Physiological alterations involved in inactivation of autochthonous spoilage bacteria in orange juice caused by Citrus essential oils and mild heat.

This study investigated physiological alterations involved in the inactivation of Levilactobacillus (L.) brevis and Leuconostoc (Lc.) mesenteroides in orange juice caused by Citrus lemon essential oil (CLEO) and C. reticulata essential oil (CREO) alone and combined with mild heat treatment (MHT). Damage in DNA, membrane integrity, membrane potential, metabolic and efflux activity of bacterial cells were measured after exposure (6 and 12 min) to CLEO or CREO (0.5 μL/mL) and/or MHT (54 °C) using flow cytometry. Limonene was the major constituent in CLEO (66.4%) and CREO (89.4%). The size of the damaged cell subpopulations increased (p < 0.05) after longer exposure time and varied with the tested essential oil and/or bacterial isolate. After exposure to CLEO and CREO alone, the cell subpopulations with damage in measured physiological functions were in a range of 19.6-66.8% and 23.8-75.9%, respectively. Exposure to CREO resulted in larger Lc. mesenteroides cell subpopulations (35.4-68.7%) with damaged DNA, permeabilized and depolarized membrane and compromised metabolic or efflux activity compared to L. brevis (23.8-58.0%). In contrast, exposure to CLEO led to higher damaged L. brevis cell subpopulations (35.1-77%) compared to Lc. mesenteroides (25.3-36.6%). Exposure to combined treatments (CLEO or CREO and MHT) affected the measured physiological functions in almost the entire L. brevis and Lc. mesenteroides cell population (up to 99%), although the damage extension o...
Source: International Journal of Food Microbiology - Category: Food Science Authors: Tags: Int J Food Microbiol Source Type: research