Effect of gelled inner aqueous phase rheology on the colour degradation of muitle aqueous extracts incorporated into water-in-oil-in-water double emulsions

The aim of this work was to study different W1/O/W2 double emulsions in preserving color muitle aqueous extract (MAE), for which the work was divided into two fold, formulation and analysis of primary emulsion W1/O and W1/O/W2 double emulsions. Sodium alginate (SA), xanthan gum, guar gum, locust bean gum were used as gelling agents of MAE, and it was found that SA produced inner aqueous phase with enhanced viscoelastic properties, resulting in a W1/O primary emulsion with more uniform mean droplet size and distribution than when using the other gelling agents or ungelled MAE. Subsequently W1/O/W2 double emulsions were produced containing MAE gelled with SA or ungelled in the inner aqueous phase stabilized using pure gum Arabic (GA) or a blend of GA-mesquite gum (MG) in a 70:30 ratio in the outer aqueous phase. The double emulsion formulated with gelled MAE and 70:30 GA-MG blend exhibited more uniform mean inner water and outer oil droplet sizes, and protected best the anthocyanins contained in MAE to preserve its color when exposed to 8 h sunlight, providing a half-time life (t1/2) of 55.23 h. The double emulsion formulated with ungelled MAE and stabilized with pure GA displayed a t1/2 of 7.40 h. Keywords: double emulsions, muitle aqueous extract, gelling agents, viscoelastic properties, droplet size, half-time life

Moisture sorption properties and storage stability conditions of a nutraceutical system microencapsulated by spray drying

The adsorption isotherms of a nutraceutical system microencapsulated by spray drying were determined at 20, 35 and 40 °C. Experimental data of the isotherms were fitted using the GAB and Caurie models and the integral thermodynamic functions (enthalpy and entropy) were estimated by the Clausius-Clapeyron equation. The Kelvin and Halsey equations were adequate for calculation of pore radius which varied from 0.67 to 8.15 nm. The point of maximum stability (minimum integral entropy) was found between 3.61 and 3.81 kg H2O/100 kg d.s. (corresponding to water activity, aW, of 0.19-0.37). Enthalpy-entropy compensation for the microcapsules showed two isokinetic temperatures. The first isokinetic temperature was observed at low moisture contents (< 3.81 kg H2O/100 kg d.s.) and was controlled by changes in the entropy of water, whereas the second isokinetic temperature was considered to be enthalpy-driven (3.81-20 kg H2O/100 kg d.s.). Keywords: sorption isotherms, pore radius, minimum integral entropy, enthalphy-entropy compensation, water activity