Free-standing carboxymethyl cellulose film incorporating nanoformulated pomegranate extract for meat packaging.

This study aimed to explore an innovative approach to enhancing the shelf-life and quality of meat products through the application of an active packaging system. The study involved the development of new free-standing carboxymethyl cellulose (CMC) nanocomposite films incorporated with nanoencapsulated flavonoids derived from pomegranate extract. The loaded flavonoids, known for their antioxidant and antimicrobial properties, were nanoencapsulated via a self-assembly approach in a mixture of chitosan and sodium alginate to improve their stability, solubility, and controlled release characteristics. Chemical structure, size, and morphology of the obtained nanoparticles (Pg-NPs) were studied with FTIR, zeta-sizer, and TEM. The Pg-NPs showed particle size of 232 nm, and zeta-potential of -20.7 mV. Various free-standing nanocomposite films were then developed via incorporation of Pg-NPs into CMC-casted films. FTIR, SEM, thermal and mechanical properties, and surface wettability were intensively studied for the nanocomposite films. Barrier properties against water vapor were investigated at 2022 g·m-2d-1. The nanocomposite films possessed superior properties for inhibiting bacterial growth and extending the shelf-life of beef and poultry meat for 12 days compared with the Pg-NPs-free CMC films. This study presented a promising approach for development of active packaging systems with improved antimicrobial and antioxidant properties, and economic and environmental impacts.

Inactivation of Polymicrobial Biofilms of Foodborne Pathogens Using Epsilon Poly-L-Lysin Conjugated Chitosan Nanoparticles.

A mixed culture (polymicrobial) biofilm provides a favorable environment for pathogens to persist in the food processing environment and to contaminate food products. Inactivation and eradication of such biofilms from food processing environments are achieved by using harsh disinfectants, but their toxicity and environmentally hostile characteristics are unsustainable. This study aims to use food-grade natural nanoparticulated antimicrobials to control mixed-culture biofilms. Chitosan, a natural broad-spectrum antimicrobial biopolymer (polysaccharide) from crustaceans, was derivatized to produce chitosan nanoparticles (ChNP) as a carrier for another broad-spectrum antimicrobial agent, ε-poly-L-lysine (PL), to synthesize ChNP-PL conjugate. The antimicrobial activity of ChNP and ChNP-PL was tested against mixed-culture biofilms. ChNP-PL (~100 nm) exhibited a synergistic antimicrobial and anti-biofilm effect against mono or mixed-culture biofilms of five foodborne pathogens, including Listeria monocytogenes, Staphylococcus aureus, Salmonella enterica serovar Enteritidis, Escherichia coli O157:H7, and Pseudomonas aeruginosa. ChNP-PL treatment prevented biofilm formation by mono or mixed cultures of L. monocytogenes, P. aeruginosa, and E. coli O157:H7, and bacterial counts were either below the detection limit or caused 3.5-5 log reduction. ChNP-PL also inactivated preformed biofilms. In monoculture biofilm, ChNP-PL treatment reduced L. monocytogenes counts by 4.5 logs, S. Enteritidis by 2 logs, E. coli by 2 logs, and S. aureus by 0.5 logs, while ChNP-PL had no inhibitory effect on P. aeruginosa. In vitro mammalian cell-based cytotoxicity analysis confirmed ChNP-PL to have no deleterious effect on intestinal HCT-8 cell line. In conclusion, our results show ChNP-PL has strong potential to prevent the formation or inactivation of preformed polymicrobial biofilms of foodborne pathogens.

Inactivation and Attachment of Listeria monocytogenes on Beef Muscle Treated with Lactic Acid and Selected Bacteriocins.

Cubical pieces (1 cm3) of aseptically obtained beef muscle were treated with lactic acid (2%), nisin (4 × 104 IU/ml) and pediocin PO2 (a bacteriocin produced by Pediococcus acidilactici PO2; 3.2 × 103 arbitrary units/ml). Treated meat was immersed for 1 min in a cell suspension of a mixture of two strains of Listeria monocytogenes and then stored for 48 h at 4°C. Meat cubes were analyzed immediately after immersion in the cell suspension, then after 1, 24, and 48 h of storage. Count of L. monocytogenes per cube and percentage of attached cells were determined. Data indicated that the antimicrobial agents significantly (p = 0.05) decreased the count of L. monocytogenes during the 48-h storage by 1.7, 1.1, and 0.6 log10 CFU/6 cm2 of meat surface for lactic acid, nisin, and pediocin PO2 treatments, respectively. Lactic acid on the meat surface had an immediate and also a delayed listericidal action, but bacteriocins only inhibited L. monocytogenes immediately, and had little or no delayed antilisterial effect. The percentage of Listeria cell attached to the beef muscle significantly (p = 0.05) increased in the presence of lactic acid, but the value did not change significantly or slightly decreased in the presence of nisin and pediocin PO2, respectively.