**1. Introduction**

The food and beverage industries face increasingly challenging scenarios, as they need to meet consumers' desires, and use ingredients that are natural, and that fulfill their technological roles in processed foods. Among these ingredients, gums and hydrocolloids are the compounds most widely used as agents of innovation in the food industry.

Gums, also known as hydrocolloids or polysaccharides, are very versatile biopolymers, extensively used in the food sector as ingredient or additive, which fulfill several technological and, sometimes, nutritional functions. This versatility is intrinsically related to their molecular composition, which gives these polysaccharides certain properties such as gelling, thickening, moisture retention, emulsification, and stabilization. In the food industry, they are widely used in confectionery, as ice cream stabilizers, food emulsions, in the microencapsulation of flavors and dyes, clarifiers, and beverage stabilizers.

Therefore, information on the molecular structure, thermal stability, interaction with water, and rheological behavior are essential knowledge for prospecting and developing applications for each type of polysaccharide, whether isolated or in mixtures.

Another important fact, in this sense, is the constant search for new sources of polysaccharides that might have similar and/or better effects than those already known. This is important because it also shows regional valorization, source of income, and new business opportunities.

Thus, this chapter aims to discuss the physical, chemical, and molecular knowledge of polysaccharides, in addition to their versatility of applications in the food industry.

## **2. Gums: origin and definition**

The term gum is generally used to define hydrophilic or hydrophobic molecules of high molar mass, which have colloidal properties [1]. Classified according to origin, behavior, and chemical structure, gums can be derived from plant seed endosperm (guar gum) [2], plant exudates (tragacanth), shrubs or trees (gum arabic, karaya gum, cashew gum) [2–5], algae extracts (agar) [6], bacteria (xanthan gum), animal source (chitin), and others [7–10].

Vegetable exudates are fluids that flow spontaneously from trees, due to adaptations to climatic conditions (physiological gummosis) or in response to any injury suffered, whether mechanical, such as cutting, or by the action of microorganisms, which dry out when exposed to air [11].

Hillis [12] describes in detail the differences between exudates from tree trunks, specifically the differences between resins and gums, and their formation. The author defines resins as materials composed largely by terpenoids, and that may contain phenolic compounds (coumaric, caffeic, and ferulic acids), with few fatty acids and glycerides. They may be formed within plastids present in epithelial cells of plants [13] or even synthesized in spherosomes, both in resin duct cells and in parenchymal cells [14].

Hillis [12] also defines gums as products composed mainly of complex carbohydrates, soluble in water, which can form gels and mucilages. They have high molar mass and can be formed by galactose, arabinose, rhamnose, xylose, galacturonic acid, and other compounds. In some species, they are secreted by organelles present in the bark or between barks, whose main function is protecting the plant from injuries caused by cuts or microbial attack [15–17].

The interest in gums exuded from plants is due to their structural properties and respective functions in food, pharmaceutical, cosmetic, textile, and biomedical products [18]. Water-soluble gums, also known as hydrocolloids, can have various applications such as: dietary fibers, texture modifiers, gelling agents, thickeners, stabilizers, emulsifiers, coatings, films, and as encapsulants [19, 20]. There has been a strong trend towards replacing synthetic materials by natural gums due to their non-toxicity, low cost, safety, and availability [21].

#### **3. Structural aspects of gums**

All the properties and applications of gums are closely linked to their chemical structures. Gums can be formed by numerous sugars, in their main chains and/or side chains, and can be more or less branched, which determines, in general, their complexity [15].

Among the most well-known and commercialized gums [22], the gum arabic, produced by the species *Acacia senegal*, presents in its structure a main chain formed by β-D-galactopyranose joined by bonds (1➔3), alternated by highly branched bonds (1➔6), and shows lateral chains constituted by 4-O-methyl-glucuronic acid (1.5%), glucuronic acid (17.5%), galactose (39%), arabinose (28%), and rhamnose (14%) [23]. Anderson; Hirst; Stoddart [24] proposed the structure presented in **Figure 1** for acacia gum. The authors indicated, as possible replacement units, those represented by the radical "R": (L-Araf); (L-Araf 1➔3 L-Araf); (β-L-Arap 1➔3 L-Araf);

**235**

**Figure 1.**

*referring to the fragment shown.*

*Gums—Characteristics and Applications in the Food Industry*

ranoside is Galp. The radicals "R" are not shown in **Figure 1B**.

(L-Araf 1➔3 L-Araf 1➔3 L-Araf); (β-L-Arap 1➔3 L-Araf 1➔3 L-Araf); (β-D-Galp 1➔3 L-Araf). Arabinofuranoside is Araf, arabinopyranoside is Arap, and galactopy-

Gum ghatti is also important among exudate gums because of its high emulsifying capacity [25]. It is extracted from the trunk of *Anogeissus latifolia*, an abundant tree in India [26]. Its molecular structure is formed by a main chain of (1➔6)-β-Galactose bonds, whose branches at positions O-3 and O-4 are replaced, consisting of ➔2)-Araf-(1➔4)-GlcpA-(1➔6)-Galp-(1➔6)-Galp-(1➔. The terminal

*Structural fragment of gum arabic (*Acacia senegal*). (A) Scheme and (B) three-dimensional structure* 

*DOI: http://dx.doi.org/10.5772/intechopen.95078*

*Gums—Characteristics and Applications in the Food Industry DOI: http://dx.doi.org/10.5772/intechopen.95078*

*Innovation in the Food Sector Through the Valorization of Food and Agro-Food By-Products*

Thus, this chapter aims to discuss the physical, chemical, and molecular knowledge of polysaccharides, in addition to their versatility of applications in the food

The term gum is generally used to define hydrophilic or hydrophobic molecules of high molar mass, which have colloidal properties [1]. Classified according to origin, behavior, and chemical structure, gums can be derived from plant seed endosperm (guar gum) [2], plant exudates (tragacanth), shrubs or trees (gum arabic, karaya gum, cashew gum) [2–5], algae extracts (agar) [6], bacteria (xanthan

Vegetable exudates are fluids that flow spontaneously from trees, due to adaptations to climatic conditions (physiological gummosis) or in response to any injury suffered, whether mechanical, such as cutting, or by the action of microorganisms,

Hillis [12] describes in detail the differences between exudates from tree trunks,

Hillis [12] also defines gums as products composed mainly of complex carbohydrates, soluble in water, which can form gels and mucilages. They have high molar mass and can be formed by galactose, arabinose, rhamnose, xylose, galacturonic acid, and other compounds. In some species, they are secreted by organelles present in the bark or between barks, whose main function is protecting the plant from

The interest in gums exuded from plants is due to their structural properties and respective functions in food, pharmaceutical, cosmetic, textile, and biomedical products [18]. Water-soluble gums, also known as hydrocolloids, can have various applications such as: dietary fibers, texture modifiers, gelling agents, thickeners, stabilizers, emulsifiers, coatings, films, and as encapsulants [19, 20]. There has been a strong trend towards replacing synthetic materials by natural gums due to their

All the properties and applications of gums are closely linked to their chemical structures. Gums can be formed by numerous sugars, in their main chains and/or side chains, and can be more or less branched, which determines, in general, their

Among the most well-known and commercialized gums [22], the gum arabic, produced by the species *Acacia senegal*, presents in its structure a main chain formed by β-D-galactopyranose joined by bonds (1➔3), alternated by highly branched bonds (1➔6), and shows lateral chains constituted by 4-O-methyl-glucuronic acid (1.5%), glucuronic acid (17.5%), galactose (39%), arabinose (28%), and rhamnose (14%) [23]. Anderson; Hirst; Stoddart [24] proposed the structure presented in **Figure 1** for acacia gum. The authors indicated, as possible replacement units, those represented by the radical "R": (L-Araf); (L-Araf 1➔3 L-Araf); (β-L-Arap 1➔3 L-Araf);

specifically the differences between resins and gums, and their formation. The author defines resins as materials composed largely by terpenoids, and that may contain phenolic compounds (coumaric, caffeic, and ferulic acids), with few fatty acids and glycerides. They may be formed within plastids present in epithelial cells of plants [13] or even synthesized in spherosomes, both in resin duct cells and in

**234**

industry.

**2. Gums: origin and definition**

gum), animal source (chitin), and others [7–10].

injuries caused by cuts or microbial attack [15–17].

non-toxicity, low cost, safety, and availability [21].

**3. Structural aspects of gums**

complexity [15].

which dry out when exposed to air [11].

parenchymal cells [14].

(L-Araf 1➔3 L-Araf 1➔3 L-Araf); (β-L-Arap 1➔3 L-Araf 1➔3 L-Araf); (β-D-Galp 1➔3 L-Araf). Arabinofuranoside is Araf, arabinopyranoside is Arap, and galactopyranoside is Galp. The radicals "R" are not shown in **Figure 1B**.

Gum ghatti is also important among exudate gums because of its high emulsifying capacity [25]. It is extracted from the trunk of *Anogeissus latifolia*, an abundant tree in India [26]. Its molecular structure is formed by a main chain of (1➔6)-β-Galactose bonds, whose branches at positions O-3 and O-4 are replaced, consisting of ➔2)-Araf-(1➔4)-GlcpA-(1➔6)-Galp-(1➔6)-Galp-(1➔. The terminal

#### **Figure 1.**

*Structural fragment of gum arabic (*Acacia senegal*). (A) Scheme and (B) three-dimensional structure referring to the fragment shown.*

lateral chains are formed by residues of arabinofuranoside (Araf) and occasionally by rhamnopyranoside (Rhap), arabinopyranoside (Arap), galactopyranoside (Galp) or glucuronopyranoside (GlcpA) [27, 28]. The structure of gum ghatti is shown in **Figure 2**.

Karaya gum is also on the list of exudates from commercially interesting plants, and is extracted from *Sterculia urens* tree. Structurally, it is a complex, partially acetylated polysaccharide, composed of 55–60% of rhamnose and galactose, 8% of acetyl groups, and 37–40% of uric acid residues (galacturonic and glucuronic acids) [29]. Its structure can be seen in **Figure 3**.

#### **3.1 Gum structure of exudates from arecaceae family species**

The Arecaceae (Palmae) family consists of a large variety of monocot plants found predominantly in tropical and subtropical environments, mostly in South America, and contains 457 palm species distributed in 50 genera [30, 31].

Nussinovitch [26] described, in general, three types of gum from plants of the Arecaceae family, with sensory information about them. According to the author, *Borassus flabellifer* palm gum is a black glassy exudate, which swells and is insoluble in water; *Cocos nucifera* L. gum has coloration ranging from light brown to red, and in water, it presents certain insolubility, forms gel, and has low adhesiveness; *Corypha utan Lam*. gum has sweet odor and brown coloration, being used in medicine.

#### **Figure 2.**

*Structural fragment of gum ghatti. (A) Scheme and (B) three-dimensional structure referring to the fragment shown.*

**237**

**Figure 4.**

**Figure 3.**

*shown.*

*Gums—Characteristics and Applications in the Food Industry*

Gums from exudates of Chinese fan palm trunk (*Livistona chinensis*) [32] and jerivá (*Syagrus romanzoffiana*) [33] were presented as heteroxylans, whose main chain is joined by β-(1➔4) bonds, highly substituted at O-2 and O-3 positions by

*Structural fragment of karaya gum. (A) Scheme and (B) three-dimensional structure referring to the fragment* 

The exudate from Uricuri palm (*Scheelea phalerata*) was also identified by Fernanda F. Simas et al., [34]. The authors found a water-insoluble polysaccharide with a branched structure. Units of Xylp (~8%) were replaced at O-2, whereas Araf units (12%) were replaced at O-3. They also found non-reducing units of Araf (15%), Fucp (fucopyranose - 10%), Xylp (4%), and Arap (6%) as side chains attached to the main chain composed of Xylp units joined by β-(1➔4) bonds, which

The structure of the gum obtained from coconut tree trunk exudate (*Cocos nucifera*) was elucidated by Simas-Tosin et al., [35]. This gum is a glucuronoarabinoxylan composed of Fuc, Ara, Xyl, and GlcpA at molar ratio of 7:28:62:3.

*Three-dimensional representation of the heteroxylan present in* Scheelea phalerata *(Uricuri) palm gum, with*  β*-(1*➔*4) bonds. Main chain branches are substituted at O-2 or O-3 positions by arabinose and xylose units.*

units of arabinose, xylose, and terminal fucose, as shown in **Figure 4**.

were replaced at 3-O-(9%), 2-O-(13%), and 2,3-di-O-(13%) positions.

*DOI: http://dx.doi.org/10.5772/intechopen.95078*

*Gums—Characteristics and Applications in the Food Industry DOI: http://dx.doi.org/10.5772/intechopen.95078*

#### **Figure 3.**

*Innovation in the Food Sector Through the Valorization of Food and Agro-Food By-Products*

shown in **Figure 2**.

[29]. Its structure can be seen in **Figure 3**.

**3.1 Gum structure of exudates from arecaceae family species**

lateral chains are formed by residues of arabinofuranoside (Araf) and occasionally by rhamnopyranoside (Rhap), arabinopyranoside (Arap), galactopyranoside (Galp) or glucuronopyranoside (GlcpA) [27, 28]. The structure of gum ghatti is

Karaya gum is also on the list of exudates from commercially interesting plants, and is extracted from *Sterculia urens* tree. Structurally, it is a complex, partially acetylated polysaccharide, composed of 55–60% of rhamnose and galactose, 8% of acetyl groups, and 37–40% of uric acid residues (galacturonic and glucuronic acids)

The Arecaceae (Palmae) family consists of a large variety of monocot plants found predominantly in tropical and subtropical environments, mostly in South America, and contains 457 palm species distributed in 50 genera [30, 31].

Nussinovitch [26] described, in general, three types of gum from plants of the Arecaceae family, with sensory information about them. According to the author, *Borassus flabellifer* palm gum is a black glassy exudate, which swells and is insoluble in water; *Cocos nucifera* L. gum has coloration ranging from light brown to red, and in water, it presents certain insolubility, forms gel, and has low adhesiveness; *Corypha utan Lam*. gum has sweet odor and brown coloration, being used in medicine.

*Structural fragment of gum ghatti. (A) Scheme and (B) three-dimensional structure referring to the fragment* 

**236**

**Figure 2.**

*shown.*

*Structural fragment of karaya gum. (A) Scheme and (B) three-dimensional structure referring to the fragment shown.*

Gums from exudates of Chinese fan palm trunk (*Livistona chinensis*) [32] and jerivá (*Syagrus romanzoffiana*) [33] were presented as heteroxylans, whose main chain is joined by β-(1➔4) bonds, highly substituted at O-2 and O-3 positions by units of arabinose, xylose, and terminal fucose, as shown in **Figure 4**.

The exudate from Uricuri palm (*Scheelea phalerata*) was also identified by Fernanda F. Simas et al., [34]. The authors found a water-insoluble polysaccharide with a branched structure. Units of Xylp (~8%) were replaced at O-2, whereas Araf units (12%) were replaced at O-3. They also found non-reducing units of Araf (15%), Fucp (fucopyranose - 10%), Xylp (4%), and Arap (6%) as side chains attached to the main chain composed of Xylp units joined by β-(1➔4) bonds, which were replaced at 3-O-(9%), 2-O-(13%), and 2,3-di-O-(13%) positions.

The structure of the gum obtained from coconut tree trunk exudate (*Cocos nucifera*) was elucidated by Simas-Tosin et al., [35]. This gum is a glucuronoarabinoxylan composed of Fuc, Ara, Xyl, and GlcpA at molar ratio of 7:28:62:3.

#### **Figure 4.**

*Three-dimensional representation of the heteroxylan present in* Scheelea phalerata *(Uricuri) palm gum, with*  β*-(1*➔*4) bonds. Main chain branches are substituted at O-2 or O-3 positions by arabinose and xylose units.*

Non-reducing units substituted at 3-O (Araf - 8%); 3,4-di-O-(15%); 2,4-di-O (5%); and 2.3.4-tri-O (Xylp 17%) positions were also found, attached to a main chain composed of Xylp joined by β-(1➔4) bonds.
