Category Archives: Microbiology

MDPI

Listeria monocytogenes is a serious public health hazard responsible for the foodborne illness listeriosis. L. monocytogenes is ubiquitous in nature and can become established in food production facilities, resulting in the contamination of a variety of food products, especially ready-to-eat foods. Effective and risk-based environmental monitoring programs and control strategies are essential to eliminate L. monocytogenes in food production environments. Key elements of the environmental monitoring program include (i) identifying the sources and prevalence of L. monocytogenes in the production environment, (ii) verifying the effectiveness of control measures to eliminate L. monocytogenes, and (iii) identifying the areas and activities to improve control. The design and implementation of the environmental monitoring program are complex, and several different approaches have emerged for sampling and detecting Listeria monocytogenes in food facilities. Traditional detection methods involve culture methods, followed by confirmation methods based on phenotypic, biochemical, and immunological characterization. These methods are laborious and time-consuming as they require at least 2 to 3 days to obtain results. Consequently, several novel detection approaches are gaining importance due to their rapidness, sensitivity, specificity, and high throughput. This paper comprehensively reviews environmental monitoring programs and novel approaches for detection based on molecular methods, immunological methods, biosensors, spectroscopic methods, microfluidic systems, and phage-based methods. Consumers have now become more interested in buying food products that are minimally processed, free of additives, shelf-stable, and have a better nutritional and sensory value. As a result, several novel control strategies have received much attention for their less adverse impact on the organoleptic properties of food and improved consumer acceptability. This paper reviews recent developments in control strategies by categorizing them into thermal, non-thermal, biocontrol, natural, and chemical methods, emphasizing the hurdle concept that involves a combination of different strategies to show synergistic impact to control L. monocytogenes in food production environments.

Journal of Food Protection

Listeria monocytogenes is a foodborne pathogen associated with fresh produce vectors such as leafy greens. Recent outbreaks and recalls associated with red cabbage-containing salads have brought attention to this food commodity. While data on the proliferation of L. monocytogenes is available for different varieties of white cabbage, no information is available on the fate of this pathogen on red cabbage. The aim of this study was therefore to explore the survival of L. monocytogenes on cut red cabbage (var. capitata f. rubra ) during storage at different temperatures. Red cabbage was cut into 5 × 4 cm pieces and spot inoculated with a six-strain cocktail of rifampicin-resistant L. monocytogenes , resulting in an initial inoculation level of at 4 log CFU/g. Samples were stored at 5 or 10°C for 14 d, or at 25°C for 7 d. At intervals during storage, L. monocytogenes was enumerated by homogenization of cabbage with Butterfield’s phosphate buffer (BPB), and serial dilutions were plated onto Brain Heart Infusion (BHI) agar supplemented with rifampicin. No growth of L. monocytogenes was observed on cut red cabbage during storage at 5°C, and only minimal proliferation was observed at the higher temperatures. Significant population increases of 0.83 and 1.07 log CFU/g were determined after 3 d storage at 10 and 25°C, respectively. The modeled growth rates for L. monocytogenes on cut red cabbage storage at 5 and 10°C were 0.11±0.03 and 0.27±0.07 log CFU/g per d, with calculated times to a 1 log CFU/g increase of 9.51 and 3.70 d, respectively; however, L. monocytogenes did not achieve a 1 log increase at either temperature in this study. At 25°C, the modeled growth rate of L. monocytogenes on cut red cabbage was 1.15±0.36 log CFU/g, leading to calculated and observed 1 log increases in 0.87 and 3.00 d, respectively. Results from this study aid in understand the fate of L. monocytogenes on cut red cabbage during storage at different temperatures.