A comprehensive review on the functionality and biological relevance of pectin and the use in the food industry

Review A comprehensive review on the functionality and biological relevance of pectin and the use in the food industry Luna Barrera-Chamorro a,b,1 , ´ Africa Fernandez-Prior a,b,1 , Fernando Rivero-Pino a,b,c,*,2 , Sergio Montserrat-de la Paz a,b a Department of Medical Biochemistry, Molecular Biology, and Immunology, School of Medicine, University of Seville, Av. Sanchez Pizjuan s/n, 41009 Seville, Spain b Instituto de Biomedicina de Sevilla, IBiS/Hospital Universitario Virgen del Rocio/CSIC/Universidad de Sevilla, 41013 Seville, Spain c European Food Safety Authority, Nutrition and Food Innovation Unit, Novel Foods Team, Parma, Italy ARTICLE INFO Keywords: Pectin By-products Food waste Polysaccharides Prebiotics ABSTRACT Pectin is a natural biopolymer, which can be extracted from food by-products, adding value to raw material, with a structure more complex than that of other polysaccharides. The gelling properties of these molecules, together with the bioactivity that these can exert, make them suitable to be used as ingredients and bioactive agents. In this review, the characterization of pectin (structure, sources, techno-functional, and biological properties), the extraction methods, and their use in the food industry (food packaging, as carriers, and as ingredients) are described. Different by-products can be used as substrates to extract pectin, enhancing a sustainable food system as described by the circular economy principles. Pectin is characterized for their techno-functional and biological properties, such as gelling and thickening properties or modulation of microbiota both in animals and humans. Such properties make these molecules suitable for a wide range of applications within the food chain, serving as packaging or carriers in foodstuff, or for direct use as functional ingredients as fiber. Overall, pectin has been shown to exert as promising components to be introduced in the food system, although further research on scaling-up the production process and feasibility has to be done. 1. Introduction The food processing industry annually generates around 100 Mt. of food waste and by-products only in the EU, representing a harvesting and processing loss of >35 %. Production and preservation of fruits and vegetables produce the largest amounts of food waste, which could be transformed into by-products (14.8 %). The effective utilization of byproducts has huge potential for obtaining functional ingredients. For instance, valorization can be achieved by separating the valuable compounds such as polysaccharides, polyphenols, essential oils, pigments, proteins, flavor compounds, enzymes, and dietary fibers using different extraction methods (Mari´ c et al., 2018). Pectin is a natural carbohydrate biopolymer, which can be extracted from food by-products biomass, adding value to raw material. It acts as a binding agent for cellulose and helps maintain cellular assembly (Roy et al., 2023), as it has a highly complex structure. Pectin is a heteropolysaccharide occurring in the cell walls located in the middle lamella, and primary and secondary cell wall of plant tissue and account for 30 % of the total dry weight of plants, contributing to the textural quality of products made from them (Roman-Benn et al., 2023). To date, pectin is thought to be composed of at least of 17 kinds of monosaccharides, D-galacturonic acid (D-GalA) being the predominant one, followed by D-galactose (D-Gal) or L-arab- inose (L-Ara). To meet the standards set by EU regulation No. 231/2012 for food-grade pectin, the D-GalA content must be at least 65 % (Commission Regulation, 2012). The primary use of pectin is for food design due to its versatile gelling, emulsifying, glazing, stabilizing, and/ or thickening properties utilized in jellies, jams, marmalades, fruit juice, confectionery products, among others (Chan et al., 2017). The Global * Corresponding author at: Department of Medical Biochemistry, Molecular Biology, and Immunology, School of Medicine, University of Seville, Av. Sanchez Pizjuan s/n, 41009 Seville, Spain. E-mail address: [email protected] (F. Rivero-Pino). 1 To be considered as equal first author. 2 Disclaimer: The author F. Rivero-Pino is carrying out a temporal secondment at European Food Safety Authority – EFSA- from June 1st, 2024, to May 31st, 2025. The work described in this article is not related to his current work at EFSA, it is published under the sole responsibility of the author and may not be considered as an EFSA scientific output. The views and opinions expressed in this manuscript do not represent those of EFSA. Contents lists available at ScienceDirect Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol https://doi.org/10.1016/j.carbpol.2024.122794 Received 25 July 2024; Received in revised form 12 September 2024; Accepted 22 September 2024 Carbohydrate Polymers 348 (2025) 122794 Available online 26 September 2024 0144-8617/© 2024 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ ). Pectin Market is valued at USD 1.2 Billion in 2022 and is expected to reach USD 1.9 billion by 2030 at a CAGR of 6.8 % over the forecast period of 2023–2030. Currently, commercial pectin (coded E440a for low methoxyl pectin (LMP) and high methoxyl pectin (HMP), and E440b for amidated pectin) is mainly extracted from citrus peels (85.5 %) and apple pomace (14.0 %) (EFSA ANS Panel, 2017). However, the increasing interest in the valorization of food byproducts and the high global market demand have led researchers to explore emerging sources of pectin. Several studies have focused on the extraction and characterization of different agro-industrial wastes-derived pectin, such as pumpkin and melon peels (Lalnunthari et al., 2020; Golbargi et al., 2021), mango and banana peels (Mao et al., 2024; Torres-Gallo et al., 2022), eggplants (Higuera-Coelho et al., 2023), tomatoes (Liu, Qu, et al., 2023) cocoa pod husks (Anoraga et al., 2024), olive pomace (Bermúdez-Oria et al., 2023), and potato peels (Xie et al., 2018). These alternative sources effectively captured the attention of researchers as potential sustainable alternatives for pectin production. The aim of this review was the characterization of food-waste- derived pectin (i.e., structure, sources, extraction, techno-functional, and biological properties), highlighting promising updates on their use in the food industry (food packaging, as carriers to increase bioavailability, and as ingredients). By comprehensively examining the potential of food waste as a source of pectin, we contribute to the ongoing efforts in creating a circular economy and reducing the environmental impact of waste disposal. 2. Pectin 2.1. Definition and structure of pectin Pectin is a nontoxic, natural, and versatile heteropolysaccharide mainly composed of glycan domains that contain of a backbone of α -(1 → 4)-linked D-GalA, an isomer of D-glucuronic acid (D-GlcA), which comprises approximately 70 % of pectin structure (Dranca & Oroian, 2018). D-GalA is present in three carbohydrate polymers: homogalacturonan (HG), type I rhamnogalacturonan (RG-I), and type II rhamnogalacturonan (RG-II) as depicted in Fig. 1. Additionally, xylogalacturonan (XGA) and apiogalacturonan (APGA) are often considered to be pectin because they have the same backbone as HG. The general description of pectin is composed of an alternation of ‘smooth’ and ‘hairy’ regions along the entire length of the biomolecule. Smooth regions are represented by HG, which forms the linear backbone and RG-I and RG-II represent the hairy regions (Pang et al., 2024). HG is a linear homopolymer of α -(1 → 4)-linked D-GalA that comprises ~65 % of pectin (Du et al., 2022). Generally, HG comprises D- GalA monomers in long stretches of at least 72 to 100 residues linked together. RG-I is a repeating disaccharide of [→4- α -D-GalA-(1 → 2)- α -L- Rhamnose (Rha)-(1→] with many O-4 positions containing other neutral sugars, such as D-Gal or L-Ara. Rha is a naturally occurring deoxy sugar, which can be classified as either a methyl-pentose or a 6-deoxy-hexose. Rha predominantly occurs in nature in its L-form as L-Rha (6-deoxy-L- mannose) (Wagstaff et al., 2021). The length of the backbone of RG-I is about 100 to 300 repeating units. Side chains varying by plant sources, such as arabinan, β-(1 → 4)-galactan, type I arabinogalactan (AG-I), and type II arabinogalactan (AG-II) exist. Arabinan consist of α -(1 → 5)- linked L-Ara backbone, which is usually substituted with α -L-Ara in different linkages. AG-I is composed out of a β-(1 → 4)-linked D-Gal backbone with α -L-Ara residues attached to the O-3 position. The terminal galactose of β-(1 → 4) galactan is frequently linked to L-Ara by α -(1 → 5) glycoside bonds. AG-II is composed of a β-(1 → 3)-linked D-Gal backbone, containing short side chains of α -L-Ara-(1 → 6)-[β-D-Gal-(1 → 6)] n . The galactosyl residues of the side chains can be substituted with α -(1 → 3)-linked L-Ara residues (Kaczmarska et al., 2022). AG-II is mainly associated with proteins (3–8 %), so called arabinogalactan proteins (AGPs), which are rich in proline/hydroxyproline, alanine, serine, and threonine (Leszczuk et al., 2023). D-GalA residues in the backbone of RG-I may be highly O-acylated on O-2 and/or O-3, but they are not usually methyl esterified. Ferulic acid groups in RG-I may be ester-linked to O-2 of the arabinose residues and to O-6 of the galactose residues. Finally, RG-II, a highly conserved structure, is a homogalacturonic backbone with numerous complex side chains at C-2 and C- 3 positions containing L-Rha and other neutral sugars, up to 13 types of sugar may be present, including the rarely observed sugars D-apiose (D- Api), aceric acid, 3-deoxy-lyxo-2-heptolusaric acid (DHA), 3-deoxy- manno-2-octulosonic acid (KDO), D-xylose (D-Xyl), and L-fucose (L- Fuc), in over 21 different linkages (Roman-Benn et al., 2023). As depicted in Fig. 2, RG-II generally consists of seven branched chains Fig. 1. Schematic molecular structure of main chains of pectin. L. Barrera-Chamorro et al. Carbohydrate Polymers 348 (2025) 122794 2 (chains A-F) (Ndeh et al., 2017). RG-II can complex together with Boron, forming a borate–diol ester, which can crosslink two HG molecules (Voragen et al., 2009). Additionally, XGA is an α -(1 → 4)-linked D-GalA chain, which is highly substituted with β-D-xylose (β-D-Xyl) at the C-3 position, which has occasionally been found to be further substituted at O-4 position with an additional β-D-Xyl and APGA resulting from D- Apiofuranose substitution at O-2 or O-3 positions. The degree of xylosidation can vary between 25 % (watermelon) and 75 % (apple) (Voragen et al., 2009). α -D-GalA units may be substituted by methyl residues, in which some of the C-6 carboxyl groups are methyl-esterified. In this context, the degree of methoxylation is defined as the percentage of esterified D- GalA units of the total number of D-GalA units in the molecule. In addition, D-GalA may be O-acetylated at the O-2 or O-3 position. The degree of esterification (DE) of pectin is important to the functional properties of the plant cell wall and also affects its physicochemical properties and applications. For instance, pectin is classified into two major groups depending on the DE: HMP (DE >50 %) and LMP (DE < 50 %). HMP and LMP have different physicochemical properties, and thus diverse applications, such as the stability of pectin emulsion, formation and strength of pectin gel (Cui, Zhang, et al., 2023). Pillai et al. (2020) found that the critical pH of complex formation shifted significantly to higher pH as the DE of the pectin decreased. HMP displayed greater interactions with proteins at optimal mixing conditions compared to LMP (Warnakulasuriya et al., 2018). DE of pectin could influence the bioaccessibility of carotenoids loaded in the oil phase of emulsions (Verrijssen et al., 2014). What’s more, it has been verified that the interfacial and emulsifying properties of citrus pectin changed with different DE, and HMP was characterized as smaller hydrodynamic radii and faster adsorption kinetics (Schmidt et al., 2017). The gelation of pectin was closely related to its DM value. In general, HMP generates a gel network at acidic pH (lower than 3.5) in the presence of large amounts of sugars (65 %, w/w) or other co-solutes, by stacking of the methoxyl groups through hydrophobic interactions and hydrogen bonding. Gelation of LMP is ionically mediated through divalent cations called “egg-box model” over a wide range of pH with and without sugar (Wan et al., 2019). Thus, LMP is more preferred in low calorie or dietetic food industry, meeting the increasing consumer demand for healthy diet. Finally, amidated pectin is synthesized through the reaction of ammonia with carboxymethyl groups (–COOCH 3 ) on the pectin molecule. The degree of amidation (DA) is defined as the percentage of carboxylic acid groups of pectin present in amide form. The replacement of methoxyl groups with amide groups modifies some properties of the pectin gels; for instance, amidation increases the water solubility of pectin and enables it to be more thermoreversible and withstand more calcium variation (Chen et al., 2015). 2.2. Pectinolytic enzymes The chemical and structural properties of pectin is especially prone to changes in the fruit due to solubilization and enzymatic degradation which are considered to be the key processes responsible for the softening of fruit during ripening. Structural changes that occur in the middle lamella and primary cell wall during ripening result in cell separation and softening of the tissues. The molecular components of primary walls are modified during fruit ripening by the temporally and spatially regulated action of endogenous enzymes (Zheng et al., 2021; Liu, Zhou, et al., 2023). Pectinase is a generic term used for a group of enzymes that catalyse the degradation of pectin by hydrolysis, transelimination, as well as de-esterification reactions. The degradation of pectic polymers is mainly caused by exo- and endo-polygalacturonases (exo- and endo-PGs), pectate and pectin lyases (PLs), pectin methylesterase (PME) and acetylesterase (PAE), β-galactosidase (β-Gal), and α -L-arabinofuranosidase ( α -L-Af), among others (Satapathy et al., 2020). Endo-PG (E.C. 3.2.1.15) is known to be the most important enzyme responsible for pectic depolymerization and solubilization. This enzyme Fig. 2. Representative molecular structure of type II rhamnogalacturonan. L. Barrera-Chamorro et al. Carbohydrate Polymers 348 (2025) 122794 3 hydrolyses the α -1 → 4 glycosidic bonds of the methyl de-esterified HG backbone. The enzyme randomly attacks its substrate and produces a number of D-GalA oligosaccharides. Exo-PG (E.C. 3.2.1.67 and E.C. 3.2.1.82) attacks the substrate from the non-reducing end and is able to remove terminally (1→)–linked D-GalA residues from HG chains. The enzyme requires a non-esterified D-GalA unit at subsites −2, −1, and +1 and is tolerant for xylose substitution (able to remove a D-GalA-Xyl dimer), hence XGA is also an exo-PG substrate. PLs (pectate lyases, E.C. 4.2.2.2, and pectin lyases, E.C. 4.2.2.10) acts through the β-elimination of methyl esterified HG in the presence of Ca 2+ , Mn 2+ , or Ni 2+ (Satapathy et al., 2020). PME (E.C. 3.1.1.11) and PAE (E.C. 3.1.1.6) deesterifies HG chains by removing the methoxyl and acetyl residues, respectively. It decreases the degree of pectin methylation thereby providing suitable conditions for the hydrolysis of the α -1 → 4 link in the HG backbone by PG. The degradation of RGs involves the participation of numerous enzymes. RG hydrolase (RGH, E.C. 3.2.1.171) hydrolyses the α -D-1 → 4-D-GalA- α -L-1 → 2-Rha linkage in the RG-I backbone, leaving Rha at the non-reducing side. RG lyase (RGL, E.C. 4.2.2.23) hydrolyses RG-I α -L-1 → 2-Rha- α -D-1 → 4-GalA backbone leaving a 4- deoxyβ -L-threo-hex-4-enepyranosyluronic acid (unsaturated GalA) group at the non-reducing end. RG rhamnohydrolase (RGRH, E.C. 3.2.1.174) is an exo-acting pectinase, which possesses the specificity to release terminal rhamnosyl residues (1 → 4)-linked to α -galacturonosyl residues. RG galacturonohydrolase (RGGH, E.C. 3.2.1.173) is able to Table 1 Summary of enzymes involved in pectin degradation. PUL CAZyme families EC number Accepted name Reaction HGPUL PL1 EC4.2.2.2 Pectate lyase Eliminative cleavage of (1 → 4)- α -D-galacturonan to give oligosaccharides with 4-deoxy- α -D-galact-4- enuronosyl groups at their non-reducing ends PL1 EC4.2.2.10 Pectin lyase Eliminative cleavage of (1 → 4)- α -D-galacturonan methyl ester to give oligosaccharides with 4-deoxy- 6-O-methyl- α -D-galact-4-enuronosyl groups at their non-reducing ends GH28 EC3.2.1.67 Galacturonan 1,4- α -galacturonidase [(1 → 4)- α -D-galacturonide] n +H 2 O =[(1 → 4)- α -D-galacturonide] n-1 +D-galacturonate GH28 EC3.2.1.82 Exo-poly- α -digalacturonosidase [(1 → 4)- α -D-galacturonosyl] n +H 2 O = α -D-galacturonosyl-(1 → 4)-D-galacturonate +[(1 → 4)- α -D- galacturonosyl] n-2 GH28 EC3.2.1.15 Endo-polygalacturonase (1,4- α -D-galacturonosyl) n+m +H 2 O =(1,4- α -D-galacturonosyl) n +(1,4- α -D-galacturonosyl) m CE8 EC3.1.1.11 Pectinesterase Pectin +n H 2 O =n methanol +pectate CE4 EC3.1.1.6 Acetylesterase An acetic ester +H 2 O =an alcohol +acetate RG-I PUL PL9 EC4.2.2.23 Rhamnogalacturonan endolyase Endotype eliminative cleavage of L- α -rhamnopyranosyl-(1 → 4)- α -D-galactopyranosyluronic acid bonds of rhamnogalacturonan I domains in ramified hairy regions of pectin leaving L-rhamnopyranose at the reducing end and 4-deoxy-4,5-unsaturated D-galactopyranosyluronic acid at the non-reducing end GH28 EC3.2.1.171 Rhamnogalacturonan hydrolase Endohydrolysis of α -D-GalA-(1 → 2)- α -L-Rha glycosidic bond in the rhamnogalacturonan I backbone with initial inversion of anomeric configuration releasing oligosaccharides with β-D-GalA at the reducing end. GH2 EC3.2.1.146 β-Galactofuranosidase Hydrolysis of terminal non-reducing β-D-galactofuranosides, releasing galactose GH138 EC3.2.1.173 Rhamnogalacturonan galacturonohydrolase Exohydrolysis of the α -D-GalA-(1 → 2)- α -L-Rha bond in rhamnogalacturonan oligosaccharides with initial inversion of configuration releasing D-galacturonic acid from the non-reducing end of rhamnogalacturonan oligosaccharides GH105 EC3.2.1.172 Unsaturated rhamnogalacturonyl hydrolase 2-O-(4-deoxy-β-L-threo-hex-4-enopyranuronosyl)- α -L-rhamnopyranose +H 2 O =5-dehydro-4-deoxy- D-glucuronate +L-rhamnopyranose GH106 EC3.2.1.174 Rhamnogalacturonan rhamnohydrolase Exohydrolysis of the α -L-Rha-(1 → 4)- α -D-GalA bond in rhamnogalacturonan oligosaccharides with initial inversion of configuration releasing β-L-rhamnose from the non-reducing end of rhamnogalacturonan oligosaccharides GH43 EC3.2.1.99 Arabinan endo-1,5- α -L- arabinanase Endohydrolysis of (1 → 5)- α -arabinofuranosidic linkages in (1 → 5)-arabinans GH51 EC3.2.1.55 Non-reducing end α -L- arabinofuranosidase Hydrolysis of terminal non-reducing α -L-arabinofuranoside residues in α -L-arabinosides GH146 EC3.2.1.185 Non-reducing end β-L- arabinofuranosidase β-L-arabinofuranosyl-(1 → 2)-β-L-arabinofuranose +H 2 O =2 β-L-arabinofuranose GH53 EC3.2.1.89 Arabinogalactan endo-β-1,4- galactanase The enzyme specifically hydrolyses (1 → 4)-β-D-galactosidic linkages in type I arabinogalactans GH43 EC3.2.1.145 Galactan 1,3-β-galactosidase Hydrolysis of terminal, non-reducing β-D-galactose residues in (1 → 3)-β-D-galactopyranans GH27 EC3.2.1.88 Non-reducing end β-L- arabinopyranosidase Removal of a terminal β-L-arabinopyranose residue from the non-reducing end of its substrate GH43 EC3.2.1.181 Galactan endo-β-1,3- galactanase The enzyme specifically hydrolyses β-1,3-galactan and β-1,3-galactooligosaccharides CE12 EC3.1.1.86 Rhamnogalacturonan acetylesterase Hydrolytic cleavage of 2-O-acetyl- or 3-O-acetyl groups of α -D-galacturonic acid in rhamnogalacturonan I. RG-II PUL GH43 EC3.2.1.55 Non-reducing end α -L- arabinofuranosidase Hydrolysis of terminal non-reducing α -L-arabinofuranoside residues in α -L-arabinosides CE19 EC3.1.1.11 Pectinesterase Pectin +n H 2 O =n methanol +pectate GH142 EC3.2.1.185 Non-reducing end β-L- arabinofuranosidase β-L-arabinofuranosyl-(1 → 2)-β-L-arabinofuranose +H 2 O =2 β-L-arabinofuranose GH78 EC3.2.1.40 α -L-Rhamnosidase Hydrolysis of terminal non-reducing α -L-rhamnose residues in α -L-rhamnosides GH33 EC3.2.1.124 3-deoxy-2-Octulosonidase Endohydrolysis of the β-ketopyranosidic linkages of 3-deoxy-D-manno-2-octulosonate in capsular polysaccharides GH95 EC3.2.1.63 1,2- α -L-Fucosidase Methyl-2- α -L-fucopyranosyl-β-D-galactoside +H 2 O =L-fucose +methyl β-D-galactoside GH2 EC3.2.1.31 β-Glucuronidase a β-D-glucuronoside +H 2 O =D-glucuronate +an alcohol GH2 EC3.2.1.23 β-galactosidase Hydrolysis of terminal non-reducing β-D-galactose residues in β-D-galactosides GH138 EC3.2.1.173 Rhamnogalacturonan galacturonohydrolase Exohydrolysis of the α -D-GalA-(1 → 2)- α -L-Rha bond in rhamnogalacturonan oligosaccharides with initial inversion of configuration releasing D-galacturonic acid from the non-reducing end of rhamnogalacturonan oligosaccharides GH141 EC3.2.1.51 PUL, polysaccharide utilization loci. L. Barrera-Chamorro et al. Carbohydrate Polymers 348 (2025) 122794 4 release a GalA moiety connected to a rha residue from the non-reducing side of RG-I chains but is unable to liberate GalA from HG. β-Gal (E.C. 3.2.1.23) and α -L-Af (E.C. 3.2.1.55) are two enzymes responsible for removing galactosyl and arabinosyl residues from the RG-I backbone, respectively, while the acetyl groups are liberated by the action of RG acetylesterase (RGAE, E.C. 3.1.1.86). These genes encode highly specific enzymes to cleave distinct glycosidic linkages, and the enzyme family to which they belong as well as corresponding EC activities are shown in Table 1. Overall, the chemical and structural properties of pectin depend on at least three main factors: the plant species, the ripening/biological stage, and the extraction method (Mao et al., 2019). Presumably, this is one of the main reasons for the general impression that the family structure and functionality of pectin is not yet fully recognized despite the huge amount of fundamental and technological research which has been done. 2.3. Sources of pectin Pectin can be obtained from various natural sources. Most of these resources are fruit and vegetable peels, which can be considered a sustainable source for extracting this biopolymer as they are usually discarded as by-product during juice processing. Commercial pectin is commonly derived from the peels of citrus fruits such as lemons, oranges, limes, and grapefruit (Roy et al., 2023). Citrus fruits are mainly consumed in juice form, resulting in the production of a large amount of by-products such as peel and pomace, which are a rich source of pectin. The peel accounts for 15–50 % of the total weight of these citrus fruits and has been estimated to contain 20–30 % pectin (Dranca & Oroian, Table 2 Yield of extracted pectin, GalA content, and DE from different sources. Sources of pectin Yield of extracted pectin (%) GalA content (%) DE (%) Other structural features Reference Peel Lime (Citrus limon) 13–26 (according to the method of extraction used) 63–85 81–86 MeC (%) 9–13 Colour: Pale yellow (Twinomuhwezi et al., 2020) Tangerine (Citrus reticulate) 11–15 (according to the method of extraction used) 78–91 76–80 MeC (%) 10–13 Colour: Slightly brownish (Twinomuhwezi et al., 2020) Orange (Citrus sinensis) 11–16 (according to the method of extraction used) 91–105 82–87 MeC (%) 13–16 Colour: Pale yellow (Twinomuhwezi et al., 2020) Lime (Citrus aurantifolia) 12–15 43–46 61–72 Neutral sugar content (%) 46–61 Uronic acid content (%) 35–50 Colour: Pale yellow (Bezus et al., 2022) Grapefruit (Citrus paradise) 6–37 80–85 76–81 Sugar content (mol%) (Rha 1.7; Ara 9; Gal 4.9) HG region (80.2 %) RG-I side chains (17.3 %) Colour: Pale yellow (Zhang, Cui, et al., 2023) Pomelo (Citrus maxima) 14–38 84–85 39–78 Sugar content (mol%) (Rha 1.8; Ara 5.6; Gal 3.7) HG region (84.5 %) RG-I side chains (13 %) Colour: Pale yellow (Chuenkaek et al., 2023; Zhang, Cui, et al., 2023) Watermelon (Citrullus spp.) 14–20 68–75 61–63 Sugar content (mol%) (Rha 2.4; Ara 0.7; Gal 20.2) HG region (65.8–71.8 %) RG-I side chains (25.7–29.0 %) Protein (%) 3.6–3.9 Phenolics (%) 0.38 (Petkowicz et al., 2017) Mango (Mangifera indica) 16 65 74 Sugar content (mol%) (Rha 1.35; Ara 2.64; Gal 31.11) HG region (63 %) RG-I side chains (36 %) (Cui, Zhang, et al., 2023) Melon (Cucumis melo) 17 55 50 Sugar content (mol%) (Rha 0.51; Ara 4.37; Gal 8.05) HG region (77.75 %) RG-I side chains (22.03 %) Protein (%) 6.1 Phenolics (%) 0.33 (Rico et al., 2020) Jackfruit (Artocarpus heterophyllus) 17 52–57 61–74 Sugar content (mol%) (Rha 9.14–9.68; Ara 8.11–5.18; Gal 24.35–23.31) Degree of branching of the RG-I domain ((Gal +Ara)/Rha 3.56–2.94) (Li et al., 2019) Pomegranate (Punica granatum) 12–15 66–72 49–54 MeC (%) 1.55–2 (Haque, 2023) Pomace Apple (Malus domestica) 7–20 47–79 37–74 MeC (%) 5–7 Pectin extracted with higher PY (19.88 %) and higher AUA content (73.02 %) resulted in pectin with DE below 50 % (38.69 %) due to the extraction method applied and the quality of pomace obtained from Golden Delicious apples with reduced firmness after 10 months of storage (at the end of one season). (Gurev et al., 2023) Grape (Vitis vinifera) 9–11 79–85 80–83 MeC (%) 5–7 Sugar Content (mol%) (Rha 2–3; Ara 3–7; Glc 3–4) Grape pomace pectin contains polyphenols and other watersoluble compounds that are trapped within the pectin by precipitation. (Spinei & Oroian, 2023) Pear (Pyrus spp.) 6–68 >65 63–89 NA (Luisa Franchi, 2014) Kiwi (Actinidia spp.) 80–85 61–64 NA Sugar content (mol%) (Rha 7.95; Ara 12.72; Gal 10.44; Glc 0.81) (Zhu et al., 2022) Pulp Beet (Beta vulgaris) 24 72 39–41 NA (Huang et al., 2017) DE, degree of esterification; GalA, galacturonic acid; MeC, methoxyl content; NA, not analyzed. L. Barrera-Chamorro et al. Carbohydrate Polymers 348 (2025) 122794 5 2018), although this value varies depending on the variety within the Citrus genus and the extraction method used. In addition, apple pomace is seen as the second most used source to obtain pectin, whose yield depends on the apple variety used and the extraction method and can range from 6.76 % to 19.88 % pectin (Gurev et al., 2023). Finally, beet pulp, from the sugar industry, has been used as a natural emulsifier due to the molecular structure of beet pulp pectin, with yields up to 24 % pectin, depending on the extraction conditions (Huang et al., 2017). However, the growing interest in the re-use of agro-industrial byproducts due to the increasing demand for pectin for its wide applications in different markets, has led to the search for other possible alternative sources of this bioactive polysaccharide. The most traded fruit is watermelon, whose peel accounts for one third of the total mass of watermelon and contains 19–21 % pectin (Petkowicz et al., 2017). Other potential sources are mango, melon, and pomegranate peels. In the case of mango, processing produces up to 50 % of its dry weight in the form of peels, pulp, and seeds, from which 13–30 % pectin can be extracted depending on the degree of maturity of the fruit (Torres-Gallo et al., 2022), where it has been observed that the lower the maturity, the higher the pectin yield and the higher DE. On the other hand, melon (Cucumis melo) is used to produce juices and jams, giving up about a third of its weight in the form of by-products, mainly in the form of peel (Rico et al., 2020). Also pomegranate (Punica granatum) peel is rich in pectin (11.70 %) (Haque, 2023), as well as jackfruit (Artocarpus heterophyllus), which contains approximately 15 % pectin (Li et al., 2019). Grape pomace (Spinei & Oroian, 2023), olive pomace (Rivero-Pino et al., 2023), kiwi pomace (Zhu et al., 2022) and pear pomace (Luisa Franchi, 2014) are also used as sources of pectin. Among them, grape and olive pomace as sources of pectin to be exploited are of high interest recently. Grapes (Vitis spp.) can be consumed raw, but are also used for the production of wine, grape juice, seed oil, raisins, vinegar, and gelatin. A large amount of by-products are produced in this processing, the most important of which is grape pomace. It contains various active compounds, such as pectin. Although there are currently few studies on the extraction of pectin from grape pomace, it has been reported that up to 11.23 % pectin can be extracted, depending on the extraction technique and the grape variety used (Spinei & Oroian, 2023). As shown in Table 2 within vegetables, carrot (Dranca & Oroian, 2018), potato (Yang et al., 2018) and pumpkin byproducts stand out as a source of pectin. Table 3 Extraction techniques and their effects on pectin yield and quality on the main sources of pectin extraction. Extraction technique Types Plant source Operating conditions Effect on yield and quality References Traditional methods Solvent extraction Aqueous solution Sour orange peel Solvent: water Liquid/solid ratio: 20–40:1 (v/w) Temperature: 75–95 ◦C Time: 30–90 min The highest extraction yield was 18.35 % at the optimal condition (95 ◦C, 90 min, and liquid/solid ratio of 25:1 (v/w)). The DE values for the pectin ranged from 17 to 30.5 %, and GalA content ranged from 57 to 83 %. (Hosseini et al., 2016a) Acid solutions Orange peel Solvent: 0.03 N HCl Temperature: 70 ◦C ± 0.5 ◦C Time: 1 h pH: 1.27 The yield of pectin extracted was 16.01 %. Methoxyl content and DE were 14.94 % and 84.68 %, respectively. (Twinomuhwezi et al., 2020) Alkaline solutions Orange peel Solvent: Sodium hydroxide Liquid/solid ratio: 30:1 (v/w) Temperature: 80 ◦C Time: 1 h The yield of pectin extracted was 23 %. GalA content and DE of the extracted pectin ranged from 36.5 % and 2.0 %, respectively. (Cui et al., 2020) Organic acid mixture Residues from apple Solvent: citric acid, ascorbic acid, and acetic acid. pH: 1.9 Temperature: 25 ◦C Time: 10 min Continuous stirring The yield of pectin extracted was 14 %. DE values of the pectin and GalA content were 64.55 % and 87.58 %, respectively. (Mahmoud et al., 2022) Pressure-based extraction Subcritical water extraction (SWE) Orange peel Solvent: water Temperature: 145.3–165.6 ◦C Water flow rate: 2.25 mL/ min Mode: semi-continuous The highest yields of bioactive flavonoids ranged from 87.8 to 98.9 %. (Kim & Lim, 2020) Supercritical carbon dioxide (ScCO 2 ) extraction Orange peel Pressure: 74–351 bar Temperatures: 33 ◦C–67 ◦C Holding times: 20–70 min The percentage of PME reduction widely ranged from 13.7 % to 91.8 %. (Argun et al., 2022) Green extraction Heat based extraction Microwave-assisted extraction (MAE) Orange peel Microwave power: 700 W pH: 1.50 Irradiation time: 3 min The yield of pectin extracted was 29.1 %. Under optimal conditions, the GalA content and DE values of pectin were 71 % and 1.7 % to 37.5 %, respectively. (Hosseini et al., 2016b) Ultrasound-assisted extraction (UAE) Orange peel Solvent: 100 % methanol Time: 85 min Temperature: 55 ◦C Ultrasonic frequency: 40 kHz The highest extraction yield was 17.19 %. (Feng, 2022) Enzyme assisted extraction Endo-xylanase and endo-cellulase Apple pomace Time: 10 h pH: 5.0 Temperature: 40 ◦C Constant shaking The highest extraction yield was 19.8 % using the endoxylanase. However, the pectin extracted with endo-cellulase contained significantly more GalA (70.5 %) and high DE (66.3 %). (Wikiera et al., 2016) L. Barrera-Chamorro et al. Carbohydrate Polymers 348 (2025) 122794 6 3. Extraction methods of pectin The pectin extraction process is not simple, mainly due to the complex composition of pectin and their interactions with other polysaccharides, phenols, and proteins present in the cell wall. In addition, it is conditioned by factors such as pH, temperature, time, and the solvents used. In general, pectin production involves several steps such as a first process of raw material selection, extraction, clarification, concentration, precipitation, washing, and drying. However, it is important to note that the extraction process may vary depending on the specific type of pectin being produced and the manufacturer’s practices. Some manufacturers may also use additional processing steps, such as enzymatic treatment or de-esterification, to modify pectin properties for specific applications. In Table 3, a summary of extraction techniques and their effects on pectin yield and quality on the main sources of pectin extraction is shown. 3.1. Solvent extraction method Pectin extraction in the food industry is carried out conventionally using hot water, but also using acids (Belkheiri et al., 2021) such as hydrochloric, acetic, sulfuric, or nitric acids, all of which are highly toxic and pollutants. It has been reported that, based on the acid employed, the yield might highly vary, as demonstrated in the extraction of potato (Yang et al., 2018) where yields ranged from 14.34 to 4.08 %. These treatments require high temperatures and long times to increase the yield, though it implies high energy consumption. The use of organic acids such as citric or oxalic acid has made its way in recent years in terms of replacing the more aggressive and expensive methods, in order to improve yields and improve the structure from a biotechnological and functional point of view. Other emerging technique is the use of ionic liquids (Liu & Zhu, 2023), however it is an economically less viable option than the use of conventional solvents. The current trend is the use of other more environmentally friendly extractant solutions such as the new natural eutectic solvents (NADES). NADES are special types of ionic liquids, which are cheaper, less toxic, and more biocompatible than other ionic liquids. When these components come into contact with the raw material, additional interactions are generated with the different plant components, including pectin, facilitating their extraction (Chen & Lahaye, 2021). Their use prior to the extraction with hot water allows reducing the DE to obtain LMP, affecting the composition of the pectin (Chen & Lahaye, 2021). Acid extraction involves the use of acidic solutions to disrupt cell walls and hydrolyse pectin molecules, breaking them down into soluble fragments for extraction. This method is relatively straightforward and commonly used in industry but may require careful control of acidity to prevent degradation of the extracted pectin. On the other hand, eutectic solvent extraction utilizes specially formulated ionic liquid mixtures to dissolve pectin by disrupting cell wall structures. This method offers advantages such as high solvation power and lower environmental impact but may require more specialized equipment and expertise. The choice between them depends on factors such as the desired purity of the extracted pectin, environmental considerations, and the availability of resources (Belkheiri et al., 2021; Chen & Lahaye, 2021). 3.2. Pressure-based extraction This extraction method consists of subjecting the plant substrates to a pressure gradient that leads to the disintegration of the cell wall, favouring the penetration of the solvent that facilitates the extraction (Hemker et al., 2020). In a first step a sudden pressure increases of between 100 and 1000 MPa is performed and maintained for a certain time after which the pressure is suddenly released until it drops to atmospheric pressure. Overpressure does not affect the integrity of the primary structure of pectin, but it causes partial degradation of the side chains. Instant controlled pressure drops are based on the thermomechanical effect that combines heat and pressure so that the raw material is placed in the pre-processing vessel and subjected to saturated steam generating heat for a very short period of time, then the pressure drops sharply to vacuum pressure. This procedure might increase the solubilization of the insoluble fraction increasing the final yield of the process (Zhou et al., 2022). One of the most innovative techniques currently being applied is the use of subcritical water whose conditions reduce the dielectric constant of water. Water is considered to be in a subcritical state when it is in a liquid state between 100 ◦C and 374 ◦C, which implies high pressures to keep the water liquid during the process. An increase in temperature occurs as a result of intermolecular vibrations leading to a reduction in surface tension (Costa et al., 2023) making it easier for water to penetrate into the matrix. Studies show that modulation of temperature and pH during subcritical water extraction modifies the molecular properties of pectin increasing its yield (Yilmaz-Turan et al., 2023). A promising method has been studied using pressurized carbon dioxide treatments, which compared to conventional extraction with hydrochloric acid does not present any interest in terms of yield but improves the DE, reaching 94 % compared to 75 % in the case of acid extraction, in satsuma mandarin orange peels (Tsuru et al., 2021). 3.3. Heat-based extraction Undoubtedly, the most commonly used extraction methods for obtaining pectin are based on heat, either using solvents or as a complement to those that use pressure. But a new classification of methods could be those based on the type of heat source and how it is applied to the extraction material. In this sense, ohmic heating is an interesting heat source that is currently being explored. Ohmic heat is produced when an electric current passes through a food, causing the temperature to rise as the current passes through and improving mass transfer. In the specific case of pectin extraction from grapefruit peel, Sharifi et al. studied and analyzed the yield and the amount of GalA obtained by this method compared to acid extraction. According to the results, under the conditions of 10 V/cm and 18 min of treatment the yield reached 8.16 % and 82.86 % of GalA versus the conventional method whose percentage yield was slightly higher when HCl was used reaching 8.93 %. However, the amount of GalA did not exceed 73.84 % values were not reached in acid. It was demonstrated that these results were maintained even with different particle sizes and homogenization (Sharifi et al., 2022). In recent years there have been a large number of studies showing that microwave-assisted (MW) pectin extraction can be an adequate alternative. The energy produced by MW causes the bipolar molecules of matter to be agitated, generating heat. A review of the last six years shows that the yields of processes using MW heat can vary from extreme values of 2 to 42 %, the most frequent values ranging from 15 to 25 % with applied extraction times and powers reaching 120 min and 600 W, respectively (Mao et al., 2023) providing promising results also in life cycle analysis, too. Ultrasound-assisted extraction (UAE) involves vibrations of a highfrequency mechanical nature (20 and 100 kHz) (Rutkowska et al., 2017). The waves are transmitted through a fluid giving rise to microbubbles that transform into microjets altering the cellular level and it facilitates the penetration of the solvent and making the extraction more efficient. It has been shown that this technique has a number of advantages in terms of reduced extraction time, lower energy and solvent consumption as well as increased extraction yield compared to conventional extractions. For example, in the case of sour orange peel, optimized results show up to 28 % yield when 150 W ultrasonic power is applied with only 10 min of treatment and under acidic conditions of pH 1.5 (Hosseini et al., 2019) and a high GalA content. 3.4. Enzyme-assisted extraction Enzymes are used to hydrolyse the raw material and improve the L. Barrera-Chamorro et al. Carbohydrate Polymers 348 (2025) 122794 7 extraction of bioactive components, and their efficacy depends on the reaction time and conditions, the nature of the enzyme and the concentration (Mari´ c et al., 2018). The extraction of pectin with enzymes allows obtaining high quality pectin that improve the final product and also reduces the production time, while also reducing the energetic expense compared to traditional methods. Temperature is one of the limiting factors in this process since most enzymes are inactivated above 50 ◦C, as well as the economic cost of using enzymes. Nevertheless, studies presented by several authors claim that the pectin obtained by this method is of better quality due to the high efficiency and specificity of the enzymes. At the industrial level, commercial enzymes are used for the extraction of polysaccharides assisted by MW, ultrasound, supercritical fluids, or high pressures. Commercial enzymes used for extracting polysaccharides are enzyme mixtures of arabanase (breaks down arabinose-containing polysaccharides), cellulase (breaks down cellulose into glucose units), β-glucanase (hydrolyzes β-glucans, which are polysaccharides found in the cell walls), hemicellulose (hydrolyzes hemicellulose), and xylanase (catalyzes the hydrolysis of xylan), among others (Nadar et al., 2018). 4. Pectin in the food industry Pectin hydrocolloids are the main ingredient for the preparation of intermediate moisture foods, such as jellies, jams, marmalades, confectionery, pastries and yogurts, etc., due to their versatile gelling (Chandel et al., 2022) and emulsifying properties, which have been used as effective stabilizers in fruit juices and acidified milk drinks, and as fat replacers in ice creams and spreads (Dranca & Oroian, 2018). The gelling properties of pectin have been extensively studied over the years and are the main focus of numerous investigations on the structurefunction relationships of pectin in food. It has been reported how gelation is promoted by intrinsic factors such as high GalA content, molecular weight, and DE, and is influenced by some extrinsic factors including pectin concentrations, temperature, pH, type and concentration of soluble solids, and type and concentration of divalent cations (Dranca & Oroian, 2018). Pectin is added late in the process, subjecting it to less heating and leading to convenient and complete dissolution. HMP is used as the gelling and texturizer agent in jams and jellies. However, the trend for products without or with low sugar, such as dietetic foods, low-calorie jams and carbonated beverages, particularly due to calorie conscious consumers and to fill the need for sugar-free products for diabetics, has led to an increase in demand for LMP. Among pectin, sugar beet pectin has shown excellent emulsifying properties mainly due to many factors such as the highly branched polysaccharide structures, high content of hydrophobic acetyl groups on the GalA chain, and protein moiety, which plays an important role (Dranca & Oroian, 2018). On top of that, pectin can be used as a structure-forming agent, an oxidizing effect enhancer in the dough production process and as a sorbent for improving the quality of bakery products (Chandel et al., 2022). 4.1. Food packaging Food packaging traditionally served as basic wrapping and physical protection for transport, ensuring the integrity of the food from manufacturer to consumer. However, packaging products with plastics has become increasingly common, resulting in extensive waste that, if not properly disposed of, contributes to contamination of aquatic and terrestrial environments, yielding microplastics that enter the food chain (Muhib et al., 2023). Recently, there has been an increasing practical use of edible coatings and films in the food industry, referring to a preformed layer or layers made of edible materials. Meanwhile, an edible coating is a very thin layer applied around a food by dipping the food into a solution (Han & Aristippos, 2005). Both methods serve to prolong the product’s shelf life while safeguarding it against environmental hazards. This ensures the product remains fresh and prevents changes in its sensory properties and potential microbial contamination. Moreover, it protects the contents from oxygen, slows down oxidation, and maintains their taste and aroma. The use of additives to improve coating application processes is very recurrent in the food coating industry. Many authors report the poor mechanical properties of pectin which necessitate the addition of additives such as essential oils during the application process to improve flexibility (Othman et al., 2023). As an edible coating or film, pectin is a useful biomaterial for producing eco-friendly packaging coatings on different food items like fresh or cut fruits and vegetables, meat, and fish, among others. Pectin has a multitude of functional properties that can be modified to meet the needs of active packaging through plasticizers, emulsifiers, and bioactives, as it has been reported that they increase and improve mechanical performance, stability, and adhesion or functionality (Roy et al., 2023). Table 4 is an excerpt from the one presented by Zhang, Waterhouse, et al. (2023) and summarizes of studies in which edible coatings based on pectin have been developed. The most common method used in the food industry for the preparation of packaging films is the casting or solvent casting method, which requires solubilization of the biopolymer and casting of the biopolymer solution into a mold and subsequent drying (Xie et al., 2022). Jridi et al. (2020) tested this method for coating with edible fish gelatin-based films enriched with pectin from orange peel. They observed improved texture, a significant reduction in film moisture, and antioxidant protection and microbial stability in cheese during refrigerated storage. Furthermore, extrusion is a common method in film manufacturing due to its high yield and mass production efficiency, modifying the material’s structure to enhance its physic-chemical qualities. The process involves a feeding phase, followed by kneading, where food grade plasticizers can be added, and heating in the final phase. A novel technique involves utilizing new deep eutectic solvents, such as a mixture of choline chloride and glycerol, as plasticizers. By using this method, pectin powders can be plasticized when mixed at 80 ◦C for 30 min. The extrusion conditions allowing to obtain thermosensitive and semitransparent films were using temperatures of 110–130 ◦C, compression time of 15–25 min, compression load of 176.5–215.7 KN (Gouveia et al., 2019). When coating solutions have high viscosity, the best way to create a coating is by dipping the product into the coating solution. This ensures that the protective layer covers the entire surface of the product (Suvarna et al., 2022). A composition consisting of carboxymethylcellulose (CMC), bacterial cellulose fibril (dietary/bulking ingredient), pectin (gelling agent), and blackberry pomace powder (antioxidant) was characterized and used as a coating by this technique. The influence of pectin, the amount of bacterial cellulose and temperature was observed by means of a factorial experiment. The most effective temperature for the formation of the coating was 90 ◦C, behaving as pseudoplastic fluids that improve the resistance to humidity and also increase the antioxidant activity (Isopencu et al., 2021). 4.2. Carriers of bioactive compounds Due to their interesting structural properties, pectin has been postulated as interesting and effective carriers of bioactive compounds both to improve food stability and to provide a nutritional benefit to the consumer (Table 5). From the point of view of food protection, they are also widely used as natural preservatives (Morales-Medina et al., 2022) as already discussed in previous sections of this review. The property of forming gels, makes pectin an extraordinary candidate for the manufacture of encapsulates that coat bioactive compounds as interesting for health as antioxidants, antimicrobials, anticancer, anti-inflammatory, prebiotics, and probiotics (Khotimchenko, 2020). In addition, another great advantage of pectin is that they are easily metabolized and disposed of in a way that minimizes the risk of unwanted toxic effects after ingestion. Pectin-based nanoencapsulates are used as a matrix material to transport bioactive compounds, forming different structures L. Barrera-Chamorro et al. Carbohydrate Polymers 348 (2025) 122794 8 such as pectin hydrogels (i.e., hydrogels, cryogels, aerogels, xerogels, and oleogels), emulsions, microparticles, and nanoparticles (Said et al., 2023; Wusigale et al., 2020). There are also wide applications for the administration of anti-inflammatory drugs or for detecting specific physiological conditions (control of blood glucose, pH, uric acid, temperature) (Zhu et al., 2023). These structures improve the bioaccessibility, biocompatibility, and biodegradability of bioactive compounds against chemical and enzymatic changes that occur during the gastro-intestinal track. In addition, when they reach the intestine, they improve absorption of active principles by functioning as extraordinary carriers of compounds such as protein, polyphenols, vitamins, and minerals (Rosales & Fabi, 2023). 4.2.1. Carriers of vitamins Vitamins play a key role by contributing to nutrition, health, food fortification, product preservation, and meeting the demands of the health-conscious consumer. In this sense, pectin is used as an effective matrix for the formation of hydrogels that retain these vitamins. A hydrogel prepared from natural polymers of bovine serum albumin combined with citrus peel pectin form a framework whose electrostatic and covalent interactions provide the hydrogel with stable and robust rheological and morphological properties. This structure was used for the assembly of vitamin C and encapsulation efficiencies close to 70 % were achieved, maintaining the retention of vitamin C up to 74 % for 10 weeks (Peng et al., 2016). The consumption of vegetable diets is spreading worldwide and, therefore, the intake of vitamins B12 and D3 is reduced. A study found that gels filled with emulsions based on pectin supplemented with linseed oil, inulin, and gum Arabic are capable of transporting these vitamins, providing stability and extending the useful life of vitamin D3 and B12 up to 30 days (Ghiraldi et al., 2021). The use of this type of emulsions can be a good alternative as a food supplement for vegan and vegetarian groups. 4.2.2. Carriers of phenolic compounds Phenolic compounds are present in plants as secondary metabolites Table 4 Pectin-based composite film preparation and performance evaluation. Technological conditions Method Results Ref. Pectin-corn flour/beetroot/ orange peel/muesli/rice flour Pure pectin. 100 rpm/95 ◦C, 30 min Pectin +corn flour. 100 rpm/95 ◦C, 30 min Pectin +corn flour +beetroot powder/orange peel powder +sodium alginate/muesli root powder/rice flour. 100 rpm/95 ◦C, 30 min TGA, rheological, thickness, MC, TS, Wa, barrier, optical and AP The mechanical, structural, thermal or microscopic properties of the composite edible films were significantly improved when starch was added to the pectin-based films formulations at a ratio of 1:1 or 60:40. Rai et al., 2019 Gelatin-chitosan-pectin 65.2 % glycerol, 24.3 % gelatin, 10.0 % chitosan, and 0.5 % pectin were mixed at 40 ◦C for 30 min Barrier, optical, mechanical, AnP Great improvement in color, water vapor barrier, light transmission, swelling properties, antioxidant and antimicrobial activities. Yeddes et al., 2020 Potato starch-pectin/nanotitania inclusions Starch: pectin is 3:1(w/w), 30 % glycerol, 90 ◦C, 30 min TGA, DSC, rheological, thickness, MC, Wa, optical, MP Adding TiO2 to the starch-pectin films improved its emulsifying and mechanical properties. Dash et al., 2019 Pectin-copaiba oil nanoemulsions The ratio of solution to nanoemulsions is 1:1, solution: 6 % pectin solution mixes with 15 % glycerol, 12,000 rpm/20 min TGA, DS, Bi, MC, optical, Wa, AnP. The copaiba oil nanoemulsions improved the antimicrobial activities, thermal behaviour, the mechanical and extensibility properties of the films, and decreasing their stiffness Norcino et al., 2020 Pectin/sodium alginate-citric acid/tartaric acid A certain amount of citric acid/tartaric acid, 20 % (on weight of citric acid/tartaric acid used), and 40 % pectin/sodium, 75–80 ◦C for 40 min, cooled to 50 ◦C TGA, Aa, edibility, Bi, Mp. The physicochemical properties of the film has been improved, edible, biodegradable, and have moderate thermal stability Singh et al., 2020 Pectin-fish gelatin/ hydroxytyrosol/3,4- dihydroxyphenylglycol 2.5 % pectin and fish gelatin were stirred at room temperature for 2 h (pH is 8), then adjust pH to 3, add beeswax and stir vigorously for 15 min, finally add 0.1–0.5 % hydroxytyrosol and 3,4-dihydroxy- phenylglycol, dried for 48 h. Thickness, barrier, optical, solubility. The film exhibited adequate mechanical and barrier property, the wrapped beef reduces the formation of oxides (TBARS). Rodríguez et al., 2023 Pectin-gamma-aminobutyric acid 2 % pectin, add 0.2 % glycerol or gammaaminobutyric acid (0.1 %, 0.2 %, 0.3 %), stirred until completely mixed, then dried at 50 ◦C for 12 h. DSC, thickness, barrier, optical, solubility, moisture, TC, Mp, AP Add 5 % gamma-aminobutyric acid to pectin film, the properties (water barrier, solubility, mechanical and antioxidant properties) have been improved. Meerasri & Sothornvit, 2020 Pectin-konjac glucomannan/ tea polyphenol Solution composition: 1.75 % pectin, 0.75 %, glucomannan 0.65 % tea polyphenol. Stir at 100 rpm/40 ◦C for 30 min, then add tea polyphenols (0 ‰, 0.25 ‰, 0.5 ‰, 0.75 ‰, 1 ‰, 1.25 ‰), finally dried at 45 ◦C for 10 h. TGA, thickness, density, barrier, optical, Mc, Wp, Mp, Ap The addition of tea polyphenol makes the structure of pectin film more stable and improves its performance including barrier, optical, mechanical and antioxidant properties Lei et al., 2019 Alginate/pectin/ Lactobacillus plantarum KMC 45 Sorbitol account for 60 % of polymer, stirred at 50 ◦C for 1 h, then inoculated with. KMC 45, and finally dried by air-blown at 37 ◦C for 12–18 h. Thickness, Mc, Wa, solubility, barrier, optical, Mp The increasing of pectin proportion in films significantly increased the thickness, opacity, water vapor permeability and water content of polysaccharide composite films Shahrampour et al., 2020 Fish gelatin-pectin Solution composition: Pectin/protein solutions (3 %) are mixed in a certain ratio (90:10, 70:30, 50:50), 0.45 % glycerol. Stirred until uniform, then dried at 25 ◦C for 12 h. Thickness, DSC, Wp, Aa, Mp The transparency of the film added with pectin is reduced, but it does not affect the ability to block ultraviolet rays. gelatin-pectin blending improved heat resistance, degradability, mechanical properties, and antibacterial activity. Jridi et al., 2020 Pectin-curcumin/sulfur nanoparticles Dissolve sulfur nanoparticles (40, 80, 120 mg, respectively) in 150 mL distilled water and homogenized for 10 min at a high speed, add curcumin (40 mg), then add 4 g pectin and 1.2 g glycerol, finally dried at 25 ◦C for 2 days. 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