The beneficial health effects of extracts from many types of plants that are used as seasoning agents in foods and beverages have been claimed for centuries. The purpose of this study was to examine the effectiveness of selected herb and spice essential oils for control of growth and survival of microorganisms. Inhibition of growth was tested by the paper disc agar diffusion method. Antibiotic susceptibility discs were used as control. Minimum lethal concentration (MLC) was determined by the tube dilution method. Essential oils from anise, angelica, basil, carrot, celery, cardamom, coriander, dill weed, fennel, oregano, parsley, and rosemary were evaluated. Inhibition ranged from complete with oregano to no inhibition with carrot oil for each of the test strains that included: Listeria monocytogenes, Staphylococcus aureus, Escherichia coli O:157:H7, Yersinia enterocolitica, Pseudomonas aeruginosa, Lactobacillus plantarum, Aspergillus niger, Geotrichum, and Rhodotorula. Oregano essential oil showed the greatest inhibition (zone, > or = 70 to 80 mm) (MLC, approximately 8 ppm). Coriander and basil were also highly inhibitory (MLC, approximately 25 to 50 ppm) to E. coli O:157:H7 and to the other bacteria and fungi tested. Anise oil was not particularly inhibitory to bacteria (inhibition zone, approximately 25 mm); however, anise oil was highly inhibitory to molds. Because some of the herbal and spice essential oils are highly inhibitory to selected pathogenic and spoilage microorganisms, they may provide alternatives and supplements to conventional antimicrobial additives in foods.

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.

In three replicate trials, a total of 36 pigs that had been cannulated at the terminal ileum were used to determine the effects of a Saccharomyces cerevisiae culture in a phase feeding program (phase I was d 0 to 7 and phase II was d 8 to 21) on performance, ileal microflora, and short-chain fatty acids in weanling pigs. Pigs were cannulated at approximately 12 d of age, weaned at 17 d of age, and randomly assigned to one of three treatments: 1) a pelleted phase feeding program, 2) a similar program with the inclusion of a live S. cerevisiae culture (1 g/ kg), and 3) a nonpelleted feeding program otherwise similar to program 2. Ileal samples were collected at 17, 20, 24, 27, 31, 34, and 38 d of age, and samples were analyzed for total E. coli, streptococci, lactobacilli, yeast, short-chain fatty acids, pH, and dry matter. Performance data were also collected. At 41 d of age, pigs were killed and digesta were collected from various regions of the gastrointestinal tract. Total intake was less for pigs fed the control diet than for pigs fed the yeast diets, and overall gains tended to be greater for pigs fed diets including yeast. Treatment differences were not observed for ileal microflora or short-chain fatty acids in samples obtained from cannulas or from the various sites of the gastrointestinal tract. Inclusion of a live yeast culture in weanling pig diets affected intake and performance but did not alter tested intestinal microflora or net concentrations of fermentation products.

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.

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