Pectin emulsions and emulgels: Bridging the correlation between rheology and microstructure

Abstract

Pectin stabilized emulgel was fabricated following an emulsion guided approach. Properties of emulgel strongly depend on the properties of the emulsion which in turn is affected by the emulsifier (gelator). Fabrication of emulsion (20–40% oil v/v) using pectin isolated from passion fruit rind (2.0–4.0% w/v) was investigated to understand the changes in structural and rheological features on transformation from emulsion to emulgel. Passion fruit rind pectin demonstrated excellent emulsifying capacity by lowering the interfacial tension to 6 mN/m (for 4% w/v of pectin) of water and oil from an initial value of 12 mN/m. Concentration of pectin and the proportion of oil phase with respect to the water phase have a direct and inverse effect, respectively, on the physical stability of emulsion. Rheological evaluation showed yield stress for both emulsion and emulgel. Emulsion with 4% w/v of pectin and 20% v/v of oil was the most stable. Yield stress, yield strain and elastic modulus were found to increase on converting the emulsion to emulgel. Microstructure has given evidences of droplet aggregate formation and droplet entrapment inside the biopolymer matrix on emulgel formation. This study paves way towards understanding design, macroscopic properties and structure of sustainable fat substitutes for commercial purposes.