Process–Structure–Function Relations of Pectin in Food

Pectin, a complex polysaccharide rich in galacturonic acid, has been identified as a critical structural component of plant cell walls. The functionality of this intricate macromolecule in fruit- and vegetable-based–derived products and ingredients is strongly determined by the nanostructure of its most abundant polymer, homogalacturonan. During food processing, pectic homogalacturonan is susceptible to various enzymatic as well as nonenzymatic conversion reactions modifying its structural and, hence, its functional properties. Consequently, a profound understanding of the various process–structure–function relations of pectin aids food scientists to tailor the functional properties of plant-based derived products and ingredients. This review describes the current knowledge on process–structure–function relations of pectin in foods with special focus on pectin's functionality with regard to textural attributes of solid plant-based foods and rheological properties of particulated fruit- and vegetable-derived products. In this context, both pectin research performed via traditional, ex situ physicochemical analyses of fractionated walls and isolated polymers and pectin investigation through in situ pectin localization are considered.     

Rethinking the impact of RG-I mainly from fruits and vegetables on dietary health

Abstract

Rhamnogalacturonan I (RG-I) pectin is composed of backbone of repeating disaccharide units →2)-α-L-Rhap-(1→4)-α-D-GalpA-(1→ and neutral sugar side-chains mainly consisting of arabinose and galactose having variable types of linkages. However, since traditional pectin extraction methods damages the RG-I structure, the characteristics and health effects of RG-I remains unclear. Recently, many studies have focused on RG-I, which is often more active than the homogalacturonan (HG) portion of pectic polysaccharides. In food products, RG-I is common to fruits and vegetables and possesses many health benefits. This timely and comprehensive review describes the many different facets of RG-I, including its dietary sources, history, metabolism and potential functionalities, all of which have been compiled to establish a platform for taking full advantage of the functional value of RG-I pectin.     

Dietary pectic substances enhance gut health by its polycomponent: A review

Pectic substances, one of the cell wall polysaccharides, exist widespread in vegetables and fruits. A surge of recent research has revealed that pectic substances can inhibit gut inflammation and relieve inflammatory bowel disease symptoms. However, physiological functions of pectins are strongly structure dependent. Pectic substances are essentially heteropolysaccharides composed of homogalacturonan and rhamnogalacturonan backbones substituted by various neutral sugar sidechains. Subtle changes in the architecture of pectic substances may remarkably influence the nutritional function of gut microbiota and the host homeostasis of immune system. In this context, developing a structure–function understanding of how pectic substances have an impact on an inflammatory bowel is of primary importance for diet therapy and new drugs. Therefore, the present review has summarized the polycomponent nature of pectic substances, the activities of different pectic polymers, the effects of molecular characteristics and the underlying mechanisms of pectic substances. The immunomodulated property of pectic substances depends on not only the chemical composition but also the physical structure characteristics, such as molecular weight (M_w) and chain conformation. The potential mechanisms by which pectic substances exert their protective effects are mainly reversing the disordered gut microbiota, regulating immune cells, enhancing barrier function, and inhibiting pathogen adhesion. The manipulation of pectic substances on gut health is sophisticated, and the link between structural specificity of pectins and selective regulation needs further exploration.     

山楂果胶寡糖及其复合物对枯草杆菌的抗菌作用

由于独特的胶凝性和增粘稳定性而在食品添加剂领域表现出广泛用途的山楂果胶,其低分子的分解产物—山楂果胶寡糖对枯草芽孢杆菌具有很强的抗菌性。进一步对山楂果胶寡糖与其他天然食品添加剂进行复配后的抗菌性进行分析的结果表明,山楂果胶寡糖与乳酸钠的复合物与二者单独使用相比对枯草芽孢杆菌具有更强的抗菌作用,在pH=5的条件下,5mg/mL的山楂果胶寡糖与10mg/mL乳酸钠的复配物即可完全抑制枯草芽孢杆菌的生长,在天然食品防腐添加剂的开发利用领域表现出了良好的应用前景。     

苹果果胶研究进展

苹果(Malus pumila Mill.)是我国北方广泛种植的经济作物。近年来,很多学者从苹果渣中提取分离得到苹果果胶。现代医学和生物学研究表明,苹果果胶具有抗氧化、降血脂、抗菌及抗癌的功效。本文介绍了苹果果胶的结构、组分分级与特性研究,着重阐述了目前国内外对于苹果果胶的提取、分离的最新进展及其生物活性,讨论了目前研究中存在的问题,并对其发展前景进行了展望。     

果胶寡糖的制备、分离纯化及其生物活性研究进展

果胶寡糖是由果胶经不同方法制备得到的小分子聚合物,与天然果胶相比,其具有较低的分子质量、较好的水溶性、较高的生物利用度以及丰富的生物活性。在不同的制备条件下,可以得到一系列分子质量和结构不同的果胶寡糖。而果胶寡糖的生物活性与其分子质量和结构之间有着密切关系。本文就果胶寡糖的制备、分离纯化、结构鉴定及其生物活性等方面进行综述,以期为果胶寡糖作为天然活性物质在食品、医药和保健品等领域的应用提供一定的参考。     

果胶的分类、功能及其在食品工业中应用的研究进展

果胶是一类结构复杂的天然多糖,是高等植物细胞壁的重要组成部分.根据其单糖组成及分子结构的差异,可分为同型半乳糖醛酸聚糖、I型鼠李半乳糖醛酸聚糖、II型鼠李半乳糖醛酸聚糖、木糖半乳糖醛酸聚糖等类型.果胶结构复杂,生物活性多样,如免疫调节作用、抗肿瘤、抗氧化、降血糖、改善胃肠道功能等.一些特定来源的果胶可作为天然的多功能型...     

Towards a better understanding of the pectin structure–function relationship in broccoli during processing: Part II — Analyses with anti-pectin antibodies

To investigate the structure–function relationship of pectin during (pre)processing, broccoli samples (Brassica oleracea L. cultivar italica) were subjected to one of the following pretreatments: (i) low-temperature blanching (LTB), (ii) LTB in combination with Ca²⁺ infusion, (iii) high-pressure pretreatment (HP), (iv) HP in combination with Ca²⁺ infusion, or (v) no pretreatment (control sample), whether or not in combination with a thermal treatment of 15 min at 90 °C. Anti-homogalacturonan antibodies were used to perform in situ (microscopy) and ex situ (immuno-dot assays) analyses on broccoli pectin which resulted in information concerning the localisation of defined pectic domains in broccoli cell walls and pectin's structure. Water-soluble pectin appears to contain unbranched, high-esterified pectin and some pectic polymers with abundant side chains that are less esterified. Ionically cross-linked pectin, on the other hand, contains low-esterified pectin with either highly branched or unbranched domains. The in situ visualisation of pectin in broccoli suggested that de-esterification of pectin by PME during LTB as well as during HP mainly takes place in the tricellular junctions of adjacent cells in broccoli tissue. Ca²⁺-cross-linked pectin could be found in cell walls lining intercellular spaces and was particularly abundant at the corners of intercellular spaces, indicating its important role in cell–cell adhesion. Both LTB and HP created pectin–Ca²⁺-cross-links in parts of the cell wall where these cross-links were originally absent. The influence of thermal processing and the effect of pressurisation on the pectic components in the cell wall could also be visualised using the antibodies.     

Towards a better understanding of the relationship between the β-carotene in vitro bio-accessibility and pectin structural changes: A case study on carrots

The quality of fruit and vegetables based products is affected by processing. Two important parameters to consider are the structural characteristics and the nutritional value. As pectin is a major constituent of plant cell walls, pectin structure engineering can be used as a tool to affect the structural quality of plant based food products. During thermal processing, pectin characteristics are influenced. Recently, it has been highlighted that nutrient bio-accessibility is affected by food structure. The intracellular localization of nutrients implies that their accessibility can be hindered by several structural elements.Therefore, this investigation focused on the relation between the structural quality and the nutritional value of carrots. Texture was measured as an indication for the structural quality, while the β-carotene in vitro bio-accessibility was selected as a parameter reflecting the nutritional value. The effect of thermal (pre)processing on this relationship was investigated. The results clearly indicate that the structural quality of carrots and the β-carotene in vitro bio-accessibility are inversely correlated. Moreover, it was hypothesized that pectin changes during thermal processing play a key role in this inverse relationship.     

The Emulsifying and Emulsion‐Stabilizing Properties of Pectin: A Review

Pectin, a plant cell wall polysaccharide, is a natural multifunctional ingredientwhich imparts textural and rheological properties to a wide range of food systems. Up to the last decade, most pectin blank applications stemmed from its gel‐forming ability. Nowadays, pectin is gradually gaining acceptance as an effective emulsifier in numerous food applications. Accordingly, the emulsifying and emulsion‐stabilizing properties of this hydrocolloid are increasingly being assessed. These pectin functionalities are controlled by both the properties of the carbohydrate moieties and of the often attached protein groups. Generally, the protein moiety, feruloyl, and acetyl groups, play a major role in pectin emulsifying activities, while the emulsion‐stabilizing properties of the polymer are controlled by the homogalacturonan (HG) domain and the neutral sugar side chains of the rhamnogalacturonan‐I (RGI) structural element. However, the neutral sugar side chains might obstruct the accessibility of pectin hydrophobic species to the oil/water interface, thereby hampering emulsification. In addition, the contribution of HG to emulsion stabilization might be dependent on the polymer HG:RGI ratio. Hence, the influence of pectin structural features on the polymer emulsifying potentials is yet to be fully unraveled, as identified in this review. Furthermore, the emulsifying and emulsion‐stabilizing properties of pectin are influenced by the composition of emulsions.     

Possibilities for application of laser ablation in food technologies

This work considers the possibility for using laser ablation in food technologies. It was found for the fruits and vegetables under study that laser ablation provided an efficient peeling of the materials while preserving the organoleptic properties, such as freshness, naturalness, and texture.After a laser treatment of citrus fruit (oranges and lemons), the fruits were peeled and pectin was extracted from the peels via a classical type of extraction in HCl water solution. The pectins obtained were assayed for yield, degree of esterification, polyuronic content, molecular weight, gel strength and other physico-chemical properties. For all samples it was found that laser pretreatment of the materials led to an increase in pectin yield, gel strength and purity, at an insignificant reduction of molecular weight and degree of esterification.Laser ablation of fruits and vegetables was used as an alternative to traditional methods for producing edible films. The cell particles, removed by means of laser ablation and containing plant waxes, cellulose fibers and pectic substances, were applied aseptically onto a hard surface and the obtained edible films showed a lasting antimicrobial effect.As a result of the treatment of fruits and vegetables with CO₂ laser, a number of aroma substances were released and they could be captured and used.

Industrial relevance

The work described in this research is relevant to the laser ablation of peeled fruit and vegetables used in food technologies. Laser treatment for peeling fruit and vegetables can be used not only by food processing enterprises, by catering companies and by fast food establishments as a preliminary treatment of fruit and vegetables, but also by pectin producers. There is also a prospect for the application of laser ablation in extracting aroma substances from various materials, as well as in obtaining edible films.     

The chemical characteristics of apple pectin influence its fermentability in vitro

The aim of the present study was to characterize the fermentability of different apple pectins, as soluble dietary fibres, in vitro. High- and low-methoxyl pectins were fermented completely and very fast by human colonic bacteria, whereas pectic acid and amidated pectin were degraded more slowly. The main fermentation metabolites, i.e. short-chain fatty acids (SCFA) and gases, were produced in lower amounts from pectic acid and amidated pectin. Based on the higher production of SCFA, pectins with a higher degree of methoxylation might be the best candidates for food enrichment due to a beneficial effect on colonic health. On the other hand, the longer persistence of the slowly degraded pectins in the gut may be of advantage as binding and diluting agents for carcinogens.     

Isolation and characterisation of pectic substances from murta (Ugni molinae Turcz) fruits

Cell walls polysaccharides from murta fruit (Ugni molinae Turcz), an endemic Chilean species with relevant food uses, were fractionated by water, ammonium oxalate, hot diluted HCl and cold diluted NaOH extractions. The polysaccharide fractions were analysed for monosaccharide composition and physicochemical properties. Pectic substances were found in all extracts, but mainly in the oxalate and acid soluble fractions, in which they appear as homogalacturonan polymers. Murta pectin was further extracted by hot diluted acid treatment using industrial conditions, yielding 30% by weight of dry fruit. The polymer showed similar composition and physicochemical properties to those of commercial citrus pectin, presenting a galacturonic acid content of 70.9% (w/w), a molecular weight of 597 kDa, and a methoxylation degree of 57%. The FT-IR spectrum of murta pectin suggests the presence of ferulic acid residues on its structure and the NMR analysis confirmed the structure of this polysaccharide. It is concluded that murta fruit can be considered as a valuable source of high quality pectin.     

Mechanistic insight into common bean pectic polysaccharide changes during storage,soaking and thermal treatment in relation to the hard-to-cook defect

Different mechanisms responsible for the development of the hard-to-cook defect in common beans during storage, their soaking behavior and softening during thermal treatment have been previously suggested. However, these mechanisms have not been sufficiently confirmed by direct molecular evidence. This research aimed at gaining a detailed mechanistic insight into changes occurring in Canadian wonder bean pectic polysaccharides during storage, soaking and/or thermal treatment in different brine solutions in relation to the development and manifestation of the hard-to-cook (HTC) defect. Both fresh or easy-to-cook (ETC) and stored (HTC) bean samples were either soaked or soaked and thermally treated in demineralized water, solutions of Na₂CO₃ and CaCl₂ salts followed by extraction of cell wall materials. Pectic polysaccharide properties examined included sugar composition, degree of methylesterification (DM), extractability and molar mass (MM). The DM of pectin from ETC and HTC beans was similar but low (< 50%). Upon (pre)treatment in a Na₂CO₃ solution, solubilization of pectic polysaccharides, especially the strongly bound chelator- (CEP) and Na₂CO₃- (NEP) extractable pectins was enhanced leading to increased amounts of water extractable pectin (WEP). Also, there was a decrease in high MM polymers paralleled by an increase in β-elimination degradation products. These observations are in line with the fast cooking behavior of beans (pre)treated in a Na₂CO₃ solution. In contrast, (pre)treatment in a CaCl₂ solution hindered softening leading to the failure of the beans to cook. The beans (pre)treated in a CaCl₂ solution showed increased high MM polymers and lack of cell wall separation. Therefore, it can be inferred that development of the hard-to-cook defect in Canadian wonder beans during storage and its manifestation during soaking and subsequent thermal treatment is largely reflected by the pectic polysaccharide properties in line with the pectin hypothesis. Our data suggest the release of Ca⁺⁺ leading to pectin cross-linking and the increase or decrease of β-elimination depolymerization. However, the relatively high amounts of neutral sugars and strongly bound NEP in HTC seeds do not allow to rule out the possible existence of non-Ca⁺⁺ based pectin cross-linking.     

Pectic substances in onion and garlic skins

Pectic substances from onion (white and red varieties) and garlic skins were isolated by extraction with ammonium oxalate. White onion and garlic skins were found to contain 11 to 12% pectin which can be recovered as a by-product in the dehydration industries. Characterisation of these pectic substances in terms of jelly grade, molecular weight, degree of esterification, methoxyl and uronide content was attempted. Pectins from white onions were superior to red onions in terms of jelly grade. Both types of onion pectins appeared to be of the rapid set type while the garlic skin pectin was of the medium set variety. Equivalent weight, methoxyl content and degree of esterification by themselves did not give any clear indication of pectin grade. Intrinsic viscosity values gave good correlation between jelly grade and molecular weight. The pectic substances from garlic skin differed from onion skin in certain respects and most remarkably in its viscosity behaviour.     

Pectins in Processed Fruits and Vegetables: Part II—Structure–Function Relationships

ABSTRACT: Pectin represents a very heterogeneous biopolymer whose functionality remains largely puzzling. The link between the pectin fine structure and functional properties with relevance to plant growth and development, as well as food processing, is continually being explored. This review describes the current knowledge of pectin structure–function relationships. Key mechanisms dictating pectin structure–function relationships are discussed, including the polymer biosynthesis, cross‐linking mechanisms, enzymatic and nonenzymatic conversion reactions, solubility properties, and more. Insight into the polymer structure–function relationships is highlighted by examining traditional and advanced methodologies used in pectin research. The role of pectin in modulating the quality characteristics of plant‐based foods is underlined while pin‐pointing some of the main challenges and perspectives. An integrated approach using the pectin structure–function relationship in the precision engineering of mechanical properties of tissue‐based systems is proposed.     

Texture and distribution of pectic substances of mango as affected by infusion of pectinmethylesterase and calcium

Fresh cut mangos were infused with pectinesterase (PME) and calcium chloride, and the effect on textural properties, distribution of pectic substance and degree of esterification was determined. Temperature gradient infusion with PME and/or calcium chloride increased gumminess and chewiness, but had no impact on hardness and adhesiveness. The distribution of pectic substances, as protopectin or alkaline soluble pectin, was approximately twice that of water‐ or chelator‐soluble pectin. The degree of esterification of water‐ and chelator‐soluble pectic substances was near 50–60%, and less than 10%, respectively. Heat‐sensitive PME inhibitor in mango was detected. The initial hardness of Kent mango was variable, and differences in distribution of pectic substances were observed. Texture of Kent mango is most likely moderated by changes in the solubility of insoluble pectin or by non‐pectin components in the cell wall. Copyright © 2004 Society of Chemical Industry     

果胶结构、提取方法及乳化特性研究进展

果胶是一种重要的酸性大分子多糖物质,具有良好的凝胶性、增稠性和乳化特性,被广泛应用于食品加工业中。果胶的结构及乳化特性会受到提取方法的影响,本文综述了果胶的分子结构及不同提取方法的应用特点,并介绍了影响果胶乳化特性的结构因素(蛋白质、阿魏酸、乙酰基、中性糖侧链、分子量)和环境因素(果胶浓度、油相浓度、pH、盐离子)及果胶与蛋白质结合用于稳定乳化液的研究现状,最后对果胶的研发前景进行展望,以期为果胶的开发和应用提供一定的理论参考。     

Pectin recovery from apple pomace: physico-chemical and functional variation based on methyl-esterification

This study explored the valorisation of apple pomace by extracting pectin with both high and low degrees of esterification (DM). Two types of pectin were extracted with a DM of 43.29% being low methoxyl (LM) pectic polysaccharide and high methoxyl (HM) pectin with a DM of 65.88%. HM pectin was characterised by a WHC and OHC of 1.3 g g⁻¹ and 0.4 g g⁻¹, respectively, compared to 0.32 g g⁻¹ and 0.14 g g⁻¹, respectively, for LM pectic polysaccharide. HM pectin possessed greater purity indicated by 69.18% GalA, whereas LM pectic polysaccharide possessed 41.26% GalA. HM pectin revealed better functionality in terms of high emulsifying activity which was concentration-dependent, and emulsion stability than LM pectic polysaccharide. The solubility of HM pectin was 90.8%, which is preferable for various industrial applications. LM pectic polysaccharide was characterised by a higher % radical-scavenging activity in a concentration-dependent manner. XRD analysis revealed LM pectic polysaccharide to possess higher crystallinity (53%) and SEM analysis revealed its surface to be rough and coarse.     

A study on the composition of garlic skins and the structural features of the isolated pectic acid

An investigation of the composition of garlic skins showed the presence of proteins, lipids, lignin, mannitol, pectin and polysaccharides. Garlic skins are rich in pectin (27%), combined rhamnose (11.42%) and galactose (5.6%). Periodate oxidation studies of pectic acid showed the absence of 1,3-linked residues and branch points and indicated a linear galacturonan of 1,4-linked D-galacturonic acid. Chromatographic analyses were carried out on the hydrolysis products of pectic acid, which had been oxidised by periodate plus bromine, and also on those obtained after reduction of the periodate-oxidised pectic acid.