Application of Konjac glucomannan to encapsulate and stabilize the curcumin in milk system

Abstract

This study investigated the influence of different concentration of konjac glucomannan (KGM) (0, 0.1, 0.2, 0.3 % (w/v)) on the stability of curcumin emulsion in milk system containing 10%, 20%, and 30% (v/v) oil volume fraction. The data of creaming index, curcumin concentration, apparent viscosity, and color were obtained to investigate the stability of the system. Emulsions that reached the physical stability until 14 days of storage at 4ᵒC were subjected to further analysis including antioxidant, particle size, zeta potential, and bioaccessibility by the simulated gastrointestinal tract (GIT). The result suggested that increasing KGM concentration significantly increased the viscosity of the water phase, following by increasing the viscosity of the emulsion system. The viscosity result is related to the increase of creaming stability when KGM concentration is increased from 0.1% to 0.2% w/v KGM containing higher oil volume fraction. However, emulsions containing 0.3% KGM showed poor creaming stability due to depletion flocculation. The result showed that increasing KGM concentration had no significant impact on the concentration of curcumin and had no significant impact on the yellowness (b* value) in the final emulsion. However, the increased oil phase volume fraction significantly increased the curcumin concentration and b* value of emulsions due to the increasing of curcumin content that added together with oil into the system. The emulsions containing 20% v/v oil significantly showed a better loading capacity compared to 10% v/v and 30% v/v oil, suggesting that there were a sufficient concentration of native emulsifier (milk protein) and KGM to cover and stabilize oil droplet containing curcumin in 20% v/v oil. DPPH and FRAP assay showed the antioxidant activity of emulsion remained stable over 14 days of storage at 4ᵒC and was related to the concentration of curcumin in the system. However, there is no significant effect of KGM concentration on the antioxidant activity. Addition of KGM can potentially slower the release of curcumin from the emulsion droplet during the upper part of GIT. The result indicated that introducing KGM to the water phase of emulsions is feasible to achieve a controlled release of curcumin from emulsions. Finding in this study denoted that structuring water phase with the low concentration of KGM could be possible to design curcumin in milk system containing high oil-phase fraction with potential emulsion stability and control release properties.