Pectin Type Research Articles

Effects of the Type of Pectin and Concentration of Citric Acid on Digestive Behavior of a Bubble-containing Gel: Evaluation Using a Human Gastric Digestion Simulator

Effects of the Type of Pectin and Concentration of Citric Acid on Digestive Behavior of a Bubble-containing Gel: Evaluation Using a Human Gastric Digestion Simulator

Physico-Chemical Properties of Sugar Beet Pectin-Sodium Caseinate Conjugates via Different Interaction Mechanisms.

Polysaccharides and proteins are frequently conjugated through electrostatic attraction, enzymatic cross-linking, and heat treatment (Maillard reaction) to obtain food structuring ingredients, mostly for their application as emulsifiers. The conjugate partners and their interaction type affect performance at acidic or neutral pH and during thermal processing, thus requiring careful selection. Here, the aggregate properties (particle size, conjugate charge, shear viscosity) of three types of sugar beet pectin (SBP)-sodium caseinate (SC) 1:1 conjugates, at acidic and neutral pH (4.5; 7), as well as their thermal processing stability (80 °C), were investigated. The enzymatically cross-linked SBP:SC was more acid tolerant than the electrostatically interacting conjugates. Maillard cross-linked conjugates aggregated at pH 4.5, suggesting poor emulsifier performance in acidic conditions. At pH 7, the three conjugate types showed similar aggregate properties. The results are discussed in terms of structural re-arrangement.

Dual-Crosslinked Polyacrylamide Binders with Various Polysaccharides and Their Application to High Capacity Anodes

Over the last 20 years, much attention has been devoted to developing new electrode materials with high energy and power densities for lithium ion batteries (LIBs). However, a binder material providing an integrity in a composite electrode seems to have an attention recently due to its great influence on the long-term cyclic stability, rate capability, and irreversible capacity loss of the electrodes. High capacity anodes experiencing large volume change such as silicon is strongly dependent on proper choice of polymeric binder. Polyvinyledene difluoride (PVdF) is the most common binder in commercial LIBs. However, the Si electrode fabricated with PVdF binder showed rapid capacity fades for the first tens of cycles caused by the poor adhesion strength of PVdF on current collector. Moreover, it dissolves only in toxic and expensive organic solvent, m-methyl-2-pyrrolidone, leading to environmental issues for the electrode manufacturing process. To replace the organic solvent, environmental-friendly water soluble polymers such as, polyacrylic acid (PAA), polyvinyl alcohol (PVA), carboxymethyl cellulose, and sodium-alginate (SA) began to be applied to high capacity Si-based anodes and showed excellent binder performance, when compared to conventional PVdF binder due to their robust adhesion to active material and current collector and low electrolyte swelling to maintain the mechanical properties of binder. In spite of these endeavors, further improvement in the binder materials is still required, especially for the use high capacity anodes to have sufficiently stable cyclic performance for commercial application. In this presentation, water-treated dual-crosslinked binder systems will be introduced for a high capacity silicon/graphite electrode. A polysaccharide is first grafted with polyacrylamide (PAAm), and ionic and chemical crosslinkings are subsequently performed to complete dual-crosslinking in the grafted polymer. Three types of polysaccharides, sodium-alginate, sodium-carboxymethyl cellulose, and pectin, will be employed and compared for their performance as a binder material for high-capacity anodes. A variety of characterization tools will used to examine the electrochemical performance of the electrodes containing the dual-crosslinking binder systems.

A new model for the biochemistry of pectin synthesis: GAUTs synthesize diverse HG glycans in structurally and functionally distinct plant cell wall polymers

Each year more than 100 billion tons of carbon dioxide are fixed via photosynthesis into plant biomass, the base of our food chain and a renewable resource for production of chemicals, fuels, materials and bio‐based products. The bulk of plant biomass is plant cell walls, which have evolved during hundreds of millions of years of biotic and abiotic challenge into very complex polymers that support plant longevity up to thousands of years and provide mechanical strength needed for trees to reach heights of 90 meters. Such striking mechanical and physical properties arise from the fine structure of individual wall polymers, the covalent and non‐covalent interactions between them, and the architectural arrangement between the polymers. Among the three major types of cell wall polysaccharides, cellulose, hemicellulose and pectin, pectin is the most complex. Pectin is comprised of the three pectic polysaccharides, homogalacturonan (HG), rhamnogalacturonan I (RG‐I) and rhamnogalacturonan II (RG‐II). Our research focuses on the synthesis of the most abundant pectic polysaccharide, HG, which is a partially methyl‐esterified and acetylated homoglycan of α‐1,4‐linked D‐galacturonic acid. HG is synthesized by the GAUT gene family of 15 proven and putative HG:α‐1,4‐galacturonosyltransferases (HG:GalATs) in Arabidopsis. This family has expanded in grasses and in trees. Our long term goal is to understand which HG glycans are synthesized by the diverse GAUTs, and how the polymers containing these HG glycans contribute to cell wall structure, integrity, plant growth, cell adhesion and plant development. The current biochemical, transgenic and mutant studies showing that at least 6 of the 15 Arabidopsis GAUTs encode HG:GalATs will be summarized and data in support of the hypothesis that different GAUTs synthesize HG glycan regions in unique polymers with different functions in the wall will be presented. Enzymatic properties of a heterologously expressed GAUT1:GAUT7 HG:GalAT complex will be described and a two‐phase model for the non‐processive biosynthesis of homogalacturonan polysaccharides by the GAUT1:GAUT7 complex will be presented. We show that the GAUT1:GAUT7 complex is a distributive glycosyltransferase that catalyzes polymerization of high‐molecular‐weight polysaccharides and has full activity only with acceptors longer than a critical chain length.Support or Funding InformationResearch was supported by USDA AFRI 2010‐65115‐20396 and the BioEnergy Science Center and the Center for Bioenergy Innovation which are US Department of Energy Bioenergy Research Centers supported by the Office of Biological and Environmental Research in the Department of Energy's Office of Science. Also partially funded by Department of Energy Center Grant DESC0015662.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Complexation of pectins varying in overall charge with lysozyme in aqueous buffered solutions

We examined how a particular structural characteristic of pectin, namely its degree of methoxylation (DM), affects its complexation with lysozyme (lys), whereby the phase behavior of the complex system as a whole as well as the aggregation state of the complex phase are considered. Low and medium methoxylated pectins bind lys at pH 5.1 and low ionic strength (I = 0.01) forming highly concentrated gel like complex particles, whereas highly methoxylated pectins undergo liquid/liquid phase separation with lys. “Mother” pectin with DM = 95.1% does not form complexes with lys. Highly charged pectins (low DM) already form complex particles at low pectin/lys weight ratios and have a high yield of the complex phase that consists of relatively large particles. The distribution of pectin within the complex particles has an irregular character for both pectin types. However, whereas for low DM pectin the complex composition reflects that of the mixture, the complex composition with high DM pectin is less sensitive to the mixture composition. Moreover, at low DM, the maximum complexation corresponds to charge neutralization whereas at high DM maximum complexation requires a larger than stoichiometric amount of lys. The minimal I and pH value at which complexation is completely suppressed, decreases with increasing DM of pectin, indicating the presence of electrostatic interactions in all systems. However, the differences in composition of the complexes and the protein/polysaccharide charge ratio at maximal complexation indicate that the exact binding mechanism depends on the pectin DM.

Microgel particle formation: Influence of mechanical properties of pectin-based gels on microgel particle size distribution

Microgel particle formation usually requires a dispersing/emulsifiying step of macrogel into pieces, or of direct-gelled droplets. Either liquid or solid-like, yields and fails under given critical conditions. In this work we studied the influence of a gel's mechanical properties on the resulting particle/droplet sizes. As the structure of the polymer influences its mechanical properties, the viscoelastic and mechanical response of pectin gels towards shear, compressive and tensile stress were analysed. Gels were prepared with different pectin types (amidated pectin and citrus pectin) and pectinic acid, at a constant stoichiometric molar ratio R = 2 x [Ca2+]/[COO−] = 1. A dependency of storage modulus G′, Young's modulus E, and critical breakup stresses and strains on the pectin type used for gelation was shown. Values of the storage modulus G′ were influenced by the degree of methyl-esterification (DM), indicating an increase on the cross-linking density of gels. Gels prepared with pectinic acid (DM = 2) showed overall the highest values of G’. Values of the Young's modulus E as well as fracture stresses and strains depended on the type of strain applied to the gel and the pectin type. Concordant with the G′ values, gels become stiffer and brittle with increasing DM, resulting in higher E values, lower fracture strains and higher fracture stresses. In addition, under compressive stress, gels investigated sustained lower stress values before structural failure. The findings of mechanical and rheological analyses were compared with the particle size distribution of microgels produced from the prepared gels at constant process conditions. Gels with high values for G′ and E, and low fracture stresses and strains were shown to be dense cross-linked gels of brittle material characteristics which resulted in smaller particles compared to more elastic gels.

Drug Release Profiles and Disintegration Properties of Pectin Films.

We assessed the disintegration profiles of the film dosage forms (FDs) prepared using pectin by measuring the amount of pectin dissolved from the films in a limited amount of aqueous medium. Furthermore, we used miconazole and dexamethasone as standard drugs and investigated the relationship between the disintegration rate of the FDs and the rate of drug release. We used two types of pectin in this study to develop thin films with a thickness of approximately 25–35 μm. The FDs gradually disintegrated in the aqueous medium, and the disintegration profile of the FDs differed depending on the types of pectin. In addition, the rate of disintegration of the film matrix affected the dissolution rate of the drug incorporated into the FD. Thus, our results show that FDs prepared using pectin are beneficial because of their high solubility in a limited amount of medium, and the rate of drug release from the FDs can be regulated by selecting a specific type of pectin or by altering the concentration of the film base.

Measuring Pectin Properties to Track Cell Wall Alterations During Plant-Pathogen Interactions.

Plant cell walls act both as a barrier to pathogen entry and as a source of signaling molecules that can modulate plant immunity. Cell walls consist mainly of three polymeric sugars: cellulose, pectin, and hemicellulose (Mohnen et al., Biomass Recalcitrance: deconstructing the plant cell wall for bioenergy, 2008). In Arabidopsis more than 50% of the primary cell wall is pectin (Zablackis et al., Plant Physiol 107:1129-1138, 1995). There are various types of pectin, but all pectins contain galacturonic acid subunits in their backbone (Harholt et al., Plant Physiol 153:384-395, 2010; Mohnen, Curr Opin Plant Biol 11:266-277, 2008). Many pathogens secrete pectin-degrading enzymes as part of their infection strategy (Espino et al., Proteomics 10:3020-3034, 2010; ten Have et al., Mol Plant-Microbe Interact 11:1009-1016, 1998). Pectin is synthesized in a highly esterified fashion and is de-esterified in the cell wall by pectin methylesterases (Harholt et al., Plant Physiol 153:384-395, 2010; Mohnen, Curr Opin Plant Biol 11:266-277, 2008). During plant-pathogen interactions, both the amount and the patterns of pectin methylesterification in the wall can be altered (Bethke et al., Plant Physiol 164:1093-1107, 2014; Lionetti et al., J Plant Physiol 169:1623-1630, 2012). Pectin methylesterifications influence mechanical properties of pectin, and pectins must be at least partially de-methylesterified to be substrates for pectin-degrading enzymes (Levesque-Tremblay et al., Planta 242:791-811, 2015). Additionally, alterations of pectin methylesterification or pectin content affect pathogen growth (Bethke et al., Plant Physiol 164:1093-1107, 2014; Lionetti et al., J Plant Physiol 169:1623-1630, 2012; Bethke et al., Plant Cell 28:537-556, 2016; Raiola et al., Mol Plant-Microbe Interact 24:432-440, 2011; Vogel et al., Plant Cell 14:2095-2106, 2002; Vogel et al., Plant J 40:968-978, 2004; Wietholter et al., Mol Plant-Microbe Interact 16:945-952, 2003). This chapter explains a simple protocol that can be used in any molecular biology laboratory to estimate total pectin content using a colorimetric assay and pectin composition using antibodies raised against specific pectin components.

Immunolocalization of a Normal Wood Specific Pectin Methylesterase (CoPME) and Quantification of PME Gene Expression in Differentiating Xylem of <i>Chamaecyparis obtusa</i>

The transverse section of compression wood tracheids has a circular shape and intercellular spaces. The cause has not been determined yet; however, we hypothesized that peeling of the cell wall adhesion would cause cellular intervals, resulting in circularity of the transverse section of tracheids. Homogalacturonan, a type of pectin, functions in cell wall adhesion. Further, pectin methylesterase (PME) is involved in functionalization of homogalacturonan. We quantitated PME gene expression levels in differentiating xylem cells using different degrees of compression wood samples and examined the correlation with circularity of the transverse section of tracheids in each sample. We found that lower gene expression level of the sample corresponded with increasing circularity of the transverse section of tracheids. It is considered that the transverse section of compression wood tracheids becomes circular by suppression of PME gene expression during differentiation. Further, we observed the normal wood specific pectin methylesterase (CoPME) localization in differentiating xylem tracheids by immunolabeling. Labels localized at the entire perimeter of the compound middle lamella in normal wood, whereas sparse labeling was found in compression wood. It suggests that cell walls adhere at sites of CoPME function in differentiating xylem tracheids, but there is inadequate adhesion between cell walls where CoPME does not function. At the end of the expansion zone, the volume of the cell decreases due to a decrease in the turgor pressure of the tracheid. Further, due to moisture shrinkage of the tracheid, the adhesion begins to peel off in places of inadequate adhesion between cell walls, resulting in cell gaps and, thereby, generating a circular cell shape of cell wall formation in compression wood.

Microencapsulación de aceite de semilla de uva mediante secado por aspersión utilizando proteína de suero lácteo y pectina de tejocote

Introduction: Grape seed oil (GSO) contains unsaturated fatty acids that make it susceptible to degradation, causing it to deteriorate. In this sense, microencapsulation in biopolymer matrices is a good alternative to protect it. Objective: To microencapsulate GSO by spray drying of emulsions stabilized with biopolymer complexes formed from whey protein concentrate (WPC) and hawthorn pectin (HP) from two different cultivars. Methodology: Emulsions were developed with different wall material: GSO ratios (2:1 and 3:1) and percentage of total solids (30 and 40 %). The wall materials were WPC-citrus pectin and WPC-HP from two cultivars (HP55 and HP100, with an esterification degree of 70.3 and 61 %, respectively). The factors evaluated were viscosity, mean surface diameter (d3,2) and morphology of the emulsions, and d3,2, microencapsulation efficiency (MEE) and electron microscopy of the microcapsules. Results: The d3,2 of the emulsions ranged from 1.45 to 2.54 μm, where EWPC-HP100,3:1 exhibited the smallest d3,2. These values were related to the type of pectin and were inversely proportional to the viscosity and solids content. The highest MEE was presented by MWPC-HP100,3:1 (71.29 %), which had the highest viscosity and the lowest d3,2 in the emulsion. Study limitations: The behavior of only two hawthorn cultivars is presented. Originality: There are no reports of the use of HP biopolymer complexes from national cultivars and WPC as wall materials for the protection of bioactive materials. Conclusions: The use of novel biopolymers such as HP (HP55 and HP100) allowed obtaining microcapsules with adequate morphology and high ME

Evaluation of adhesion properties of blends of cottonseed protein and anionic water-soluble polymers

There is increasing interest in agro-based, biodegradable and eco-friendly wood adhesives as partial replacements for petroleum-based adhesives. In this work, we studied the adhesion of cottonseed protein isolate (CPI) blended with several anionic water-soluble polymers. Anionic vinyl polymers studied included poly(acrylate), poly(acrylate-co-acrylamide), poly(vinyl sulfate), poly(vinyl sulfonate), and poly(vinyl phosphonate). Anionic polysaccharides studied included three types of carrageenan, carboxymethyl cellulose (CMC), low-methoxy pectin, alginate, and chondroitin sulfate. In general, the adhesive strength of CPI increased with the addition of anionic polymer up to a certain level and then decreased with further polymer addition. Different anionic polymers showed different enhancements. The best result for vinyl polymers was observed for the CPI/poly(vinyl sulfate) blend, which exhibited a 30% improved dry strength over CPI alone. The best results for the polysaccharides were obtained for the CPI/CMC and CPI/pectin blends, with improvements in dry adhesive strength over the CPI control of 66% and 50%, respectively. The CPI/CMC and CPI/pectin blends also showed improved hot water resistance. These findings suggest that the CPI/anionic polymer blends might be useful components in biobased wood adhesive formulations.

Gelatin and pectin complex coacervates as carriers for cinnamaldehyde: Effect of pectin esterification degree on coacervate formation, and enhanced thermal stability

This study developed the multinuclear microcapsules by the complex coacervation between gelatin (G) and high methyl pectin (HMP), low methyl pectin (LMP) as a delivery system for cinnamaldehyde. The parameters affecting the formation of such carriers were investigated by dynamic light scattering and microscopic techniques. Fluorescence analysis and Fourier-transform infrared (FTIR) were used to study protein conformation change during coacervate formation between gelatin and pectin. The results showed that high yield of coacervates with good size and morphology occurred at pH 4.23 and 4.37 for G/HMP with a ratio of 3:1 and G/LMP with a ratio of 6:1 respectively. Fluorescence and FTIR analysis further confirmed their electrostatic interaction and gelatin molecules exhibited a conformational change following the complexation. Thermal gravimetric analysis revealed that microencapsulation of cinnamaldehyde by complex coacervation using gelatin and pectin significantly increased the degradation temperature from 180-220 °C to 350–400 °C. Moreover, high methyl pectin revealed a higher encapsulation efficiency (89.2%) and controlled release of cinnamaldehyde in hot water (33% for 120 min at 80 °C). It could be suggested conformation of pectin types and gelatin might significantly contribute to the overall complexation and cinnamaldehyde microcapsule properties. These findings could be useful for design an ideal carrier to deliver flavors like cinnamaldehyde by complex coacervation using protein and different pectin types.

Effects of Pectin on the Pasting, Rheological, and Textural Properties of Lotus Root Starch

To determine the effects of hydrocolloids on starch properties, high‐methoxyl pectin (HMP), and low‐methoxyl pectin (LMP) are mixed with lotus root starch (LRS). Changes in pasting, rheological, and textural properties, and microstructure of LRS composites are analyzed. LMP increases final viscosity, peak viscosity, breakdown viscosity, retrogradation value, and peak time of starch paste. HMP increases the peak time, but it decreases all other four pasting parameters. LMP increases shearing stress of LRS paste. The shearing stress of LRS paste is proportional to LMP concentration. With increasing consistency coefficient K, the flow behavior index n decreases. Opposite results are observed in HMP. In the LRS/HMP and LRS/LMP, G′ and G″ are positively correlated with LMP content, but these are negatively correlated with HMP. The minimum tanδ is achieved when LRS:LMP = 8:2, thereby indicating the strongest elasticity features. HMP can well inhibit short‐term retrogradation of LRS. Pectin decreases LRS hardness but increases cohesiveness, thereby forming a softer gel. Variations of adhesiveness and springiness are related with pectin type. According to SEM observation, the involvement of LMP destroys the original structure of LRS and forms a stable network structure, which is rare in the LRS/HMP system.

Application of Response Surface Methodology in the Preparation of Pectin-Caseinate Nanocomplexes for Potential Use as Nutraceutical Formulation: A Statistical Experimental Design Analysis

Background: The formation of electrostatic complexes between two types of biopolymers, sodium Caseinate (a derivative from most abundant milk protein) and Pectin (a natural hetro polysaccharide), was studied as a function of biopolymers concentrations and pH of solutions (3.9- 4.3). Method: The size and morphology of the resulted complexes were investigated by using of laser light scattering and transmission electron microscopy, respectively. Response surface methodology (A three-factor, three levels Box-Behnken design) was used for the optimization procedure with pH, pectin and sodium Caseinate concentrations as independent variables. Particle size and polydispersity index of nanocomplexes were considered as dependent variables. Results: Negatively charged nanocomplexes were produced below the isoelectric point of protein (5.4), at pH 4.1 with a suitable colloidal stability and average particle size of about 100 nm. It was found that the particle size of nanocomplexes could be controlled by changing in variables. Conclusion: In conclusion response surface methodology are simple, rapid and beneficial approach for preparation, optimization and investigation of the effect of independent variables on the properties of products.

Adhesive properties of calcium pectinate gels prepared from callus cultures pectins

The aim of this research is to investigate the influence of the surface morphology of the calcium pectinate gel (CaPG) beads as well as the physicochemical characteristics of pectins and the CaPG beads on the adhesive properties of gels against the Gram-negative bacteria Escherichia coli and the Gram-positive bacteria Bacillus subtilis. The adhesion of the bacteria depends on the type of pectin and the surface morphology of the beads. The faster adhesion on CaPG beads appeared to be related to a lower degree of methyl esterification (DE), a higher molecular weight (Mw) and specific viscosity of the pectin and a higher gel strength. Surface roughness measurements were performed using an atomic force microscope. The beads from pectins with a higher Mw, a higher specific viscosity and a lower DE had a higher surface roughness. The surface roughness was one of the factors promoting adhesion of the bacteria onto the calcium pectinate gels. The surface morphology was observed under a scanning electron microscope (SEM). SEM images illustrated that E. coli and B. subtilis adhered on the beads with a rough surface. CaPG beads obtained from callus culture pectins can be proposed for the preparation of gels with adhesive and antiadhesive properties.

Eco-Friendly Synthesis of Biocompatible Pectin Stabilized Graphene Nanosheets Hydrogel and Their Application for the Simultaneous Electrochemical Determination of Dopamine and Paracetamol in Real Samples

The development of novel and simple active sensing materials is still interested to fabricate a new and improved sensing devices for many industrial, medical and environmental applications. In this work, we have synthesized a new type of pectin (PT) and reduced graphene oxide (RGO) hydrogels (PT/RGO) by using simple sonochemical methods and further used as an active sensing material for simultaneous electrochemical detection of dopamine (DA) and paracetamol (AC). In general, PT and RGO have substantial electrocatalytic activity due to the presence of active functional groups. Herein, the successful formation of PT wrapped RGO was studied by using various analytical techniques. Subsequently, the electrochemical performance of PT/RGO modified glassy carbon electrode (GCE) toward the detection of DA and AC were systematically examined by using cyclic voltammetry (CV) and linear sweep voltammetry (LSV) techniques. As the results, PT/RGO/GCE exhibits the excellent electrochemical activity with a low detection limit (LOD) of 1.5 nM and 1.8 nM, for DA and AC respectively. Especially, the possible mechanism behind the proposed sensor (PT/RGO/GCE) toward detection of DA and AC was clearly scrutinized. In addition, the observed excellent stability, and selectivity of PT/RGO/GCE greater support for the real time detection of DA and AC in human serum and pharmaceutical samples. Thus, the proposed PT/RGO is believed as an exclusive active sensing material with desired properties for future electrochemical sensor applications.

The Effectiveness Biosorption of Durian (Durio zibhetinus) Rind Pectin on Handling Liquid Waste Containing Heavy Metal (Pb II)

Heavy metal is one of the most substances occur in water pollutants. It is harmful to humans and other living things. The biosorption of pectin from durian rind is used as a heavy metal binder. However, the type of pectin presented in organic waste is generally HMP (High Methoxyl Pectin), which previously should be demethylation. Durian rind used in this study are originated from Bogor West Java. This study aims to determine the effectiveness of pectin biosorbent in reducing the concentration of heavy metal (Pb II). Pectin extraction was carried out at 80 °C within a time variation of 1; 5; and 6 hours. The results showed that the most optimum pectin is with 6 hours of extraction time where the methoxyl content is 3.46%; weight equivalent 3860 % galacturonate content; the degree of esterification 20.29%; and lead (Pb II) uptake 97%. While durian seeds do not contain pectin.

Use of a plant based polymeric material as a low cost chemical admixture in cement mortar and concrete preparations

Aqueous extract of okra called here as bio-admixture was characterized and tested for using as a sustainable chemical admixture in the production of cement mortar and concrete. Several fresh and hardened states properties of cement mortars and concrete with and without the presence of bio-admixture were evaluated. Interactions of bio-admixture with cement particles during hydrations were also investigated by using conductometric and FTIR spectroscopic methods. Moreover, an improved method was developed to determine water retention capacity of cement pastes. Results indicate that the investigated bio-admixture exhibits viscosity enhancing property. In comparison to the reference cement paste, bio-admixture containing cement pastes have shorter setting times due to increasing hydration rate of cement particles. Solution chemistry and FTIR spectroscopic investigation indicate that the addition of bio-admixture enhances cement hydration rate. Increase hydration rate can be related with the interactions of pectin type heteropolysaccharides present in bio-admixture with Ca2+ ions of cement paste. Compressive strengths of bio-admixture containing mortar and concrete are higher than that of the reference specimens at the investigated curing period. Deterioration of strength of bio-admixture based mortars cured in MgSO4-NaCl solution is distinctly less in comparison to reference, depicting higher durability under such conditions. Most of the properties of cement mortar and concrete are also dependent on the concentrations of bio-admixture in aqueous solution. Therefore, investigated bio-admixture can be considered as a low-cost, environmentally benign viscosity enhancing admixture for producing sustainable cement composites having improved mechanical and durability properties.

Polysaccharides from the South African medicinal plant Artemisia afra: Structure and activity studies

Artemisia afra (Jacq. Ex. Willd), is an indigenous plant in South Africa and other parts of the African continent, where it is used as traditional medicine mostly for respiratory conditions. The objective of this study was to investigate the structural features of the polysaccharides from the leaves of this plant, as well as the biological activities of the polysaccharide fractions against the complement assay. Leaves of Artemisia afra were extracted sequentially with organic solvents (dichloromethane and methanol), 50% aqueous ethanol, and water at 50 and 100°C respectively. The polysaccharide extracts were fractionated by ion exchange chromatography and the resulting fractions were tested for biological activity against the complement fixation assay. Active fractions were further fractionated using gel filtration. Monosaccharide compositions and linkage analyses were determined for the relevant fractions. Polysaccharides were shown to be of the pectin type, and largely contain arabinogalactan, rhamnogalacturonan and homogalacturonan structural features. The presence of arabinogalactan type II features as suggested by methylation analysis was further confirmed by the ready precipitation of the relevant polysaccharides with the Yariv reagent. An unusual feature of some of these polysaccharides was the presence of relatively high levels of xylose as one of its monosaccharide constituents. Purified polysaccharide fractions were shown to possess higher biological activity than the selected standard in the complement assay. Digestion of these polysaccharides with an endo-polygalacturonase enzyme resulted in polymers with lower molecular weights as expected, but still with biological activity which exceeded that of the standard. Thus on the basis of these studies it may be suggested that immunomodulating properties probably contribute significantly to the health-promoting effects of this medicinal plant.

Acid and Deep Eutectic Solvent (DES) extraction of pectin from pomelo (Citrus grandis (L.) Osbeck) peels

Abstract Pectin was extracted from pomelo peel using citric acid. A Box–Behnken design was employed to optimize the yield and the Degree of Esterification (DE) of pectin. The effects of pH, temperature, extraction time and liquid-solid ratio on the yield were investigated. It was found that under optimized conditions at pH 1.80, extraction time of 141 min, temperature of 88 °C and a liquid-solid ratio of 29:1 mL/g, a pectin yield of 39.72% and a DE value of 57.56% were obtained. The results indicate that the pectin extracted from pomelo peel is a slow set high methoxyl type of pectin. pH was found to have the greatest influence on pectin yield and DE. Varying pH at a narrow range between 1 and 2 interestingly showed the formation of diverse pectin functional groups with different structural modifications. The findings suggest that extraction conditions could influence pectin extraction performance, chemical structure, as well as morphological and gelling properties. This study also explored various acid based Deep Eutectic Solvents (DESs) in pectin extraction. The lactic acid–glucose–water DES with a ratio of 6:1:6 gave the highest pectin yield of 23.04%. Citric acid was found to have a better yield performance and more energy saving as compared to DES in pectin extraction.