Abstract
Emulsions can be used as delivery systems for bioactive ingredients for their incorporation in food products. Essential oils are natural compounds found in plants that present antioxidant and antimicrobial activity. Therefore, the main goal of this work was to develop emulsions, containing mandarin essential oil stabilized by two food-grade surfactants and guar gum, and to evaluate their physical stability. The initial droplet size of emulsions developed by microfluidization was optimized, obtaining diameters below one micron regardless of the processing conditions. However, the emulsion processed at 25,000 psi and one pass exhibited the lowest mean droplet sizes and polidispersity, and therefore, a higher stability. Different ratios of Tween 80 and Span 80 were assessed as stabilizers. Results obtained indicated that the ratio of surfactants had a significant effect on the mean droplet sizes, physical stability, and rheological properties. Thus, we found that the optimum ratio of surfactants was 75/25 (Tween80/Span80) on account of the lowest droplet mean diameters, lack of coalescence, and a low creaming rate. The rheological characterization of the stable emulsions showed a shear thinning flow behavior, and G″ (loss modulus) values higher than G′ (storage modulus) values, in all the frequency range. The rheological behavior may be governed by the guar gum, which was confirmed by field emission scanning electron microscopy (FESEM). This research can be considered as the starting point for future applications of mandarin essential oil in emulsions, which can be incorporated in products as food preservatives.
Highlights
In recent years, the importance of using essential oils in the formulation of antimicrobial products and their role as natural biocides has increased [1,2]
Mandarin essential oils were successfully incorporated as dispersed phase in stable food-grade
Mandarin essential oils were successfully incorporated as dispersed phase in stable food-grade emulsions formulated with guar gum
Summary
The importance of using essential oils in the formulation of antimicrobial products and their role as natural biocides has increased [1,2]. Most essential oils are generally recognized as safe (GRAS) substances [3]. Due to their antibacterial [4], antifungal [5], antiviral [6], and insecticidal activities [7], essential oil-based products are used in the food, agrochemical, pharmaceutical, cosmetic, and medical fields. The lipophilic character of essential oils means that these solvents cannot be directly dispersed into an aqueous phase. This fact, in combination with their antioxidant activity [9], means that they are suitable for being encapsulated into a variety of different colloidal delivery systems, with the most common being emulsions [10]
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