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Many traditional industrial products are being gradually replaced by environmental friendly alternatives. N,N-Dimethyldecanamide and D-limonene are solvents that fulfil the requirements to be considered green solvents and may find application in agrochemicals. This contribution deals with the study of emulsions formulated with a mixture of these solvents and an eco-friendly emulsifier. The procedure followed for the development of these formulations was based on the application of product design principles. This led to the optimum homogenization rate and subsequently to the optimum ratio of solvents. The combination of different techniques (rheology, laser diffraction, confocal laser-scanning microscopy, and multiple light scattering) was demonstrated to be a powerful tool to assist in the prediction of the emulsions destabilization process. Thus, we found that the optimum ratio of solvents was 75/25 (N,N-dimethyldecanamide/D-limonene) on account of the lack of coalescence and of a low creaming rate.Standard deviation of the mean (three replicates) for D 2,3 < 5%. Standard deviation of the mean (three replicates) for uniformity < 5%.

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BACKGROUND: White thyme essential oil, which can be incorporated in clean-label and food emulsion-based products, is a natural antimicrobial agent. However, emulsions containing essential oils commonly undergo Ostwald ripening as the main destabilization process. The main objective of this work was to evaluate various strategies for the inhibition of Ostwald ripening so as to develop stable nanoemulsions containing white thyme essential oil as food preservative and Kolliphor EL as surfactant.RESULTS: In a first approach, the influence of the surfactant/dispersed phase ratio and the number of cycles through a microfluidizer on droplet size distribution was evaluated. Unfortunately, these emulsions underwent Ostwald ripening, which was demonstrated by the application of the Lifshitz-Slyozov-Wagner theory. In order to reduce this destabilization mechanism, two different techniques based on the modification of the formulation (addition of rosin gum or Aerosil COK84) were analysed using laser diffraction and multiple light scattering techniques. The addition of rosin gum inhibited the Ostwald ripening mechanism, but only partially. Conversely, the incorporation of Aerosil COK84 to the continuous phase led to a gel-like rheological behaviour which seemed to practically avoid Ostwald ripening. CONCLUSIONS: Aerosil particles cover the droplets and form a three-dimensional network suggesting a Pickering stabilization, which was confirmed using transmission electronic microscopy. The results confirmed the role of Aerosil COK84, not only as a thickener or gelling agent, but also as an Ostwald ripening inhibitor.

10Finding alternatives to traditional organic solvents is one area in green chemistry, 11 which has generated great interest in recent years. This work provides new possibilities 12 for the preparation of ecological oil-in-water (O/W) emulsions. Model emulsions that 13 may be used as matrices for agrochemical formulations have been investigated. 14 Specifically, this paper deals with O/W emulsions formulated with a mixture of green 15 solvents and a polyoxyethylene glycerol ester as emulsifier. Firstly, an optimum ratio of 16 solvents was found, after which the droplet size distribution, physical stability and flow 17 properties of emulsions obtained using two rotor-stator devices (toothed geometry vs 18 emulsor screen) and two high-pressure homogenizers (high pressure valve 19 homogenizer, HPVH, vs Microfluidizer) were compared using several processing 20 variables. Considering its low Turbiscan stability index and the absence of 21 coalescence, 75/25 (N,N-dimethyldecanamide/α-pinene) was the optimum ratio of 22 biosolvents. All samples showed droplet sizes with submicron diameters (both 23 volumetric and Sauter means). However, both high-pressure homogenizers yielded 24 smaller droplet sizes than rotor-stators. The combined use of multiple light scattering, 25Rheology and Laser Diffraction allowed the destabilisation processes of emulsions to 26 be monitored. The results obtained demonstrated that the emulsions prepared with a 27 Y-shaped Microfluidizer at 15000 psi (103.4 MPa) and 1-pass exhibited the highest 28 physical stability. 29