Composition of Candelilla Wax Fractions and Their Relationship to Microstructural and Rheological Properties of W/O Emulsions

Abstract

Using candelilla wax (CW) fractions obtained through solid–liquid extraction with solvents of different polarity, we established the role of the CW components to develop W/O emulsions. The CW fractions obtained had different proportions of n-alkanes, triterpenic alcohols, fatty acids, fatty alcohols, and long chain esters. All CW fractions insoluble in the solvents formed oleogels that, upon water addition (50:50 wt:wt) and stirring, developed W/O emulsions structured by water droplets stabilized through a Pickering effect. The fractions with the higher concentration of long chain esters and n-alkanes (≈77%–80%) developed the emulsions with the smaller water droplet diameter (WDD; 97.5% of the droplets had WDD ≤ 20 μM) and the higher elasticity (G′ = 5758 Pa). In contrast, fractions with lower concentration of long chain esters and n-alkanes (≈61%–63%) developed emulsions with larger WDD (≤ 28.5 μM) and lower G′ (1734 Pa). The fraction with the highest concentration of fatty acids (≈26%) developed emulsions with WDD ≤ 20 μM and G′ = 2205 Pa and showed high stability to freeze–thaw cycles despite having the lower long chain esters and n-alkanes concentrations (≈60%). We concluded that the emulsions' elasticity depended on the microstructure developed in the continuous phase by the co-crystallization of n-alkanes and long chain esters, and on the emulsions' WDD. The results obtained showed that the fatty acids and n-alkanes stabilized the emulsions through a Pickering effect. Although during emulsification, the triterpenic alcohols might decrease the surface tension at the oil–water interface, they were not involved in the Pickering effect observed in the W/O emulsions developed by the CW.