Pectin Modification Research Articles

Targeted modifications of citrus pectin to improve interfacial properties and the impact on emulsion stability

In the present work, three specific low weight average molecular weight (M w ) demethoxylated citrus pectin derived compounds (oligosaccharides) (CP 25 kDa , CP 3 kDa and CP 3.8 kDa ) were generated by means of enzymatic degradation and subsequent chemical demethylesterification of three starting pectin materials (CP74 144 kDa , CP53 151 kDa and CP38 116 kDa , respectively). These pectin oligosaccharides were structurally characterized, evaluated for their physicochemical properties, and their emulsifying and emulsion stabilizing (E F E S ) potential. In terms of structure, significant differences in M w , degree of methylesterification (DM), monosaccharide and protein contents were observed between the initial and the generated pectin-derived samples. Interestingly, upon evaluation of the physicochemical properties of the generated pectin-derived materials, it was observed they exhibited considerably improved interfacial tension properties in comparison to the initial pectin samples. Furthermore, all pectin materials were negatively charged to similar extents. On the negative side, the low viscosity of the generated pectin compounds was observed to significantly hinder their E F E S properties. Upon refrigerated storage of the pectin emulsions, it was observed that the initial pectin materials (at pH 2.5) exhibited better E F E S potential in comparison to the generated pectin materials, despite the superior interfacial potential of the latter samples. This was mainly ascribed to the higher viscosity of the non-degraded pectin samples, in turn attributed to their larger M w . Overall, the results obtained indicated that the M w and DM of the polymer played an important role in the interfacial tension properties of pectin. However, viscosity of the continuous phase of the dispersion is a critical factor in the E F E S potential of pectin. • All modified citrus pectin samples (M w <25 kDa) evaluated exhibited enhanced surface activity. • Coalescence and flocculation were considered the main destabilizing mechanisms in the emulsions formulated with low M w (<25 kDa) pectins. • Differences in viscosity increasing capacity, among the mother and modified pectin samples, are suggested to be the main factor influencing the stability of the formulated emulsions.

Effect of electrochemistry modification on the macromolecular, structural, and rheological characteristics of citrus peel pectin

Electrochemical techniques including electrophoresis, electrolysis, and electrophoretic deposition have been widely used in the construction and modification of biomacromolecules such as proteins and chitosan. In this study, the negatively charged citrus peel pectin (CPP) was used to explore its modification by electrochemistry. The electrochemically modified CPPs were successfully fabricated by an H-type cell in anodic and cathodic regions at 25V for 1, 2, 4 and 8h. After 8h, the pH of anodic region was reduced from 3.62 to 1.76, whereas the cathode region was elevated to 11.61. Oxidation reduction potential (ORP) of anodic region was increased from 316 to 463 mV, whereas the cathode region was decreased to −273 mV. Molecular weight distribution (Mw), neutral sugar (NS), degree of methylation (DM) and acetylation (DA), Fourier transform-infrared spectra (FT-IR), and thermogravimetric analysis (TGA) were examined to investigate the structure changes of CPPs. The results showed the Mw, NS, DM and DA of modified CPPs decreased, while the content of galacturonic acid (GalA) increased. The hydrogels modified by cathodic region displayed superior gel characteristics, while hydrogels modified by anodic region demonstrated effective antibacterial properties. The correlation analysis demonstrated storage (G′) and loss modulus (G″) values of hydrogels were negatively correlated with DM and Mw. Our results provide valuable insight into modification of pectins by electrochemistry, which may be applied in food and pharmaceutical applications.

Auxin triggers pectin modification during rootlet emergence in white lupin.

Emergence of secondary roots through parental tissue is a highly controlled developmental process. Although the model plant Arabidopsis has been useful to uncover the predominant role of auxin in this process, its simple root structure is not representative of how emergence takes place in most plants, which display more complex root anatomy. White lupin is a legume crop producing structures called cluster roots, where closely spaced rootlets emerge synchronously. Rootlet primordia push their way through several cortical cell layers while maintaining the parent root integrity, reflecting more generally the lateral root emergence process in most multilayered species. In this study, we showed that lupin rootlet emergence is associated with an upregulation of cell wall pectin modifying and degrading genes under the active control of auxin. Among them, we identified LaPG3, a polygalacturonase gene typically expressed in cells surrounding the rootlet primordium and we showed that its downregulation delays emergence. Immunolabeling of pectin epitopes and their quantification uncovered a gradual pectin demethylesterification in the emergence zone, which was further enhanced by auxin treatment, revealing a direct hormonal control of cell wall properties. We also report rhamnogalacturonan-I modifications affecting cortical cells that undergo separation as a consequence of primordium outgrowth. In conclusion, we describe a model of how external tissues in front of rootlet primordia display cell wall modifications to allow for the passage of newly formed rootlets.

Discovery of novel secretome CAZymes from Penicillium sclerotigenum by bioinformatics and explorative proteomics analyses during sweet potato pectin digestion.

Novel selective enzymatic refining of sweet potato processing residues requires judicious enzyme selection and enzyme discovery. We prepared a pectinaceous cell wall polysaccharide fraction from sweet potato using an enzymatic a treatment to preserve the natural linkages and substitutions. Polysaccharide composition and linkage analysis data confirmed the pectinaceous polysaccharide fraction to be a rhamnogalacturonan I-rich fraction with a high content of arabinogalactan Type I. We hypothesized that the post-harvest tuber pathogenic fungus Penicillium sclerotigenum would harbor novel enzymes targeting selective sweet potato pectin modification. As part of the study, we also report the first genome sequence of P. sclerotigenum. We incubated the sweet potato pectinaceous fraction with P. sclerotigenum. Using proteomics accompanied by CUPP-bioinformatics analysis, we observed induced expression of 23 pectin-associated degradative enzymes. We also identified six abundantly secreted, induced proteins that do not correspond to known CAZymes, but which we suggest as novel enzymes involved in pectin degradation. For validation, the predicted CUPP grouping of putative CAZymes and the exo-proteome data obtained for P. sclerotigenum during growth on sweet potato pectin were compared with proteomics and transcriptomics data reported previously for pectin-associated CAZymes from Aspergillus niger strain NRRL3. The data infer that P. sclerotigenum has the capacity to express several novel enzymes that may provide novel opportunities for sweet potato pectin modification and valorization of sweet potato starch processing residues. In addition, the methodological approach employed represents an integrative systematic strategy for enzyme discovery.

Current Advancements in Pectin: Extraction, Properties and Multifunctional Applications.

Pectin is a heterogeneous hydrocolloid present in the primary cell wall and middle lamella in all dicotyledonous plants, more commonly in the outer fruit coat or peel as compared to the inner matrix. Presently, citrus fruits and apple fruits are the main sources for commercial extraction of pectin, but ongoing research on pectin extraction from alternate fruit sources and fruit wastes from processing industries will be of great help in waste product reduction and enhancing the production of pectin. Pectin shows multifunctional applications including in the food industry, the health and pharmaceutical sector, and in packaging regimes. Pectin is commonly utilized in the food industry as an additive in foods such as jams, jellies, low calorie foods, stabilizing acidified milk products, thickener and emulsifier. Pectin is widely used in the pharmaceutical industry for the preparation of medicines that reduce blood cholesterol level and cure gastrointestinal disorders, as well as in cancer treatment. Pectin also finds use in numerous other industries, such as in the preparation of edible films and coatings, paper substitutes and foams. Due to these varied uses of pectin in different applications, there is a great necessity to explore other non-conventional sources or modify existing sources to obtain pectin with desired quality attributes to some extent by rational modifications of pectin with chemical and enzymatic treatments.

Atmospheric pressure pin-to-plate cold plasma modification of high methoxyl apple pectin: Impact on functional properties

Modification of hydrocolloids by employing “green” processes such as cold plasma has gained attention in recent times. Apple pectin is a highly branched pectin, which leads to a low emulsification capacity. This study aims to understand the effect of cold plasma on the structural and functional properties of pectin, ranging from emulsification to antioxidant properties. In this study, atmospheric pressure cold plasma (230 V|3–15 min) was used for the modification of apple pectin (Degree of esterification (DE)∼68%). The viscosity-average-molecular weight decreased from 160677.4 to 98352.3 g mol −1 within 6 min of plasma treatment. A decrease in DE from 68 to 54% was observed after 15 min of treatment. An increase in galacturonic acid from 0.653 to 0.816 g g −1 and reducing sugars from 0.243 to 1.134% was noted after 15 min of treatment. The highest amount of unsaturated GalA residues (2.36 mmol/g) was formed after 12 min of treatment. The Ca 2+ sensitivity of the acid-sugar-pectin gels increased from 22.2 to 65.3 mPa s after 15 min of treatment. An increase in the whiteness index and a decrease in flow properties of the pectin powder were observed with the increasing duration of the treatment. This was well-evidenced in the Hausner's and Carr's indices, which increased from 1.23 to 1.48 and 0.24 to 0.35, respectively after 12 min of treatment. Prolonged treatments (>9min) negatively impacted emulsion stability. The DPPH radical scavenging activity and reducing power of pectin increased with the duration of plasma treatments for low concentrations of pectin (0.5–1.5%). The maximum DPPH radical scavenging activity (26.11%) was observed for 2% pectin dispersions, which were made from 12 min-plasma modified pectin. The future course of work can include the exploration of advanced applications of plasma-treated pectin in food matrices. • Cold plasma is a “green” method of pectin modification. • A decrease in degree of esterification and an increase in reducing sugars was observed. • Plasma modification decreased the viscosity and textural properties of pectin-sugar-acid gels. • An increase in emulsifying, foaming and antioxidant properties after the plasma treatment was identified.

Laccaria bicolor pectin methylesterases are involved in ectomycorrhiza development with Populus tremula × Populus tremuloides.

The development of ectomycorrhizal (ECM) symbioses between soil fungi and tree roots requires modification of root cell walls. The pectin-mediated adhesion between adjacent root cells loosens to accommodate fungal hyphae in the Hartig net, facilitating nutrient exchange between partners. We investigated the role of fungal pectin modifying enzymes in Laccaria bicolor for ECM formation with Populus tremula × Populus tremuloides. We combine transcriptomics of cell-wall-related enzymes in both partners during ECM formation, immunolocalisation of pectin (Homogalacturonan, HG) epitopes in different methylesterification states, pectin methylesterase (PME) activity assays and functional analyses of transgenic L. bicolor to uncover pectin modification mechanisms and the requirement of fungal pectin methylesterases (LbPMEs) for ECM formation. Immunolocalisation identified remodelling of pectin towards de-esterified HG during ECM formation, which was accompanied by increased LbPME1 expression and PME activity. Overexpression or RNAi of the ECM-induced LbPME1 in transgenic L. bicolor lines led to reduced ECM formation. Hartig Nets formed with LbPME1 RNAi lines were shallower, whereas those formed with LbPME1 overexpressors were deeper. This suggests that LbPME1 plays a role in ECM formation potentially through HG de-esterification, which initiates loosening of adjacent root cells to facilitate Hartig net formation.

Arabidopsis root responses to salinity depend on pectin modification and cell wall sensing.

ABSTRACTOwing to its detrimental effect on plant growth, salinity is an increasing worldwide problem for agriculture. To understand the molecular mechanisms activated in response to salt in Arabidopsis thaliana, we investigated the Catharanthus roseus receptor-like kinase 1-like family, which contains sensors that were previously shown to be involved in sensing the structural integrity of the cell walls. We found that herk1 the1-4 double mutants, lacking the function of HERKULES1 (HERK1) and combined with a gain-of-function allele of THESEUS1 (THE1), strongly respond to salt application, resulting in an intense activation of stress responses, similarly to plants lacking FERONIA (FER) function. We report that salt triggers pectin methyl esterase (PME) activation and show its requirement for the activation of several salt-dependent responses. Because chemical inhibition of PMEs alleviates these salt-induced responses, we hypothesize a model in which salt directly leads to cell wall modifications through the activation of PMEs. Responses to salt partly require the functionality of FER alone or HERK1/THE1 to attenuate salt effects, highlighting the complexity of the salt-sensing mechanisms that rely on cell wall integrity.

Preparation and Antibacterial Activity of New Iodine-Containing Materials based on Pectin Modified with Pharmacologically Active Acids

A new approach has been developed for obtaining stable iodine-containing powders based on pectins modified with pharmacologically active (nicotinic, salicylic, 5-aminosalicylic, anthranilic) acids. A set of methods (IR-, UV-, 13C NMR-spectroscopy, elemental, thermogravimetric analysis, viscometry, polarimetry, electron microscopy) were used to characterize the physicochemical properties of iodine-containing compositions. It has been established that the modification of pectin with organic pharmacophores leads to an increase in the iodine content in the modified samples by 4-7 times and makes it possible to obtain compounds not only with a high iodine content from 30 to 60 % but also with its controlled and prolonged release. Furthermore, according to the results of microbiological tests against soil bacteria Bacillus megaterium, Pseudomonas aureofaciens, and lactic acid bacterium Lactococcus lactis, a high antibacterial activity of the obtained iodine-containing materials was established.

High pressure processing improves the texture quality of fermented minced pepper by maintaining pectin characteristics during storage.

Texture quality affects the sensory and market acceptance of fermentation minced pepper (FMP), but it will deteriorate during storage. Thus, high pressure processing (HPP) and thermal pasteurization (TP) were used to improve the texture quality of FMP during storage. The results showed that variations in texture quality and pectin characteristics under HPP and TP treatments were similar during storage. The hardness, cell wall material (CWM) and sodium carbonate-soluble pectin (SSP) content, water-soluble pectin (WSP) molecular weight (Mw ) decreased, while WSP content and sodium chelate-soluble pectin (CSP) Mw increased after storage. HPP-treated FMP showed higher hardness (66.64-85.95 N) than that in TP-treated one (57.23-62.72 N) during storage. Rhamnose (Rha), arabinose, mannose, and glucose were the crucial compositions in three pectins, and their total molar ratios, respectively, reached 89.19% and 87.97% after HPP and TP treatment. However, the molar ratio of most monosaccharide in three pectins decreased after storage. Atomic force microscope images indicated the short chains and branch structures increased but aggregates decreased in most pectin components during storage. Pearson correlation analysis demonstrated FMP hardness was extremely (p<0.01) positively correlated with CWM and SSP content, and extremely (p<0.01) negatively correlated with WSP content. Compared to TP treatment, HPP presented higher hardness, SSP content and Mw , Rha content, CSP Mw , and lower WSP content during storage. Hence, HPP was an effective method to improve the texture quality of FMP by maintaining pectin characteristics during storage. PRACTICAL APPLICATION: Softening is one of the main factors affecting market value and consumer preferences for FMP, and it is closely related to the modification and depolymerization of pectin. Changes of texture quality and pectin properties in HPP- and TP-treated FMP during storage were assessed, including hardness, the content, monosaccharide compositions, Mw distribution, and nanostructure of WSP, SSP, and CSP. Compared to TP treatment, HPP could effectively improve the texture quality of FMP by inhibiting pectin degradation during storage. All the findings presented in this study would help to provide new insights into regulating the texture quality of FMP.

Impact of atmospheric pressure cold plasma on the rheological and gelling properties of high methoxyl apple pectin

Cold plasma is an emerging sustainable method for modification of hydrocolloids. In the present study, atmospheric pressure pin-to-plate cold plasma was employed for modification of high-methoxyl apple pectin (DE∼68%). Chemical modifications are rigorous, and often require huge amounts of solvents and chemicals. Hence, the use of sustainable and “green” techniques such as cold plasma need to be investigated for their ability to impact the rheological and gelling properties of pectin. Intrinsic viscosity, apparent viscosity and viscoelastic properties of cold plasma-treated pectin dispersions and gels were studied. Kinetic studies were undertaken to evaluate the effect of cold plasma on the degradation and gelation of pectin. Improvement in rheological properties was observed for short plasma treatments at lower voltages (190 V|9 min and 210 V|6 min). Prolonged treatments at higher voltage treatments (210 and 230 V) had a negative impact on the rheological and gelling properties. The depolymerization, monitored by the intrinsic viscosity exhibited second-order degradation kinetics. The pseudoplastic pectin dispersions transitioned towards Newtonian-like behavior after plasma treatments. The thermal stability of the pectin dispersions decreased by 29% after a plasma treatment of 230 V for 15 min. A decline in gel strength and stability was confirmed by the decline in critical and cross-over strain during strain-sweep experiments. The gel formation of pectin in the presence of sucrose was a two-step process. The energy gap between the high-temperature and low-temperature region decreased as the plasma treatment progressed. To summarize, it is necessary to optimize the intensity of the plasma treatments to achieve the desired rheological properties.

With a Little Help from My Cell Wall: Structural Modifications in Pectin May Play a Role to Overcome Both Dehydration Stress and Fungal Pathogens.

Cell wall structural modifications through pectin cross-linkages between calcium ions and/or boric acid may be key to mitigating dehydration stress and fungal pathogens. Water loss was profiled in a pure pectin system and in vivo. While calcium and boron reduced water loss in pure pectin standards, the impact on Allium species was insignificant (p > 0.05). Nevertheless, synchrotron X-ray microscopy showed the localization of exogenously applied calcium to the apoplast in the epidermal cells of Allium fistulosum. Exogenous calcium application increased viscosity and resistance to shear force in Allium fistulosum, suggesting the formation of calcium cross-linkages (“egg-box” structures). Moreover, Allium fistulosum (freezing tolerant) was also more tolerant to dehydration stress compared to Allium cepa (freezing sensitive). Furthermore, the addition of boric acid (H3BO3) to pure pectin reduced water loss and increased viscosity, which indicates the formation of RG-II dimers. The Arabidopsis boron transport mutant, bor1, expressed greater water loss and, based on the lesion area of leaf tissue, a greater susceptibility to Colletotrichum higginsianum and Botrytis cinerea. While pectin modifications in the cell wall are likely not the sole solution to dehydration and biotic stress resistance, they appear to play an important role against multiple stresses.

Preparation of functionalized pectin through acylation with alkyl gallates: Experiments coupled with density functional theory

The covalent grafting of alkyl gallates onto pectin using a lipase-catalyzed reaction in a tetrahydrofuran/aqueous medium process acylated pectin molecules with excellent antioxidant and antibacterial properties. The alkyl gallates including methyl, ethyl, and propyl gallates were enzymatically grafted onto pectin molecule, in order to study the effect of alkyl gallates on the functional modification of pectin. The grafting mechanism was analyzed by ultraviolet-visible spectrum (UV–Vis), Fourier transform infrared spectrum (FTIR), proton nuclear magnetic resonance (1HNMR), and density functional theory (DFT). Results suggested that lipase grafted 4-OH of alkyl gallate onto pectin by catalyzing esterification in organic/aqueous solution, and the grafting rate was affected by the length of alkyl chain of the gallates molecule. In vitro experiments, the acylated pectins exhibited stronger antioxidant activity in the DPPH test and β-carotene bleaching test and were found to have obvious antimicrobial performance against Escherichia coli and Staphylococcus aureus.

Changes of pectin structure and microbial community composition in strawberry fruit (Fragaria × ananassa Duch.) during cold storage

Strawberry is very perishable fruit with rapid postharvest loss of quality and high susceptibility to microbial infections. In this work we study pectin modifications and microbiota and mycobiota composition in strawberry in conventional and organic cultivation systems. The enzymatic activity during postharvest storage of both types of strawberry was divided at the fifth day of storage into two phases: postharvest changes and rotting. Pectin molecules extracted from organic strawberries were longer and more branched compared to the conventional strawberries; however a more noticeable reorganization of molecular structure occurred. The sequential action of the pectinolytic enzymes had a direct effect on the molecular structure of pectin fractions. The observed changes in pectin structure relate to the synergistic activity of pectinolytic enzymes and some microorganisms. The organic system was characterized by a greater number and variety of bacteria and fungi during storage as compared to the conventional system.

Polygalacturonase activity promotes aberrant cell separation in the quasimodo2 mutant of Arabidopsis thaliana

In plants, cell adhesion relies on balancing the integrity of the pectin-rich middle lamella with wall loosening during tissue expansion. Mutation of QUASIMODO2 (QUA2), a pectin methyltransferase, causes defective hypocotyl elongation and cell adhesion in Arabidopsis thaliana hypocotyls. However, the molecular function of QUA2 in cell adhesion is obscured by complex genetic and environmental interactions. To dissect the role of QUA2 in cell adhesion, we investigated a qua2 loss-of-function mutant and a suppressor mutant with restored cell adhesion, qua2 esmeralda1, using a combination of imaging and biochemical techniques. We found that qua2 hypocotyls have reductions in middle lamellae integrity, pectin methyl-esterase (PME) activity, pectin content and molecular mass, and immunodetected Ca2+-crosslinking at cell corners, but increased methyl-esterification and polygalacturonase (PG) activity, with qua2 esmd1 having wild type-like or intermediate phenotypes. Our findings suggest that excessive pectin degradation prevents pectin accumulation and the formation of a sufficiently Ca2+-crosslinked network to maintain cell adhesion in qua2 mutants. We propose that PME and PG activities balance tissue-level expansion and cell separation. Together, these data provide insight into the cause of cell adhesion defects in qua2 mutants and highlight the importance of harmonizing pectin modification and degradation during plant growth and development.

Cloning and Functional Identification of SlPG49 in Solanum lycopersicum

The modification and degradation of pectin in cell walls are necessary for the fruit softening process, which involves a series of pectin-modifying enzymes. Polygalacturonases (PGs) are a major group of pectin-hydrolyzing enzymes, which participate in fruit maturation, organ shedding, pollen development, and other processes by catalyzing the degradation of polygalacturonic acid. However, their function in plants has not yet been fully elucidated. In this paper, a full-length cDNA encoding SlPG49 was cloned from a tomato. Sequence alignment and phylogenetic analysis demonstrated that SlPG49 contains four typical conserved domains and belongs to clade E in PG classification. Quantitative real-time PCR analysis showed that SlPG49 was highly expressed in fruits during the softening stage, indicating that SlPG49 may be involved in fruit softening. Subcellular localization results revealed that SlPG49 was located in the cell membrane and the cell wall. In addition, an in vitro enzymatic activity assay confirmed that SlPG49 does have the ability to catalyze the hydrolysis of polygalacturonic acid. These results indicate that SlPG49 is a newly discovered PG gene involved in tomato fruit softening, and provide an experimental basis for elucidating the biological functions of plant PGs during fruit softening.

High-pressure and thermal processing of cloudy hawthorn berry (Crataegus pinnatifida) juice: Impact on microbial shelf-life, enzyme activity and quality-related attributes

The study aimed to evaluate the effect of high-pressure (HPP, 300/600 MPa for 2 and 6 min) and thermal processing (TP, 65 °C/30 min) on microbial shelf-life, enzyme-activity and quality-attributes of cloudy hawthorn berry juice (CHBJ) after processing and during storage (4 °C). The CHBJ shelf-life was at least 150 days when processed by HPP. No significant difference was observed in pH and titratable acidity (p > 0.05), while HPP significantly increased soluble sugar (p < 0.05) and simulated some fruity aroma compounds which improved the taste and flavor of CHBJ. However, HPP inhabited ineffectively enzyme-activity in comparison to TP, causing significant color changes (ΔE = 4.98 ± 0.03–5.10 ± 0.07) during 30-day storage (p < 0.05). Although particle size increased after HPP treatment, significant increases (68.76%-926.95%) were observed in viscosity (p < 0.05), due to enhanced extractability or modification of pectin induced by HPP, resulting in higher consistency of CHBJ. HPP is promising to extend shelf-life and improve quality-attributes of CHBJ.

Effect of postharvest storage on potato (Solanum tuberosum L.) texture after pulsed electric field and thermal treatments

Pulsed electric field (PEF) and mild thermal pretreatments at 60 °C (T60) may help preserve texture of plant tissue during thermal processing through pectin modification. However, potato starch may counteract the adhesive role of pectin during thermal processing. Furthermore, postharvest storage of potatoes may result in compositional and textural changes. Therefore, the effect of postharvest storage on potato composition and on texture of untreated, PEF treated and thermally treated tissue was studied. The composition remained unchanged (p-value <0.05), whereas the fresh tissue hardness slightly decreased (p-value ≤0.0001–0.1387) during storage. Prolonged storage resulted in a softer texture after PEF treatments with total specific energy input (WT) ≤ 0.6 kJ/kg at electric field strengths of 0.74–1.01 kV/cm, whereas the hardness was independent of the storage time if WT > 0.6 kJ/kg. Slower texture degradation at 95 °C was observed after T60 and, especially, PEF-T60 pretreatment, independently of the storage time.

Investigation of the pectin grafting with gallic acid and propyl gallate and their antioxidant activities, antibacterial activities and fresh keeping performance

In this paper, a method for the enzymatic modification of pectin, in which gallic acid (GA) and propyl gallate (PG) were grafted onto pectin molecules in an aqueous/organic two-phase system catalyzed by lipase, was proposed. The potential reaction mechanism was explored through UV–Vis, FTIR and 1H NMR spectroscopic methods and density functional theory. Results suggested that the lipase played a dual role during the modification by catalyzing the hydrolysis of methyl ester bonds of pectin in the aqueous phase and the esterification between the 4-OH of GA and PG and the –COOH of pectin in the organic phase. Moreover, the effects of GA and PG on the antioxidant and the antibacterial activities of pectin were evaluated, and results showed that the antioxidant and the antibacterial activities of modified pectin were better than those of native pectin. The effect of modified pectin on the quality of fresh bass (Lateolabrax maculatus) was further studied. Results suggested that, compared to control group, the total viable count, histamine level, malondialdehyde content and acid value of bass fillets treated with modified pectin were significantly reduced, whereas the sensory score was significantly increased.

Chemical modification of pectin and polygalacturonic acid: A critical review

Pectin, as a sustainable biopolymer with its two complementary functionalities (carboxyl and hydroxyl moieties) imparted in the α-1,4-galacturonic acid repeating unit, has gained increasing attention in the last few years. The interest in this ubiquitously occurring plant originating polysaccharide (PS) has shifted slowly from applications as a food additive to a broader range of potential applications in medicine, cosmetics, and other industries. Due to the increasing interest in alternatives for petrochemical materials, PSs as biomaterials have gained increasing attention in industrial processes in general. In the last decade, an increasing number of chemical transformations related to pectin have been published, and this is a prerequisite for the design of the structure and hence properties of novel biopolymer-based materials. This work aims to review the chemical modifications of pectin by covalent linkage of the last decade and analyze the materials obtained with these chemical methods critically.