Surface properties modification of vanilla pods (Vanilla planifolia) treated with ultrasound probe to increase the efficiency of solid-liquid extraction

Karen Aylin Vargas García¹Magbis Azgad Aguilar García¹Luz Araceli Ochoa Martínez²Blanca Edith Esquivel González²Karina Bustos Ramirez¹Gilda Avendaño Vásquez¹Elizabeth del Carmen Varela Santos^1*

• ¹Instituto Tecnológico Superior de Tierra Blanca, Tierra Blanca, Mexico
• ²Instituto Tecnologico de Durango, Durango, Mexico

Vanilla is a flavoring of great culinary value worldwide. The conventional extraction process represents long time and high production costs, due to the characteristics of the pod, which contains compounds such as waxes, gums, resins, and fixed oils among others. This research introduces an ecofriendly methodology to increase the efficiency of solid-liquid extraction on vanilla pods using a sustainable alternative. Ultrasound processing conditions were time (2, 4, 6, 8 and 10 min), amplitude (50, 75 and 100 %), and solvent (0, 60 and 100 % EtOH), a solid: liquid ratio 1:10 (pod: solvent) was used. The effect of the pre-treatment on extraction efficiency was evaluated as a function of the vanillin concentration (yield). The optimization of the process was carried out with the Minitab 17 software. Surface properties were evaluated in terms of contact angle, adhesion work and surface energy using the drop method (Drop snake software and LB-ADSA) and the Young and Dupré equations. Surface contact regime was employed to show the induced microstructure and hydrophobic-hydrophilic character after ultrasound pre-treatment. Results suggested that the optimal pre-treatment was 10 min, 100 % amplitude, and 60 % ethanol; obtaining an extraction yield of vanillin of 2703.45±33.25 μg/mL with significant difference respect at control by Natural Convection (1701.33±23.85 μg/mL, p>0.05, R2>99). Reductions in contact angle in addition to high work adhesion and surface tension values showed the hydrophilic character of the vanilla pods, and confirmed the modification of surface properties and the open of diffusion channels related to the increase of the solvent intrusion on the vanilla pods surface after the ecological physical treatment. Results from this work indicate that the applicability of ultrasound as a pre-treatment in the solid-liquid extraction process might further improve the performance in the extraction of vanillin, and the reduction in the extraction time.