Pectin Composition Research Articles

Cell Wall Composition and Ultrastructural Immunolocalization of Pectin and Arabinogalactan Protein during Olea europaea L. Fruit Abscission.

Cell wall modification is integral to many plant developmental processes where cells need to separate, such as abscission. However, changes in cell wall composition during natural fruit abscission are poorly understood. In olive (Olea europaea L.), some cultivars such as 'Picual' undergo massive natural fruit abscission after fruit ripening. This study investigates the differences in cell wall polysaccharide composition and the localization of pectins and arabinogalactan protein (AGP) in the abscission zone (AZ) during cell separation to understand fruit abscission control in 'Picual' olive. To this end, immunogold labeling employing a suite of monoclonal antibodies to cell wall components (JIM13, LM5, LM6, LM19 and LM20) was investigated in olive fruit AZ. Cell wall polysaccharide extraction revealed that the AZ cell separation is related to the de-esterification and degradation of pectic polysaccharides. Moreover, ultrastructural localization showed that both esterified and unesterified homogalacturonans (HGs) localize mainly in the AZ cell walls, including the middle lamella and tricellular junction zones. Our results indicate that unesterified HGs are likely to contribute to cell separation in the olive fruit AZ. Similarly, immunogold labeling demonstrated a decrease in both galactose-rich and arabinose-rich pectins in AZ cell walls during ripe fruit abscission. In addition, AGPs were localized in the cell wall, plasma membrane and cytoplasm of AZ cells with lower levels of AGPs during ripe fruit abscission. This detailed temporal profile of the cell wall polysaccharide composition, and the pectins and AGP immunolocalization in the olive fruit AZ, offers new insights into cell wall remodeling during ripe fruit abscission.

PMR5, an acetylation protein at the intersection of pectin biosynthesis and defense against fungal pathogens.

Powdery mildew (Golovinomyces cichoracearum), one of the most prolific obligate biotrophic fungal pathogens worldwide, infects its host by penetrating the plant cell wall without activating the plant's innate immune system. The Arabidopsis mutant powdery mildew resistant5 (pmr5) carries a mutation in a putative pectin acetyltransferase gene that confers enhanced resistance to powdery mildew. Here, we show that heterologously expressed PMR5 protein transfers acetyl groups from [14 C]-acetyl-CoA to oligogalacturonides. Through site-directed mutagenesis, we show that three amino acids within a highly conserved esterase domain in putative PMR5 orthologs are necessary for PMR5 function. A suppressor screen of mutagenized pmr5 seed selecting for increased powdery mildew susceptibility identified two previously characterized genes affecting the acetylation of plant cell wall polysaccharides, RWA2 and TBR. The rwa2 and tbr mutants also suppress powdery mildew disease resistance in pmr6, a mutant defective in a putative pectate lyase gene. Cell wall analysis of pmr5 and pmr6, and their rwa2 and tbr suppressor mutants, demonstrates minor shifts in cellulose and pectin composition. In direct contrast to their increased powdery mildew resistance, both pmr5 and pmr6 plants are highly susceptibile to multiple strains of the generalist necrotroph Botrytis cinerea, and have decreased camalexin production upon infection with B.cinerea. These results illustrate that cell wall composition is intimately connected to fungal disease resistance and outline a potential route for engineering powdery mildew resistance into susceptible crop species.

INFLUENСE OF SEASONAL FACTOR ON THE CHEMICAL COMPOSITION OF PERSIMMON

Persimmon is one of the most popular and favorite fruits not only in Georgia, but also in other countries. People love it for its unique specific taste and high nutritional value. There are more than 500 types of persimmon, properties and tastes which depend on the persimmon growing conditions.
 The purpose of this project was to study the persimmon fruit chemical composition, the regularity in the quantity changes of the bioactive substances and technical-economical persimmon parameters during its storage and technological processing; to develop a highly profitable and efficient composite production technology for a new assortment of products and high quality beverages. Organoleptic and chemical tests of 12 persimmon fruit varieties were made. The content and composition of sugars, polyphenols, pectin, and tanning substances, were defined; and the relation of these parameters to the fruit maturity degree, the dynamics of their change in the ripening and storage process were determined. In addition, we determined the content of sugars ( inverted, total, saccharose), tanning substances (free, total), polyphenols and nitrogen through a spectrophotometric method, dry solids through a refractometric method, pectin (total, soluble, protopectin) and acidity through a potentiometric method, and cellulose through a chlorite method. The feasibility of the persimmon fruit industrial processing was established. Persimmon fruit of Khachia and Khiakume varieties were proved to be the best raw material for the industrial production of a fruit alcohol and beverages. It should be noted here that persimmon fruit must be harvested in November when they have a dark orange colouring and their dry solids content reaches 18%, inverted sugars make up 16-16.5%, and the acidity is 0.12%. For concentrate production, persimmon must be harvested in October when the fruit are yellow and their tanning and colouring substances reach 1.24%, and pectin substances make up 0.77%. The fruit sugars are glucose and fructose, generally in equal quantities. Tanning substances, leicoantocianes, in particular, are responsible for the tart taste; the lower their content is, the less the tart taste is felt, moreover, ripe fruit are less tart in flavour which is due to the tanning substances getting bound with high molecular substances. All the 12 persimmon varieties cultivated in Georgia can be used as raw material, including substandard and overripe fruit that are not marketable and do not have a long shelf life.

Craterostigma plantagineumcell wall composition is remodelled during desiccation and the glycine‐rich protein CpGRP1 interacts with pectins through clustered arginines

Craterostigma plantagineum belongs to the desiccation-tolerant angiosperm plants. Upon dehydration, leaves fold and the cells shrink which is reversed during rehydration. To understand this process changes in cell wall pectin composition, and the role of the apoplastic glycine-rich protein 1 (CpGRP1) were analysed. Cellular microstructural changes in hydrated, desiccated and rehydrated leaf sections were analysed using scanning electron microscopy. Pectin composition in different cell wall fractions was analysed with monoclonal antibodies against homogalacturonan, rhamnogalacturonan I, rhamnogalacturonan II and hemicellulose epitopes. Our data demonstrate changes in pectin composition during dehydration/rehydration which is suggested to affect cell wall properties. Homogalacturonan was less methylesterified upon desiccation and changes were also demonstrated in the detection of rhamnogalacturonan I, rhamnogalacturonan II and hemicelluloses. CpGRP1 seems to have a central role in cell adaptations to water deficit, as it interacts with pectin through a cluster of arginine residues and de-methylesterified pectin presents more binding sites for the protein-pectin interaction than to pectin from hydrated leaves. CpGRP1 can also bind phosphatidic acid (PA) and cardiolipin. The binding of CpGRP1 to pectin appears to be dependent on the pectin methylesterification status and it has a higher affinity to pectin than its binding partner CpWAK1. It is hypothesised that changes in pectin composition are sensed by the CpGRP1-CpWAK1 complex therefore leading to the activation of dehydration-related responses and leaf folding. PA might participate in the modulation of CpGRP1 activity.

Binding kinetics of blueberry pectin-anthocyanins and stabilization by non-covalent interactions

The effect of pectin composition on the binding selectivity to anthocyanins was investigated by Langmuir isotherms with two blueberry pectins, water soluble fraction (WSF) and chelator soluble fraction (CSF). Adsorption was four times higher between CSF and anthocyanins, than WSF and anthocyanins. Higher adsorption was attributed to the more linear, more negatively charged homogalacturonan region of CSF, compared to the more branched, neutral sugar rich WSF. The CSF binding sites (qmax) to anthocyanins were estimated at 1413–1904 μg/mg pectin, which was about eight times higher than WSF binding sites. No difference was observed in binding affinity (KL) among blueberry pectins. WSF, rich in neutral sugar side chains, showed lower and more variable interaction with anthocyanins. Binding studies also showed that blueberry pectin-anthocyanins adsorption was highest at pH 3.0 and lowest at pH 4.0. Increasing concentration from 25 to 200 mM citrate-phosphate (CP) weakened the pectin-anthocyanins interaction between pH values 3.0 and 4.0. However, no significant difference in binding was observed at pH 2.6 with increasing CP. As pH values changed from 4.0 to more acidic pH, electrostatic interaction decreased while hydrophobic interactions increased between blueberry pectin and anthocyanins, and hydrogen bond likely remained constant. Putative health benefits of anthocyanins are probably influenced by small pH and ionic strength changes in food matrixes.

The Formulation of Low Methoxyl Pectin-Based Polyelectrolyte Complexes for Colonic Coating of Probiotic Cells

Polyelectrolyte Complex (PEC) was formed by a cross-linking process of different charges of two or more polymers with cation. The structure of a three-dimensional network of PEC facilitated encapsulation of probiotic cells. Some natural poly-ions belonging to polysaccharides and proteins were used for the PEC formation extensively. This study was aimed to obtain a positively charged polyelectrolyte complex as a colonic coating for probiotic cells using Layer-by-Layer (LbL) technique. This research was undertaken in completely randomized design with three replicates. Treatments comprised formulas containing the composition of Low Methoxyl Pectin (LMP), lysine and diethylamine at different levels of chitosan concentration (T1: chitosan of 0.050%, T2: chitosan of 0.075%; T3: chitosan of 0.100%) compared with control (T0: chitosan of 0%). Results showed that the treatments contributed to viscosity and nitrogen content of PEC. This research gained the best result on T3, where the use of chitosan of 0.100% in the formula made up of LMP, chitosan, lysine and diethylamine characterized by stable positive charges, nitrogen content of 0.00688% and viscosity of 18.53 cP. The application of LMP polyelectrolite (LMPpe) complex of the T3 for probiotic cells coating resulted in good viability until it reached colon with population of 7.67 log cfu/mL (4.67x107 cfu/mL).

Cytological attributes of storage tissues in nematode and eriophyid galls: pectin and hemicellulose functional insights.

Cell walls and protoplast may work together or distinctly in the establishment of the functional profiles of gall tissue compartments. This presumption is herein evaluated in three gall systems by immunocytochemical and ultrastructural analyses. The common storage tissues (CSTs) of leaf galls induced by Eriophyidae on Miconia ibaguensis leaves and by Ditylenchus gallaeformans on M. ibaguensis and M. albicans have rigid and porous cell walls due to their composition of pectins. Hemicelluloses in CST cell walls are scarcer when compared to the cell walls of the control leaves, being functionally compensated by rigid pectate gels. The typical nutritive tissues (TNTs) in galls induced by Ditylenchus gallaeformans are similar to promeristematic and secretory cells regarding their enriched cytoplasm, several mitochondria, and proplastids, as well as multivesicular and prolamellar bodies in cell membranes. The cytological features of the feeding cells of Eriophyidae galls indicate that they are not as metabolically active as the cells of the TNT in nematode galls. However, their cell wall composition suggests more plasticity and porosity than the cells of the TNT, which can compensate the less production of nutrients with more transport. The ultrastructural and immunocytochemical profiles of CST cells reveal functional similarities, which are independent of the taxa of the gall inducer or of the host plant. Despite their analogous functionalities, the protoplast and cell wall features of TNT cells of nematode galls and of the feeding cells of the Eriophyidae galls are distinct, and work out through different strategies toward keeping gall developmental site active.

Pectin extraction from common fig skin by different methods: The physicochemical, rheological, functional, and structural evaluations

Four extraction methods of hot-water (HWE), ultrasound-assisted (UAE), microwave-assisted (MAE), and ultrasound-microwave assisted (UMAE) were utilized to determine the best technique to extract pectin from the common fig (Ficus carica L.) skin. UMAE (11.71%) significantly showed a more extraction yield than MAE (9.26%), UAE (8.74%), and HWE (6.05%). A significant dose-dependent antioxidant capacity for pectins 1,1-diphenyl-2-picryl-hydrazyl (DPPH), and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulphonicacid) (ABTS) radical scavenging activity was found. The UMAE-pectin with the maximum galacturonic acid content (76.85%) and molecular weight (6.91 × 103 kDa) presented the highest emulsifying activity (61.2–61.3%) and emulsion stability (94.3–95.2%) with a monomodal droplet size distribution at cold and ambient storage temperatures. A non-Newtonian shear-thinning behavior was detected at 1.5–3.0% pectic-solutions. X-ray diffraction (XRD) analysis showed a non-crystalline nature for pectins extracted by UMAE. FTIR spectroscopy and HPLC photodiode array detector revealed that conventional and novel extraction technologies do not change the chemical structure and monosaccharide composition of pectin significantly.

Structural characterisation of pectin obtained from cacao pod husk. Comparison of conventional and subcritical water extraction

Pectin was obtained with citric acid and subcritical water extraction from cacao pod husk with or without a previous step consisting of a supercritical fluid extraction of phenols. By subcritical conditions a higher yield (10.9%) was attained in a time 3-fold shorter than that obtained by conventional extraction (˜8%) and a greater effectiveness in the recovery of pectin with higher molecular weight (750 kDa) was also found. Regarding pectin structure, galacturonic acid and degree of methyl esterification content were similar (˜55 and ˜36%, respectively) in both methods. Moreover, pectin recovered by citric acid presented 2-fold higher amount of impurities as compared to subcritical water extraction. Hardly any effects of a previous supercritical treatment were observed in the structure and composition of pectin, indicating the efficiency of the integrated supercritical carbon dioxide and subcritical water extraction as green processes for the obtainment of phenol and pectin from cacao pod husk.

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.

Adsorption of HA (humic acid) using sulfuric acid-crosslinked chitosan/pectin polyelectrolyte complex film

A sulphuric acid-crosslinked chitosan/PEC film had been synthesized and applied for adsorption of HA from aqueous solution. The parameters for adsorption study were an optimum ratio of chitosan/pectin composition, contact time, the effect of the solution pH, and HA concentration. The model for adsorption kinetics and isotherm adsorption as well as desorption study were also conducted. The result showed that the film was durable in water at pH 2 to 12. The analysis using FTIR indicated a shift of absorption peak at 1527 cm−1 (bending vibration N−H in −NH3+). Analysis with SEM showed the morphological differences of the film before and after adsorption and after desorption. Adsorption reached its optimum capacity in the film with a ratio of chitosan and pectin composition 70:30, at pH 6, contact time of 480 mins and HA concentration of 450 mg L−1. The kinetic model of HA adsorption could be explained by the second-order kinetic model of Ho & McKay and the adsorption isotherm follows the Langmuir isotherm model with a maximum adsorption capacity of 50.0 mg g−1, the Langmuir constant (KL) of 1.49×105 L mol−1 and the adsorption energy was found to be 29.7 kJ mol−1. The highest desorption was 82.5% using 1 M NaOH.

Contrasting pectin polymers in guard cell walls of Arabidopsis and the hornwort Phaeoceros reflect physiological differences

In seed plants, stomata regulate CO2 acquisition and water relations via transpiration, while minimizing water loss. Walls of guard cells are strong yet flexible because they open and close the pore by changing shape over the substomatal cavity. Pectins are necessary for wall flexibility and proper stomata functioning. This study investigates the differences in pectin composition in guard cells of two taxa that represent key lineages of plants with stomata: Arabidopsis, an angiosperm with diurnal stomatal activity, and Phaeoceros, a bryophyte that lacks active stomatal movement. Using immunolocalization techniques in transmission electron microscopy, this study describes and compares the localization of pectin molecule epitopes essential to stomata function in guard cell walls of Arabidopsis and Phaeoceros. In Arabidopsis, unesterified homogalacturonans very strongly localize throughout guard cell walls and are interspersed with arabinan pectins, while methyl-esterified homogalacturonans are restricted to the exterior of the wall, the ledges and the junction with adjacent epidermal cells. In contrast, arabinans are absent in Phaeoceros, and both unesterified and methyl-esterified homogalacturonans localize throughout guard cell walls. Arabinans and unesterified homogalacturonans are required for wall flexibility, which is consistent with active regulation of pore opening in Arabidopsis stomata. In contrast, the lack of arabinans and high levels of methyl-esterified homogalacturonans in guard cell walls of Phaeoceros are congruent with the inability of hornwort stomata to open and close with environmental change. Comparisons across groups demonstrate that variations in guard cell wall composition reflect different physiological activity of stomata in land plants.

Structural variation among leaves in Aechmea distichantha Lem. (Bromeliaceae) rosettes, considering apical and basal differences

In tank-dependent bromeliads, leaves may exhibit anatomical and functional differences along the apical and basal regions, or according to the different positions in the rosette. Thus, the apical region of the leaf may invest in photosynthetic tissues, while the basal one invests in structures for water and nutrient storage. We suppose here, that differences among the tissue functions are strongly related to anatomical traits, especially the degree of methyl-esterification of pectins in the cell walls, at different positions along the rosette. Thus, the aims of this study were to quantify anatomical variations and describe the pectin composition of the cell wall, along the Aechmea distichantha Lem. rosette, to assess how the different tissues varied. We found that the water storage tissue showed higher variation between the apex and the base of the leaves than the other tissues, with higher expansion between the fourth leaf in development and the outer leaf in the rosette. Moreover, its cells were intensely labeled for epitopes of high methyl-esterified HGs, recognize by JIM7 antibody. The presence of pectin with high methyl-esterified groups in water storage tissue provides greater cell wall elasticity. The chlorenchyma showed the lowest Relative Distance Plasticity Index values, and its development in A. distichantha seems to occur early, in a very young leaf and inside the rosette tank.

Yield and structural composition of pomelo peel pectins extracted under acidic and alkaline conditions

Extraction of pectin from pomelo peel was performed using water, acid and alkaline solutions with a microwave power of 1100 W for 2 min, and yield and structural/chemical characteristics of the extracted pectins were investigated. Extraction of pectin with water gave the lowest yield (6.5%, dry weight basis). The water-extracted pectin contained the highest amount of neutral sugar (29.5%), while equivalent molecular weight (MWeq) and degree of methylation (DM) were 43 kDa and 29.7%, respectively. Extraction of pectin with HCl solutions at concentrations of 25, 50, 100 and 200 mM resulted in a significant increase of pectin yields (12.1–20.5%) and pectins with high amount of galacturonic acid (83.3–85.6%). The MWeq and DM of the acid-extracted pectins ranged from 171 to 368 kDa and 53.9–82.5%, respectively. Compared to the acid, extraction with NaOH solutions at the same concentrations provided higher yields (13.9–24.2%), smaller size (142–187 kDa) and lower DM (<1.7%) pectins, while amount of galacturonic acid was comparable. The highest yield of extraction was found at a concentration of 50 mM for both HCl and NaOH solutions. Extraction of pomelo peel with 50 mM NaOH solution by reduction of the microwave power to 550 W and extending the extraction time to 15 min resulted in an increase of pectin yield (29.2%) and pectin with smaller size (76 kDa).

Expanding roles for pectins in plant development.

Pectins are complex cell wall polysaccharides important for many aspects of plant development. Recent studies have discovered extensive physical interactions between pectins and other cell wall components, implicating pectins in new molecular functions. Pectins are often localized in spatially-restricted patterns, and some of these non-uniform pectin distributions contribute to multiple aspects of plant development, including the morphogenesis of cells and organs. Furthermore, a growing number of mutants affecting cell wall composition have begun to reveal the distinct contributions of different pectins to plant development. This review discusses the interactions of pectins with other cell wall components, the functions of pectins in controlling cellular morphology, and how non-uniform pectin composition can be an important determinant of developmental processes.

Rheological behavior and electrokinetic properties of pectin extracted from pumpkin (Cucurbita maxima) pulp and peel using hydrochloric acid solution

The aim of this study is to investigate the chemical composition, hydrodynamic, rheological, and electrokinetic properties of pectin extracted from pulp and peel of pumpkin “Cucurbita maxima” by hydrochloric acid solution at pH 1.8. Chemical analysis of the extracted pectin showed an abundance of galacturonic acid which represents the totality of the uronic acid. Its content in the pulp and peel pectin extracts was 52.91 ± 0.02 g/100 g and 55.14 ± 0.10 g/100 g of dried samples, respectively. The results for intrinsic viscosity [η] ranged from 5.13 ± 0.04 to 5.65 ± 0.08 dl/g and for molecular weight from 234.64 ± 2.33 to 267.40 ± 5.39 kDa. These macromolecules are semi-flexible chain biopolymers with flexibility values of 0.07 ± 0.00. The parameter measurement of the pectin such as hydrodynamic radius (Rh) ranged from 32.39 ± 0.19 to 34.93 ± 0.40 nm, the relaxation time (tr) from 2.77 ± 0.02 × 10−7 to 11.26 ± 0.00 × 10−7 ms, and the diffusivity coefficient (D) from 2.17 ± 0.00 to 8.73 ± 0.00 cm2/s. The rheological behavior was suitably represented by the Bingham and Herschel–Bulkley models for all concentrations. The electrokinetic behavior of pectins allows control of electrostatic interactions. The calculated Zp of the system constituted by pumpkin pectin and citric acid/sodium citrate buffer ranged from − 28.10 ± 0.20 to + 0.35 ± 0.65 mV.

Boron Deficiency in Trifoliate Orange Induces Changes in Pectin Composition and Architecture of Components in Root Cell Walls.

Boron (B) is a micronutrient indispensable for citrus and B deficiency causes a considerable loss of productivity and quality in China. However, studies on pectin composition and architecture of cell wall components in trifoliate orange roots under B deficiency condition are not sufficient. In this study, we investigated the alteration in pectin characteristics and the architecture of cell wall components in trifoliate orange [Poncirus trifoliata (L.) Raf.] roots under B starvation. The results showed that B-deficient roots resulted in a significant enlargement of root tips and an obvious decrease in cell wall B and uronic acid content in Na2CO3-soluble pectin compared with B-adequate roots. Meanwhile, they showed a decrease of 2-keto-3-deoxyoctanoic acid in CDTA-soluble and Na2CO3-soluble pectin in cell walls, while the degree of methylation (DM) of CDTA-soluble pectin was significantly increased under B deficiency. Transmission electron microscope (TEM) micrographs of B deficient plants showed a distinct thickening of the cell walls, with the thickness 1.82 times greater than that of control plant roots. The results from Fourier-transform infrared spectroscopy (FTIR) showed that B deficiency changed the mode of hydrogen bonding between protein and carbohydrates (cellulose and hemicellulose). The FTIR spectra exhibited a destroyed protein structure and accumulation of wax and cellulose in the cell walls under B starvation. The 13C nuclear magnetic resonance (13C-NMR) spectra showed that B starvation changed the organic carbon structure of cell walls, and enhanced the contents of amino acid, cellulose, phenols, and lignin in the cell wall. The results reveal that the swelling and weakened structural integrity of cell walls, which induced by alteration on the network of pectin and cell wall components and structure in B-deficient roots, could be a major cause of occurrence of the rapid interruption of growth and significantly enlarged root tips in trifoliate orange roots under B-insufficient condition.

Characterization and physicochemical properties of pectins extracted from agroindustrial by-products

The composition and fine structure of pectins found in plant cell walls are heterogeneous, with striking differences, depending on their source, and this eventually determines their functional and technological properties. The aim of this study was to extract and determine the chemical composition and physicochemical properties of pectins from different sources: passion fruit peel, orange pomace, and soy hull. Pectin extraction was performed with heated hydrochloric acid solution, followed by precipitation with 96% ethanol. Extraction yield, chemical composition, molar mass, physicochemical properties (fat absorption capacity, cation exchange capacity, water holding capacity, and antioxidant activity) of pectin were measured. Pectin extraction efficiency was higher for passion fruit peel and orange pomace (15.71 and 17.96%, respectively). Soy hull had low pectin extraction (5.66%). Galacturonic acid content was 23.21% for passion fruit peel pectin and 16.01% for orange pomace pectin. Water holding capacity, fat absorption capacity, and cation-binding capacity present in pectin extracted from passion fruit peel were higher, suggesting this poorly investigated product could be used as thickening and emulsifying agents in food preparations. Phenolic compounds with antioxidant capacity provide pectins with additional properties and expand their industrial use.

Changes in pectin characteristics during the ripening of jujube fruit

Pectin is related to fruit maturation and loss of flesh firmness. In this research, changes in pectin characteristics, including pectin content, neutral sugar composition, molecular weight (Mw ) distribution and degree of methylesterification (DM), in six different growth stages (S1 to S6) of jujube fruit were assessed. The growth of jujube fruit corresponded to an increase in water-soluble pectin (WSP) and a decrease in sodium carbonate-soluble pectin (SSP). The chelate-soluble pectin (CSP) content reached a maximum level at S3 but decreased significantly from S3 to S4. Arabinose proved to be the principal branched neutral monosaccharide in pectin during growth and was lost from WSP, CSP and SSP in S4 to S6. The ratios of (arabinose + galactose)/rhamnose indicated that the branched chains of WSP, CSP and SSP degraded in S2, S3 and S4 respectively. SSP depolymerized from S2 and increased as jujube fruit ripened. By contrast, WSP depolymerized throughout ripening. The DM of pectins ranged from 45.38 to 92.21%. Among the obtained DMs, the lowest was observed in WSP from ripened jujube fruit (S6). The content, neutral sugar composition, DM and Mw distribution of pectins changed markedly as jujube fruit ripened. Jujube fruit could be a promising alternative source of pectins in terms of maturation degree. WSP from S6 and CSP from S1 or S2 could be used as gelling agents in low-sugar-containing products because of their low methoxyl pectin contents. WSP from S1 could also be applied as a thickener or emulsifier owing to its high Mw distribution. © 2017 Society of Chemical Industry.

Using the high temperature resistant pH electrode to auxiliarily study the sugar beet pectin extraction under different extraction conditions

A full two-level factorial experiment design was employed to investigate the effects of temperature (75 and 85 °C), time (2 and 3 h) and initial pH(1.5 and 2.0) on the molecular composition of sugar beet pectin extracted by citric acid. And the high temperature resistant pH electrode was used to monitor the pH variation during pectin extraction. The results showed that the pH of pectin extraction solution was not constant during pectin extraction, and the pH of extraction solution fluctuated more widely at 85 °C than at 75 °C. In the experiment design, the initial pH was the most significant factor on pectin composition such as arabinose, total neutral sugars, and degree of acetylation, while the temperature became the most important factor for yield, galacturonic acid, rhamnose, galactose, and weight-average molar mass. The degree of methoxylation was significantly affected by extraction time. It was observed that the emulsifying properties of the extracted pectin samples were significantly affected by the extraction conditions. All the results revealed that 1.) the pH value of extraction solution is directly related to the yield and the degradation of the extracted pectin during sugar beet pectin extraction, 2.) the extraction temperature could significantly affect the pH fluctuation of extraction liquid, 3.) the most significant effect factor for a given pectin composition is dominated by the pH fluctuation of the extracting liquid and acid stability of this discussional pectin composition, 4.) beet pectin extracted by citric acid is an effective emulsifier.