Satchithanandam Eswaranandam

Electrostatic spraying of organic acids on biofilms formed by E. coli O157:H7 and Salmonella Typhimurium on fresh produce

Electrostatic spraying which has an even and retained surface coverage could be an effective novel technique to completely cover the surface of fresh produce to disrupt biofilm formation by pathogenic bacteria. Spinach leaves and cantaloupe rind were spot-inoculated with a bacterial culture and stored at 8°C for 72h to allow biofilm formation. Among various green fluorescent protein-labeled strains, ED 14 strain of E. coli O157:H7 and SD 10strain of Salmonella Typhimurium had the best attachment based on colony counts. The produce samples were electrostatically sprayed with malic (MA) and lactic (LA) acid solutions alone (1.0/2.0/3.0/4.0% w/v) or in combination (0.5+0.5/1.0+1.0/1.5+1.5/2.0+2.0% w/v) to test for a reduction in the attached bacteria. A combined treatment of LA 2.0% w/v+MA 2.0% w/v had the highest log reduction (CFU/disk) of 4.14 and 3.6 on the attached E. coli strain ED 14 (spinach) and Salmonella strain SD 10 (cantaloupe), respectively. Crystal violet assay demonstrated the disruptive effect of organic acids on biofilms formed by the pathogenic bacteria. Application of electrostatic spray with a combination of malic and lactic acids resulting in a log reduction (CFU/disk) of 3.6 or higher can improve the microbial safety of spinach and cantaloupe by preventing the pathogenic biofilm formation and bacterial growth.

Effect of Elicitor Spray at Different Reproductive Stages on Saponin Content of Soybean

The beneficial health effects of soybeans may be enhanced by increasing bioactive compounds including soyasaponins (ssp). The objective of this study is to elucidate the effect of elicitors sprayed on Ozark variety soybeans, on ssp content. Different concentrations of elicitors, ethyl acetate (EA) and methyl jasmonate (MJ), were sprayed at 4 different growth stages (1-bloom, 2-pod development, 3-seed development, and 4-seed maturity). Seeds were ground, defatted, ssp was extracted and identified and quantified with HPLC. Elicitor and growth stage had an effect on βg and βa contents of soybeans compared with control (P < 0.05). Elicitor had an effect on total ssp content (P < 0.001) and αg and γg content of soybeans compared with control (P < 0.05). Total ssp content of EA 0.05 M, MJ 0.001 M, and 0.005 M sprayed soybeans were higher than EA 0.001 M, which is higher than control (P < 0.05; 3.62, 3.56, 3.56, 3.29, and 2.98 μmol/g soybean, respectively). The overall effect of elicitor on total ssp content was not dependent on growth stage, however, elicitors sprayed at growth stages 1, 2, and 3 showed differences among elicitor applied soybeans. Elicitors applied at growth stage 4 did not have any effect on total ssp content compared to control. Elicitors EA 0.05 M, MJ 0.001, and 0.005 M can be applied on any growth stage to increase total saponin content of soybean variety Ozark. Higher saponin content may improve the beneficial health effects of soybean consumption.