Control of Enterobacter aerogenes by high-intensity, pulsed electric fields in horchata, a Spanish low-acid vegetable beverage Original Research Article

High-intensity pulsed electric fields (HIPEF) is a non-thermal technology used in the processing of liquid foods. Inactivation of foodborne micro-organisms by this novel technology is an important alternative to traditional thermal methods with a great potential for new liquid products. However, the existence of a resistant proportion of microbial population presents a problem to establish the parameters that can guarantee the safety during the shelf-life of each food. The aim of this study was to investigate the influence of field strength, substrate inoculum size (initial cell concentration) and storage conditions after HIPEF treatment to evaluate the potential growth and subsequent spoilage by Enterobacter aerogenes in horchata, a Spanish low-acid vegetable beverage. Although no more than 1.1-log reductions were obtained by any of the HIPEF conditions applied, E. aerogenes growth in both substrates (horchata and a standard broth) at 10°C, 12°C and 16°C was affected by HIPEF treatments compared to untreated samples. The specific growth rate of the bacteria after HIPEF treatment was not modified, but the lag period was increased. A synergistic effect of HIPEF treatment, low temperature (10°C) and low inoculum size on the delay in lag phase was observed.