Antimicrobial Effects of Plant Compounds against Virulent <i>Escherichia coli</i>O157:H7 Strains Containing Shiga Toxin Genes in Laboratory Media and on Romaine Lettuce and Spinach

Escherichia coli strains produce Shiga-toxins Stx-1 and Stx-2 that contribute to their virulence. The objective was to evaluate antimicrobial activities of plant essential oils (oregano, cinnamon, lemongrass), their active components (carvacrol, cinnamaldehyde, citral) and plant-extracts (green tea polyphenols, apple skin, black tea, decaffeinated black tea, grapeseed and pomace extracts) against E. coli O157:H7 strains containing Stx-1 and Stx-2 genes, as determined by Multiplex Polymerase Chain Reaction, in vitro and on leafy greens. Antimicrobials at various concentrations in sterile PBS were added to bacterial cultures (~3 - 4 logs CFU/ml), mixed thoroughly, and incubated at 37°C. Surviving bacteria were enumerated at 0, 1, 3, 5 and 24 h. The most effective essential oil (oregano oil;0.5%) and plant extract (green tea;3%) were evaluated against E. coli O157:H7 on romaine lettuce and spinach stored at 4°C for 7 days. Microbial survival was a function of the concentration of antimicrobials and incubation times. All antimicrobials reduced bacterial population to below detection levels in vitro;however, essential oils and active components exhibited greater activity than plant extracts. Oregano oil and green tea reduced E. coli O157:H7 on lettuce and spinach to below detection. Plant-based antimicrobials have the potential to protect foods against E. coli O157:

Development of an Infusion Based on Romaine Lettuce and Banana for Treating Insomnia

An infusion was developed based on green romaine lettuce leaves and banana. Further, its sensorial acceptability was evaluated as a possible alternative treatment for insomnia. The romaine lettuces and bananas used were washed, chopped, dehydrated and ground. Optimal lettuce dehydration time was determined through charting the weight lost and examining the curve. This was found after 180 minutes at 60°C. Two formulas were developed, the first with 1.1 g of dehydrated romaine lettuce and 0.2 g of dehydrated banana, and the second with 1.1 g of dehydrated romaine lettuce and 0.4 g of dehydrated banana. Sensory analysis was conducted using sorting tests for taste, aroma, paired preferences and intention to purchase. Tasters preferred the formula with a lower quantity of dehydrated banana. 85% of tasters indicated that they would buy this infusion due to its potential functional properties for overcoming insomnia.