Effect of cosolutes on the rheological and thermal properties of Tara gum aqueous solutions
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ORIGINAL ARTICLE
Effect of cosolutes on the rheological and thermal properties of Tara gum aqueous solutions Renata Alves Fernandes1 • Edwin Elard Garcia-Rojas1,2
Revised: 31 August 2020 / Accepted: 9 September 2020 Ó Association of Food Scientists & Technologists (India) 2020
Abstract The influence of the concentration (5–20 mg/m L) of different cosolutes (sucrose and NaCl) on the rheological and thermal properties of concentrated Tara gum (TG) solutions (1.5–2.5% w/v) was investigated. Furthermore, the structural properties of the TG, TG-sucrose and TG-NaCl solutions were studied. The TG, TG-sucrose and TG-NaCl solutions exhibited a pseudoplastic and typical viscoelastic behavior of an entangled network structure. An increase in the TG concentration increased the pseudoplasticity and the elasticity of the solutions, while the incorporation of NaCl reduced these properties. Sucrose had little influence on the rheological properties of the TG solutions. The texture profile and the water holding capacity of the TG solutions were significantly influenced by the concentration of the TG and did not change with the addition of the cosolutes. The thermal stability of the TG solutions was reduced by NaCl and was not altered by sucrose. The microstructures of the TG solutions was significantly affected by NaCl, supporting the results obtained from rheological and thermal analyses. The results of this study may be useful for the formulation and processing of foods containing TG.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13197-020-04785-9) contains supplementary material, which is available to authorized users. & Edwin Elard Garcia-Rojas [email protected] 1
Po´s Graduac¸a˜o em Engenharia Mecaˆnica (PGMEC), Universidade Federal Fluminense (UFF), Av. dos Trabalhadores, 420, Volta Redonda, RJ 27255-125, Brazil
2
Laborato´rio de Engenharia e Tecnologia Agroindustrial (LETA), Universidade Federal Fluminense (UFF), Av. dos Trabalhadores, 420, Volta Redonda, RJ 27255-125, Brazil
Keywords Galactomannans Concentrated solution Interfacial tension Pseudoplastic
Introduction Tara gum (TG) is a white or beige powder obtained by grinding the seed endosperm of the Tara tree (Caesalpinia spinosa), which is native to Peru´, and approximately 80% of TG is composed of the galactomannan polysaccharide (Mathur 2012). Galactomannans are neutral hydrophilic polysaccharides obtained from the endosperm of some leguminous seeds. Structurally, galactomannans consist of a major linear chain of (1 ? 4)-b-D-mannopyranose, to which the a-D-galactopyranosyl units are linked via (1 ? 6) glycosidic linkages (Cui et al. 2007; Srivastava and Kapoor 2005). In galactomannans, the lower the degree of substitution by galactose units is, the lower their solubility and the greater their potential for molecular association in solution (Picout et al. 2002). The M/G ratio varies considerably depending on the galactomannan source, as do the distribution pattern of the side chains and the average molecula
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