Enhancement effect of carvacrol on yeast inactivation by mild pressure carbon dioxide

Saccharomyces cerevisiae is one of the common spoilage microorganisms in fruit juices. This paper investigated the influences of carvacrol on S. cerevisiae inactivation by mild pressure carbon dioxide (MPCO2). The results demonstrated that carvacrol synergistically enhanced the antifungal activity against S. cerevisiae of MPCO2. With the increase of carvacrol concentration (20-160 µg/mL), CO2 pressure (1.5-3.5 MPa), process temperature (20-40 °C), and treatment time (15-60 min), the inactivation effect of carvacrol combined with MPCO2 on S. cerevisiae was gradually increased and significantly stronger than either single treatment. In the presence of carvacrol, MPCO2 severely disordered the plasma membrane of S. cerevisiae, including the increase of membrane permeability, and the loss of membrane potential and integrity. MPCO2 and carvacrol in combination also aggravated the mitochondrial depolarization of S. cerevisiae and reduced intracellular ATP and protein content. This study suggests the potential of carvacrol and pressurized CO2 as an alternative technology for food pasteurization.

Sodium copper chlorophyll mediated photodynamic treatment inactivates Escherichia coli via oxidative damage

Photodynamic technology (PDT) is an emerging non-thermal processing technique, however, due to a lack of edible photosensitizers, its application to the food industry is limited. To better understand sodium copper chlorophyll (SCC) feasibility as a photosensitizer, we analyzed the effects of PDT-SCC on Escherichia coli O157:H7 inactivation using different lighting times (15, 30, 45, 60, and 75 min), lighting power (30, 60, 90, 120, and 150 W), and SCC concentrations (2, 4, 6, 8, and 10 mM). We showed that bactericidal effects depended on all three parameters, but the most suitable sterilization condition for E. coli occurred at 10 mM SCC, for 60 min at 120 W. We also investigated cell morphology, reactive oxygen species (ROS) production, the activity of three oxidative response enzymes (superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX)), and ompA, ompF, uvrA, and recA expression. When compared with the control group, PDT-SCC destroyed bacterial morphology, increased ROS production, decreased antioxidant enzyme activity (SOD, CAT, and GPX), down-regulated membrane protein gene expression, including ompA and ompF, and up-regulated the DNA damage-repair related genes, uvrA and recA. Thus, bacterial rupture caused by oxidative damage could be the main mechanism underpinning PDT-SCC action.

Inactivation of Salmonella Typhimurium and Escherichia coli O157:H7 on black pepper powder using UV-C, UV-A and TiO2 coating

This study was conducted to measure the inactivation characteristics of UVs and TiO2 against Salmonella. Typhimurium and Escherichia coli O157:H7 on black pepper powder. The sample was irradiated by UV-A and UV-C combined with TiO2 coating. After treatment, microbial and physicochemical analysis was carried out. Among various sterilization conditions, the largest number of pathogen in black pepper powder was inactivated by UV-A and UV-C combined with TiO2 coating. The microbial count of black pepper powder treated simultaneously with UV-A and UV-C was less than that of black pepper powder treated with alone. The inactivation effect of UV-A and UV-C was increased when TiO2 coating was combined. Moisture content was decreased with increasing treatment time, but color did not change. In this study, it was indicated that the combined treatment of UV-C, UV-A and TiO2 coating was effective for reducing S. Typhimurium and E. coli O157:H7 on black pepper powder.

Comparative study of survival of Escherichia coli O157:H7 inoculated in pork batter after ohmic cooking and water bath cooking

In this study, the effects of ohmic cooking (OH) and water bath cooking (WB) on the reduction of Escherichia coli O157:H7 inoculated in pork batter with addition of sodium chloride (NaCl) were studied, and the recovery and growth of OH and WB treated E. coli O157:H7 were also investigated during storage. The time for samples cooked by OH to reach the targeted endpoint temperature (61, 65, and 72 °C) was shorter than that of WB, and the addition of NaCl dramatically shortened the cooking time of OH treated samples, however, no significant effect was observed by WB. Samples with NaCl and cooked by OH had lower cooking loss than that of WB, but the inactivation effect of E. coli O157:H7 by OH was comparable to WB. During storage, the recovery and growth of sublethally injured E. coli O157:H7 were slower at 4 °C, and storage at 4 °C for 24 h delayed their recovery at 37 °C from 36 h to 48 h. These results indicated that OH had greater potential in the application of meat batter processing.

Potential application of high pressure carbon dioxide in treated wastewater and water disinfection: Recent overview and further trends

Recently emerging disadvantages in conventional disinfection have heightened the need for finding a new solution. Developments in the use of high pressure carbon dioxide for food preservation and sterilization have led to a renewed interest in its applicability in wastewater treatment and water disinfection. Pressurized CO2 is one of the most investigated methods of antibacterial treatment and has been used extensively for decades to inhibit pathogens in dried food and liquid products. This study reviews the literature concerning the utility of CO2 as a disinfecting agent, and the pathogen inactivation mechanism of CO2 treatment is evaluated based on all available research. In this paper, it will be argued that the successful application and high effectiveness of CO2 treatment in liquid foods open a potential opportunity for its use in wastewater treatment and water disinfection. The findings from models with different operating conditions (pressure, temperature, microorganism, water content, media …) suggest that most microorganisms are successfully inhibited under CO2 treatment. It will also be shown that the bacterial deaths under CO2 treatment can be explained by many different mechanisms. Moreover, the findings in this study can help to address the recently emerging problems in water disinfection, such as disinfection by-products (resulting from chlorination or ozone treatment).