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L. grow spontaneously in forests and jungles in the North of Argentina and adjacent regions of Bolivia, Paraguay, Brazil and Uruguay.
“Espina corona”, is one of the closest forest specie of Ceratonia silicua L., also form the Fabaceae Family or European carob, whose seeds are used to obtain locust bean gum (LBG) [40]. The trees reach 12–15 m in height and 30–60 cm in diameter (Figure 2.3a). The fruit is a legume, 6–8 cm long and 2–3 cm in width, containing 6–10 seeds form oblong-ovoid, olive to cinnamon color (Figure 2.3b) [40].
Vinal is a very abundant tree growing in South American semiarid areas [41]. Figure 2.4 shows vinal seeds extracted from pods by milling, their endosperm after alkaline treatment and tegument separation, and the ethanol purified freeze dried VG. It can be noted that the obtained VG has whitish color, and fibrous and scaly appearance. Many interesting functionalities have been reported from galactomannans extracted from Prosopis spp. seeds: Prosopis flexuosa DC. and Prosopis pallida Humb. & Bonpl. as thickening agents [42, 43] and as synergic gel formers [44]; Prosopis chilensis (Molina) Stuntz as texturing agent [45] and foam stabilizer [46]; Prosopis glandulosa Torr. as emulsifying agent [46]; Prosopis africana Guill. & Perr, Taub. as thickening agent [47], as drug release controller [48], as emulsifying agent and film former [46]; Prosopis juliflora (Sw.) DC. as thickening and stabilizer agent [49], as encapsulating agent and wall material [50], as synergic gel former [51], and as release controller [52]; Prosopis velutina Wooton as thickening and stabilizing agent [53].
ECG and VG are galactomannans, with a molecular weight of about 1,400 kDa and mannose/galactose (M/G) ratio of 2.5 and 1.6, respectively. Both galactomannans consist of b-mannose units (1→4) linked with α-D-galactose residues at C-6 [54]. The reference gum, guar gum (GG) has a M/G of 1.8 [55]. Since linear polysaccharides occupy a greater volume than branched polymers, at the same concentration and similar molar mass, they exhibit higher viscosity [55]. Therefore, ECG and VG form highly viscous dispersions in hot and cold water, but they are non-gelling biopolymers.
VG and ECG display different rheological behavior according to the deformation rates and concentrations. At low deformation rates they develop thixotropic behavior, while at high deformation rates the behavior becomes Newtonian. At all deformation rates and concentrations tested, ECG solutions were more viscous than those of guar gum [56].
Figure 2.3 G. amorphoides Griseb., Taub. (a) tree and (b) pods.
Figure 2.4 P. ruscifolia Griseb. seeds, endosperm after alkaline treatment, and the obtained vinal gum are shown.
When dispersed in water, ECG and VG shows a pseudo-plastic behavior [57] in the concentration ranges 0.25–1.50% w/w and above 0.04% (w/v). At intermediate concentrations, in high frequency range there is a cross point where the solid behavior (represented by the elastic modulus G′) becomes higher than the viscous behavior (represented by the loss modulus, G”). Meanwhile, in the low frequency range, G” prevails over G’ [57].
Zeta potential is an important property in coacervation processes and other applications, including molecular interactions with other components. VG, as GG and other galactomannan gums, is nearly neutral with weak acid behavior in solution and high stability to pH changes [58].
Galactomannans (such as ECG, GG and VG) are able to produce stable emulsions and reduce oil in water interfacial tensions. The emulsifying activity of galactomannans is not completely explained. The possible reasons are their non-polar regions, their protein content, or the protein moieties bounded to the gum, besides to their ability to thicken the aqueous phase [59, 60].
2.2.4.2 Gums From Fabaceae Family Exudates
The international market of exudate gums comprises only few varieties: arabic gum (Acacia Senegal Willd.), karaya (Sterculia urens Roxb.), tragacanth (Astragalus gummifer (Labill.) Podl.) and gatti (Anogeissus latifolia Roxb.) Wall., which producer trees are confined to specific Asian regions [61]. Certain trade difficulties related to sustained supply, variable quality and high importation costs has focused the researchers’ attention on the search and exploitation of non-conventional exudate gums to find local alternatives to commercially available gums [36]. The environment particularities and botanical identity of gum producer trees, impart distinctive functional properties resulting in gums with different applications.
Exudate gums are generated in response to stress conditions, such as mechanical injuries, dehydration, microorganisms and insects attack [62]. Their main components are different carbohydrates, and also proteins, minerals and also polyphenols, among other antioxidant compounds [63].
Their appropriate physical properties and biocompatibility favored their use from ancient times [63]. Particularly, the exudate gum obtained from P. alba Griseb. trees or “algarrobo blanco”, PAEG (Figure 2.5) is comparable to arabic gum [37]. It grows in South America arid and semi-arid regions [38], and its seeds and pods are often employed as ingredient for a variety of food products [64]. The exudate gum is hand collected in several locations in Chaco, Argentine, and purified by dissolution in water, heat treatment, filtration to remove impurities and finally dried [37]. Obtained gum powder exhibits a bright brown color and transparent shiny appearance (Figure 2.5).
Protein fraction in PAEG is markedly higher than in arabic gum, with better interfacial and emulsifying properties. PAEG is able to lower the interfacial tension and to stabilize emulsions based on high charge distribution (negative ζ-potential) and good interfacial rheological properties [37]. When PAEG was included in beads obtained by ionic gelation, fish oil oxidation was inhibited [65–67]. Additionally, PAEG affected water–solid interactions of the beads, favoring the formation of glassy matrices and improving the protection against lipid oxidation [68].
Figure 2.5 P. alba exudate gum, spontaneous exudation, raw gum samples and purified powder.
In 2011 the Argentine Administration of Drugs and Foods (ANMAT) accepted ECG to be used as thickener and stabilizer agent [69] and, more recently, in 2018, the flour of vinal seed has also been included. In pharmaceutical formulations, ECG and VG could be used as binder, suspending, thickening and stabilizing agents due to their capability of fast hydration.
Gums may also be used in alginate pH-dependent hydrogels for controlled release of drugs [66], with minimal release in the stomach, increasing in the intestinal tract [67].
2.2.5 Healthy Fatty Acid Sources From Ibero America
Besides representing a major energy supply in the human diet, vegetable oils are an excellent source of essential unsaturated fatty acids, which participate extensively in the metabolism, generating many bioactive molecules which are fundamental mediators of multiple signalling pathways, and as components of biomembranes [70]. The intake of saturated fatty acids has been associated with