Physical and biological properties of alginate-based cinnamon essential oil nanoemulsions: Study of two different production strategies

Nanoemulsions are a promising alternative for essential oil incorporation into active coatings. The influence of the preparation steps order on nanoemulsions' physical properties is still little explored. This study aimed to analyze the effect of the sequence of preparation steps and of the oil and polymer concentration on the stability, physical properties, and antifungal activity of alginate-based cinnamon essential oil nanoemulsions. The nanoemulsions were produced by two strategies: (I) preparation directly into an alginate solution (Ultra-Turrax at 10,000 rpm for 5 min + Ultrasound 150 W for 3 min); and (II) preparation in water (Ultra-Turrax at 10,000 rpm for 5 min + Ultrasound 150 W for 3 min) followed by homogenization with a sodium alginate solution (Ultra-Turrax at 10,000 rpm for 1, 3 or 5 min). The nanoemulsion prepared by the second strategy showed better stability, physical properties, and antifungal activity. In general, the presence of alginate hindered the cavitation effects of ultrasound, leading to the increase of droplets size and consequently affecting emulsions stability, turbidity, and antifungal properties.