**1. Introduction**

In food industry, it is common to add ingredients that have in aqueous solution thickening, stabilizing, or gelling properties to the formulation of food products. These ingredients are interesting for the appearance and organoleptic characteristics but can also become innovative ingredients in the search for original textures or to support the use of alternative chemical additives. In bioprocessing, the field of ingredients or additives authorized in this framework is more limited than in conventional processing. However, a number of gums, starches, fibers, or flours can be used. Among them, two vegetable gums, extracted from the endosperm of legume seeds, were commonly used with similar properties: guar gum and locust bean gum. These natural polysaccharides are extensively used in a wide range of applications in food, medical, pharmaceutical, textile, paper, hydraulic fracturing, explosives, agriculture, cosmetic, bioremediation, and petroleum industries because of their ability to modify the rheological properties and in the aim of green chemistry approach [1–5]. Guar gum (GG), named E412 in European additive list, is a polysaccharide of natural origin, extracted from the seed of *Cyamopsis tetragonoloba* L. (Fabaceae), a plant also called guar or guar bean and native. The world's production of guar is concentrated in India, Pakistan, and the United States with limited amounts grown in South Africa and Brazil. The annual guar plant grows to about 0.6–1 m in height and produces seed pods growing in clusters giving guar pods the common name cluster bean (6–9 guar beans per pod). Locust bean gum (LBG) or E410 is the crushed endosperm of locust bean tree seeds, a dioecious evergreen tree grown in a Mediterranean climate, botanically known as *Ceratonia siliqua* L., belonging to the subfamily *Caesalpinioideae* of the *Fabaceae* family. It is abundant in Spain, Italy, and Cyprus and is also found in other Mediterranean countries, in various regions of North Africa, South America, and Asia. It can reach 8–15 m in height and live up to 500 years. Its fruits are long thick and tough pods containing 10–15 oval-shaped locust bean seeds or kernels. The locust tree can produce annually 300–800 kg of locust bean seeds from which LBG will be produced, also referred as locust bean seed gum, locust bean flour, or *ceratonia*. The guar seed is smaller than the locust bean seed but they both have the same structure. They consist of four elements (**Figure 1**): the tegument (outer husk or seed coat), a translucent endosperm representing 40–50% of the weight of the locust bean seed and 35–45% of the weight of the guar seed, two cotyledons, and an embryo (or germ) [6].

The number of tissues within the locust bean would even be 10 according to microscopic studies [7]. These seeds are a basic material for the manufacture of gum and contain hydrocolloids (polysaccharides), called galactomannans, which serve as a reserve for the embryo during germination. With the help of various thermal, mechanical, or chemical processes [2, 5], the seeds are dehusked without damaging the endosperm and the embryo (germ). After this peeling process, the endosperm is split from the cotyledons and then it is ground to produce gum. To eliminate protein content and impurities for certain industrial applications, the gum is purified by washing with solvent or dispersing in boiling water, followed by filtering, evaporation, and drying [2, 5, 6, 8]. Galactomannans are heterogeneous polysaccharides with a high molecular weight, composed by linear chain of β-(1-4)-D-mannopyranosyl units with a single α-D-galactopyranosyl (1-6) linked residue, a conformation similar to that of cellulose. The structure of these gums differs according to the distribution and the number of galactose residue along the mannose chain, randomly arranged in pairs and triplets in the case of the GG [5] leading to regions of low or high substitution, or in blockwise while LBG presents a random, blockwise, and ordered distribution of α-D-galactopyranosyl residues along the β-D-mannose backbone [9]. The degree of galactosyl substitution is responsible for water solubility differences of galactomannans; an increase in the substitution leads to higher solubility through steric effects, whereas galactose-poor regions are less soluble and can involve both inter- and intramolecular associations. Then, GG is dissolved in cold water, while heating is needed to solubilize LBG. The

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**Table 1.** *Gum suppliers.*

*Discrimination by Infrared Spectroscopy: Application to Micronized Locust Bean and Guar Gums*

ratio of mannose to galactose can vary because of the extraction process (particularly purification conditions depending of the end of the desired product) and plant source (geographic location with various climate). The average ratio of galactose to mannose has been estimated to be 1/2 for GG (typically in the range 1/1.4–1.8) [2, 10, 11] and 1/4 (found in the range 1/2.3–6.0) [2, 11, 12] for LBG according to the different chemical techniques (high-performance liquid chromatography, gas chromatography, 13C NMR spectroscopy, or enzymatic method with β-D-mannase). Because of its good sensitivity and its simplicity in sample preparation, Fourier Transform InfraRed (FTIR) spectroscopy has been common to differentiate GG and LBG and mixtures [10, 12, 13], to study galactomannose interaction with solids [14], to control the gum quality after chemical treatments modifying their properties [15, 16], and to predict the origin [17] with a partial least squares

The aim of this work is to confirm the potential of FTIR technique for the discrimination and the classification of the nature of LBG and GG with the help of chemometric treatments such as principal component analysis (PCA) and partial least squares regression. Moreover, linear-discriminant analysis (LDA) was used to predict the percentage of adulteration by using Scheffé's simplex network to generate simulated binary blends taking into account the variability of the

chemical composition of GG and LBG because of their different geographic origins

Guar (n = 74) and locust bean (n = 25) commercial gums were obtained from different suppliers without information about their geographic origins, manufacturing processes, mannose/galactose ratios, and the mesh size of particles (**Table 1**). These powders were freeze-dried before spectroscopic characterization to eliminate the available water interactions. Mathematical binary blends were also built with simplex approach in different GG percentages (varying between 0 and 100% in weight) from simplex method to take into account the variability of spectral

Pure sugars (D-mannose and D-galactose) were purchased from Sigma-Aldrich (99% of purity) to obtain its FTIR-ATR profile in the same conditions of the gum

The technique of attenuated total reflectance (ATR) is making easier the solid and liquid analysis by reducing the sample preparation time and increasing spectral

LBG Alliance Gums & Industries, ARLES, Chemcolloids Ltd, Iranex, Pharmacie des Rosiers, Santeflor,

GG Alliance Gums & Industries, ARLES, Chemcolloids Ltd, Associated Dichem corporation, Iranex, Laviosa MPC, Nitrochemie, SEATH International, Sigma Aldrich, Santeflor, Starlight, ROTH,

SEATH International, Sigma Aldrich, Tassy & Cie, Viscogum FA

**2.2 Attenuated total reflectance (ATR) characterization**

*DOI: http://dx.doi.org/10.5772/intechopen.87568*

regression-discriminant analysis (PLS-DA).

and manufacturing processes.

**2. Materials and method**

signature of GG and LBG.

**Gum Suppliers**

Tassy & Cie, Viscogum FA

**2.1 Sampling**

sample.

**Figure 1.** *Scheme of gum seed cross-section.*

*Discrimination by Infrared Spectroscopy: Application to Micronized Locust Bean and Guar Gums DOI: http://dx.doi.org/10.5772/intechopen.87568*

ratio of mannose to galactose can vary because of the extraction process (particularly purification conditions depending of the end of the desired product) and plant source (geographic location with various climate). The average ratio of galactose to mannose has been estimated to be 1/2 for GG (typically in the range 1/1.4–1.8) [2, 10, 11] and 1/4 (found in the range 1/2.3–6.0) [2, 11, 12] for LBG according to the different chemical techniques (high-performance liquid chromatography, gas chromatography, 13C NMR spectroscopy, or enzymatic method with β-D-mannase).

Because of its good sensitivity and its simplicity in sample preparation, Fourier Transform InfraRed (FTIR) spectroscopy has been common to differentiate GG and LBG and mixtures [10, 12, 13], to study galactomannose interaction with solids [14], to control the gum quality after chemical treatments modifying their properties [15, 16], and to predict the origin [17] with a partial least squares regression-discriminant analysis (PLS-DA).

The aim of this work is to confirm the potential of FTIR technique for the discrimination and the classification of the nature of LBG and GG with the help of chemometric treatments such as principal component analysis (PCA) and partial least squares regression. Moreover, linear-discriminant analysis (LDA) was used to predict the percentage of adulteration by using Scheffé's simplex network to generate simulated binary blends taking into account the variability of the chemical composition of GG and LBG because of their different geographic origins and manufacturing processes.
