Effects of chitosan coating on curcumin loaded nano-emulsion: Study on stability and in vitro digestibility

• Nano-emulsion loaded with curcumin increased its water dispersibility.
• Chitosan with various molecular weight was used to coat nano-emulsion.
• Chitosan coating increased physical and chemical stability of curcumin.
• Chitosan coating slightly decreased the bio-accessibility of curcumin.

Nano-emulsion (NE) composed of MCT oil, Tween 80 and lecithin was fabricated by ultrasonication method to encapsulate curcumin. Loading ability and efficiency of curcumin were 0.548 mg/mL and 95.10% respectively which indicated its water dispersibility was increased by 1400 fold. Chitosan with low, middle and high molecular weight (3 kDa, 30 kDa and 190–310 kDa respectively) was applied for coating the prepared NE. After chitosan coating, zeta potential value of NE was changed from negative to positive. At the same time, chitosan coating prevented NE phase separation in ionic strength test and inhibited degradation of curcumin during thermal and UV irradiation treatment. Using pH-stat method, it was found that middle and high molecular weight chitosan coating may interfere with lipolysis of NE during the in vitro digestion which also slightly decreased curcumin bio-accessibility. Therefore, NE coated with chitosan is a promising delivery system to promote the applications of curcumin in functional food and beverage system.

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