Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 2/9/2005
Publication Date: 8/16/2005
Citation: Niemira, B.A., Gutsol, A., Fridman, A. 2005. Cold, atmospheric pressure plasma reduces listeria innocua on the surface of apples.Annual Meeting of International Association of Food Protection (IAFP), August 14-17, 2005, Baltimore, MD. p. 2-40. Interpretive Summary:
Technical Abstract: Fresh produce can be contaminated with bacterial pathogens, leading to increased risk of food-borne illness. High energy plasma discharges effectively inactivate bacteria on inert surfaces, and have potential application to fragile surfaces such as fruits and vegetables. A novel technology, the gliding arc plasma discharge apparatus, allows the deposition of a cold, atmospheric pressure plasma (CAPP) onto surfaces through the used of forced air, thereby reducing the potential for excessive heat or spot damage to the surface. Golden delicious apples were spot inoculated with approximately 8 log10 cfu of the non-pathogenic surrogate Listeria innocua in log growth phase. On separate sets of apples, the spot was left untreated (control) or treated with one of two levels of CAPP discharge. In the first ('Low'), the discharge amperage was set to 115mA, placing the CAPP discharge height approximately 1cm away from the apple surface, and the treatment lasted for 2 minutes. In the second ('High'), the discharge amperage was set to 150mA, placing the plasma discharge in full contact with the apple surface, and the treatment lasted for 4 minutes. The voltage was held constant at 10.02kV. Separate sets of inoculated apples were treated with either 2 or 4 minutes of forced air with no CAPP discharge. Apple surfaces with sampled with sterile swabs and phosphate buffer, serially diluted and plated on PALCAM agar. There were no significant (P<.05) differences in L. innocua recovery among the control, Air-2 or Air-4 treatments, which had 4.29, 4.36 and 4.42 log10 cfu, respectively. The CAPP treatments significantly reduced the recoverable L. innocua, by 0.39 log10 cfu in the case of 'Low', and by 1.10 log10 cfu in the case of 'High'. The apples were examined for gross changes in color and appearance at the site of treatment immediately after treatment, and after 2 and 5 days in storage at 8C. No changes were observed. These results suggest that CAPP may be an effective treatment for the reduction of microbial populations on fragile produce surfaces. The results of optimized treatments will be discussed.