Emulsification effect of gum tragacanth (GT) obtained from Astragalus species is gaining particular interest in recent years. In this study, stabilization effect of GT, xanthan gum (XG), and sucrose monopalmitate (SMP) was investigated by keeping their concentration constant (0.5% w/v) for the oil-in-water emulsions containing 20% (v/v) sun flower oil and 2% (w/v) whey protein isolate. Emulsification was achieved by using high shear homogenization. Particle size and T2 (spin-spin relaxation time) measurements were performed for the characterization and repeated over the course of 28 days. Emulsion stability index (ESI [%]) was measured and rheological characterization was also performed. The lowest particle size was found for the XG emulsions and this was attributed to the pseudoplastic behavior of xanthan compared to GT (nXanthan = 0.188 ≪ nGT = 0.721). Xanthan emulsions thinned out dramatically when sheared during homogenization, and consequently, floccules formed could have been disrupted more resulting in smaller particle size. Result of rheological experiments showed that SMP emulsions were fit to Newtonian model, while XG and GT showed shear thinning behavior and fit to a power law model. Apparent viscosity of XG emulsions was found significantly higher than the GT ones. The most stable emulsions were the ones prepared by XG and they remained stable during 28 days. Although GT emulsions could not protect their stability during 28 days, ESI (%) results were found similar with XG indicating promising emulsification effect of GT. PRACTICAL APPLICATION: Gum tragacanth, xanthan gum, and sucrose monopalmitate have been used to formulate oil-in-water emulsions. The final formulated products can be used in emulsion-based food products to increase their stability and shelf life.
Keywords: gum tragacanth; oil-in-water (O/W) emulsion; stability; sucrose monopalmitate; xanthan gum.
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