A study was conducted to determine the effect of one atmosphere uniform glow discharge plasma (OAUGDP) on inactivation of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes on apples, cantaloupe, and lettuce, respectively. A five-strain mixture of cultured test organisms was washed, suspended in phosphate buffer, and spot inoculated onto produce (7 log CFU per sample). Samples were exposed inside a chamber affixed to the OAUGDP blower unit operated at a power of 9 kV and frequency of 6 kHz. This configuration allows the sample to be placed outside of the plasma generation unit while allowing airflow to carry the antimicrobial active species, including ozone and nitric oxide, onto the food sample. Cantaloupe and lettuce samples were exposed for 1, 3, and 5 min, while apple samples were exposed for 30 s, 1 min, and 2 min. After exposure, samples were pummeled in 0.1% peptone water-2% Tween 80, diluted, and plated in duplicate onto selective media and tryptic soy agar and incubated as follows: E. coli O157:H7 (modified eosin methylene blue) and Salmonella (xylose lysine tergitol-4) for 48 h at 37 degrees C, and L. monocytogenes (modified Oxford medium) at 48 h for 32 degrees C. E. coli O157:H7 populations were reduced by >1 log after 30-s and 1-min exposures and >2 log after a 2-min exposure. Salmonella populations were reduced by >2 log after 1 min. Three- and 5-min exposure times resulted in >3-log reduction. L. monocytogenes populations were reduced by 1 log after 1 min of exposure. Three- and 5-min exposure times resulted in >3- and >5-log reductions, respectively. This process has the capability of serving as a novel, nonthermal processing technology to be used for reducing microbial populations on produce surfaces.

Natural antimicrobials are gaining increased interest from researchers and food manufacturers alike seeking to discover label-friendly alternatives to the widely implemented synthetic compounds. Naturally occurring antimicrobials can be applied directly to food to protect food quality, extend food shelf life by inhibiting or inactivating spoilage microorganisms, and improve food safety by inhibiting or inactivating food-borne pathogens. There are a great number of natural antimicrobials derived from animal, plant, and microbial sources. This manuscript reviews their efficacy against spoilage and pathogenic organisms, their methods of evaluation, and their application in various foods as well as the development of novel delivery systems and incorporation with other hurdles.

No abstract

No abstract

This study was conducted to determine the efficacy of a one atmosphere uniform glow discharge plasma (OAUGDP) for inactivation of foodborne pathogens and to evaluate the influence of growth temperature, pH, and culture age on their inactivation. Escherichia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, Salmonella Enteritidis, Vibrio parahaemolyticus, Yersinia enterocolitica, and Shigella flexneri were evaluated. Three-strain mixtures of each bacterium were inoculated (6-7 log CFU/cm(2)) onto microscope slides containing nonselective agar media adjusted to pH 5 or 7. Samples were exposed to plasma for 0-240 sec immediately, or after incubation for 24 h at 10 degrees C or 35 degrees C. After exposure, the agar was removed from the slides and pummeled in 0.1% peptone water with a stomacher, serially diluted, surface plated onto nonselective media, and incubated at 35 degrees C. Exposure time, pH, incubation temperature, and culture age affected survival of all pathogens exposed to plasma (P < 0.05). The greatest reduction of pathogens generally occurred during the initial exposure time of 30 or 90 sec. Pathogens incubated for 24 h before exposure were more resistant than those exposed immediately after inoculation. Incubation at 35 degrees C before exposure resulted in greater resistance to plasma inactivation than incubation at 10 degrees C. No appreciable differences between gram-positive and gram-negative pathogens were observed, although the spore-forming B. cereus was more resistant to plasma than non-spore-formers. These findings support the potential for plasma treatment of foods or surfaces for pathogen reduction. Increased sensitivity of pathogens to plasma at reduced pH and temperature is encouraging, since these conditions are applicable to many foods during processing, handling, and storage.