## 3 Results and Discussion  
### Characterization of Emulsions  
The main reasons of using chitosan of medium molecular weight with moderate deacetylation degree (DD) were that it had been proven to have excellent film-forming properties, presenting higher mechanical properties (higher tensile strength) and better barrier properties (better weight loss control, lower water vapor permeability, lower respiration rate, lesser loss of flavor volatiles, and delay of the microbial growth) than those of lower molecular weight [14; 36; 37]. On the other hand, it is generally accepted that chitosan antimicrobial properties vary depending on the molecular weight and deacetylation degree. Usually, chitosan with lower molecular weight has higher antimicrobial activity than chitosan with high molecular weight [38; 39], supposedly due to an increased water solubility that stimulates the reaction with the active sites of the microorganisms [40]. When the antimicrobial activity depends on the polycation water-soluble structure, the increase in the deacetylation degree will improve this activity due to the electrostatic interaction between NH\({}^{+}\) groups of chitosan and the phosphoryl groups of the phospholipid component of the cell membrane of the microorganisms [41; 42; 43]. However, depending on the microorganism and the composition of its cells, the antimicrobial activity of chitosan can also be due to adsorption on the cell surface, which is also favored by a higher molecular weight (more hydrophobic interactions), especially for Gram-positive bacteria and fungi [44; 45]. Thus, we decided to combine the use of a polymer matrix and Rue essential oil, reinforcing the antimicrobial properties, which also allows a reduction of the diffusion rate and higher amounts of the antimicrobial agent on the surface of the fruit. In addition, chitosan in several investigations has been proved to inhibit microbial spoilage in fresh and minimally processed fruits and vegetables [36]. The potential of coatings to protect the fruit depends on the properties and stability of their forming emulsions [46]. The properties of the coating will depend on the molecular structure rather than the molecular size or the composition. Good elasticity and flexibility are essential in layers to prevent cracking during handling and storage. Usually, adding plasticizers like glycerol and sorbitol to the emulsion will accomplish this requirement. On the other hand, emulsifiers like tween 80 are added to improve the homogeneity of the hydrocolloid-forming emulsions, improving wettability also suppressing the ripening process without negatively affect the fruit quality [47]. Coatings should be prepared from materials than can solubilize in water and some additives such as plasticizers, antimicrobials, antioxidants, colors, flavors, that improve the quality and the perception of the fruits can be added to the emulsions. The pH and temperature can be adjusted to facilitate the dispersion of the polymer. For that reason, the pH of the emulsions was acid in all cases (Table 1). Acid pH will support chitosan dissolution. However, it increased with the essential oil content due probably to the adsorption of the CS chains on the surface of the essential oil drops, decreasing the amount of availability of some hydrogen ions and increasing the pH of the solutions. It has been recognized that the introduction of essential oil amounts to chitosan emulsions will decrease the overall availability of CS chains and a net charge change as a consequence, which also affects the hydrodynamic volume and zeta potential of the emulsions [48; 49]. The results obtained from the density analysis of the different emulsions show typical values of diluted emulsions. However, the values significantly increased (\(p<0.05\)) with the RGEO content, probably due to the increased concentration of essential oil in the dispersed phase of the emulsion. Similarly, the incorporation of RGEO had a significant effect (\(p<0.05\)) on the apparent viscosity.