Research Article Conditions to Prolonged Release of Microencapsulated Carvacrol on Alginate Films as Affected by Emulsifier Type and PH Silvia Matiacevich, 1 Natalia Riquelme, 1 and María Lidia Herrera 2 1 Departamento de Ciencia y Tecnolog´ıa de los Alimentos, Facultad Tecnol´ ogica, Universidad de Santiago de Chile, Obispo Uma˜ na 050, Estaci´ on Central, 9170201 Santiago, Chile 2 Instituto de Tecnolog´ıa en Pol´ımeros y Nanotecnolog´ıa ITPN (UBA-CONICET), Facultad de Ingenier´ıa, Universidad de Buenos Aires, Avenida Las Heras 2214, Ciudad Aut´ onoma de Buenos Aires, Argentina Correspondence should be addressed to Silvia Matiacevich; silvia.matiacevich@usach.cl Received 23 July 2015; Revised 13 October 2015; Accepted 20 October 2015 Academic Editor: Dilip Depan Copyright © 2015 Silvia Matiacevich et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Alginate from algal biomass is used as edible film and the incorporation of antimicrobial agents improves its performance to increase the shelf-life of fresh foods. However, environmental conditions and intrinsic properties of films influence their release. e aim of this study was to investigate the effect of the concentration and type of encapsulating agent and pH of emulsions on the physical and antimicrobial properties of alginate-carvacrol films. Films containing alginate, carvacrol as antimicrobial agent, and Tween 20 or trehalose (0.25 and 0.75%w/w) as encapsulating agents were obtained from suspensions at pH 4 and pH 8. Physical characterization of emulsions and films and antimicrobial properties (E. coli and B. cinerea) was evaluated. Results showed that droplets size depended on trehalose concentration, but emulsion stability depended on pH and type of encapsulating agent, being more stable samples with trehalose at pH 4. Although films with Tween 20 presented the highest opacity, they showed the best antimicrobial properties at initial time; however, during storage time, they lost their activity before samples with trehalose and relative humidity (RH) was the principal factor to influence their release. erefore, sample formulated with 0.25% trehalose at pH 4 and stored at 75% RH had the best potential as edible film for fresh fruits. 1. Introduction Edible films and coatings can be considered an additional stress factor for preserving food products, assuring its quality as well as an increased shelf-life. e use of edible films is gaining importance in the protection and preservation of fresh food, as they have the ability to contain antimicrobial active ingredients and compounds that can prolong their shelf-life and reduce the risk of pathogen growth on its surface [1–6]. Films and coatings can support antimicrobials agents, but matrix structure stability, concentration of the product on the surface, and gradual release into food are all important characteristics for its functionality; therefore it is important to take into account these characteristics in the use of films or coatings [2]. In development of active edible films and coatings with antimicrobial properties, addition of essential oils (EOs) from herbs and spices has been extensively used as antimicrobial agents. In this sense, Rojas-Gra¨ u et al. [7, 8] evaluated the antimicrobial activities against E. coli O157:H7 of sev- eral EOs (oregano, cinnamon, and lemongrass) and active oil compounds (OCs), such as carvacrol, cinnamaldehyde, and citral, incorporated on alginate-apple puree edible film in concentrations lower than 0.5%w/w. In those systems, carvacrol exhibited the strongest antimicrobial activity as measured by the film disk agar diffusion assay as a qual- itative test for antimicrobial activity of the films. Besides, optimal antimicrobial effects were observed using carvacrol concentration of 1.0% w/w added to the initial apple [9] and tomato [10] films preparation against E. coli O157:H7. Hindawi Publishing Corporation International Journal of Polymer Science Volume 2015, Article ID 173193, 12 pages http://dx.doi.org/10.1155/2015/173193