Inhibition of Salmonella spp. and Escherichia coli by Lentil Protein Edible Films with Added Natural Antimicrobials

Introduction: New packaging materials are developed to increase potential applications by adding antimicrobial compounds. Lentils have the second-highest ratio of protein per calorie of any legume, after soybeans, and its protein can be used as a source of polymers to form edible films. Antimicrobial films have the potential to inhibit the growth of pathogens and deteriorative microorganisms present in foods.

Purpose: The aim of this work was to evaluate the inhibition of Salmonella spp. and Escherichia coli by lentil protein edible films with added natural antimicrobials.

Methods: Lentil protein concentrated was combined with water and glycerol to form edible film solutions; thymol and carvacrol were incorporated at different concentrations (0, 250, 500, 1000, and 1,500 mg/L). Minimal inhibitory concentration (MIC) was determined against Salmonella spp. and E. coli by the Kirby-Bauer method. To evaluate death curves, subletal concentrations were applied and evaluated by plate count method.

Results: Active edible films showed MIC values of 500 and 1500 mg/L for thymol and carvacrol, respectively, for Salmonella spp.; while E. coli appeared to be more sensitive to these compounds, with MIC values of 250 and 500 mg/L for thymol and carvacrol, respectively. For both microorganisms at 24 hours, subletal concentrations increased the lag phases and decreased the growth rates.

Significance: These results can help us understand how antimicrobials incorporated into protein edible films can inhibit foodborne pathogens.