Food preservation is a critical issue in ensuring food safety and quality. Growing concern around industrial pollution of food and demand for environmentally sustainable food has led to increased interest in developing effective and eco-friendly preservation techniques. Gaseous ClO2 has gained attention for its strong oxidizing properties, high efficacy in microorganism inactivation, and potential for preserving the attributes and nutritional quality of fresh food while avoiding the formation of toxic byproducts or unacceptable levels of residues. However, the widespread use of gaseous ClO2 in the food industry is limited by several challenges. These include large-scale generation, high cost and environmental considerations, a lack of understanding of its mechanism of action, and the need for mathematical models to predict inactivation kinetics. This review aims to provide an overview of the up-to-date research and application of gaseous ClO2 . It covers preparation methods, preservation mechanisms, and kinetic models that predict the sterilizing efficacy of gaseous ClO2 under different conditions. The impacts of gaseous ClO2 on the quality attributes of fresh produce and low-moisture foods, such as seeds, sprouts, and spices, are also summarized. Overall, gaseous ClO2 is a promising preservation approach, and future studies are needed to address the challenges in large-scale generation and environmental considerations and to develop standardized protocols and databases for safe and effective use in the food industry.

The oil in low-moisture foods (LMFs) shows protective effects on bacteria during thermal processing. However, the circumstances under which this protective effect strengthens remain unclear. This study aimed to understand which step of the oil exposure to bacterial cells (inoculation, isothermal inactivation, or recovery and enumeration step) in LMFs can enhance their heat resistance. Peanut flour (PF) and defatted PF (DPF) were selected as the oil-rich and oil-free LMF models. Salmonella enterica Enteritidis Phage Type 30 (S. Enteritidis) was inoculated into four designated PF groups representing different oil exposure stages. It was isothermally treated to obtain heat resistance parameters. At a constant moisture content (aw,25°C = 0.32 ± 0.02) and controlled aw,85°C (0.32 ± 0.02), S. Enteritidis exhibited significantly high (p < 0.05) D values in oil-rich sample groups. For instance, the heat resistance values of S. Enteritidis in the PF-DPF and DPF-PF groups were D80°C of 138.22 ± 7.45 min and 101.89 ± 7.82 min; however, the D80°C in the DPF-DPF group was 34.54 ± 2.07 min. The oil addition after the thermal treatment also helped injured bacterial recovery in the enumeration. For instance, the D80°C, D85°C, and D90°C values in the DFF-DPF oil groups were 36.86 ± 2.30, 20.65 ± 1.23, and 7.91 ± 0.52 min, respectively, which were higher than those in the DPF-DPF group at 34.54 ± 2.07, 17.87 ± 0.78, and 7.10 ± 0.52 min. We confirmed that the oil protected S. Enteritidis in PF in all three stages: desiccation process, heat treatment, and recovery of bacterial cells in plates.

In previous studies, parabens in model systems enhanced the thermal inactivation of foodborne pathogens, including Cronobacter sakazakii, Salmonella enterica serotype Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes. However, few studies have been conducted to evaluate this phenomenon in actual food systems. In the present study, the potential enhancement of thermal inactivation of C. sakazakii by butyl para-hydroxybenzoate (BPB) was evaluated in powdered infant formula (PIF) and nonfat dry milk (NFDM) in dry and rehydrated forms. When PIF was rehydrated with water at designated temperatures (65 to 80°C) in baby bottles, BPB did not enhance thermal inactivation. When rehydrated NFDM and lactose solutions with BPB were inoculated and heated at 58°C, BPB enhancement of thermal inactivation of C. sakazakii was negatively associated with the concentration of NFDM solutions in a dose-dependent manner, whereas thermal inactivation was enhanced in the presence of lactose regardless of its concentration, suggesting an interaction between proteins and BPB. Fluorescence testing further indicated an interaction between BPB and the proteins in PIF and NFDM. In inoculated dry NFDM with and without BPB stored at 24 and 55°C for 14 days, BPB did not substantially enhance bacterial inactivation. This study suggests that BPB is not likely to enhance mild thermal bacterial inactivation treatments in foods that have appreciable amounts of protein.

Microorganisms in low-moisture foods (LMFs) exhibit prolonged survivability and high heat resistance. Various external factors (water, food texture, nutritional compounds, etc.) influence the microbial heat resistance in LMFs; yet, the influential degree of each factor is not fully understood. In this study, the thermal resistance parameters (D and z values) of Salmonella enterica Enteritidis PT 30 (S. Enteritidis) at 80, 85, and 90 °C at the room-temperature water activity (aw, 25°C) of 0.32 ± 0.02 were measured. A series of egg powders with different fat and protein ratios (obtained by mixing egg white and yolk powders) were chosen as the model foods. Primary and secondary models were built from the isothermal inactivation kinetics of S. Enteritidis in the tested samples. The importance of fat and protein was then confirmed by controlling the water activity at the treatment temperature (aw, treatment temperature) via thermal water activity cells. The survivor curves of S. Enteritidis fitted well with the Weibull-type and log-linear models. The D values of S. Enteritidis increased with increasing fat (0-56.7%, w.b.) and decreasing protein contents (83.59-31.81%, w.b.). Incorporating the modified Bigelow model into the log-linear model yielded the zfat and zprotein of 58.96 and 57.14, respectively. At the controlled aw, 90°C of 0.32 ± 0.02, the D90°C values of S. Enteritidis increased remarkably (P < 0.05), but the values in egg white, whole egg, and egg yolk powders (11.73 ± 1.24, 23.82 ± 2.0, and 60.0 ± 2.4 min) were remarkably different. Our study identified that the influential degrees of fat, protein (zfat and zprotein values), and aw on the thermal resistance of S. Enteritidis in egg powders is in the order: aw,treatment temperature > fat > protein. Fat considerably increased the thermal resistance of S. Enteritidis even at the same aw,treatment temperature. This study quantified the effect of fat and protein on the thermal resistance of S. Enteritidis and emphasized the non-negligible effects of food components in LMFs\' microbial safety.

Many studies demonstrated that radio frequency (RF) was an effective pasteurization method for low-moisture foods (LMFs), and our previous study confirmed RF heating stress generated sublethal injured cells (SICs) of Salmonella enterica serovar Typhimurium (S. Typhimurium) in red pepper powder with initial aw ≥ 0.53. So this study investigated the potential direct protection and cross protection effects of the SICs of S. Typhimurium to multiple stresses, and analyzed fatty acid composition and cell morphology. Results showed that the SICs were repaired after incubating for 5 h, and there were no obvious direct and cross protection effects by exposing to different external stresses (heat, 15% ethanol, pH 3.0 acid buffer solution, 10% salt). According to the fatty acid composition analysis, no significant difference (p > 0.05) between the ratio of unsaturated to saturated fatty acids (UFA/SFA) was observed for SICs of S. Typhimurium and control cells, indicating the same membrane fluidity which can support the experimental results. This study investigated and confirmed there are no direct and cross protection effects for the SICs of S. Typhimurium induced by RF heating stress, and it would be helpful for deeply understand the response of pathogens under RF heating stress.

The contamination risks of microorganisms and mycotoxins in low-moisture foods have heightened public concern. Developing novel decontamination technologies to improve the safety of low-moisture foods is of great interest in both economics and public health. This review summarizes the working principles and applications of novel thermal decontamination technologies such as superheated steam, infrared, microwave, and radio-frequency heating as well as extrusion cooking. These methods of decontamination can effectively reduce the microbial load on products andmoderately destruct the mycotoxins. Meanwhile, several integrated technologies have been developed that take advantage of synergistic effects to achieve the maximum destruction of contaminants and minimize the deterioration of products.

UNASSIGNED: Evaluation of alternative detection methods for foodborne pathogens typically involves comparisons against a \"gold standard\" culture method, which may produce false-negative (FN) results, particularly under worst-case scenarios such as low contamination levels, difficult-to-detect strains, and challenging food matrices (e.g., matrices with a water activity of <0.6). We used extended enrichment times (up to 72 h for both primary and secondary enrichments) to evaluate a gold standard method for Salmonella detection (the U.S. Food and Drug Administration Bacteriological Analytical Manual [BAM] method) in two low-water-activity foods (dry pet food and chocolate) inoculated at low contamination levels (most probable number ca. 1/25 g) with five Salmonella strains. Strains were selected to include those with a poor ability to grow in enrichment media. Among the 100 pet food and 100 chocolate samples tested, 53 and 50, respectively, were positive with the standard BAM method, and 57 and 59, respectively, were positive with the extended BAM method. Thus, the FN probabilities for the standard BAM method were 7% for pet food and 15% for chocolate. An alternative enzyme immunoassay method for detection of Salmonella in chocolate produced FN probabilities of 6 and 20% when compared against the standard and extended BAM methods, respectively. Detection of Salmonella Mississippi was significantly reduced with the alternative method (P = 0.023) compared with the extended BAM method. We calculated a composite reference standard to further define FN probabilities based on variable results from multiple assays (the standard BAM, extended BAM, and alternative methods). Based on this standard, the enzyme immunoassay for Salmonella detection in chocolate had a 28% FN probability and the standard and extended BAM methods had 23 and 9% FN probabilities, respectively. These results provide a framework for how inclusion of extended enrichment times can facilitate evaluation of alternative detection methods.
CONCLUSIONS:

We used a Fick\'s unsteady state diffusion equation to estimate the time required for a single spherical shaped bacterium (assuming Enterococcus faecium as the target microorganism) in low-moisture foods to equilibrate with the environment. We generated water sorption isotherms of freeze-dried E. faecium. The water activity of bacterial cells at given water content increased considerably as temperature increased from 20 to 80 °C, as observed in the sorption isotherms of bacterial cells. When the water vapor diffusion coefficient was assumed as between 10(-12) and 10(-10) m(2) /s for bacterial cells, the predicted equilibration times (teq ) ranged from 8.24×10(-4) to 8.24×10(-2) s. Considering a cell membrane barrier with a lower water diffusion coefficient (10(-15) m(2) /s) around the bacterial cell with a water diffusion coefficient of 10(-12) m(2) /s, the teq predicted using COMSOL Multiphysics program was 3.8×10(-1) s. This result suggests that a single bacterium equilibrates rapidly (within seconds) with change in environmental humidity and temperature.