Estabilidade de emulsões á base de goma de cajueiro e óleo essencial de alecrim

Abstract

Cashew gum has been highlighted because of its marked chemical and physical properties due to its polysaccharide composition, such as gelling properties, stabilizers and, mainly, emulsifiers, among others, which allow its use in a variety of industrial applications. Thus, the present work aims at the analysis of the emulsions stability based on cashew gum with rosemary essential oil and the mixture of Span 80 and Tween 80 surfactants in different hydrophilic-lipophilic balance compositions (HLB). The analyzes of turbidity, zeta potential, mean particle size distribution and optical microscopy, as well as the macroscopic evaluation of phase separation, are performed 24 hours and 7 days after emulsion preparation, with HLB = 4.3, 5.0, 6.0, 7.0, 8.0, 9.0, 15.0, and GC (absence of surfactants). The macroscopic phase evaluation results indicates greater stability for 4,3≤HLB≤6,0 emulsions, which present foam percentage <4%, with no changes observed during 7 days. Analysis of the zeta potential for all emulsions has lower values (||>25mV) than those generally acepted for stable emulsions (||>25mV), whereas mean particle size distributions in 24 hours have diameters between 500-700nm (8.0≤HLB≤15.0) and 700-5000nm (4.3≤HLB≤7.0), corroborating with the turbidity observations, where at 24 hours presents higher values (>300 cm-1) for the emulsions with 4.3≤HLB≤7.0, while emulsions with 8.0 ≤HLB≤15.0 had values <150 cm-1, its behaviour is due to the low concentration of dispersed particles, as confirmed by the microscopy analysis, where these emulsions 8.0 ≤HLB≤15.0, also presents instability mechanisms such as flocculation and coalescence. In general, the results indicated an additional stability for the emulsions with values of 4.3≤HLB≤7.0, when compared to the emulsion GC, and, due to the analyzed properties variations with less significance in the 7- day period, then suggesting the emulsion with HLB = 6.0 as the most stable.