactness of the pork gel network. And YP-fat replacement could significantly enhance the hardness, gel strength and elasticity of sausages whereas decreasing the viscosity. Additionally, at partial or full YP-fat replacement (25-100%), the YP-added sausages scored higher in odor and texture, as well as better antioxidant stability than controls. Overall, YP can be employed as a new fat substitute for the preparation of healthy and nutritional sausages, while maintaining the sensory quality.

Isolation, structural features, rheological properties and bioactivities of polysaccharides from Lignosus rhinocerotis: A review.

L. rhinocerotis, an edible and medicinal mushroom, has long been utilized as folk medicine and nutritional food in Southeast Asia and southern China. Polysaccharides are the main bioactive substances of L. rhinocerotis sclerotia, and they have attracted extensive attention of researchers both at home and abroad. In the past few decades, various methods have been applied to extract polysaccharides from L. rhinocerotis (LRPs) and the structural features of LRPs are closely related to the used methods of extraction and purification. Many studies have confirmed that LRPs possess various remarkable bioactivities, including immunomodulatory, prebiotic, antioxidant, anti-inflammatory and anti-tumor activities and intestinal mucosa protective effect. As a natural polysaccharide, LRP has the potential to be a drug and functional material. This paper systematically reviews the recent studies on structural characteristics, modification, rheological properties and bioactivities of LRPs, and provides a theoretical basis for an in-depth study of the structure-activity relationship, and utilization of LRPs as therapeutic agents and functional foods. Additionally, the further research and development of LRPs are also prospected.

Ultrasound-induced changes in rheological behavior and hydrophobic microdomains of Lignosus rhinocerotis polysaccharide.

Ultrasound is increasingly applied to modify the structures and physicochemical properties of polysaccharides. Hence, this work investigated the ultrasound-induced changes in the rheological behavior and hydrophobic microdomains of Lignosus rhinocerotis polysaccharide (LRP). With an increase in ultrasonic time, the apparent viscosity, storage modulus, loss modulus, and the final percentage recovery of LRP/water system increased to reach the maximum after 10 min treatment and then decreased. These results indicated that short-term (10 min) ultrasound could increase the strength of the network structure of LRP/water system, while longer-term ultrasound (30 and 60 min) weakened the network structure. The self-healing properties of LRP/water system was not affected by ultrasound treatment according to repeated strain and time sweep data. The critical aggregation concentration of the LRP/water system decreased from 2.5 to 1.8 mg/mL after 10 min ultrasound and the number of hydrophobic microdomains increased, suggesting that ultrasound promoted the hydrophobic aggregation of LRP.

Rheological properties and critical concentrations of a hyperbranched polysaccharide from Lignosus rhinocerotis sclerotia.

The application of polysaccharides in the food industry mainly depends on their rheological properties and the polysaccharides in different concentration regions exhibit different rheological properties due to the interactions between polymer chains. Hence, this work investigated the concentration-dependent rheological behavior of Lignosus rhinocerotis polysaccharide (LRP) in water and determined the critical concentrations. The intrinsic viscosity of LRP was 378 ± 32 mL/g and the LRP exhibited more apparent shear-thinning behavior with increasing concentration. The LRP critical overlap and aggregation concentration in water was ~ 2.5 mg/mL, implicating the formation of hydrophobic regions may result from the aggregation and overlap between hyperbranched LRP molecules. The LRP/water system showed higher storage modulus than loss modulus with slight frequency dependence at the concentration of 15 mg/mL, exhibiting the structured liquid behavior. When the concentration increased from 10 mg/mL to 30 mg/mL, the compliance recovery percentage value increased from 58.51% to 92.30%, indicating the formation of a strong gel network in the LRP/water system. Furthermore, the micro-rheological test revealed that the LRP/water system exhibited a concentration-dependent increase in elasticity and viscosity and deterioration in fluidity.

Structure, size and aggregated morphology of a ß-D-glucan from Lignosus rhinocerotis as affected by ultrasound.

The effect of ultrasonic treatment on the structure, size and aggregated morphology of Lignosus rhinocerotis polysaccharide (LRP) was investigated. Ultrasonic treatment for 10 min has demonstrated to improve the aqueous solubility of LRP, leading to a uniform and narrow LRP particle size distribution. Meanwhile, short-time ultrasound was found to obviously decrease the molecular size parameters (Mw, Mn, z1/2, [η] and Rh) of LRP, and transform the hyperbranched LRP molecules into flexible and extended chains, which would reaggregate to form spherical aggregates under long-time ultrasonication. Additionally, Congo red experiment combined with CD analysis indicated the existence of triple helix structure in LRP, which was still retained after ultrasonic treatment. Furthermore, under short-time ultrasonication, the spherical aggregates with some branched chains in the native LRP solution could disaggregate and form triple helixes that could be further arranged to a dense network structure, but the untangled LRP chains would reaggregate after long-time ultrasonication. CHEMICAL COMPOUNDS STUDIED IN THIS ARTICLE: Congo red (PubChem CID: 11313); Sodium hydroxide (PubChem CID: 14798); Potassium bromide (PubChem CID: 253877).

A polysaccharide from Lignosus rhinocerotis sclerotia: Self-healing properties and the effect of temperature on its rheological behavior.

This work investigated the self-healing properties of Lignosus rhinocerotis polysaccharide (LRP) and the effect of temperature on its rheological behavior. Dynamic sweep tests (strain sweep, frequency sweep, and time sweep) showed that the LRP/water system possessed self-healing properties due to the entangled network formed by hyperbranched LRP molecular chains. The flow activation energy of LRP solution calculated by Arrhenius equation was shown to decrease with increasing LRP concentration, indicating that LRP solution at higher concentration was less sensitive to temperature. Temperature ramp test exhibited that LRP had a glass transition temperature (Tg) determined as 49.35 °C and the temperature effect was irreversible. Microrheological test revealed that the LRP aqueous solution can form a gel at room temperature with the concentration ≥ 20 mg/mL. This work provided a theoretical basis for the development of LRP-based self-healing materials and facilitated a deep understanding of the temperature effect on rheological behavior of LRP.

Construction and characterization of antioxidative ferulic acid-grafted carboxylic curdlan conjugates and their contributions on ß-carotene storage stability.

Grafting copolymerization of phenolic acids onto polysaccharides is an important strategy to improve their biological activities. In this study, ferulic acid (FA)-grafted carboxylic curdlan conjugates, namely, Cur-8-g-FA, Cur-24-g-FA, and Cur-48-g-FA, were synthesized by free radical-induced grafting. Results showed that FA was covalently grafted onto carboxylic curdlans via ester bonds. The grafting ratios of Cur-8-g-FA, Cur-24-g-FA, and Cur-48-g-FA were 223.03 ± 12.63, 115.63 ± 5.96, and 152.30 ± 4.57 mg FA/g, respectively, which were related with the carboxylate contents, molecular weights, and chain conformations of carboxylic curdlans. Compared with carboxylic curdlans, the FA-grafted carboxylic curdlan conjugates had lower thermal stability, molecular weight, and rheological property and looser surface morphology but had more prominent antioxidant benefits in vitro, which were proportional to their grafting ratios. Moreover, good storage stability against chemical degradation was exhibited by the ß-carotene in Pickering emulsions stabilized by Cur-8-g-FA with a high grafting ratio and molecular weight.

Production, physicochemical characteristics, and in vitro biological activities of polysaccharides obtained from fresh bitter gourd (Momordica charantia L.) via room temperature extraction techniques.

In this study, polysaccharides (BPSs) were obtained from fresh bitter gourd (Momordica charantia L.) by room temperature extraction techniques, including three-phase partitioning (TPP) and ultrasonic-assisted extraction (UAE) performed in different solvents. The results showed that the extraction methods had significant influence on the extraction yield, chemical composition, weight-average molecular weight (Mw), monosaccharide composition, preliminary structural characterization and microstructure of the BPSs. The BPS-W sample obtained from the bitter gourd residue via UAE in distilled water had a higher uronic acid content (24.22%) and possessed stronger antioxidant capacities and α-amylase and α-glycosidase inhibitory activities than BPS-C extracted with UAE in citric acid, BPS-A extracted with UAE in 1.25 mol/L NaOH/0.05% NaBH4, and BPS-J extracted from bitter gourd juice by TPP. Moreover, BPS-A, which had the lowest Mws, showed the best bile acid-binding capacity among the four BPSs. This study had great potentials for the preparation of bioactive polysaccharides from fresh vegetables.

Emulsifying properties of a ferulic acid-grafted curdlan conjugate and its contribution to the chemical stability of ß-carotene.

A biopolymer-polyphenol conjugate-stabilized oil-in-water emulsion system was established to improve the chemical stability and bioaccessibility of ß-carotene (BC). In this study, the emulsifying properties and contribution of a ferulic acid-grafted curdlan conjugate (Cur-D-g-FA) to the chemical stability of BC were investigated. Results showed that the emulsification ability of emulsions stabilized by Cur-D-g-FA remarkably increased with an increasing concentration from 0.05% to 0.8% (w/v) along with decreasing average droplet sizes, negatively charged zeta potentials, and uniform size distributions. The emulsions stabilized by 0.8% Cur-D-g-FA exhibited pronounced shear thinning and solid-like elastic properties as well as satisfactory oxidation stability. The emulsions stabilized by 0.8% Cur-D-g-FA had excellent ability to improve the chemical stability of BC when exposed to different environmental stresses and resulted in the favorable bioaccessibility of BC in vitro. The results prove that Cur-D-g-FA as a promising stabilizer has great potential to protect liposoluble nutrients in food-grade emulsion-delivery systems.

Conjugation of ferulic acid onto pectin affected the physicochemical, functional and antioxidant properties.

BACKGROUND: Pectin, as a functional ingredient, is best known as a gelling and thickening agent, stabilizer, and fat substitute in processed foods. The synthesis of pectin graft copolymers is considered one of the most fascinating ways to improve its physicochemical and functional properties. In this study, therefore, water-soluble pectin or ultrasound-treated pectins (UP30 and UP60) grafted with ferulic acid (FA) conjugates, pectin-g-FA, UP30-g-FA and UP60-g-FA, were synthesized via a free radical-mediated grafting procedure, and their physicochemical, structural, and functional characteristics were investigated. Moreover, 2,2-diphenyl-1-picryl-hydrazyl (DPPH)-radical scavenging activity, Trolox equivalent antioxidant capacity (TEAC) assay and ferric-reducing ability of plasma (FRAP) assay were used to evaluate their antioxidant activities in vitro. RESULTS: Results showed that FA was covalently grafted onto pectin or ultrasound-treated pectins, and the grafting ratios of pectin-g-FA, UP30-g-FA and UP60-g-FA were 65.43 ± 1.30, 82.55 ± 1.71 and 75.82 ± 0.89 mg FA/g, respectively. Although the molecular weights, apparent viscosities, and thermal stabilities of the three FA-grafted pectin conjugates decreased and their surface morphologies were different from those of native pectin and ultrasound-treated pectins, they possessed prominent DPPH-radical scavenging ability [half maximal inhibitory concentration (IC50 ) of 0.32 to 0.89 mg mL-1 ) and antioxidant capacity (TEAC of 100.02 to 153.42 µmol Trolox/g sample; FRAP: 166.41 to 270.27 µmol FeSO4 /g sample). Their antioxidant potentials were positively correlated with the grafting ratio. CONCLUSION: This study provided a promising strategy for the functionalization of pectin, and the prepared FA-grafted pectin conjugates could be explored as functional ingredients that showed potential for applications in food and agriculture systems. © 2020 Society of Chemical Industry.

Subcritical water extraction-based methods affect the physicochemical and functional properties of soluble dietary fibers from wheat bran.

In this study, subcritical water extraction (SWE), SWE in aqueous citric acid (pH 5.0) (SWEC), and ultrasound-assisted SWEC (USWEC) were used to extract soluble dietary fiber (SDF) from wheat bran. Results showed that SWE-based methods significantly influenced the physicochemical, functional, and biological properties of the SDF. The fraction SDF-III attained via USWEC had higher SDF yield (46.30%) and carbohydrate content (82.91%), and lower weight-average molecular weight (65.2 kDa) and particle size (1.17 µm), and looser and more porous surface structure, compared with the SDF-I and SDF-II obtained by SWE and SWEC, respectively. USWEC increased the thermal stability and homogeneity of SDF-III but decreased its apparent viscosity and dynamic viscoelasticity. Moreover, the SDF-III exhibited more significant antioxidant and α-amylase inhibitory activities in vitro than SDF-I and SDF-II. Therefore, the USWEC technique had a greater potential for the highly-efficient production of SDF from wheat bran.

Preparation, characterization, rheological and antioxidant properties of ferulic acid-grafted curdlan conjugates.

In this study, water-soluble curdlan products (Cur and Cur-D) were prepared by an alkali-neutralization treatment process, after which ferulic acid (FA)-grafted Cur conjugates (Cur-g-FA and Cur-D-g-FA) were fabricated in the presence and absence of salt by adopting an approach involving free-radicals generated by the ascorbic acid/hydrogen peroxide redox pair under an inert atmosphere. Results showed that FA was successfully grafted onto the C-6 and C-4 positions of the Cur chains through covalent linkages and that the presence of salt exerted minor influences on the grafting ratios and structural characterizations of the products. Cur-g-FA and Cur-D-g-FA showed decreased crystallinity, thermal stability, and rheological properties, as well as a distinct surface morphology, when compared with those of native Cur. However, Cur-g-FA and Cur-D-g-FA also exhibited remarkably enhanced free-radical scavenging ability and antioxidant capacity in vitro. These results indicate that FA-grafted Cur conjugates have great potential application in the field of functional foods.

Effect of ultrasonic intensity on the conformational changes in citrus pectin under ultrasonic processing.

In this study, the effects of ultrasonic intensity on conformational changes in aqueous citrus pectin solution under ultrasonic processing and its possible transition mechanism were investigated. The results demonstrated that higher ultrasonic intensity (104.7 W/cm2) caused larger alterations in the molecular and conformational parameters of the semiflexible pectin (Mark-Houwink relation exponent a: 0.820, conformational parameter α: 0.607, structural parameter ρ: 2.22) in aqueous solution. Meanwhile, the semiflexible chain of pectin became more flexible (a: 0.804, α: 0.601, ρ: 1.75) at higher ultrasonic intensity in aqueous solution, as was verified by atomic force microscopy. Moreover, conformational changes in pectin from semiflexible chains to flexible chains or even flexible coils (a: 0.791, α: 0.597, ρ: 1.70) could be attributed to the decreased degree of methoxylation and neutral sugars in side chains and the destruction of inter- and intramolecular hydrogen bonds under ultrasonic processing. Therefore, these results have important implications for understanding the ultrasonic modification of pectin.

Quaternized curdlan/pectin polyelectrolyte complexes as biocompatible nanovehicles for curcumin.

In this study, a positively charged quaternized curdlan (Qcurd) was used to fabricate polyelectrolyte complex nanoparticles (PEC NPs) with a negatively charged pectin via electrostatic complexation. Results showed that the Qcurd/pectin PEC NPs prepared with 0.5 mg/mL Qcurd and pectin solutions, 1:2 pectin/Qcurd mass ratio, and pH 4.0 in the absence of NaCl were characterized by a spherical morphology in nanoscale, an average particle size of 68 nm, and good dispersibility in aqueous solutions. Curcumin was encapsulated in the Qcurd/pectin PEC NPs through hydrogen bonding with an encapsulation efficiency of ∼82%, a loading content of 13%, and a pH-dependent controlled release. Curcumin-loaded PEC NPs exhibited a significantly enhanced water solubility, excellent free radical scavenging ability and antioxidant capacity in vitro as compared with those of free curcumin.

Conformational and rheological properties of a quaternary ammonium salt of curdlan.

This study investigated the chain conformation, microstructure, and rheological properties of a quaternary ammonium salt of curdlan (Qcurd) in aqueous medium. Results showed that Qcurd exhibited typical polyelectrolyte behavior in pure water, and the normal viscosity character was observed in 0.1 M NaCl aqueous solution. The weight-average molecular weight (Mw), z-average radius of gyration (Rg), hydrodynamic radius (Rh), conformational parameter (α), characteristic constant (a) and structure parameter (ρ) for Qcurd were determined as 8.08 × 104 g/mol, 26.7 nm, 15.0 nm, 0.54, 0.62, and 1.78, respectively, indicating that Qcurd existed as a flexible chain conformation in 0.1 M NaCl solution, verified by atomic force microscopy. Qcurd exhibited more pronounced shear-thinning behavior at higher concentrations. The flow behavior of Qcurd at different concentrations and temperature was well evaluated by power-law model and Arrhenius equation. Dynamic tests revealed that Qcurd showed oscillatory behaviors between a dilute solution and a weak elastic gel.

Effect of different drying methods on the product quality and bioactive polysaccharides of bitter gourd (Momordica charantia L.) slices.

In this study, three drying methods, namely, hot-air drying, freeze drying (FD), and infrared radiation drying (ID), were applied to dry bitter gourd (Momordica charantia L.) slices. Results showed that the drying methods had significant influences on appearance, color, rehydration ratio, and microstructure of dried bitter gourd. FD provided high-quality dried bitter gourd products due to the uniform honeycomb network and less collapsed structure. Three water-soluble bitter gourd polysaccharides (BPS-H, BPS-F, and BPS-I) were obtained from the bitter gourd dried using the three drying methods. The three polysaccharides exhibited similar preliminary structural characteristics with different monosaccharide compositions and molecular weights. BPS-I obtained from ID-dried bitter gourd had higher sugar and uronic acid contents than BPS-H and BPS-F. BPS-I exhibited stronger antioxidant activities and bile acid-binding capacity in vitro than BPS-H and BPS-F. Moreover, BPS-F and BPS-I showed significant α-amylase inhibitory activities in vitro.

pH dependent green synthesis of gold nanoparticles by completely C6-carboxylated curdlan under high temperature and various pH conditions.

A C6-carboxylated curdlan (C6-Cc) obtained from 4-acetamido-TEMPO-mediated oxidation of curdlan was used both as a reducing and stabilizing agent for green synthesis of pH-responsive AuNPs, which was carried out by controlling the pH of the C6-Cc solution at a high temperature (100°C). C6-Cc presented a semi-flexible random coil chain in the aqueous medium at pH 5.5 and became more expanded and rigid in alkaline conditions (pH 7.1-12.0), though the primary chemical structure of C6-Cc was virtually unchanged with the pH variation. The AuNPs prepared with C6-Cc at various pHs were characterized by various instrumental measurements. The shapes and sizes of AuNPs were found to be strongly dependent on the pH of the C6-Cc solution. The C6-Cc-decorated AuNPs exhibited a more well-dispersed spherical morphology with smaller particle sizes under alkaline conditions (pH 7.1-12.0). Through this study, a facile, simple, and green method has been demonstrated for preparation of stimuli-sensitive AuNPs using biocompatible polyanionic polysaccharides.

Purification, structural characterization and bioactivity evaluation of a novel proteoglycan produced by Corbicula fluminea.

A novel proteoglycan, named CFPS-11, was isolated from Corbicula fluminea, which is a food source of freshwater bivalve mollusk. CFPS-11 had an average molecular weight of 807.7kDa and consisted of d-glucose and d-glucosamine in a molar ratio of 12.2:1.0. The protein moiety (∼5%) of CFPS-11 was covalently bonded to the polysaccharide chain in O-linkage type through both serine and thereonine residues. The polysaccharide chain of CFPS-11 was composed of (1→4)-α-d-glucopyranosyl and (1→3,6)-α-d-glucopyranosyl residues, which branched at O-6. The branch chain consisted of (1→)-α-d-glucopyranosyl and (1→)-α-d-N-acetylglucosamine residues. CFPS-11 exhibited significant antioxidant activity in a dose-dependent manner and remarkable inhibition activities against α-amylase and α-glucosidase by in vitro assays. These findings indicated that the CFPS-11 from C. fluminea has the potential for development as a health food ingredient.