Antimicrobial potential of aqueous coffee extracts against pathogens and Lactobacillus species: A food matrix application

Abstract

Coffee is recognized by its bioactive potential, mainly antioxidant and antimicrobial activity. The aim of this study was to evaluate the antimicrobioal potential of aqueous extracts of Coffea arabica (AR) (roasted) and Coffea canephora [roasted (CR) and green (CG)] against patogens Salmonella Typhimurium and Escherichia coli, and probiotics Lactobacillus plantarum and Lactobacillus rhamnosus. Firstly, the strain's sensitivity were tested by disk diffusion method, followed by the evaluation of growth kinetics (lag phase duration, maximum specific growth rate and logarithmic increase in the population) in culture media and in a food matrix (milk) by the adjustment of Gompertz predictive model. In the step of strain sensivity tests, S. Typhimurium and E. coli were sensitive against all coffee extracts from 0.5% to 5.0%, while the Lactobacilli growth were not affected. In the growth kinetic tests in culture media, roasted coffees extracts reduced logarithmic increase in the population and maximum specific growth rate and improved lag phase for S. Typhimurium; for E. coli the growth was completely inhibited with 2.5% CR and 5.0% AR. The correlations between growth parameters with coffee bioactive contents suggested that melanoidins had the main antimicrobial effect. In the step of food matrix application (growth kinetics in milk), the addition of 5.0% CR reduced S. Typhimurium and E. coli multiplication, while the probiotics L. plantarum and L. rhamnosus where not inhibetd, suggesting a selective effect of coffee extracts as an antimicrobial agent, which may be of great interest for the food industry, especially for probiotic foods application.