Bacteriocins

Most of the studies related with antimicrobial packaging of dairy products are about the biologically derived antimicrobials. Bacteriocins are small bacterial peptides that show strong antimicrobial activity against closely related bacteria. Nisin and natamycin are the mostly studied bacteriocins in antimicrobial packaging of dairy products as well as of most of foods. Nisin is a polypeptide produced by Lactococcuslactis spp., and it has been approved as a food additive with GRAS status in over 50 countries worldwide (Lucera et al., 2012). Natamycin is currently used as an antimicrobial agent to prevent cheese surface spoilage. It is produced by Streptomyces natalensis and is commonly employed in dairy products to prevent yeast and mold contamination. It has been approved as a food additive in over 40 countries and has been considered as a GRAS product by the FDA and can be safely used for surface treatment of semi-hard and semi-soft cheeses according to EFSA (Olle Resa, 2014; EFSA, 2009).

In a study, two traditional Czech cheeses (Blatacke zlato-soft cheese and Olomoucke tvaruzky-surface ripened cheese) were vacuum packaged with the coextruded PA (Polyamide)/LDPE film coated with Polyvinyldichloride (PVdC) lacquer containing both nisin and natamycin (Hanusova et al., 2010). While this film was not effective to lower the number of L.monocytogenes colonies in Olomoucke tvaruzky cheese, it inhibited the present of spoilage microorganisms (Bacillus sp. and/or lactic acid bacteria growth) on the surface of the Blatacke zlato cheese during 28 days at 23°C. This study demonstrated that natamycin and nisin could be released from the synthetic lacquer coatings on polymer packaging film in amounts that could inhibit sensitive forms of microorganisms on the surface of packaged foodstuffs.

Mauriello et al., (2005) determined the efficacy of nisin coated onto LDPE film for packaging of three different kinds of milk (raw milk, pasteurized milk, and UHT milk) against the growth of Micrococcus luteus at 4°C and 25°C of storage. Nisin-coated LDPE film provided better results for raw milk and pasteurized milk and 25°C of storage temperature provided remarkable reduction in the growth of Micrococcus luteus, while 4°C of storage temperature provided slight reduction. Lee et al. (2004a) showed the antimicrobial efficacy of paperboard coated with both nisin- and chitosan for pasteurized milk at temperature of 10°C against total aerobic bacteria was higher than paperboard coated with either nisin- or chitosan, and microbial inhibition in nisin/chitosan application was most apparent at 10°C in comparison with 3°C and 20°C. The same authors incorporated the same packaging material with nisin and/or a-tocopherol and tested their antimicrobial and antioxidative effectiveness on milk cream at 10°C (Lee et al., 2004b). Incorporation of nisin effectively inhibited Micrococcus flavus, and a-tocopherol incorporation retarded lipid oxidation in the milk cream. The paperboards coated with nisin were more effective against the growth of total aerobic bacteria than in combination with a-tocopherol or alone a-tocopherol.

Scannell et al., (2000) investigated the antimicrobial activity of nisin or lacticin immobilized to Polyamide (PA)/LDPE pouches against L.inncoua and S. aureus in sliced cheese. The antimicrobial packaging film with nisin reduced the population of lactic acid bacteria, inhibited L.inncoua and S. aureus, and extended the shelf life of sliced cheese at 4°C, while adsorption of lacticin to packaging material failed.

In a study, enterocin 416K1, a bacteriocin produced by Enterococcus casseliflavus IM 416K1, entrapped in an organic-inorganic hybrid coating applied to a LDPE film was found significantly effective against L.monocytogenes in fresh cottage cheese at 4°C and 22°C storage temperature. (Isseppi et al., 2008).

Nithya et al. (2013) evaluated the effectiveness of active packaging films of LDPE and cellulose containing partially purified antibacterial peptide for paneer (a South Asian soft cheese made from buffalo or a blend of cow and buffalo milk) and cheese preservation. Active LDPE showed a bacteriostatic effect on pathogens studied, whereas a bactericidal action was observed in cheese packed in cellulose.

 
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