Antimicrobial properties of whey protein based edible films with the incorporation of liquid smoke

SOAZO, M.; PÉREZ, L.M.; BARBOZA, A.; DELORENZI, N.; RUBIOLO, A. C.; VERDINI, R. A.

Concordia (Entre Ríos)

Congreso; International Conference on Food Innovation (FoodInnova 2014); 2014

Universidad Nacional de Entre Ríos y Universitat Politecnica de Valencia

Packaging is widely used for food quality protection thereby ensuring hygiene and extending the shelf life of perishable items, especially those susceptible to oxidative and microbiological deterioration. Edible films could carry additives and thus edible packaging does not represent an inert barrier but it has an active role interacting with the food or with the surrounding media. The greater consumer awareness and concern regarding synthetic chemical additives has led to food preserved with natural additives become popular. Smoke flavorings have been used for years as preservatives. They may be added by injection, immersion, pulverization, etc.; but the incorporation into edible films was not examined. Thus, the objective of this study was to characterize the antimicrobial potential of whey protein concentrate (WPC) based edible films formulated with the addition of different concentrations of liquid smoke (LS). In a first step, minimum inhibitory concentration (MIC) and minimum bactericide concentration (MBC) of LS against Shiga toxin-producing Escherichia coli ATCC 43895, Staphylococcus aureus ATCC 43300, Salmonella typhimurium ATCC 14028 and Listeria monocytogenes ATCC 19115 were estimated. LS concentrations evaluated were 0.625, 1.25, 2.5, 5.0, and 10% (v/v). Then, aqueous solutions of WPC and glycerol (in proportion WPC/glycerol 3:1 w/w dry solid basis) with the addition of 0, 5, 10 and 15% (v/v) of LS were prepared, and films were obtained by drying and stabilization in an environmental chamber at 25 °C and constant relative humidity (58%). The antimicrobial potential of edible films incorporated with LS was determined by the inhibition zone assay in Oxford agar (for L. monocytogenes) or Mueller-Hinton agar (for E. coli, S. aureus, and Salmonella sp.) acidified to pH 5.5. Experiments were performed in triplicate. The obtained results showed that both MIC and MBC of LS were 5% (v/v) for all bacteria analyzed demonstrating bactericidal capacity in liquid medium. WPC/glycerol films incorporated LS (5%, 10% and 15% w/w) were only effective to inhibited the growth of L. monocytogenes in the diffusion test.