Eur Food Res Technol (2007) 225:375–384 DOI 10.1007/s00217-006-0427-5 ORIGINAL PAPER Antimicrobial performance of potassium sorbate supported in tapioca starch edible films Silvia Flores · Ana Silvia Haedo · Carmen Campos · L´ ıa Gerschenson Received: 13 April 2006 / Revised: 18 June 2006 / Accepted: 24 June 2006 / Published online: 26 July 2006 C  Springer-Verlag 2006 Abstract The release and antimicrobial activity of potas- sium sorbate (KS) supported in tapioca starch–glycerol ed- ible films prepared by different gelatinization/drying tech- niques against Zygosaccharomyces bailii was studied. An- timicrobial release in liquid media of different pHs (3.0– 6.0) could be approximated to a pseudo first-order kinetic model and was almost accomplished after 30 min. Filmmak- ing method involving slow gelatinization and drying rate re- sulted in the highest fraction of KS released at equilibrium. Rate constant was higher when pH of the receiving media was 4.5 and fast gelatinization/fast drying had been used. The effectiveness of the preservative released for controlling the microbial growth depended on the pH of the receiving me- dia, being higher at pH 3.0. No effect of filmmaking method was observed. In relation to film effectiveness as a barrier to contamination, it was observed that the preservative was available to prevent an external Z. bailii contamination and also to control yeast growth in an acidified (pH 4.5) high water activity (a w = 0.980) semisolid product. Keywords Starch . Sorbates . Edible film . Filmmaking method . Preservative release . Antimicrobial performance S. Flores · C. Campos · L. Gerschenson () Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Ciudad Universitaria, 1428 Buenos Aires, Argentina e-mail: lia@di.fcen.uba.ar Tel.: + 54-11-4576-3366 Fax: + 54-11-4576-3366 A. S. Haedo Departamento de Computaci ´ on, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Ciudad Universitaria, 1428 Buenos Aires, Argentina Introduction Edible films and coatings are proposed to be used for food product protection, improving quality and shelf life without impairing consumer acceptability [1–4] Edible films are not designed for totally replacing tradi- tional packaging. They might be used as a stress factor to help to assure a long and adequate shelf life. They can con- trol moisture, gases, lipid migration and can also be carriers of additives and nutrients. Hydrocolloids such as cellulose, gums, starch and proteins have been used to formulate edible films, and plasticizers are usually employed (i.e., glycerol, sorbitol, polyethylene glycol) to enhance their mechanical properties [5–7]. Edible antimicrobial films and coatings have shown to be an efficient alternative in controlling food contamination. Durango et al. [8] reported that the growth of both deteri- orating and pathogenic microorganisms may be prevented through the incorporation of antimicrobial agents into ed- ible films. In the last years, research has been performed concerning the use of edible films for surface application of natamycin, benzoate, and potassium sorbate [9, 10] and for slow release of lysozime, nisine [11–13], and propylparaben [14]. According to legislation and labeling in the USA, edible coatings and films are considered a part of the food; as a consequence, their ingredients must comply with the CFR and be declared on the label under the Federal Food, Drug, and Cosmetic Act [15]. The European Union (EU) considers that an edible film is a special active part of the food and from a legal point of view, it is to be regarded as a food- stuff, along with the food packed in the film, having to fulfill the general requirements for food [16]. However, each coun- try has clear regulations regarding the addition of preser- vatives to food, which often include purity requirements, Springer