Molecular Weight Determination of Tara Gum

POTEMSKY R., PICCO S., MASUELLI

Cordoba

Congreso; VI Congreso Internacional de Ciencia y Tecnología de Alimentos (CICYTAC 2016); 2016

VI Congreso Internacional de Ciencia y Tecnología de Alimentos (CICYTAC 2016)

Caesalpinia spinosa (Molina) Kuntze, commonly known as Tara, is a leguminous shrub native of Peru and center-South America (south Colombia, Ecuador, Bolivia and north Argentina (Jujuy and Salta). The seed endosperm produces a water soluble galactomannan (Tara gum) with a ratio of mannose/galactose in Tara gum is 3:1; in carob bean gum, this ratio is 4:1 and in guar gum 2:1. Tara gum (TG) AGLUMIX 01 were provided by INDUNOR- Argentina; 0.5 g of TG was dissolved in 200ml of distilled water, and then the mixture was centrifuged to 7000 rpm for 5 min to separate supernatant from impurities; finally, purified Tara gum was dried at 60°C for 48h. Tara gum solutions were prepared by dissolving in 100ml of distilled water 0.01, 0.02, 0.03, 0.04, 0.05, 0.07, and 0.1 g, with the addition of 1ml HCl 1M at 60°C for 2hs. Solutions and reference solvents were analyzed using an Ubbelohde 1C viscometer at 25°C, under precise temperature control using thermostatic bath. The densities of the solution and the solvent were measurement with Anton Paar densimeter. For partial specific volume determination, the following concentrations of TG were used in aqueous at 25°C. The density values of Tara gum increasing linearly with gum concentration. We can determine the value of the partial specific volume, and from this hydration value is calculated (337.22 g/g).From the Huggins method the intrinsic viscosity was measured with value of 3559.9 cm3/g, and Mark-Houwink parameters are a=0.8100 and k=0.01646 cm3/g. The calculated molecular weight is of 3770000 g/mol with hydrodynamic radius of 63.02nm), where this increase in molecular weight may be due to the high viscosity of the solutions and protons presence from HCl 0.1 M. This is evidenced by the high value of intrinsic viscosity and its difficult Tara gum in water solution. The ?a? value t showed that Tara gum for this system behaves as rod-like conformation, although others authors place it as an ellipsoid (random-coil) where ?a? is 0.70 to 0.747 for galactomannans, and 0.79 for Tara gum. Tara gum is the latter boundary between random-coil and rod-like and is although closer to the rod-like conformation (νa/b=11.12). This high molecular weight and intrinsic viscosity ranks as is an excellent food thickener, creaming and stabilizer agent.