Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/19/2014
Publication Date: 6/21/2014
Citation: Niemira, B.A., Boyd, G., Sites, J.E., Taylor, J. 2014. Thermal inactivation of Salmonella and E.coli 0157:H7 on Roma tomato stem scars using high-intensity infrared laser light. Meeting Abstract. IFT Annual Meeting., New Orleans, LA., June 21-24, 2014.,Volume 1, Page 1.
Technical Abstract: Foodborne illness associated with contaminated produce is a continuing concern. Compared to the skin surface, stem scar areas of intact fruits and vegetables harbor more bacteria and are more resistant to chemical sanitizing processes. This study evaluated a precision thermal kill process which uses a high-intensity infrared (1064nm) laser to selectively heat the stem scar area of Roma tomatoes. Cocktails of three Salmonella cultures (S. anatum F4317, S. stanley H0558, S. enteritidis PT30) or three Escherichia coli O157:H7 (C9490, 35150, 43894) were spot inoculated (10µl) onto the stem scar areas of Roma tomatoes and allowed to absorb for 30 minutes. These were exposed for 0s (control), 10s, 20s or 30s to the beam of a PicoSpark infrared laser with a beam diameter of 3mm, pulse frequency of 30 kHz, and energy output of 200µJ/pulse. The tomatoes were moved during treatment to ensure uniform beam coverage of the entire stem scar and to avoid sensory damage from excessive spot heating. For the treatments of 10, 20 or 30s, Salmonella was reduced by 0.82, 1.66 and 1.95 log cfu. The same treatments reduced E. coli O157:H7 by 0.75, 1.28 and 1.51 logs. Deposition of laser beam heating was selective. The stem scar area tended to heat on absorption of the laser energy, while the surrounding smooth skin tended to reflect the laser energy away and remain unaffected. These results suggest that high intensity infrared lasers may have potential as a means for precision thermal inactivation of human pathogens on intact fruits and vegetables with complex surfaces.