Encapsulation Properties of Mentha piperita Leaf Extracts Prepared Using an Ultrasound-Assisted Double Emulsion Method

Abstract

Double emulsions (W₁/O/W₂) have long been used in the food and pharmaceutical industries to encapsulate hydrophobic and hydrophilic drugs and bioactive compounds. This study investigated the effect of different types of emulsifiers (plant- vs. animal-based proteins) on the encapsulation properties of <i>Mentha piperita</i> leaf extract (MLE) prepared using the double emulsion method. Using response surface methodology, the effect of ultrasound-assisted extraction conditions (amplitude 20-50%; time 10-30 min; ethanol concentration 70-90%) on the total phenolic content (TPC) and antioxidant activity (percent inhibition) of the MLE was studied. MLE under optimized conditions (ethanol concentration 76%; amplitude 39%; time 30 min) had a TPC of 62.83 mg GA equivalents/g and an antioxidant activity of 23.49%. The optimized MLE was encapsulated using soy, pea, and whey protein isolates in two emulsifying conditions: 4065× <i>g</i>/min and 4065× <i>g</i>/30 s. The droplet size, optical images, rheology, and encapsulation efficiency (EE%) of the different encapsulated MLEs were compared. The W₁/O/W₂ produced at 4065× <i>g</i>/min exhibited a smaller droplet size and higher EE% and viscosity than that prepared at 4065× <i>g</i>/30 s. The higher EE% of soy and pea protein isolates indicated their potential as an effective alternative for bioactive compound encapsulation.