Antifungal and functional properties of starch-gellan films containing thyme (Thymus zygis) essential oil

[EN] Films based on starch-gellan blends at 9:1 and 8:2 ratios containing emulsified or lecithin encapsulated thyme (Thymus zygis) essential oil (EO) (0.25 or 0.5 g/g polymer), were obtained by casting method and characterized as to their structural, functional (mechanical, barrier and optical) and in vitro antifungal properties against Alternaria alternata (AA) and Botryotinia fuckeliana (BF). The EO retention during the film formation was also quantified. Lecithin encapsulation of the EO allowed for greater oil retention (45-55%), which enhanced the antifungal activity of the films, which were more effective against BF than AA. All films exhibited high oxygen barrier capacity, while lecithin improved the films water barrier properties and gloss, conferring them with a slightly brownish color. Lecithin also reduced the film stiffness and resistance to break and extensibility. Of the studied formulations, 8:2 S:G films with lecithin-encapsulated EO were very effective at controlling fungal growth, while exhibiting adequate functional properties as packaging/coating materials.The authors acknowledge the financial support for this study from the Ministerio de Economia y Competitividad (MINECO) of Spain, through the project AGL2016-76699-R. Mayra Sapper thanks the Conselleria de Educacion, Investigacion, Cultura y Deporte de la Comunitat Valenciana for the Santiago Grisolia grant GRISOLIA/2015/001.Sapper, MI.; Wilcaso, P.; Santamarina Siurana, MP.; Rosello Caselles, J.; Chiralt, A. (2018). Antifungal and functional properties of starch-gellan films containing thyme (Thymus zygis) essential oil. Food Control. 92:505-515. https://doi.org/10.1016/j.foodcont.2018.05.004S5055159

Encapsulación de aceite esencial de tomillo en lecitina para su incorporación de films de almidón-gelano

[EN] The effect of the incorporation of thyme essential oil (EO) by direct emulsification or previous encapsulation in lecithin liposomes (LEC), in cassava starch (S) and gellan gum (GG) films (90:10 and 80:20) obtained by casting, was evaluated. The 12 different formulations (with and without 0,25 or 0,5 g of AE/g of polymer) were characterized in terms of their mechanical, barrier, optical, structural and solubility properties. EO loss in the active films was determined. Essential oil retention in the film increased with the encapsulation (between 42 and 56% of the incorporated), as compared to the incorporation by direct emulsification (between 4 and 26% of the incorporated). The addition of LEC and/or AE led to changes in the film properties. From the mechanical point of view, films became less resistant to fracture, with lower values of the elastic modulus. The water vapor and oxygen permeability, and the hygroscopic character of the films (solubility and water adsorption capacity) improved in some formulations with the incorporation of EO. As regards optical properties, EO decreased the gloss of the films and the colour saturation increased with the incorporation of LEC. Thus, the formulation that allowed for obtaining the best films, considering the essential oil retention and the functional properties as packaging material, was that containing starch-gellan (80:20) and 0,25 g of EO/g of polymer encapsulated in LEC (0,5 g/g of polymer). The encapsulation of volatile active compounds in lecithin liposomes emerges as a good strategy to obtain antimicrobial films.[ES] Se ha analizado el efecto de la incorporación de aceite esencial de tomillo (AE) mediante emulsificación directa y con encapsulación previa en liposomas de lecitina (LEC), en films a base de almidón de yuca (S) y goma de gelano (GG) (90:10 y 80:20) obtenidos por casting. Las 12 formulaciones (con y sin 0,25 o 0,5 g de AE/g de polímero) se caracterizaron en cuanto a sus propiedades mecánicas, de barrera, ópticas, estructurales y solubilidad. Se analizaron las pérdidas de AE en los films activos. La retención del aceite esencial en el film incrementó considerablemente con la encapsulación (entre el 42 y 56% del incorporado), frente al emulsionado en forma libre (entre el 4 y 26% del incorporado). La adición de LEC y/o AE supuso cambios en las propiedades de los films. Desde el punto de vista mecánico, los films se volvieron menos resistentes a la fractura, con menor módulo de elasticidad. La permeabilidad al vapor de agua y al oxígeno, y el carácter higroscópico de los films (solubilidad y capacidad de adsorción de agua) mejoraron en algunas formulaciones con la incorporación del AE. Respecto a las propiedades ópticas, el AE disminuyó el brillo de las películas y la saturación del color aumentó con la incorporación de LEC. Así, la formulación que permitió obtener los mejores films, considerando la retención de aceite esencial y las propiedades funcionales como material de envase o recubrimiento fue la que contenía almidón-gelano (80:20) y 0,25 g de AE/g de polímero, encapsulado en LEC (0,5 g/g de polímero). La encapsulación de compuestos activos volátiles en liposomas de lecitina representa una buena estrategia para la obtención de films con capacidad antimicrobiana.Wilcaso Fajardo, MP. (2017). Encapsulación de aceite esencial de tomillo en lecitina para su incorporación de films de almidón-gelano. http://hdl.handle.net/10251/87246.TFG

Modeling of Production and Quality of Bioethanol Obtained from Sugarcane Fermentation Using Direct Dissolved Sugars Measurements

Bioethanol production from sugarcane represents an opportunity for urban-agricultural development in small communities of Ecuador. Despite the fact that the industry for bioethanol production from sugarcane in Brazil is fully developed, it is still considered expensive as a small rural business. In order to be able to reduce the costs of monitoring the production process, and avoid the application of expensive sensors, the aim of this research was modeling the kinetics of production of bioethanol based on direct measurements of Brix grades, instead of the concentration of alcohol, during the process of cane juice bio-fermentation with Saccharomyces cerevisiae. This avoids the application of expensive sensors that increase the investment costs. Fermentation experiments with three concentrations of yeast and two temperatures were carried out in a laboratory reactor. In each case Brix grades, amount of ethanol and alcoholic degree were measured. A mathematical model to predict the quality and production of bioethanol was developed from Brix grade measurements, obtaining an adjusted coefficient of determination of 0.97. The model was validated in a pilot plant