Preparation and characterization of water-in-oil emulsions loaded with high concentration of l-ascorbic acid

Abstract

The present study was conducted to encapsulate higher concentration of l-ascorbic acid up to (30 g 100 mL−1) in the dispersed phase of water-in-oil (W/O) emulsions. Their continuous phase contained refined soybean oil or Moringa oleifera oil and a food-grade hydrophobic emulsifier. The volume fraction of the dispersed phase was fixed as to 30%. W/O emulsions with l-ascorbic acid retention greater than 95% were prepared using rotor–stator homogenizer at 7000 rpm for 5 min. The prepared W/O emulsions under this operating conditions had average droplet diameter of 2.0–3.0 μm and coefficients of variation of 13%–22%. All the W/O emulsions were stable for more than 30 days at 4 °C or 25 °C with slight increase in average droplet diameter and without phase separation. Their l-ascorbic acid retentions were 50 g 100 g−1 at 4 °C and 30 g 100 g−1 at 25 °C after 30 days of storage. l-ascorbic acid retention ratio of the prepared W/O emulsions followed first-order kinetics with a good fit.