Pectins sources

May, C.D. (1990). Industrial pectins sources, production and applications. Carbohydrate Polymers, 12, 79-99. 

D.E. values for the citrus and tomato pectins were 56 and 40%, respectively. Thus, differences in D.E. levels rather than pectin source could have accounted for the superior effectiveness of citrus pectin. Mokady (80) and Judd et al. (81) confirmed that serum cholesterol reduction is most pronounced with high D.E., high-molecular-weight pectin (Table I). 

A representative structure of pectin is illustrated in Figure 9.2. Pectins are composed of a a-(l—>4) linked D-galacturonic acid backbone interrupted by single a-(l—>2) linked L-rhamnose residues (BeMiller, 1986). Depending on the pectin source and the extraction mode, the carboxyl groups of galacturonic acid units are partly esteri-fied by methanol and, in certain pectins, are partially acetylated. The mole-percent of rhamnose may be different depending on the source of pectins (Ryden and... 

Figure 5.The basic structure of pectin. Schematic representations of the conventional (A) and recently proposed alternative (B) structures of pectin. Source Willats et al. (2006).

Pectin source Pectin content (%) Pectin source Pectin content (%)... 

Pectin. Pectin [9000-69-5] is a generic term for a group of polysaccharides, mainly partially methoxylated polygalacturonic acids, which are located in the cell walls of all plant tissues. The main commercial sources of pectin are citms peel and apple pomace, where it represents 20—40% and 10—20% of the dry weight respectively. The pectin is extracted, the extract purified, and the pectin precipitated (50) increased extraction times lead to the production of low methoxyl pectins. 

Fungi Heterotroph Carbohydrate (sugars, starch, pectin, cellulosics) As carbon source nh3, nh4+... 

Foods such as sugars, colloidal pectins, and mayonnaise emulsions are also prime sources of foaming. 

Arabinogalactans (AGs) are widely spread throughout the plant kingdom. Many edible and inedible plants are rich sources of these polysaccharides. AGs occur in two structurally different forms described as type I and type II, associated with the pectin cell-wall component by physical bonds and some of them are covalently linked to the complex pectin molecule as neutral side chains. Commercial pectins always contain AG 10-15%). AG of type I has a linear (1 4)-y0-o-Galp backbone, bearing 20-40% of of-L-Ara/ residues (1 5)-linked in short chains, in general at position 3. It is commonly found in pectins from citrus, apple and potato [6]. Recently, this AG type has been isolated from the skin of Opuntia ficus indica pear fruits [372]. 

Pectins are heteropolysaccharides with axial-axial a(1, 4)-D galactopyranosyluronic acid units condensed in the Ci conformation and interrupted by a-(1,2)-L rhamnopyranosyl residues. The structure is based on blocks of galacturonan partly esterified (the smooth zones) and blocks of highly ramified rhamnogalacturonan regions (hairy zones). The exact structure depends on the sources but also on the methods used to isolate the pectins [1,5]. Few data are given in Table 1. 

The source materials were commercial pectins apple A30 and citrus pectin C73 kindly supplied by Unipectine (France) and Copenhagen Pectin Factory (Denmark) respectively. Polygalacturonic acid samples (named SR) were obtained by acid hydrolysis of a fully de-esterified citrus pectin as previously described [24]. Citrus pectins with different degree of esterification (DE) were obtained by controlled acid de-esterification [8]. 

Among the five different species of Azospirillurn, only A. irakeme shows clearly pectinolytic activity on solid and in liquid medium. Moreover, this species can grow under non-diazotrophic as well as diazotrophic conditions when pectin is the sole carbon source (Khammas and Kaiser, 1991). Khammas and Kaiser (1991) analysed the pectinolytic activity of seven A. irakense isolates, and gave evidence for the presence of two types of pectinolytic enzymes. All strains tested have inducible Ca dependent pectate lyase activity. Six strains, showed also pectin methylesterase activity. So far, none of the corresponding enzymes have been purified. 

Some by-products from the food industry contain high proportions of plant cell walls which can be used in human nutrition to produce "dietary fibre" or "functional fibre", i.e. compounds which can be used for their water-holding/binding properties, oil-binding capacity,... or as a source of polysaccharides such as pectins which are suitable after extraction, as gelling or thickening agents. 

Analysis of the products which become water-soluble after extrusioncooking showed that feroylated heteroxylans and glucans were solubilised from wheat bran (10), arabinans, heteroxyalans and pectins from pea hulls (11,12), and pectins from the other sources (13,14). 

To improve production of rhamnogalacturonase by Aspergillus aculeatus CBS 115.80 shake flask ejqjeriments were performed on several substrates. Cross reactivity was found after transfer to thamnose in combination with galacturonic acid and on apple pectin, citrus pectin, beet pectin and sugar beet pulp. No cross reactivity was found after transfer to meda containing simple carbon sources such as sucrose, glucose, fiuctose, rhamnose or galacturonic acid. 

The main part (80%) of pectins were in the edible apple zones but no change in galacturonic acid concentration was observed between the different tissue zones. So, carpels and epidermis zones are potentiel sources of highly methylated pectins. 

---