Category Archives: Technology

Research – Preliminary Assessment of Visible, Near-Infrared, and Short-Wavelength–Infrared Spectroscopy with a Portable Instrument for the Detection of Staphylococcus aureus Biofilms on Surfaces

Journal of Food Protection

ABSTRACT

Bacterial biofilms constitute a major source of sanitary problems and economic losses in the food industry. Indeed, biofilm removal may require intense mechanical cleaning procedures or very high concentrations of disinfectants or both, which can be damaging to the environment and human health. This study assessed the efficacy of a technique based on spectroscopy in the visible, near-infrared, and short-wavelength infrared range for the quick detection of biofilms formed on polystyrene by the pathogenic bacterium Staphylococcus aureus. To do that, biofilms corresponding to three S. aureus strains, which differed in biofilm-forming ability and composition of the extracellular matrix, were allowed to develop for 5 or 24 h, representing an active formation stage and mature biofilms, respectively. Spectral analysis of the samples, corresponding to three biological replicates of each condition, was then performed by using a portable device. The results of these experiments showed that partial least-squares discriminant analysis of the spectral profile could discriminate between surfaces containing attached bacterial biomass and noninoculated ones. In this model, the two first principal components accounted for 39 and 19% of the variance and the estimated error rate stabilized after four components. Cross-validation accuracy of this assessment was 100%. This work lays the foundation for subsequent development of a spectroscopy-based protocol that allows biofilm detection on food industrial surfaces.

HIGHLIGHTS
  • A biofilm detection spectroscopy–based technique with a portable device was tested.

  • Staphylococcus aureus biofilms of different strengths were scanned with the device.

  • Spectral data showed correlation with crystal violet staining quantification results.

  • Data from spectral analysis was suitable for prediction of biofilm contamination.

Research – High-Intensity Light Pulses To Inactivate Salmonella Typhimurium on Mexican Chia (Salvia hispanica L.) Seeds

Journal of Food Protection

ABSTRACT

Chia seeds provide a suitable environment for microorganisms. However, it is difficult to disinfect these seeds with water and/or chemical disinfectant solutions because the mucilage in the seeds can absorb water and consequently form gels. High-intensity light pulses (HILP) is one of the most promising emerging technologies for inactivating microorganisms on surfaces, in clear liquids and beverages, and on solid foods. The aim of this work was to evaluate the effect of HILP on SalmonellaTyphimurium in culture medium (in vitro tests) and inoculated onto chia seeds (in vivo tests). HILP was effective against Salmonella Typhimurium under both conditions: 8 s of treatment (10.32 J/cm2) resulted in a 9-log reduction during in vitro tests, and 15 s of treatment (19.35 J/cm2) resulted in a 4-log reduction on the inoculated chia seeds. Salmonella Typhimurium inactivation kinetics were accurately described using the Weibull model (R2 > 0.939). These results indicate that the use of HILP for microbial inactivation on seeds could generate products suitable for human consumption.

HIGHLIGHTS
  • Decontamination of chia seeds is complex because of rapid formation of gel on the seeds.

  • HILP was effective against Salmonella Typhimurium in vitro and on chia seeds.

  • The Weibull model appropriately described Salmonella Typhimurium inactivation curves.

  • HILP is a promising emerging technology for eliminating pathogens from chia seeds.

Research – Ultrasound treatment combined with fumaric acid for inactivating food-borne pathogens in apple juice and its mechanisms

Science Direct

Highlights

The combination of Ultrasound (US) and fumaric acid (FA) showed a synergistic bactericidal effect in apple juice.

US-FA combined treatment of apple juice did not affect quality.

Cell membrane damage was the main mechanism of US-FA synergistic lethal effect.

Abstract

The purpose of this study was to evaluate the synergistic bactericidal efficacy of combining ultrasound (US) and fumaric acid (FA) treatment against Escherichia coliO157:H7, Salmonella Typhimurium, and Listeria monocytogenes in apple juice and to identify the synergistic bactericidal mechanisms. Additionally, the effect of combination treatment on juice quality was determined by measuring the changes in color, pH, non-enzymatic browning index, and total phenolic content. A mixed cocktail of the three pathogens was inoculated into apple juice, followed by treatment with US (40 kHz) alone, FA (0.05, 0.1, and 0.15%) alone, and a combination of US and FA for 1, 2, 3, 4, and 5 min. Combined US and 0.15% FA treatment for 5 min achieved 5.67, 6.35, and 3.47 log reductions in E. coli O157:H7, S.Typhimurium, and L. monocytogenes, respectively, with the 1.55, 2.37, and 0.57 log CFU reductions attributed to the synergistic effect. Although the pH value slightly decreased as FA increased, there were no significant (P > 0.05) differences in color values, browning indices, and phenolic content between untreated and treated samples. To identify the mechanism of this synergistic bactericidal action, membrane integrity, malfunctions in the membrane efflux pump, and intracellular enzyme activity were measured. The analyses confirmed that damage to the cell envelope (membrane integrity and efflux pump) was strongly related to the synergistic microbial inactivation. These results suggest that simultaneous application of US treatment and FA is a novel method for ensuring the microbial safety of apple juice.

Research – Antimicrobial Activity and Action Approach of the Olive Oil Polyphenol Extract Against Listeria monocytogenes

Frontiers in Microbiology

Olive oil polyphenol extract (OOPE) has been reported to have antibacterial activity; however, its effect on Listeria monocytogenes is less studied so far. This study, thus, aimed to reveal its antimicrobial activity and action approach against L. monocytogenes via evaluating the minimum inhibitory concentration (MIC) as well as the changes of intracellular adenosine 5′-triphosphate (ATP) concentration, cell membrane potential, bacterial protein, DNA, and cell morphology. The results showed that OOPE could inhibit the growth of L. monocytogeneswith a measured MIC of 1.25 mg/ml. L. monocytogenes cells treated by OOPE showed significant reduction in intracellular ATP concentrations, bacterial protein, or DNA (p < 0.05), in comparison with those without any treatment. In addition, OOPE was observed to depolarize strain cells and alter cell morphology, resulting in damaged cell membrane and, thereby, leakage of cell fluid. These findings demonstrated that OOPE had inhibition on L. monocytogenes via its action on cells, suggesting its potential as a natural preservative.

Research – Preservation of ready-to-eat salad: A study with combination of sanitizers, ultrasound, and essential oil-containing β-cyclodextrin inclusion complex

Science Direct

Highlights

Peracetic acid is a good alternative to chlorine for fresh produce sanitization.

Ultrasound enhanced peracetic acid efficiency.

Sachet with essential oil did not contribute to salad preservation.

Complexation with β-CD did not attenuate EO odor.

EO in vitro antimicrobial activity does not imply preservative property in food.

Abstract

The microbiological quality of a ready-to-eat salad treated with different sanitizers (sodium dichloroisocyanurate (SD), peracetic acid (PA) or isolated or combined with ultrasound (US)), and packaged alongside sachets containing β-cyclodextrin/Pimenta dioica essential oil inclusion complex was evaluated. Consumer acceptability was also assessed. Furthermore, treatments were investigated against Listeria monocytogenes intentionally inoculated. SD, SD + US, and PA treatments showed similar efficiency against psychrotrophic (log reduction < 1) and lactic acid bacteria (log reductions of 1.18 ± 0.25, 1.28 ± 0.19 and 1.03 ± 0.22 for SD, SD + US, and PA, respectively). Concerning yeasts and molds, SD and SD + US reached the greatest log reduction (counts < 4 log CFU g−1), whereas PA + US was more efficient than PA. Against L. monocytogenes, SD, SD + US and PA + US led to the best results. The presence of sachet, however, did not contribute to salad preservation. Sensory evaluation showed that salads stored alongside sachets were the least accepted by consumers with scores between 5 and 6 for overall impression attribute, while samples without sachets received average scores >7. These findings are of great importance since they demonstrate the need for studies that evaluate the properties of EO when applied in a food system.

Research – Prediction of Persistence of Listeria monocytogenes ST451 in a Rabbit Meat Processing Plant in the Czech Republic

Journal of Food Protection

ABSTRACT

This study was focused on characterization of the genetic diversity of Listeria monocytogenes isolated from packed fresh rabbit meat obtained from one producer via retail outlets. The partial aim was to compare the characteristics of a suspect persistent strain with strains from human cases. The occurrence of L. monocytogenes in vacuum-packed rabbit meat was monitored during 2013 to 2016. All strains were characterized by serotyping, pulsed-field gel electrophoresis, and multilocus sequence typing (MLST). Selected strains, which represented each year, were analyzed using the whole genome sequencing method. L. monocytogenes was detected in 21 (38%) of 56 originally packed rabbit meat samples from one food producer during the whole monitored period. All strains showed the identical serotype (1/2a), AscI/ApaI pulsotype (735/2), and sequence type (ST451). The clonal similarity of strains from rabbit meat was also confirmed on the basis of core genome MLST (on 1,701 loci). This fact suggests the occurrence of a suspect persistent strain in the meat processing plant. Results of core genome MLST enabled us to unambiguously exclude rabbit meat as a source of listeriosis in humans caused by the indistinguishable AscI/ApaI pulsotype and sequence type, although all strains carried all genes important for the virulence of L. monocytogenes. No specific genes that may be associated with its persistence in the food processing environment were detected among the tested strains of ST451.

HIGHLIGHTS
  • Rabbit meat is not often reported as a source of L. monocytogenes.

  • Rare ST451 was detected as a suspect persistent strain for the first time.

  • Genetic factors linked to persistence of L. monocytogenes ST451 were not found.

  • PMSC mutations in inlA, inlB, and LIPI-1 genes were not detected in tested strains.

Research – Take two E. coli and call me in the morning

Science Daily

Millions of people take capsules of probiotics with the goal of improving their digestion, but what if those bacteria were also able to detect diseases in the gut and indicate when something is awry? New research from the Wyss Institute at Harvard University and Harvard Medical School (HMS) has created an effective, non-invasive way to quickly identify new bacterial biosensors that can recognize and report the presence of various disease triggers in the gut, helping set the stage for a new frontier of digestive health monitoring and treatment. The paper is published in mSystems.

“Our understanding of how the human gut microbiome behaves is still in its early stages, which has hindered large-scale research into creating biosensors out of living bacteria,” said David Riglar, Ph.D., a former postdoc at the Wyss Institute and HMS who now leads a research group as a Sir Henry Dale Fellow at Imperial College London. “This work provides a high-throughput platform for identifying genetic elements in bacteria that respond to different signals in the gut, putting us one step closer to engineering complex signaling pathways in bacteria that allow them to detect and even treat diseases long-term.”