Antimicrobial activity of a nisin-activated plastic film for food packaging G. Mauriello, E. De Luca, A. La Storia, F. Villani and D. Ercolini Dipartimento di Scienza degli Alimenti Universita` degli Studi di Napoli ‘Federico II’, 80055 Portici, Naples, Italy 2005/0456: received 28 April 2005, revised 16 June 2005 and accepted 18 July 2005 ABSTRACT G. MAURIELLO, E. DE LUCA, A. LA STORIA, F. VILLANI AND D. ERCOLINI. 2005. Aims: To determine the effectiveness of a packaging film coated with nisin to inhibit Micrococcus luteus ATCC 10240 in tryptone soya broth (TSB) and the microbiota of raw milk during storage. A further aim was to examine the release of nisin from the activated film. Methods and Results: An active package, obtained from nisin-treated film, was filled with 1 l of M. luteus ATCC 10240 (ML) suspension in TSB and stored at 4 and 25°C for 2 days. After 24 h at 25°C there was a remarkable reduction of M. luteus ATCC 10240 compared with the control, while at 4°C a slight reduction was observed. Moreover, microbial growth was controlled when 1 l of three different kinds of milk was poured into the active package and stored at 4°C for 7 days. The most significant results were observed in raw milk and pasteurized milk with a reduction of 0Æ9 log and 1Æ3 log, respectively. The release experiments showed that nisin release from the film was unpredictable, but it was favoured by low pH and high temperature. Conclusions: It appears that nisin-coated films were effective in inhibiting M. luteus ATCC 10240 in TSB and the bacterial flora in milk, and the release of nisin was pH and temperature dependent. Significance and Impact of the Study: Nisin-activated film may control bacterial growth, maintaining food quality, safety and extending the shelf-life of food products. Keywords: antimicrobial packaging, migration, nisin, release, viable staining. INTRODUCTION Active packaging is one of the innovative food packaging concepts that has been introduced as a response to the demands of consumers for high quality, safety and extended shelf-life of food products. It also suits the changes in retail and distribution practices, the new trends (e.g. Internet- shopping) and enlargements of markets, all resulting in increased distribution distances and longer storage times (Vermeiren et al. 1999; Quintavalla and Vicini 2002). Active packaging has been defined as ‘a type of packaging that changes the condition of the packaging to extend shelf- life or improve safety or sensory properties while maintain- ing the quality of the food’ (European FAIR-project CT 98- 4170). Among the active packaging applications, the incorpor- ation and/or slow release of antimicrobials is receiving considerable attention as a means of extending the bacterial lag phase, slowing the growth rate of micro-organisms and maintaining food quality and safety (Han 2000; Guerra et al. 2005). Direct addition of antimicrobials (organic acids or their respective acid anhydrides, spice extracts, chelating agents, metals, enzymes, bacteriocins, etc.) could result in some loss of activity because of leaching into the food matrix, and cross-reaction with other food components such as lipids or proteins (Han and Floros 1997; Davies et al. 1999; Hoffman et al. 2001). Therefore, the use of packaging films containing antimicrobial agents could be more efficient, by a controlled migration of the compound into the food, not only allowing Correspondence to: Gianluigi Mauriello, Dipartimento di Scienza degli Alimenti, Sezione di Microbiologia, Universita ` degli Studi di Napoli ‘Federico II’, 80055 Portici (NA), Italy (e-mail: giamauri@unina.it). ª 2005 The Society for Applied Microbiology Letters in Applied Microbiology 2005, 41, 464–469 doi:10.1111/j.1472-765X.2005.01796.x