Control of Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes inoculated in beetroot or watermelon juice by combined treatments with organic acid or lemon (Citrus limon) extract and mild heat.

The study aimed to evaluate the synergistic interaction of organic acids (OAAs) or lemon extract (LE) plus mild heat (MH; 55 °C) against Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes inoculated in beetroot and watermelon juices. A mixed culture cocktail of E. coli O157:H7, S. Typhimurium or L. monocytogenes was inoculated in beetroot or watermelon juice, followed by treatments with MH, citric acid + MH, malic acid + MH, tartaric acid + MH, and LE + MH. Approximately < 2.0-log reductions in the number of E. coli O157:H7, S. Typhimurium, and L. monocytogenes were observed when these bacteria were heated in juices at 55 °C for 5 min. A combination of 1.0% OAAs or 20% LE and MH (55 °C) for 5 min resulted in an additional log-reduction in the count of E. coli O157:H7, S. Typhimurium, and L. monocytogenes by 2.2-5.0, 4.5-5.0, and 1.5-5.0, respectively.

Application of sodium alginate-based edible coating with citric acid to improve the safety and quality of fresh-cut melon (Cucumis melo L.) during cold storage.

The safety and quality of fresh-cut melons is reduced by a series of decay processes by enzymatic browning and microbial contamination. This study aimed to assess the impact of a 2% sodium alginate-based edible coating (ALC) combined with different concentrations of citric acid (CA; 0.5%, 1%, 2%, and 3%) on the microbial safety and physical quality of fresh-cut melons during a 7-day storage period at 10 °C. The findings revealed that the combination of ALC and 3% CA was successful in preventing the growth of pathogenic bacteria (Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes, and Staphylococcus aureus) and natural microflora on fresh-cut melons during storage. In addition, treating fresh-cut melons with ALC containing 3% CA improved their quality by reducing browning and softening during storage at 10 °C. Based on these findings, it can be concluded that using ALC with 3% CA is an effective method to improve the safety and quality of fresh-cut melons.

Evaluation of microbiological quality and safety of fresh-cut fruit products at retail levels in Korea.

The risk of foodborne illnesses caused by pathogens could be increased in fresh-cut fruit products owing to contamination during processing. Therefore, this study was conducted to investigate the microbiological quality and safety of commercial fresh-cut fruit products in Korea. Additionally, the growth of Listeria monocytogenes in selected fresh-cut fruits was evaluated, and their growth curves were analyzed using predictive growth modeling. The mean count of total aerobic bacteria, coliforms, and yeast/mold was 3.67±1.73 log10 CFU/g, 1.54±1.01 log10 CFU/g, and 3.81±1.51 log10 CFU/g, respectively. Escherichia coli, Staphylococcus aureus, Escherichia coli O157:H7, L. monocytogenes, Salmonella spp., and Cyclospora spp. were not detected in any of the tested samples. Only Bacillus cereus was detected in a few samples at the mean level of 1.72±0.13 log10 CFU/g. The growth of L. monocytogenes varied depending on the type of fruit; they grew well in non-acidic fresh-cut fruit products during storage at 10 °C.

Development of enhanced selective media for detection of Vibrio parahaemolyticus in oysters.

This study was undertaken to develop enhanced selective media for detection of Vibrio parahaemolyticus in oysters. Primarily, tryptic soy agar (TSA) was supplemented with 4.5-5% NaCl, 0.1-0.5% oxgall, and/or 1-2% sodium citrate, and adjusted to pH 8-9. A total of 21 Vibrio spp., 24 indicators, and 26 food-borne isolates were streaked on the modified media, followed by 24 h of incubation at 37 °C. While all the indicators and isolates failed to grow on TSA containing 5% NaCl, 0.5% oxgall, and 2% sodium citrate (TSAOSS1; pH 9), V. parahaemolyticus was culturable on this selective medium. Particularly, the ability of TSAOSS1 to quantify V. parahaemolyticus in oysters was superior to thiosulphate citrate bile salts sucrose (TCBS) agar. V. parahaemolyticus distinctly produced its white-yellowish, round, and edge-pointed colony on TSAOSS1. TSAOSS1 with high selectivity potentials over TCBS may be a promising alternative for detection of V. parahaemolyticus in seafoods or natural reservoirs. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at (10.1007/s10068-021-00877-0).