Characterization of a low-methoxyl pectin extracted from red radish (Raphanus sativus L.) pomace and its gelation induced by NaCl.

There is an increasing demand for obtaining pectin from new sources. Red radish (Raphanus sativus L.) pomace pectin extracted by alkali was low-methoxyl pectin with esterification degree of 10.17 %, galacturonic acid content of 69.71 % (wt), and average molar weight of 78.59 kDa. The pectin primarily consisted of rhamnogalacturonan I and homogalacturonan domains. The predominant monosaccharides of the pectin were galacturonic acid (46.32 mol%), arabinose (16.03 mol%), galactose (10.46 mol%), and rhamnose (10.28 mol%), respectively. The red radish pomace pectin solution exhibited a shear-thinning behavior. NaCl could induce gelation of red radish pomace pectin, and the gel properties of red radish pomace pectin were considerably affected by the NaCl concentration. As the NaCl concentration (0.25-0.50 mol/L) increased, the rate of gelation accelerated, and the time to gelation point appeared earlier. There was an optimal NaCl concentration (0.50 mol/L) for the pectin to form a gel with the greatest solid-like properties, gel hardness (33.84 g) and water-holding capacity (62.41 %). Gelation force analysis indicated gel formation mainly caused by electrostatic shielding effect of Na+ and hydrogen bonding. This research could facilitate the applications of the red radish pomace pectin in the realm of edible hydrocolloids.

Structure and rheology of pectic polysaccharides from baobab fruit and leaves.

Linkage patterns and relaxation dynamics of baobab (Adansonia digitata) polysaccharides have been investigated by means of linkage analysis and rheometry. The fruit polysaccharide was mostly xylogalacturonan, with co-extracted α-glucan. The leaf polysaccharide consists predominantly of two domains, one branched at O-4 of the →2)-Rhap-(1→ residues and another branched at O-3 of the →4)-GalpA-(1→ backbone to single GlcpA-(1→ residues. Master curves of viscoelasticity of fruit polysaccharides manifested strong pH-dependency. At pH below the dissociation constant of galacturonic acid, dispersions showed liquid-like behaviour. In contrast, at neutral pH, a weak gel network formation was observed that destabilised rapidly under the influence of flow fields. The present work identifies xylogalacturonans from baobab fruit as polysaccharides with unique rheological characteristics that may point to new directions in food and pharmaceutical formulation.

Extraction optimization and structural characterization of pectin from persimmon fruit (Diospyros kaki Thunb. var. Rojo brillante).

In this work we have efficiently extracted and characterized pectin from different tissues of astringent (AS) and non-astringent (NAS) persimmon fruits (peel, pulp, whole fruit) for the first time. The highest pectin extraction (≥7.2%) was carried out at 80 °C, 120 min with 1.5% sodium citrate in peel of both AS and NAS persimmon samples. All persimmon pectins showed a molecular weight and galacturonic acid content upper than 328 kDa and 78%, respectively, indicating their suitability as food ingredient. Pectin extracted from AS pulp and peel tissues exhibited an enriched structure in rhamnose and arabinose, whereas the opposite behavior was observed in NAS persimmon whole fruit samples. Remarkably, both pulp tissues (AS and NAS) presented the highest levels of glucose and mannose, non-pectic carbohydrates. In addition, techno-functional assessment (zeta potential, particle size, apparent viscosity, gelation) showed the suitability of the persimmon pectins for a broad range of industrial applications.

Structural differences of polysaccharides from Astragalus before and after honey processing and their effects on colitis mice.

Honey-processed Astragalus is a dosage form of Radix Astragali processed with honey, which exhibits better efficacy of tonifying Qi than the raw product. Polysaccharides are its main water-soluble active components. This work was designed to study the structural differences of homogeneous honey-processed Astragalus polysaccharides (HAPS3a) and Astragalus polysaccharides (APS3a) and their effects on colitis mice. The results showed that HAPS3a (Mw = 2463.5 kDa) and APS3a (Mw = 3373.2 kDa) differed in molecular weight, monosaccharide compositions, glycosidic bonds and degree of branching (DB). Notably, the molar ratios of galactose and galacturonic acid in HAPS3a were 22.66% and 33.24%, while those in APS3a were 11.87% and 49.55%, respectively. The uronic acid residues 1,4-ß-GalpA and 1,6-α-GlcpA of the backbone in APS3a were converted into the corresponding neutral residues in HAPS3a after honey processing. The different DB of HAPS3a (15.35%) and APS3a (25.13%) suggested that the chain conformation became smoother. The anti-inflammatory effects on colitis mice revealed that HAPS3a exhibited better effects than APS3a by protecting intestinal mucosa, regulating the expression of cytokines and influencing microbiota diversity. Taken together, the differences in anti-inflammatory activity might be related to structural differences caused by honey processing. Our findings have laid a foundation for the processing mechanism of Astragalus.

Xylogalacturonan-enriched pectin from the fruit pulp of Adansonia digitata: Structural characterization and antidepressant-like effect.

The low methyl-esterified and acetylated xylogalacturonan (DM 20 %, DA 2 %, Mw ∼ 58 kDa) was isolated by water extraction for 4 h × 2 at 50 °C (yield 23 %) from the pulp of baobab fruit (Adansonia digitata L.). Subsequent tightening of the conditions for water extraction by mean increasing the temperature to 70 °C and time to 12 h led to the co-extraction of small amounts of starch components and RG I with xylogalacturonan. Structural analysis (DEAE-cellulose ion-exchange chromatography, HPSEC, monosaccharide analysis, NMR spectroscopy) revealed that about 12 mol. % of 1,4-linked α-GalpA residues were substituted by single ß-Xylp residues at the O-3 position. The xylogalacturonan was found to possess an antidepressant-like effect in mice. The study offers using the baobab fruit as a rich source of soluble dietary fiber - water-soluble pectin with beneficial physiological effect.

Physicochemical, Thermal and Rheological Properties of Pectin Extracted from Sugar Beet Pulp Using Subcritical Water Extraction Process.

The objective of this study was to characterize the properties of pectin extracted from sugar beet pulp using subcritical water (SWE) as compared to conventional extraction (CE). The research involved advanced modeling using response surface methodology and optimization of operational parameters. The optimal conditions for maximum yield of pectin for SWE and CE methods were determined by the central composite design. The optimum conditions of CE were the temperature of 90 °C, time of 240 min, pH of 1, and pectin recovery yield of 20.8%. The optimal SWE conditions were liquid-to-solid (L/S) ratio of 30% (v/w) at temperature of 130 °C for 20 min, which resulted in a comparable yield of 20.7%. The effect of obtained pectins on viscoamylograph pasting and DSC thermal parameters of corn starch was evaluated. The contents of galacturonic acid, degree of methylation, acetylation, and ferulic acid content were higher in the pectin extracted by SWE, while the molecular weight was lower. Similar chemical groups were characterized by FTIR in both SWE and CE pectins. Color attributes of both pectins were similar. Solutions of pectins at lower concentrations displayed nearly Newtonian behavior. The addition of both pectins to corn starch decreased pasting and DSC gelatinization parameters, but increased ΔH. The results offered a promising scalable approach to convert the beet waste to pectin as a value-added product using SWE with improved pectin properties.

Enzymatic Extraction and Characterization of Pectin from Cocoa Pod Husks (Theobroma cacao L.) Using Celluclast® 1.5 L.

Cocoa pod husks are a waste generated during the processing of cocoa beans. We aimed to explore the enzymatic extraction of pectin using cellulases. The extraction process was optimized using a central composite design (CCD) and analyzed by response surface methodology (RSM). The parameters optimized were feedstock concentration (%), enzyme dosage (µL/g), and time (h). Three dependent variables were studied: pectin yield (g/100 g dry husk) (R2 = 97.02), galacturonic acid content (g/100 g pectin) (R2 = 96.90), and galacturonic acid yield (g/100 g feedstock) (R2 = 95.35). The optimal parameters were 6.0% feedstock concentration, 40 µL g-1 of enzyme, and 18.54 h, conditions that produced experimentally a pectin yield of 10.20 g/100 g feedstock, 52.06 g galacturonic acid/100 g pectin, and a yield 5.31 g galacturonic acid/100 g feedstock. Using the chemical extraction method, a yield of 8.08 g pectin/100 g feedstock and a galacturonic acid content of 60.97 g/100 g pectin were obtained. Using assisted sonication, a pectin yield of 8.28 g/100 g feedstock and a galacturonic acid content of 42.77 g/100 g pectin were obtained. Enzymatically optimized pectin has rheological and physicochemical features typical of this biomaterial, which provides an interesting alternative for the valorization of cocoa husks.

Composition and structural characterization of pectin in micropropagated and conventional plants of Premma puberula Pamp.

The metabolites produced by plants can be enhanced by plant tissue culture. In Premma puberula Pamp., the pectin content in leaves is 30 %-40 %, and it is widely used in the food industry and medicine. However, inefficient propagation has seriously restricted the utilization of pectin resources. Therefore, we established an efficient micropropagation technology for P. puberula through comparative analysis in mature leaves of regenerated and conventionally propagated plants. The results showed that the pectin composition of their leaves was similar in terms of galacturonic acid, monosaccharide composition, degree of esterification, functional groups, nuclear magnetic resonance spectrum and morphological characteristics. Furthermore, micropropagated plants had better hardness, gumminess and chewiness characteristics than conventionally propagated plants and were similar in emulsion stability, adhesiveness, springiness, cohesiveness and viscoelasticity. Therefore, micropropagation technology will provide an important guarantee for the industrial production of pectin from P. puberula. The technical essentials include callus induction, embryoid formation, and root induction, followed by acclimatization and transplanting.

Using a novel polysaccharide BM2 produced by Bacillus megaterium strain PL8 as an efficient bioflocculant for wastewater treatment.

In this study, the purification and characterization of a novel polysaccharide-based bioflocculant BM2 produced by a bacterium Bacillus megaterium strain PL8 with self-flocculating property were investigated. The results showed that BM2 was an acidic polysaccharide composed of Gal, GalUA, Glc, GlcUA and Man at a molar ratio of 45.1: 33.8:9.3:9.2:2.4, respectively. The molecular weight of BM2 was 4.55 × 106 Da. BM2 had high flocculation efficiencies across a wide pH ranged from 4 to 11 and a wide temperature ranged from 20 to 100 °C towards kaolin clay. BM2 was a cation-independent bioflocculant which could achieve high flocculation activity without the addition of other cations. Adsorption bridging was the main mechanism in the flocculation process of BM2 towards kaolin clay. The BM2 also displayed a high removal efficiency in terms of Congo red (88.14%) and Pb2+ ions (82.64%). These results suggested that BM2 had a great potential as an efficient bioflocculant candidate in wastewater treatment.

Chemical structure, chain conformation and rheological properties of pectic polysaccharides from soy hulls.

We obtained a new acidic soy hull polysaccharide (SHP-1) with a molecular weight (Mw) of 4.81 × 105 g/mol through ammonium oxalate and microwave assisted extraction. SHP-1 was mainly composed of galacturonic acid, galactose, rhamnose and arabinose (molar ratio = 46.59%:17.95%:14.77%:13.97%) with small amounts of fucose, glucose, mannose and xylose. The chemical structure was presumed to be of pectin-I type, consisting of 2/3 HGA and 1/3 RG-I. Furthermore, the rheological information and the chain morphology of SHP-1 were different in five solvents. Surfactant, salt and alkali solutions enhanced the solubility and flexibility of the polysaccharide, but the polysaccharide showed decreased fluidity under acidic conditions. The addition of ions and alkali increased the consistency coefficient of the solution, but the effect was far less than that of the cross-linking morphology. The structural and morphological information of purified SHP should aid in further study of its structure-function relationships and applications.

Short communication: Stabilization of milk proteins at pH 5.5 using pectic polysaccharides derived from potato tubers.

Potato pectin has unique molecular characteristics that differentiate it from commercially available pectins sourced from citrus peels or apple pomace, including a higher degree of branching and a higher acetyl content. The objective of this study was to evaluate the ability of potato pectin to stabilize milk proteins at an acidic pH above their isoelectric point, pH 5.5, at which no citrus- or apple-derived pectins are functional. Potato pectin was extracted from raw potato tubers by heating at pH 4.5 and 120°C for 30 min after removing starch solubilized using a dilute HCl solution adjusted to pH 2. The potato pectin was found to have a galacturonic acid content of 17.31 ± 3.29% (wt/wt) and a degree of acetylation of 20.20 ± 0.12%. A portion of the potato pectin was deacetylated by heating it in an alkaline condition. The deacetylation resulted in a galacturonic acid content of 19.12 ± 4.64% (wt/wt) and a degree of acetylation of 3.03 ± 0.03%. Particle size distributions in acidified milk drink (AMD) samples adjusted to pH 5.5 demonstrated that the acetylated and deacetylated potato pectins were capable of inhibiting the aggregation of milk proteins to the largest degree at a pectin concentration of 1.0 and 0.25% (wt/wt), respectively. Pectin molecules that were not bound to milk proteins in these AMD samples were quantified after centrifugally separating milk proteins and pectin bound to them from the serum. We found that, for the acetylated and deacetylated potato pectins, all or approximately half of the pectin molecules were bound to milk proteins at a pectin concentration of 0.25 or 1.0% (wt/wt), respectively. These results suggest that the presence of acetyl groups is a critical factor that determines how potato pectin molecules bind electrostatically to milk protein surfaces, form 3-dimensional structures there, and function as a stabilizer. The present results demonstrate that potato pectin can stabilize milk proteins at pH 5.5 and potentially enable the development of novel AMD products with improved functionality for casein-containing products with moderately acidic pH profiles.

Pectin recovery and characterization from lemon juice waste streams.

BACKGROUND: Pectin characteristics from different parts of lemon fruit (Citrus limon L.) were studied as a basis for assessing their suitability for functional applications. Pectin was extracted from lemon albedo, lemon core parts and membranes, and lemon extract using an aqueous extraction protocol. The composition and structural properties of the isolated pectins were examined by means of complementary analytical methods to assess their molecular characteristics for potential industrial applications. RESULTS: The isolation protocol yielded pectins that were predominantly composed of galacturonic acid, with differences in the degree of methylation and neutral sugars content, and with low protein content, indicating high-purity materials. The same extraction protocol resulted in differences in yield and purity between the three different parts of lemon fruit, and in structural variations in the pectin backbone, as evidenced by differences in sugar composition and molecular weight. Solutions of the isolated lemon pectins exhibited pseudoplastic behavior. Macromolecular characterization showed that the lemon extract pectin had the highest molecular weight and hydrodynamic volume, followed by lemon core and lemon albedo pectin. CONCLUSION: The work demonstrates that pectins with distinct structural properties may be extracted from different parts of lemon wastes and used for different technological purposes. © 2019 Society of Chemical Industry.

Characteristics of cell wall pectic polysaccharides affect textural properties of instant controlled pressure drop dried carrot chips derived from different tissue zone.

To better understanding the role of cell wall pectic polysaccharides (CWPs) on the formation of textural properties of carrot chips dried by instant controlled pressure drop technology (French for Détente Instantanée Contrôlée, DIC), the characteristics of CWPs from ground tissue (GT), junction of ground and vascular tissue (JT), and vascular tissue (VT) of carrot were investigated. Larger expansion volume was obtained in the carrot chips derived from GT, which accompanied with superior textural qualities compared with the chips derived from JT and VT. Remarkable differences were obtained in the amount of pectic fractions, galacturonic acid content, degree of methoxylation, sugar composition and linearity of CWPs that fractionated from different tissue zones of raw carrots. The characteristics of CWPs was confirmed to be a substantial factor that significantly affected the expansion ratio and textural properties of the DIC-dried carrot chips, which providing a mechanistic insight of the relationship between variation in CWPs and the expanding behaviors of DIC-dried fruits and vegetables.

Pectin oligosaccharides from hawthorn (Crataegus pinnatifida Bunge. Var. major): Molecular characterization and potential antiglycation activities.

The crude polysaccharide was extracted from hawthorn (Crataegus pinnatifida Bunge. Var. major) and a salt-eluted polysaccharide (SPS-2) was fractionated by DEAE cellulose-52 chromatography. Monosaccharide composition and Fourier-transform infrared (FT-IR) analysis indicated that the SPS-2 contained 72.3% galacturonic acid and may be pectin. The results of antiglycation activity in vitro showed that the medium molecular weight pectin oligosaccharide (MM-POS) had the highest antiglycation activity among SPS-2 degradation products. Moreover, the MM-POS obtained by enzymatic degradation had stronger antiglycation activity than that by ultrasonic assisted enzymatic degradation. Composition analysis of MM-POS obtained from ultrasound-assisted enzymatic degradation showed that polygalacturonans content decreased from 85.1% to 61.9% but the arabinan and rhamnogalacturonans increased from 10.6% to 22.7% and from 3.5% to 13.2%, respectively, compared to the MM-POS obtained from enzymatic degradation. This study will provide a theoretical basis for the application of POSs in the food field, especially the exploitation of antiglycation agents.

Structural characterisation of polysaccharides from roasted hazelnut skins.

Two polysaccharide fractions sequentially extracted with water 1W and alkali 1A, were isolated from the hazelnut skins. The monosaccharide composition together with the FTIR and NMR analyses, indicated that both fractions are formed from a mixture of polysaccharides. The fraction 1W consists of methyl-esterified pectic polysaccharide with rhamnogalacturonan I blocks, branching with arabinose side chains, and with 1,5-, 1,3,5-arabinan and galactan polysaccharides. The fraction 1A is a mixture of deesterified rhamnogalacturonan I and 1,5-, 1,3,5-arabinan and 4-O-Me-glucuronoxylan polysaccharides. The presence of unsaturated galacturonic acid and the heterogeneity of the molecular weights, which Mw ranged between 3.6 and 39 kg mol-1, indicated the pectin degradation during roasting.

Cotyledon pectin molecular interconversions explain pectin solubilization during cooking of common beans (Phaseolus vulgaris).

Dynamics of pectin extractability in cotyledons and seed coats were explored for mechanistic insight into pectin changes due to aging and cooking of beans. In addition, changes in mineral distribution during cooking were determined in order to investigate their retention in the matrix. Pre-soaked fresh and aged beans were cooked in demineralized water for different times and the cotyledons, seed coats and cooking water were lyophilized. From cotyledon and seed coat powders, alcohol insoluble residue (AIR) was extracted and sequentially fractionated into water-, chelator- and sodium carbonate-extractable pectin (WEP, CEP and NEP, respectively). Characterization of pectin in AIR and pectin fractions revealed inherent structural differences between cotyledon and seed coat pectin with the latter exhibiting a lower degree of methylesterification (DM) and being more linear. Due to aging, WEP decreased whilst NEP substantially increased and the CEP fraction and DM of pectin in AIR did not change significantly, suggesting a more crucial role of increased covalent bonding than cation-mediated crosslinking in aging-induced hardening of beans. During cooking, some NEP was converted into WEP and no pectin depolymerization was observed from molar mass distribution profiles. Pectin changes due to aging and cooking of beans were more pronounced in the cotyledon compared to the seed coat. Whilst Ca2+, Fe2+ and Zn2+ were largely retained in the bean matrix during cooking, Mg2+ was largely leached from cotyledons into the cooking water. In conclusion, aging-induced hardening of beans and softening during cooking were found to be premised on interconversion of pectin fractions in cotyledons.

Effect of alkaline de-esterified pectin on the complex coacervation with pea protein isolate under different mixing conditions.

High methoxy citrus pectin (UM88) was saponified to produce modified pectin [M(72, 42, and 9)], with different levels of degree of esterification (DE), to investigate the complex coacervation of pea protein isolate (PPI) with pectin [UM88 and M(72, 42, and 9)]. Regardless of the DE value of pectin, the critical pH corresponding to when insoluble complexes form shifted to higher pH as the mixing ratio increased. The maximum amount of coacervates formed at a biopolymer-mixing ratio of 8:1, 8:1, 10:1 and 15:1 for PPI with UM88, M72, M42, and M9, respectively. Maximum interactions for the protein-pectin admixtures occurred between pH 3.70 and 3.85. PPI complexed with modified pectin displayed greater interactions under their optimal mixing conditions compared to the unmodified pectin. The de-esterification of pectin resulted in more rigid and stiffer pectin, which enhanced its interaction with PPI by shifting the critical parameters to a higher value.

The ratio of chelate-soluble fraction to alcohol insoluble residue is a major influencing factor on the texture of lotus rhizomes after cooking.

The differences in cell wall polysaccharides are considered as a major influencing factor on the texture of plant-based food after cooking. Here, 18 varieties of lotus rhizomes were collected from different regions of China and subjected to analysis, with the aim to identify the key factors that affect the texture of lotus rhizomes after cooking. The texture (hardness) of fresh samples and the samples after thermal treatment for different time periods was examined. The cell wall polysaccharides present in alcohol insoluble residue (AIR) were further subdivided into different fractions, and the composition of monosaccharides in each fraction was analyzed by gas chromatography. We then calculated the sugar ratios to examine the discrepancies in molecular structure among the fractions. Principal component analysis and regression analysis showed that the ratio of chelate-soluble fraction (CSF) to AIR is the major factor affecting the texture of lotus rhizomes after cooking.

Microwave heating extraction of pectin from lime peel: Characterization and properties compared with the conventional heating method.

Microwave and conventional heating methods were used to extract pectin from lime peel waste using different acid extractants (hydrochloric or citric acid) and peel-to-extractant ratios (1:20 or 1:40). Hydrochloric acid as the extractant resulted in a higher yield of pectin with both methods. The methoxyl content and galacturonic acid content of lime peel pectin were in the range 8.74-10.51% and 79.29-95.93%, respectively. The intense band around 1730 cm-1 corresponded to methyl esterified uronic carboxyl groups and confirmed the higher equivalent weight and degree of esterification for the microwave-extracted pectin than that from conventional extraction. Lime peel pectin could be classified as high methoxyl pectin having a rapid-set gel formation. The viscosity and viscoelastic properties of the pectin solution from both heating methods enhanced with increasing solid concentration. Hence, microwave heating can be a short processing time for pectin extraction from lime peel waste with suitable pectin properties.

Characterization of water status and water soluble pectin from peaches under the combined drying processing.

Characterization of water status and water soluble pectin (WSP) from peach were evaluated after different stage of combined drying in which osmotic dehydration (OD) was considered as the pre-treatment prior to instant controlled pressure drop (DIC) - assisted infrared radiation drying (IRD) (IR-DIC). Results showed that the contents of free water and immobilized water decreased to 0 g after the combined drying. The content of bound water increased after IRD treatment. The residual PME activity in peach slices was 153.3-179.6% after OD treatment, while, the PG were totally inactivated after IRD. The degree of esterification (DE), WSP content and average molar mass (Mw) decreased significantly (from 75.00 to 43.74, from 156.00 to 74.91 mg/g AIR and from 2.28 to 0.49 × 105 Da, respectively) after the combined drying. The neutral sugar of WSP was mainly composed by galactose, arabinose and rhamnose, whose contents decreased after the combined drying. However, OD treatment would slow down the degradation. There was a low peak at 1740 cm-1 in FT-IR spectrum observed for WSP after IRD and DIC treatment, which might illustrate the degradation of WSP during the combined drying.