دانلود رایگان مقاله لاتین پکتین فراکسیون از سایت الزویر
عنوان فارسی مقاله:
پکتین فراکسیون غنی سازی شده رئولوژیکی و شیمیایی منابع مختلف استخراج شده با اسید سیتریک
عنوان انگلیسی مقاله:
Rheological and chemical properties of pectin enriched fractions from different sources extracted with citric acid
سال انتشار : 2016
برای دانلود رایگان مقاله پکتین فراکسیون اینجا کلیک نمایید.
مقدمه انگلیسی مقاله:
1. Introduction
Pectins are one of the most intensively studied groups of cell wall polysaccharides due to their properties and complex structure. They are composed of a large number of different monosaccharides linked by many different chemical bonds (Lira-Ortiz et al., 2014). A more complete knowledge of their properties may be useful to the food processing and pharmaceutical industries (Pagan & Ibarz, 1999). Pectic substances mainly consist of D-galacturonic acid units (GalA) which are the main components of three pectic polysaccharides: homogalacturonan (HG), rhamnogalacturonan I (RG-I) and rhamnogalacturonan II (RG-II) (Caffal & Mohnen, 2009). The structure and composition of pectin polysaccharides forming plant cell walls depend on the source and conditions of extraction as well as their location and other environmental factors (Pérez, Carvajal, & Doco, 2003). HG, which makes up the “smooth region” of pectin chains, is composed of GalA residues with 1,4-linkages and an - configuration between the units. Residues of GalA in HG are methylesterified at the C-6 carboxyl group and in some cases they are also acetylated at O-2 or O-3 (Pérez Espitia, Du, Avena-Bustillos, Ferreira Soares, & McHugh, 2014). The degree of methyl-esterification (DM) and the degree of acetylation are fea-tures that affect pectin properties and they normally depend on the pectin source. Highly methyl-esterified pectin (DM > 50%), may gel in acidic conditions, when sugar concentrations are high, while low methoxyl pectin chains can form a gel structure by interaction with divalent calcium cations (Caffall & Mohnen, 2009; Lira-Ortiz et al., 2014). The “hairy regions” of pectin consist of RG-I and in some pectins, RG-II can also be found. Generally, RG I is composed of a [→4)--D-GalA-(1→2)--L-Rha-(1→] repeating disaccharide sequence with neutral sugar side chains such as galactan, arabinan and arabinogalactan attached to the rhamnose units. Rhamnogalacturonan II consists of a HG backbone and side chains of 28 monosaccharides such as rhamnose and unusual sugars like Kdo (3-deoxy-d-manno-oct-2-ulosonic acid), Dha (3-deoxy-d-lyxo-2- heptulosaric acid), aceric acid and apiose, attached to the GalA residues (Mazeau & Pérez, 1998; Pérez et al., 2003; Pose, Kirby, Mercado, Morris, & Quesada, 2012; Ralet, Lerouge, & Quéméner, 2012). Pectin structure and functionality is affected by the action of pectinolytic enzymes (Jayani, Saxena, & Gupta, 2005) responsible for the hydrolysis of the pectic substances during the fruit ripening process. Several enzymes are known to initiate the degradation of pectins in different locations of the pectin chain. Two of the best known fruit pectinases are pectin methylesterase (PME) and polygalacturonase (PG) (Wei et al., 2010). PME hydrolyzes the methyl-ester group at the C-6 carboxyl group producing lowmethoxyl pectin chains. PME activity results in the release of methanol as well as preparing the HG chain for the action ofPG (Arancibia & Motsenbocker, 2006). PG is responsible for the hydrolytic cleavage of -(1,4) glycosidic linkages of the polygalacturonan acid chain (Torres, Sayago, Ordonez, & Isla, 2011). An extraction of pectins from plants is usually carried out using acid solvents, i.e. hydrochloric acid, nitric acid (Methacanon, Krongsin, & Gamonpilas, 2014), oxalic acid (Kaya, Sousa, Crépeau, Sørensen, & Ralet, 2014) or citric acid (Yuliarti, Goh, Matia-Merino, Mawson, & Brennan, 2015). Conditions of extraction play an essential role in the yield, chemical composition and rheological properties of the pectic fractions obtained, with a direct effect on the functionality of the pectins. The ability of pectin to form a gel is especially important with regard to its applications in the food and pharmaceutical industries (Lima, Paiva, Andrade, & Paixão, 2010). Most studies focus on the analysis of the properties of pectin isolated from a single source of raw material for use as a potential one-component matrix in the food processing or pharmaceutical industry. Since apple and citrus pectin have shown many usefulfeatures as gelling and stabilizing agents,there is an increasing interest in their industrial applications. Therefore, other raw materials, for example: banana (Oliveira et al., 2016), gold kiwi fruit (Yuliarti et al., 2015), sugar beet (Chen, Fu, & Luo), passion fruit (Seixas et al., 2014) and mango peel (Kermani, Shpigelman, Pham, Van Loey, & Hendrickx, 2015) have been extensively studied from this point of view. The properties of isolated pectin depend on the solvent used for extraction. The use of citric acid in the study is justified by the ecological aspects of this organic acid, which is more environmentally friendly and more acceptable as a food additive. The aim of this work is to compare the physicochemical and rheological properties of polysaccharides isolated from six new potential sources and to relate these properties to the activity of cell wall pectinolytic enzymes like PME and PG. Fruit materials – peach (Prunus persica), blackcurrant (Ribes nigrum), raspberry (Rubus idaeus), strawberry (Fragaria ananasa) and plum (Prunus domestica), and a vegetable source – carrot (Daucus carrota) were used, as they have not been extensively studied for this purpose yet. These plant sources have been selected due to their availability, popularity and relatively low cost of purchase. Moreover, a literature review has shown that there is very little information available about the polysaccharides isolated from these plant sources. To the best of our knowledge, this is also the first time that properties of pectin isolated from natural plant sources have been related to the activity of cell wall pectinolytic enzymes like PME and PG.
برای دانلود رایگان مقاله پکتین فراکسیون اینجا کلیک نمایید.
کلمات کلیدی:
