Controlled release of L-tryptophan and Vitamin B2 from model water/oil/water multiple emulsions

Abstract

Stability and nutrient release from model water/oil/water (W/O/W) multiple emulsions based on kerosene oil, Span 80 and Tween 20 were studied. Multiple emulsion internal and external droplet sizes were ~1 and 7.5 μm respectively. The initial encapsulation yield was 92–98%. The apparent yield stability decreased to 85–87% after heating at 80°C for 20 min. The release of a nutrient, L-tryptophan ( L-Trp) or riboflavine-5′-monophosphate (Vitamin B2), from the W/O/W multiple emulsions was found to conform to first order kinetics for studies performed at pH 2–10. The rate of release was generally greater near the isolectric point of L-Trp or Vitamin B2. The permeability coefficient for nutrient release was in the range 0.32–1.92 × 10 −10 cm/s. This was 10 5–10 6-fold lower than the estimated permeability coefficient for water transfer across a W/O/W multiple emulsion oil phase. Therefore, we conclude that processes of nutrient release and water transfer within a W/O/W multiple emulsion occur via different routes.