ORIGINAL ARTICLE Characterization of cross-linked whey protein isolate-based films containing Satureja Khuzistanica Jamzad essential oil Farzaneh Kouravand | Hossein Jooyandeh | Hassan Barzegar | Mohammad Hojjati Department of Food Science and Technology, Faculty of Animal and Food Science, Ramin Agriculture and Natural Resources University of Khuzestan, Mollasani, Khuzestan, Iran Correspondence Hossein Jooyandeh, Department of Food Science and Technology, Faculty of Animal and Food Science, Ramin Agriculture and Natural Resources University of Khuzestan, Mollasani, Khuzestan, Iran. Email: hosjooy@yahoo.com Funding information Ramin Agriculture and Natural Resources University of Khuzestan Abstract Whey protein films containing antimicrobial compounds provide another layer of protection and thereby may extend the shelf life of food products. In this research, the effect of Satureja khuzis- tanica Jamzad essential oil (SKJEO) at the concentrations of 0 (as control), 0.5, 1, and 2% (wt/wt, in the film forming solution) on the characteristics of cross-linked whey protein isolate-based films was studied. The films incorporated with SKJEO had significantly (p < .05) lower moisture content (MC), total soluble maters (TSM), and tensile strength (TS) but the higher water vapor permeability (WVP) and elongation at break (EB) compared to the control. Control had uniform microstructure, while the films incorporated with SKJEO showed lumpy surface. The films incorporated with the SKJEO had good antimicrobial properties, the higher SKJEO concentration, and the stronger anti- microbial activity. Pseudomonas aeruginosa was the most resistant bacteria, and Staphylococcus aureus was the most sensitive bacteria against SKJEO. Based on our results, it is suggested to use of the SKJEO as a natural antibacterial agent in food packaging particularly those that are highly sensitive to microbial deterioration. Practical applications Edible films and coatings have been developed in food conservation for many years. Antimicrobial packaging is a form of active packaging that could extend the shelf life of product and provides microbial safety for consumers. Whey proteins films have good barrier properties against organic vapor, gas, and oil as related to artificial films. Our study showed that the SKJEO has remarkable antibacterial activity, which can be applicable to prevent of various food-related diseases caused by bacteria. Nevertheless, further studies are required to understand the mechanisms of anti- microbial action of SKJEO against microorganisms and more information is mandatory on safety, efficacy, and toxicity for its usage as a natural preservative in different food products. The cross- linked WPI-based film containing SKJEO is a favorable resource for the packaging industry since it offers a maintainable and biodegradable packaging material that provides all the packaging materi- als requirements. 1 | INTRODUCTION To offer healthy foods, it is important to protect them against physico- chemical and biological changes. Packaging material retains the safety and superiority of foodstuffs during transportation and storage. Edible films and coatings have been developed in food conservation for many years. Recently, a considerable interest and advances in biodegradable edible packaging have seen due to its benefits and potential uses (Atar es, De Jes us, Talens, & Chiralt, 2010). Edible films and coatings can be used to provide high quality, fresh-like, and safe food products. Precisely, an edible film is a thin continuous sheet formed from a biopolymer matrix (polysaccharides, proteins, and lipids) that is cohe- sive enough and has the physical integrity to stand-alone (Jooyandeh, 2011). Protein-based edible films and coatings have been well docu- mented due to their functional properties and nutritional aspects (Debeaufort, Quezada-Gallo, & Voilley, 1998; Krochta & De Mulder- Johnston, 1997; Jooyandeh, 2011; Ozdemir & Floros, 2008; Ramos et al., 2012). Among protein biofilms, milk proteins have been extensively studied owing to their excellent nutritional values and their numerous functional properties, which are important for the formation of edible films (Sabato et al., 2001). These edible films have good mechanical strength and are excellent oxygen, lipid, and aroma barriers; J Food Process Preserv. 2017;e13557. https://doi.org/10.1111/jfpp.13557 wileyonlinelibrary.com/journal/jfpp V C 2017 Wiley Periodicals, Inc. | 1 of 10 Received: 21 June 2017 | Revised: 14 September 2017 | Accepted: 27 October 2017 DOI: 10.1111/jfpp.13557