Survival of lactic acid and chlorine dioxide treated Campylobacter jejuni under suboptimal conditions of pH, temperature and modified atmosphere

Efficacy of Lactic Acid and Modified Atmosphere Packaging against Campylobacter jejuni on Chicken during Refrigerated Storage

The present study was conducted to evaluate the combined effect of lactic acid washing and modified atmospheres packaging on the counts of Campylobacter jejuni on chicken legs stored at 4 °C. In experiment 1, inoculated chicken legs were washed with either 1% or 2% lactic acid solution for 5 min or distilled water (control). The treatment with 2% lactic acid reduced C. jejuni counts 1.42 log units after treatment (day 0). In experiment 2, inoculated samples were packaged under different conditions: air, 100%N2, vacuum, 20%CO2/80%N2, or 40%CO2/60%N2. C. jejuni counts were higher in samples packaged under vacuum or atmospheres containing CO2 than in air. In experiment 3, inoculated chicken legs were washed with a 2% lactic acid solution for 5 min or distilled water (control). Samples were packaged under different conditions: air, vacuum, 20%CO2/80%N2, or 40%CO2/60%N2. C. jejuni counts were lower in samples treated with lactic acid than in samples non-treated. However, C. jejuni counts were higher in chicken legs treated with lactic acid and packaged in modified atmospheres than in those treated and packaged in air. Immersion of chicken legs in a solution containing 2% lactic acid can reduce C. jejuni counts on fresh chicken packaged in modified atmosphere.

Using Pretreatment of Carbon Monoxide Combined with Chlorine Dioxide and Lactic Acid to Maintain Quality of Vacuum-Packaged Fresh Beef

Due to microbial growth, beef easily gets corrupt in retail conditions, and the color and quality of the meat will be deteriorated. Therefore, hurdle technology, namely, pretreatment of carbon monoxide (CO), chlorine dioxide, and lactic acid, is used for vacuum-packaged beef to decontaminate beef and increase its quality stability. Beef was pretreated with 100% CO (C1), 100% CO and 50 mg/L chlorine dioxide (C2), and 100% CO and 50 mg/L chlorine dioxide and 30 g/L lactic acid (C3). The untreated samples were used as control (CK). During storage, thea⁎color parameters of C1, C2, and C3 were significantly higher than that of CK, indicating CO pretreatment is a good way to maintain color appearance of beef, and chlorine dioxide and lactic acid did not affect the color-protecting role of CO on beef. C3 showed the strongest antimicrobial activity with the lowest total viable counts, followed by C2, C1, and CK. Samples in C3 also showed the lowest total volatile basic nitrogen, pH, thiobarbituric acid reactive substance, and metmyoglobin during the mid-late storage. Moreover, C3 can keep beef with higher unsaturated fatty acids. In conclusion, CO pretreatment combined with chlorine dioxide and lactic acid displayed efficient antimicrobial and color-stability activity for vacuum-packaged beef. It would be a potential way to use pretreatment of CO combined with chlorine dioxide and lactic acid to maintain the quality of vacuum-packaged beef.

Antimicrobial resistance in the food chain: a review

Antimicrobial resistant zoonotic pathogens present on food constitute a direct risk to public health. Antimicrobial resistance genes in commensal or pathogenic strains form an indirect risk to public health, as they increase the gene pool from which pathogenic bacteria can pick up resistance traits. Food can be contaminated with antimicrobial resistant bacteria and/or antimicrobial resistance genes in several ways. A first way is the presence of antibiotic resistant bacteria on food selected by the use of antibiotics during agricultural production. A second route is the possible presence of resistance genes in bacteria that are intentionally added during the processing of food (starter cultures, probiotics, bioconserving microorganisms and bacteriophages). A last way is through cross-contamination with antimicrobial resistant bacteria during food processing. Raw food products can be consumed without having undergone prior processing or preservation and therefore hold a substantial risk for transfer of antimicrobial resistance to humans, as the eventually present resistant bacteria are not killed. As a consequence, transfer of antimicrobial resistance genes between bacteria after ingestion by humans may occur. Under minimal processing or preservation treatment conditions, sublethally damaged or stressed cells can be maintained in the food, inducing antimicrobial resistance build-up and enhancing the risk of resistance transfer. Food processes that kill bacteria in food products, decrease the risk of transmission of antimicrobial resistance.

Investigating the contributing factors to postmortem pH changes in springbok, eland, red hartebeest and kudu edible offal

The objective of the study was to assess pH measurements between offal organs of different species and the association between pH taken 4 h post-slaughter and different predictor variables in the liver and lungs. A linear regression analysis was conducted on selected variables to identify the main predictors and their interactions affecting the pH of meat 4 h post-slaughter. In an increasing order of magnitude during winter, the pH achieved at 16 h - 36 h post-slaughter in springbok heart, liver, spleen, kidney and lungs was significantly (p < 0.05) higher than pH 6.0. The pH attained in springbok carcasses was (p < 0.05) below 6.0, whilst no significant differences were observed from the regulatory reference (pH 6.0) in the heart. There was a positive association between the pH of game meat 4 h post-slaughter and liver congestion. The pH of game meat 4 h post-slaughter increased by 0.11 units (p < 0.05) per millilitre increase in liver congestion and decreased by 0.04 units (p< 0.05) per minute increase in the shooting-to-bleeding interval, irrespective of the species. The lack of a statistically significant association between some selected variables and pH changes in this study suggested that either the factors may have a small effect which is only detectable with large data-sets and/or the effect may be modified by other unidentified factors. As some of the offal organs had final pH readings above 6.0, alternative measures are required to inactivate certain endogenous pathogens in edible wild game offal sourced from endemic areas.

Intracellular pH distribution as a cell health indicator in Saccharomyces cerevisiae

Internal pH regulation is vital for many cell functions, including transport mechanisms and metabolic enzyme activity. More specifically, transport mechanisms are to a wide degree governed by internal pH distributions. We introduce the term standard deviation of the intracellular pH (s.d.(pH(int))) to describe the internal pH distributions. The cellular pH distributional response to external stress such as heat has not previously been determined. In this study, the intracellular pH (pH(i)) and the s.d.(pH(int)) of Saccharomyces cerevisiae cells exposed to supralethal temperatures were measured using fluorescence ratio imaging microscopy (FRIM). An exponential decline in pH(i) was observed after an initial small decline. For the first time, we report the use of FRIM for determining in vivo plasma membrane proton permeability coefficients in yeast. Furthermore, the exponential decay of pH(i) and the rupture of the cell plasma membrane, as measured by propidium iodide staining, at 70°C were not simultaneous but were separated by a significant temporal difference. Finally, a nonlinear relationship between the pH(i) and s.d.(pH(int)) was found; i.e. the s.d.(pH(int)) was significantly more sensitive to supralethal temperatures than pH(i). s.d.(pH(int)) is therefore proposed as an early health/vitality indicator in S. cerevisiae cells exposed to heat stress.