Quantifying structural characteristics of partially de-esterified pectins

Revealing methyl-esterification patterns of pectins by enzymatic fingerprinting: Beyond the degree of blockiness

Citrus pectins were studied by enzymatic fingerprinting using a simultaneous enzyme treatment with endo-polygalacturonase (endo-PG) from Kluyveromyces fragilis and pectin lyase (PL) from Aspergillus niger to reveal the methyl-ester distribution patterns over the pectin backbone. Using HILIC-MS combined with HPAEC enabled the separation and identification of the diagnostic oligomers released. Structural information on the pectins was provided by using novel descriptive parameters such as degree of blockiness of methyl-esterified oligomers by PG (DB_PGme) and degree of blockiness of methyl-esterified oligomers by PL (DB_PLme). This approach enabled us to clearly differentiate citrus pectins with various methyl-esterification patterns. The simultaneous use of PG and PL showed additional information, which is not revealed in digests using PG or PL alone. This approach can be valuable to differentiate pectins having the same DM and to get specific structural information on pectins and therefore to be able to better predict their physical and biochemical functionalities.

Dietary fibre in gastrointestinal health and disease

Epidemiological studies have consistently demonstrated the benefits of dietary fibre on gastrointestinal health through consumption of unrefined whole foods, such as wholegrains, legumes, vegetables and fruits. Mechanistic studies and clinical trials on isolated and extracted fibres have demonstrated promising regulatory effects on the gut (for example, digestion and absorption, transit time, stool formation) and microbial effects (changes in gut microbiota composition and fermentation metabolites) that have important implications for gastrointestinal disorders. In this Review, we detail the major physicochemical properties and functional characteristics of dietary fibres, the importance of dietary fibres and current evidence for their use in the management of gastrointestinal disorders. It is now well-established that the physicochemical properties of different dietary fibres (such as solubility, viscosity and fermentability) vary greatly depending on their origin and processing and are important determinants of their functional characteristics and clinical utility. Although progress in understanding these relationships has uncovered potential therapeutic opportunities for dietary fibres, many clinical questions remain unanswered such as clarity on the optimal dose, type and source of fibre required in both the management of clinical symptoms and the prevention of gastrointestinal disorders. The use of novel fibres and/or the co-administration of fibres is an additional therapeutic approach yet to be extensively investigated.

Egg-box model-based gelation of alginate and pectin: A review

Alginate and pectin are emblematic natural polyuronates that have been widely used in food, cosmetics and medicine. Ca-dependent gelation is one of their most important functional properties. The gelation mechanisms of alginate and pectin, known as egg-box model, were believed to be basically the same, because their Ca-binding sites show a mirror symmetric conformation. However, studies have found that the formation and the structure of egg-box dimmers between alginate and pectin were different. Very few studies have reviewed those differences. Therefore, this study was proposed to first summarize the intrinsic and extrinsic factors that can influence the gelation of alginate and pectin. The differences in the effect of these factors on the gelation of alginate and pectin were then discussed. Meanwhile, the similarity and difference in their gelation mechanism was also summarized. The knowledge gained in this review would provide useful information for the practical applications of alginate and pectin.

Influence of Pectin Structural Properties on Interactions with Divalent Cations and Its Associated Functionalities

Pectin is an anionic cell wall polysaccharide which is known to interact with divalent cations via its nonmethylesterified galacturonic acid units. Due to its cation-binding capacity, extracted pectin is frequently used for several purposes, such as a gelling agent in food products or as a biosorbent to remove toxic metals from waste water. Pectin can, however, possess a large variability in molecular structure, which influences its cation-binding capacity. Besides the pectin structure, several extrinsic factors, such as cation type or pH, have been shown to define the cation binding of pectin. This review paper focuses on the research progress in the field of pectin-divalent cation interactions and associated functional properties. In addition, it addresses the main research gaps and challenges in order to clearly understand the influence of pectin structural properties on its divalent cation-binding capacity and associated functionalities. This review reveals that many factors, including pectin molecular structure and extrinsic factors, influence pectin-cation interactions and its associated functionalities, which makes it difficult to predict the pectin-cation-binding capacity. Despite the limited information available, determination of the cation-binding capacity of pectins with distinct structural properties using equilibrium adsorption experiments or isothermal titration calorimetry is a promising tool to gain fundamental insights into pectin-cation interactions. These insights can then be used in targeted pectin structural modification, in order to optimize the cation-binding capacity and to promote pectin-cation interactions, for instance for a structure build-up in food products without compromising the mineral nutrition value.

Structurally modified pectin for targeted lipid antioxidant capacity in linseed/sunflower oil-in-water emulsions

The present work explored the lipid antioxidant capacity of citrus pectin addition to 5%(w/v) linseed/sunflower oil emulsions stabilized with 0.5%(w/v) Tween 80, as affected by pectin molecular characteristics. The peroxide formation in the emulsions, containing tailored pectin structures, was studied during two weeks of storage at 35°C. Low demethylesterified pectin (≤33%) exhibited a higher antioxidant capacity than high demethylesterified pectin (≥58%), probably due to its higher chelating capacity of pro-oxidative metal ions (Fe²⁺), whereas the distribution pattern of methylesters along the pectin chain only slightly affected the antioxidant capacity. Nevertheless, pectin addition to the emulsions caused emulsion destabilization probably due to depletion or bridging effect, independent of the pectin structural characteristics. These results evidence the potential of structurally modified citrus pectin as a natural antioxidant in emulsions. However, optimal conditions for emulsion stability should be carefully selected.

Effects of pectin on lipid digestion and possible implications for carotenoid bioavailability during pre-absorptive stages: A review

Pectin, an abundant polysaccharide in the human diet, has structural characteristics and functional properties that are strongly dependent on the food matrix (e.g., origin, type, cultivar/variety, ripening stage, style and intensity of processing). These polysaccharides have a strong effect on lipid digestion, which is required for the liberation of carotenoids from emulsified lipid droplets in the gastrointestinal content and for the formation of micelles, in which the carotenoids must be incorporated before absorption. Only micellarized carotenoids can be absorbed and subsequently exert protective effects on human health. The alteration of lipolysis by pectin can occur through several mechanisms; however, they have not been linked directly to carotenoid micellarization. This paper provides an overview of the effects of the properties of pectin on the ion concentration in the digestive content, the viscosity of the digestive medium, the properties of the lipid droplet surfaces and lipase activity and analyzes the impact of these events on lipid digestion and subsequent carotenoid micellarization.

Microscopic evidence for Ca(2+) mediated pectin-pectin interactions in carrot-based suspensions

This study explored the use of fluorescently labeled pectin to obtain evidence for Ca(2+) mediated pectin-pectin interactions in situ. Specifically, carrots were either blanched at low temperature (LTB) or blanched at high temperature (HTB) to activate or inactivate endogenous pectin methylesterase, respectively. Consequently, pectin in tissue particles of LTB and HTB carrots exhibited low degree of methylesterification (DM) and high DM, respectively. Pectin present in the LTB carrot serum exhibited a lower DM, was more branched, and showed a higher molar mass compared to HTB carrot serum pectin. Ca(2+) mediated pectin-pectin interactions were influenced by serum pectin molecular structure, increased with increasing pH and Ca(2+) concentration, and decreasing DM. Presence of more linear pectin in the serum created a competition, leading to less intense interactions between labeled pectin and pectin at tissue particle surfaces. Generally, the most intense Ca(2+) mediated pectin-pectin interactions were observed for pectin of LTB carrot particles.

FT-IR spectroscopy, a reliable method for routine analysis of the degree of methylesterification of pectin in different fruit- and vegetable-based matrices

The use of Fourier transform infrared (FT-IR) spectroscopy as a method for routine analysis of the degree of methylesterification (DM) of pectin was validated. The relationship between the ratio of the intensity of the peak at around 1740cm(-1) (due to ester carbonyl group stretching) to the sum of the intensities of the peaks at around 1740 and 1630-1600cm(-1) (due to carboxylate group stretching) and the DM of pectin in model and real systems was investigated. In model systems of low to medium DM with low added protein (⩽20%), accurate DM determinations were obtained without spectra deconvolution whilst for medium to high DM pectin with high added protein (⩾30%), peak deconvolution was vital. In real systems, good DM determinations were obtained without peak deconvolution except for broccoli-derived samples. Considering that broccoli is a protein-rich vegetable, better determinations of the DM were obtained using deconvoluted FT-IR spectra.

Innovative enzymatic approach to resolve homogalacturonans based on their methylesterification pattern

Three series of model homogalacturonans (HGs) covering a large range of degree of methylesterification (DM) were prepared by chemical and/or enzymatic means. Randomly demethylesterified HGs, HGs containing a few long demethylesterified galacturonic acid stretches, and HGs with numerous but short demethylesterified blocks were recovered. The analysis of the degradation products generated by the action of a purified pectin lyase allowed the definition of two new parameters, the degree of blockiness, and the absolute degree of blockiness of the highly methylesterified stretches (DBMe and DB(abs)Me, respectively). By combining this information with that obtained by the more traditional endopolygalacturonase digestion, the total proportion of degradable zones for a given DM was measured and was shown to permit a clear differentiation of the three types of HG series over a large range of DM. This double enzymatic approach will be of interest to discriminate industrial pectin samples exhibiting different functionalities and to evaluate pectin fine structure dynamics in vivo in the plant cell wall, where pectin plays a key mechanical role.