Development of food-grade Pickering emulsions stabilized by a biological macromolecule (xanthan gum) and zein.

In this work, food-grade sunflower oil/W Pickering emulsions stabilized by xanthan gum-zein complex were developed. For this purpose, laser diffraction, rheological, multiple light scattering, confocal laser scanning microscopy (CLSM) and field emission scanning electron microscopy (FESEM) measurements were carried out. A response surface methodology was used to determine the optimized zein and oil concentration of the emulsion by using D4,3 and Turbiscan Stability Index (TSI) as objective functions to minimize. Subsequently, the optimized formulation with minimum D4,3 was selected and the biological macromolecule, advanced performance xanthan gum (APXG), was added. CLSM results of emulsions without gum showed the location of zein in the oil-water interface protecting droplets against coalescence as Pickering stabilizer. They also demonstrated that zein did not present important aggregation at the working pH. The addition of APXG changed the flow behaviour from Newtonian to shear thinning which fitted to the Cross model. This fact provoked the occurrence of viscoelastic properties and an increase in stability. FESEM results suggested the formation of a zein-gum complex, which forms a layer covering the droplets, protecting them against oxidation and physical destabilization. Therefore, this research supports the role of zein-APXG complex as a stabilizer of future emulsions.

Protein-polysaccharide complex coated W/O/W emulsion as secondary microcapsule for hydrophilic arbutin and hydrophobic coumaric acid.

This study aimed to examine the modification effect of whey protein concentrate (WPC), WPC-gum arabic (WPC-GA) or WPC-high methoxyl pectin (WPC-PEC) complex to tailor-modify W/O/W emulsion for secondary microencapsulation of hydrophilic arbutin and hydrophobic coumaric acid. The stability and rheological properties of coated emulsions, encapsulation yield, release and degradation kinetics of arbutin and coumaric acid were investigated. Results revealed that WPC-PEC complex (at the ratio of 1:3) coating W/O/W emulsion exhibited the highest viscosity and stability, with the highest encapsulation yield of 91.08% for arbutin and 80.92% for coumaric acid, respectively. Tighter coating structure of the WPC-PEC complex (1:3) forming a stronger gel network structure was confirmed, accounting for the larger mean particle size of 569.67 nm. Moreover, the WPC-PEC (1:3) coating W/O/W emulsion also showed controlled release of arbutin and coumaric acid in simulated conditions. The k value of degradation kinetics for arbutin (7.99 × 10-4 at pH = 1.2, 4.19 × 10-4 at 90 °C and 7.52 × 10-4 at UV-C treatment) and coumaric acid (5.18 × 10-4 at pH = 1.2, 3.24 × 10-4 at 90 °C and 6.90 × 10-4 at UV-C treatment) indicated low degradation rate. The present study revealed that the WPC-PEC (1:3) coating W/O/W emulsion could provide a better synergistic effect on higher encapsulation yield and stability of arbutin and coumaric acid.

Scrutinizing the different pectin types on stability of an Iranian traditional drink "Doogh".

Doogh is a fermented dairy drink which is highly consumed by Iranian people. Stability of this healthy drink was investigated in terms of sedimentation rate, viscosity, density and particle size characteristics including surface-weighted mean diameter (D32), Span and particle uniformity. Eight treatments were performed as randomized complete block design (RCBD) with three replications. Three types of pectin (high methoxyl pectin (HMP), grapefruit-seed extract pectin (GSEP) and amidated pectin (Ceamsa pectin (CSP)) at a constant concentration (0.35%w/w), three levels of salt (0.50, 0.75 and 1.00%w/w) and two dry matter contents (DMCs, 4 and 5% w/w) were used to produce the Dooghs. The results showed that the maximum stability and viscosity, and the minimum D32 were obtained by application of CSP, GSEP and HMP, respectively (p<0.05). Pectin type had no significant difference on the density values of Dooghs. The lowest sedimentation rate, viscosity, density and D32 were achieved in the minimum concentrations of salt and dry matter. The ANOVA analysis also revealed that the interaction of pectin type, salt concentration and DMC had a significant effect on the Span and particle uniformity. A maximum physical stability was found for the prepared samples with 0.35%w/w CSP, 0.5%w/w salt and 4%w/w dry matter. Evaluation of sensory attributes also confirmed that this formulation had the highest overall acceptability value.