Water-in-oil microemulsion: effect of Desmodium intortum protein isolate–emulsifier interaction, and its stability

Abstract

Water-in-oil (W/O) microemulsions exhibit delivery matrix and exhibit poor lipid solubility. Therefore, increasing the stability of W/O microemulsions is necessary to broaden their applications. In our experiment, a protein microemulsion system was constructed and its stability was investigated. The effects of surfactants, co-surfactants, quality ratio of them (Km) and hydrophilic-lipophilic balance (HLB) values were determined by using the pseudo-ternary phase diagrams and the area of microemulsions (MEs) as the indexes. The results showed that MEs’ stability was the best when the limonene was used as oil phase, Tween 20 + span 80 as the surfactant, and anhydrous alcohol as co-surfactant, if and only if HLB = 6.0 and Km = 3:1. Under this condition, the area of micro-emulsion was the largest, and the quality of microemulsion was better when the mass ratio of oil phase and emulsifier was 7:5.The protein microemulsion was a water-in-oil type, with a particle size of 1.41 ± 0.03 μm, containing 1127.37 ± 30.87 μg/g of proteins. Moreover, the temperature, light, and sample observation tests showed that the solution’s protein retention rate was lower than those in the microemulsion. Low-concentration NaCl, less than 9% of glucose and maltose exerted no significant influence on the protein microemulsion stability.