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Compositional characterization and rheological properties of an anionic gum from Alyssum homolocarpum seeds

2015; Elsevier BV; Volume: 52; Linguagem: Inglês

10.1016/j.foodhyd.2015.07.030

1873-7137

Mohammad Anvari, Mehdi Tabarsa, Rong‐An Cao, Sanguan You, Helen S. Joyner, Shabnam Behnam, Masoud Rezaei,

Proteins in Food Systems

Compositional and rheological properties of Alyssum homolocarpum seed gum, as a new source of thickening agent for application in food industries, were investigated in this study. The extracted gum primarily comprised carbohydrates (61.0 ± 0.6%), proteins (17.9 ± 1.0%) and uronic acids (10.9 ± 0.8%); the main carbohydrates were galactose (65.7%) and rhamnose (18.3%). The polysaccharide backbone was chiefly composed of 1,2-rhamnose, 1,3- and 1,3,6-galactose glycosidic linkages. The average molecular weight of the polymer was 122.5 × 10 6 g mol −1 . Attenuated total reflectance-Fourier transform infrared spectroscopy and ζ-potential measurements revealed that A. homolocarpum seed gum with multiple carboxylic groups was negatively charged in water in the pH range 3–11. Rheological behaviors of the extracted gum were investigated between 0.5 and 5.0% (w/w) concentrations and temperatures of 5–50 °C. Viscosity profile showed shear thinning behavior at all concentrations and temperatures. The pseudoplasticity degree ( N ) of the extracted polymers increased with concentration while temperature changes did not show any specific trend on N values. The flow activation energy, quantified using an Arrhenius equation decreased from 11.00 to 5.17 (kJ/mol) as shear rate increased, which implied that the aqueous solutions flowed more easily at higher shear rates. The mechanical spectra derived from strain sweep and frequency sweep measurements indicated viscoelastic behavior in all of samples. Frequency sweep data showed that aqueous solutions of gum, displayed weak gel behavior over the range of tested concentrations and temperatures: as dynamic moduli increased with the increased frequency and storage modulus was always greater than loss modulus. • The gum from A. homolocarpum seed is a rhamnogalactan with the average molecular weight of 122.5 × 10 6 g mol −1 . • The A. homolocarpum seed gum with multiple carboxylic groups possesses negative charges in water. • The A. homolocarpum seed gum showed non-Newtonian behavior and the activation energy decreased with increase of shear rate. • The extracted gum showed weak gel properties at different temperatures and concentrations.