Predictive modelling of foodborne bacteria inhibition by pomegranate (Punica granatum L.) peel extracts using response surface methodology

In this work, predictive models based on response surface methodology (RSM) were developed, to describe the inhibition of foodborne bacteria (Bacillus subtilis, Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Serratia marcescens), using pomegranate (Punica granatum L.) peel extracts. The extraction conditions (solid/solvent ratio, 1.0: 10-5.0: 10), incubation time, 10-60 min and extraction temperature, 30-60 degrees C) were varied using a 23 factorial design with six axial points and three central points and different extracts were obtained. The antibacterial activity of the extracts was determined by the disk diffusion method and Gram-positive bacteria showed more sensitivity to them than Gram-negative bacteria. The RSM showed that the temperature and solid/solvent ratio, were the most significant parameters to obtain extracts with antimicrobial potential against B. subtilis, S. aureus, E. faecalis, E. coli and S. marcescens. The extraction conditions 4 (extraction temperature = 54 degrees C, solid/solvent ratio = 4.2: 10, incubation time 20.0 min) and 12 (extraction temperature = 45 degrees C, solid/solvent ratio = 5.0: 10, incubation time 35.0 min) resulted in extracts with the highest antibacterial activity against the tested bacteria with minimum inhibitory and minimum bactericide concentrations of 400 and > 400 mu l/ml, respectively. This is the first study about mathematical models for inhibition of foodborne bacteria using pomegranate peel extract. The results may help food industries to select optimal conditions for the preparation of pomegranate peel extracts able to inhibit foodborne bacteria.