Characterisation of whey protein isolate-gum tragacanth electrostatic interactions in aqueous solutions

Thermodynamic compatibility of gelatin and tragacanth gum in aqueous systems

The influence of total concentration, biopolymer mixing ratio, and ionic strength on the association of tragacanth gum (TG) and gelatin (G) in the aqueous system during acidification was investigated. The onset of soluble complex formation appeared at pH_c, where both biopolymers carried a negative charge. Insoluble complexes were formed at pH_φ1 by a further pH decrease, owing to increased interactions between the polymers. The complexes formed at pH_φ1 still had partly high negative surface charge. Complex coacervation was observed at pH_opt due to the growing size and number of insoluble complexes. The ζ value of the G- TG significantly decreased at pH_opt, which was subjected to phase separation. Turbidity decreased at pH_φ2 as a result of complex decomposition. The maximum efficiency of complex formation was at the salt-free samples. NaCl reduced critical pHs and complex formation efficiency by screening the ionized groups on the biopolymers.

Complexing hemp seed protein with pectin for improved emulsion stability

Hemp seed protein has the potential to be used in food systems as an emulsifying agent; however, there are still some shortcomings associated with hemp seed protein, such as poor solubility and tendency to aggregate. This study aims to improve the dispersibility of hemp seed protein as an emulsifier by complexing with pectin, driven by electrostatic force. Three protein to pectin ratios were used for complexation, from 1:1, 2:1 to 4:1. The complexation improved the polydispersity of hemp seed protein when dispersed in the aqueous phase. The hemp seed protein displayed multimodal size distribution in water at pH = 3.0 due to aggregation, while the incorporation of pectin helped to diminish those aggregated proteins. When the hemp seed protein was used to stabilize the oil-in-water emulsion, its stabilized emulsion showed promising homogenous droplet size distribution after emulsification. However, during the accelerated storage conditions (55°C), the emulsion stabilized solely by hemp seed protein was subjected to extensive coalescence. From day 0 to 9, the droplet size (d_4,3 ) increased by 50 folds from 3.215 to 161.6 µm. In contrast, the hemp seed protein-pectin complex exhibited extraordinary stability during the storage test, where size evolution in all three samples was negligible compared to the emulsion stabilized by hemp seed protein. Rheological characterization suggests that pectin provided physical strength, which may help the emulsion droplets to maintain structural integrity under environmental stress. The underlying mechanism could be associated with the formation of a three-dimensional structure by pectin through bridging adjacent emulsion droplets. PRACTICAL APPLICATION: Hemp seed protein is gaining more and more attention as an emerging plant protein. Recently, hemp seed protein has been explored as an emulsifier, but its stabilized emulsion encounters instability issues during storage. Our study suggests pectin could be used as a co-stabilizer for hemp seed protein emulsions.

pH-Induced structural transitions in whey protein isolate and ultrasonically solubilized Persian gum mixture

The present work evidently reports that ultrasonic depolymerization strongly enhanced complex coacervation between Persian gum (PG) and whey protein isolate (WPI). PG was sonicated at 60 °C, operating frequency of 20 kHz and nominal power output of 800 W for various times followed by mixing with WPI. Acid-induced interaction between the two biopolymers was studied by turbidity, light scattering, zeta potential and viscosity measurements over a wide pH range. Sonication of intact PG (IPG) for 10 min considerably reduced the molecular weight from 4.12 × 10⁶ to 0.76 × 10⁶ g/mol. Besides, ultrasonic fragmentation of water insoluble fraction of PG drove protein containing chains into the soluble phase. Sonicated PG (SPG) was shown to be more flexible with higher number of carboxyl groups available for electrostatic interaction with WPI, such that the complete neutralization did not occur even at protein to polysaccharide ratio of 50: 1. Additionally, scattered light intensity and viscosity measurements revealed two maxima in the pH ranges of 4.4-4.85 and 3.27-4.0, being highly intense for the gum sonicated for 10 min and longer. Considering the pH-behavior of WPI components, the former peak was related to interpolymer complex formation between β-lactoglobulin and long chain fraction of SPG, while the latter was attributed to intrapolymer association of α-lactalbumin with the short chain oligosaccharides arising from ultrasonic degradation of PG.

Characterization of Emulsion Stabilization Properties of Gum Tragacanth, Xanthan Gum and Sucrose Monopalmitate: A Comparative Study

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 (n_Xanthan = 0.188 ≪ n_GT = 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.

Ultrasonic degradation of Persian gum and gum tragacanth: Effect on chain conformation and molecular properties

The present study introduces the ultrasonic modification of two Iranian native gum exudates, Persian gum (PG) and gum tragacanth (GT) for the first time. They were sonicated at a constant frequency of 20 kHz and temperature of 60 °C for various times (0, 2, 5, 10, 20, 30 and 40 min) and the changes in their molecular properties were investigated using oven drying, gel permeation chromatography-multiangle laser-light scattering (GPC-MALLS), rheometery and FTIR analysis. Results indicated that the soluble dry mass of both hydrocolloids was extensively enhanced (from less than 10% at time zero to more than 90% at the end of treatment time) by sonication. Moreover, the molecular weight and viscosity of gums dispersions were decreased with the increase of the treatment time. Fracture in polysaccharide chains was confirmed by analysis of the molecular weight parameters. Calculation of chain breaks and polydispersity index (PDI) revealed that scissions occurred at the backbone as well as the side branches. PG, owing to its higher molecular weight, displayed more extensive and faster degradation than GT. However, the chain rupture of GT was twice more than that of PG at the end of sonication time. The specific volume for gyration (SV_g) and molecular density (ρ) showed that intact PG contains compactly packed molecules with greater number of cross-linked bonds compared to GT. Furthermore, the conformational changes into semi-flexible chains and worm-like coils were determined for both gums after 40 min sonication. Variation of the molecular density along with the results of FTIR analysis demonstrated that ultrasonication broke C-O-C bonds in both PG and GT leading to more flexible chains.