Heat-induced amorphous aggregates assembly of soy protein modulate in vitro digestibility of potato starch.

This research focused on the characteristics of amorphous aggregates derived from soy protein (SPAA), and their effects on the structural, physicochemical, and digestive properties of potato starch (PS). The SPAA induced by different heating temperatures at pH 7.0 formed an inhomogeneous spherical structure. The presence of SPAA could improve the degree of short-range order of starch, increase thermal stability, reduce pasting viscosity and breakdown, and setback viscosity values of PS. For the PS complexed with SPAAs under simulated cooking conditions, the fraction of digested starch at 300 min (C300) decreased by 6-14 %, and rapid digestible starch content (RDS) decreased by 18-25 %, while the slowly digestible starch (SDS) and resistant starch (RS) increased by 0.4-3 % and 15-23 %, respectively. The SPAA at higher temperature treatment (SPAA130) reduced digestive rate coefficient (k) values more significantly than SPAA at a lower temperature (SPAA70, SPAA90, SPAA110). And the SPAA had no inhibitory effect on α-amylase. The results of this study would significantly contribute to expanding the theoretical information about protein regulation in starch digestion and promoting the development of healthy foods with digestion-resistant properties.

Physicochemical characteristics and in vitro biological activities of polysaccharides derived from raw garlic (Allium sativum L.) bulbs via three-phase partitioning combined with gradient ethanol precipitation method.

In the present study, three-phase partitioning (TPP) coupled with gradient ethanol precipitation (GEP) was developed for the first time to extract and isolate polysaccharides (GPSs) from raw garlic (Allium sativum L.) bulbs. Four kinds of fructose polymers, namely, GPS35, GPS50, GPS65, and GPS80, were obtained at the final ethanol precipitation concentrations of 35%, 50%, 65%, and 80% (v/v), respectively, and their physicochemical characteristics and in vitro biological activities were investigated. Results indicated that GPS80 had higher carbohydrate (86.68% ± 0.90%) and uronic acid (12.89% ± 0.09%) contents, lower weight-average molecular weight (8.93 × 103 Da), and looser surface morphology than the other three GPSs. Furthermore, among the four GPSs, GPS80 exhibited the strongest antioxidant capacities, inhibitory effects on α-amylase and α-glycosidase, and nitric oxide stimulatory activity on RAW264.7 macrophage cells in vitro. Therefore, this study provides a simple and feasible technological strategy for producing bioactive polysaccharides from raw Allium vegetables.

Effects of structural and conformational characteristics of citrus pectin on its functional properties.

Ultrasonic degradation has become a fascinating strategy for preparing modified pectin, contributing to the improvement of pectin's functional characteristics. In this study, the impacts of structural and conformational characteristics of original and ultrasound-treated citrus pectins on their functional properties were examined. The results showed that compared with ultrasound-treated pectins, untreated pectin presented higher rheological and gelling properties primarily attributed to its larger weight-average molecular weight (Mw), degree of methoxylation, amount of neutral sugar side chains, and z-average radius of gyration, as well as the more extended flexible-chain conformation. However, the ultrasound-treated pectins had better emulsifying properties than untreated pectin in an oil-in-water emulsion system. These properties, visually suggested by morphology analysis, including enhanced emulsifying capacity, emulsifying stability, reduced mean droplet size and negatively charged zeta potential. Moreover, the Mw and chain conformation of untreated and ultrasound-treated pectins played more decisive roles in their functional properties than the others.

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.

Ultrasonic treatment at different pH values affects the macromolecular, structural, and rheological characteristics of citrus pectin.

Ultrasonic degradation has become a promising strategy for producing modified pectin (MP). In this study, the impact of ultrasonic treatment at various pH values (4.0, 7.0, and 10.0) on the macromolecular, structural and rheological characteristics of citrus pectin was investigated. Results demonstrated that ultrasonic irradiation at the higher pH led to larger reductions in the intrinsic viscosity and weight-average molecular weight of pectin. The degradation kinetics of pectin at different pH values under ultrasound well fitted to a second-order reaction kinetics model. Acoustic cavitation, ß-elimination, and demethylation led to the breakage of glycosidic linkages of side chains and methoxyl groups of pectin, but did not have noticeable influences on the main chain of pectin. The ultrasonic treatment at a high pH led to an apparent change in the rheological characteristics of pectin. Therefore, ultrasonic treatment at various pH values can be developed as a viable means to prepare desirable MP.

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.

Proteoglycan isolated from Corbicula fluminea exerts hepato-protective effects against alcohol-induced liver injury in mice.

Corbicula fluminea (Asian clam), a freshwater bivalve mollusk, has been consumed in China for centuries as a health food and traditional Chinese medicine for treating liver diseases and alcoholism. This study aimed to evaluate the hepato-protective effects and potential mechanisms of a proteoglycan (PSP) from C. fluminea on alcohol-induced liver injury in mice. Results showed that PSP pretreatment significantly antagonized the increases in serum alanine aminotransferase, aspartate aminotransferase, triacylglycerides, and hepatic malondialdehyde levels; elevated the antioxidant enzyme activities and hepatic glutathione levels; and suppressed the levels of hepatic inflammatory cytokines in alcohol-induced liver injury in mice (P < 0.05). Histopathological observation further revealed the potential hepato-protective effect of PSP against alcohol damage. Particularly, PSP pretreatment resulted in significantly decreased expression of cytochrome P450 2e1 (CYP2E1) while significantly upregulating the expression of hemeoxygenase-1 (HO-1) (P < 0.05). These results suggested that PSP could protect the liver from hepatocyte injury induced by alcohol possibly by alleviating hepatic lipid metabolism, elevating antioxidant-enzyme activity, suppressing the immune inflammatory response, and reversing the expression levels of CYP2E1 and HO-1. Therefore, PSP may be developed as a food supplement that can be used to prevent liver diseases.

Pectin-decorated selenium nanoparticles as a nanocarrier of curcumin to achieve enhanced physicochemical and biological properties.

In this study, the authors developed pectin-stabilised selenium nanoparticles (pectin-SeNPs) for curcumin (Cur) encapsulation and evaluated their physicochemical properties and biological activities. Results showed that pectin-SeNPs and Cur-loaded pectin-SeNPs (pectin-SeNPs@Cur) exhibited monodisperse and homogeneous spherical structures in aqueous solutions with mean particle sizes of ∼61 and ∼119 nm, respectively. Cur was successfully encapsulated into pectin-SeNPs through hydrogen bonding interactions with an encapsulation efficiency of ∼60.6%, a loading content of ∼7.4%, and a pH-dependent and controlled drug release in vitro. After encapsulation was completed, pectin-SeNPs@Cur showed enhanced water solubility (∼500-fold), dispersibility, and storage stability compared with those of free Cur. Moreover, pectin-SeNPs@Cur possessed significant free radical scavenging ability and antioxidant capacity in vitro, which were stronger than those of pectin-SeNPs. Antitumour activity assay in vitro demonstrated that pectin-SeNPs@Cur could inhibit the growth of HepG2 cells in a concentration-dependent manner, and the nanocarrier pectin-SeNPs exhibited a low cytotoxic activity against HepG2 cells. Therefore, the results suggested that pectin-SeNPs could function as effective nanovectors for the enhancement of the water solubility, stability, and in vitro bioactivities of hydrophobic Cur.

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.

Construction, stability, and enhanced antioxidant activity of pectin-decorated selenium nanoparticles.

Selenium nanoparticles (SeNPs) as a new replacement source of other Se forms applied in nutritional supplements have been associated with health-related issues. Pectin (PEC) as a well-known food-grade polysaccharide has been considered as a potential soft template for the preparation and stabilization of SeNPs in aqueous medium. In this study, therefore, PEC was used as a stabilizer and dispersing agent to form well-dispersed and stable SeNPs under a simple redox system of selenite and ascorbic acid. Se/PEC ratios significantly affected the color of the suspension, particle size, and surface morphology of the as-prepared SeNPs in the presence of PEC. PEC-SeNPs with a Se/PEC ratio of 1:2 appeared amorphous and exhibited a well-dispersed and stable spherical structure with an average size of ∼41 nm, which corresponds to the strong hydrogen bonding between the hydroxyl groups of PEC and SeNPs. The PEC-SeNPs (Se/PEC = 1:2) remained highly stable in different acidic solutions for at least 1 month. Small and highly stable PEC-SeNPs (Se/PEC = 1:2) possessed the strongest DPPH radical scavenging ability and antioxidant capacity among the evaluated PEC-SeNPs. They also possessed a low cytotoxic activity against cancer cells (SPCA-1 and HeLa) and normal cells (RWPE-1) in vitro. These findings suggested that pectin as a surface decorator could be effectively used to improve the stability and antioxidant capacity of SeNPs remarkably.

Three-phase partitioning as an elegant and versatile platform applied to nonchromatographic bioseparation processes.

In recent years, a big trend has been the development of rapid, green, efficient, economical, and scalable approaches for the separation and purification of bioactive molecules from natural sources, which can be used in food, cosmetics, and medicine. As a new nonchromatographic bioseparation technology, three-phase partitioning (TPP) is attracting the attention of a growing number of scientists and engineers. Although a number of studies have been published in the last 40 years regarding the extraction, separation, and purification of numerous bioactive molecules using TPP systems, a background review on TPP partitioning fundamentals and its applications is much needed. Therefore, the present review focuses in detail on the TPP separation process, including the definition of TPP, partitioning mechanisms, parameters for establishing the suitable condition to form precipitate such as concentration of ammonium sulfate, content of tert-butanol, pH and temperature, and the application for separation and purification of protein, enzyme, plant oil, polysaccharide, and other small molecule organic compounds. In addition, the possible directions of future developments in TPP technology are discussed. The review presents a good opportunity, as well as a challenge for scientists, to understand the detailed partitioning rule and to take better use of TPP for the production and separation of various bioactive molecules, which have been intensively applied in the food and medical fields.

Biocompatible Polyelectrolyte Complex Nanoparticles from Lactoferrin and Pectin as Potential Vehicles for Antioxidative Curcumin.

Polyelectrolyte complex nanoparticles (PEC NPs) were fabricated via electrostatic interactions between positively charged heat-denatured lactoferrin (LF) particles and negatively charged pectin. The obtained PEC NPs were then utilized as curcumin carriers. PEC NPs were prepared by mixing 1.0 mg/mL solutions of heat-denatured LF and pectin at a mass ratio of 1:1 (w/w) in the absence of NaCl at pH 4.50. PEC NPs that were prepared under optimized conditions were spherical in shape with a particle size of ∼208 nm and zeta potential of ∼-32 mV. Hydrophobic curcumin was successfully encapsulated into LF/pectin PEC NPs with high encapsulation efficiency (∼85.3%) and loading content (∼13.4%). The in vitro controlled release and prominent antioxidant activities of curcumin from LF/pectin PEC NPs were observed. The present work provides a facile and fast method to synthesize nanoscale food-grade delivery systems for the improved water solubility, controlled release, and antioxidant activity of hydrophobic curcumin.

Structure and antioxidative property of a polysaccharide from an ammonium oxalate extract of Phellinus linteus.

In this paper, the novel polysaccharide PL-A11 was purified from an ammonium oxalate extract of Phellinus linteus mycelia. Its physicochemical properties, structural characteristics, and antioxidant activities were investigated. Results showed that PL-A11 had a weight-average molecular weight (Mw) of 13.8kDa and was mainly composed of arabinose, xylose, mannose, and glucose in a molar ratio of 1.1:1.3:1.0:6.6. The backbone of PL-A11 was composed of (1→4)-α-d-glucopyranosyl, (1→2)-α-d-xylopyranosyl, and (1→3)-α-d-arabinofuranosyl residues, whereas the (1→6)-α-d-mannopyranosyl residues formed branches at the O-2 position with 1-linked-α-d-glucopyranosyl terminal residues. From the antioxidative activity tests in vivo, the administration of PL-A11 obviously enhanced the activity of antioxidant enzymes and significantly reduced the level of malondiadehyde (MDA) in the serum and liver of d-galactose-treated aging mice in a dose-dependent manner, as well as effectively stimulated the immune system of aging mice. These findings implied that PL-A11 could be developed as a potential antioxidant for applications in the functional food, pharmaceutical, cosmetic or nutraceutical industries.

Structural features and antitumor activity of a novel polysaccharide from alkaline extract of Phellinus linteus mycelia.

A novel high molecular weight polysaccharide (PL-N1) was isolated from alkaline extract of the cultured Phellinus linteus mycelia. The weight average molecular weight (Mw) of PL-N1 was estimated at 343,000kDa. PL-N1 comprised arabinose, xylose, glucose, and galactose in the molar ratio of 4.0:6.7:1.3:1.0. The chemical structure of PL-N1 was investigated by FTIR and NMR spectroscopies and methylation analysis. The results showed that the backbone of PL-N1 comprised (1→4)-linked ß-D-xylopyranosyl residues, (1→2)-linked α-D-xylopyranosyl residues, (1→4)-linked α-D-glucopyranosyl residues, (1→5)-linked ß-D-arabinofuranosyl residues, (1→4)-linked ß-D-xylopyranosyl residues which branched at O-2, and (1→4)-linked ß-D-galactopyranosyl residues which branched at O-6. The branches consisted of (1→)-linked α-D-arabinofuranosyl residues. Antitumor activity assay in vitro showed that PL-N1 could inhibit the growth of HepG2 cells to a certain extent in a dose-dependent manner. Thus, PL-N1 may be developed as a potential, natural antitumor agent and functional food.

Recent advances in Cordyceps sinensis polysaccharides: Mycelial fermentation, isolation, structure, and bioactivities: A review.

Cordyceps (Ophiocordyceps sinensis) sinensis, the Chinese caterpillar fungus, is a unique and precious medicinal fungus in traditional Chinese medicine which has been used as a prestigious tonic and therapeutic herb in China for centuries. Polysaccharides are bioactive constituents of C. sinensis, exhibiting several activities such as immunomodulation, antitumour, antioxidant and hypoglycaemic. As natural C. sinensis fruiting body-caterpillar complexes are very rare and expensive, the polysaccharides documented over the last 15-20 years from this fungal species were mostly extracted from cultivated fungal mycelia (intracellular polysaccharides) or from mycelial fermentation broth (exopolysaccharides). Extraction and purification of the polysaccharides is a tedious process involving numerous steps of liquid and solid phase separations. Nevertheless, a large number of polysaccharide structures have been purified and elucidated. However, relationships between the structures and activities of these polysaccharides are not well established. This review provides a comprehensive summary of the most recent developments in various aspects (i.e., production, extraction, structure, and bioactivity) of the intracellular and exopolysaccharides from mycelial fermentation of C. sinensis fungi. The contents and data will serve as useful references for further investigation, production and application of these polysaccharides in functional foods and therapeutic agents.