Food & Beverages

Biography

Biography: Sandra N Guerrero

Abstract

The application of non-thermal emerging preservation technologies in the food industry has received increasing attention as traditional thermal processing may have undesirable effects over fruit juices. PL is actually limited to treatments of transparent liquid foods or surfaces, though it can be combined with other hurdles to increase its effectiveness. This study was aimed to evaluate the single and combined effects of static PL (Xenon lamp; 3 pulses/s; 10 cm; 71.6 J/cm2; 44-56 °C) and US (600 W, 20 kHz, 95.2 µm; 10-30 min; 44 °C) applied to commercial (CAJ, pH:3.5; 12.5°Brix) and natural (NAJ, pH:3.4; 12.6°Brix) apple juices. When some indicator microorganisms were inoculated, US+PL led up to 5.8-6.4 log reductions in NAJ and CAJ respectively, whilst single PL provoked only 2-3 log reductions. Induced damage was evaluated by detecting through flow cytometry, membrane integrity and esterase activity on inoculated and labeled Saccharomyces cerevisiae KE162 cells. Cells shown permeabilized membrane when 10 min-US+PL, 30 min-US and 30 min-US+PL was applied (91.6-99.0%). Sub-lethal damage was observed after exposure to single PL in NAJ as ~18% of cells were double stained. Additionally, damage of US+PL treated S. cerevisiae cells and Alicyclobacillus acidoterrestris ATCC49025 spores was evaluated by transmission electron microscopy (TEM). Treated yeast cells revealed altered or destroyed plasma membrane and cell wall with coagulated inner content while treated A. acidoterrestris spores exhibited induced coagulation of inner content with no possibility of distinguish any structure. This study contributed to a better understanding on the microbial damage caused by PL combined with US treatment applied to apple juice.