Antimicrobial films for food applications: a quantitative analysis of their effectiveness

Abstract

A tremendous effort has been made over the last decade to develop and test films with antimicrobial properties to improve food safety and shelf life. This review catalogues and analyses the outcome of these research efforts. The bacteriocin nisin was the antimicrobial most commonly incorporated into films, followed by foodgrade acids and salts, chitosan, plant extracts, and the enzymes lysozyme and lactoperoxidase. The methodologies for measuring antimicrobial activity of both edible and inedible films varied considerably among the studies. Results, defined as the difference in the log 10 colony-forming unit (CFU) of a test organism exposed to a control film and the log 10 CFU of the organism exposed to the antimicrobial film, ranged from 0 to 9 for many of the antimicrobials tested. Even for antimicrobials such as nisin, chitosan or antimicrobial acids with a 'long' history of studying their incorporation into antimicrobial films, the majority of results centred around 2 log 10 reductions. The results suggest that antimicrobial films still face limitations and are perhaps still best viewed as part of a hurdle strategy to provide safe foods. SCOPE AND LIMITATIONS OF THE REVIEWThe development and testing of antimicrobial films for wrapping or coating foods has become a worldwide endeavour over the last decades, and this effort has produced a diverse range of film types utilizing an assortment of antimicrobial compounds. A number of review articles have described the nature of these films and their antimicrobial constituents, their construction and general effectiveness, 1-9 but what appears to be absent from the literature is a comparative analysis of how well the different types of films have performed overall towards the goal of eliminating or reducing foodborne pathogens or of extending shelf life. Therefore, this review aims to summarize and, as much as possible, analyse quantitative results of microbiological assays conducted over the last decade involving antimicrobial films intended for use in foods.An even very cursory glance at the literature of antimicrobial film studies reveals a field that uses multiple methodological approaches to the common goal of measuring the efficacy of newly created films. The literature is not only diverse with respect to the way experiments were carried out, but also the way the results were reported.

Development of activate-at-home-type edible antimicrobial films: An example pH-triggering mechanism formed for smoked salmon slices using lysozyme in whey protein films

“…Different natural antimicrobials including antimicrobial enzymes, bacteriocins, essential oils and phenolic compounds can be employed in active packaging (Cha & Chinnan, 2004;Cooksey, 2005;Joerger, 2007;Mastromatteo, Mastromatteo, Conte, & Del Nobile, 2010). Lysozyme (LYS) obtained from hen egg white is one of the most potential candidates for antimicrobial packaging since it has a Generally Recognized as Safe (GRAS) status.…”

“…Also, it shows good stability and activity in different films and food systems under refrigerated storage temperatures (Mecito glu et al, 2006;Unalan, Korel, & Yemenicio glu, 2011). LYS has been tested extensively in different edible materials including zein, gelatin, soy protein, carrageenan, whey protein, chitosan, alginate and pullulan (Cha, Choi, Chinnan, & Park, 2002;Park, Daeschel, & Zhao, 2004;Bower, Avena-Bustillos, Olsen, McHugh, & Bechtel, 2006;Mecito glu et al, 2006;Joerger, 2007;Mendes de Souza, Fern andez, L opez-Carballo, Gavara, & Hern andez-Muñoz, 2010).…”

Use of Turmeric (Curcuma longa L.) Essential Oil Added to an Egg White Protein Powder-Based Film in the Storage of Çökelek Cheese

“…Edible films are used as carrier matrixes for antimicrobial substances. The antimicrobial properties of herbal essential oils (EOs), which have become prominent in recent years, are frequently used to control pathogenic bacterial growth and spoilage in food products [12].…”

Susceptibility of foodborne Pathogens and Spoilage Microorganisms to seed extracts of Citrullus Vulgaris and Citrus Reticulata

“…Microbial contamination reduces the shelf life of foods and increases the risk of food-borne illness. An application of antimicrobial preservative treatment in food packaging is gaining interest from researchers due to its potential to provide quality, safety benefits and to extend the shelf life of the food (Devlieghere et al 2000, Church andPersons 2007).…”