Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 3/6/2010
Publication Date: 7/19/2010
Citation: Niemira, B. 2010. Short pulse cold plasma treatment reduces salmonella and E.coli O157:H7 on almonds [abstract].Institute of Food Technologies Annual Meeting.Chicago,IL.p.1. Interpretive Summary:
Technical Abstract: Contamination of dry nuts, including almonds is a food safety concern. A nonthermal method for reducing or eliminating is a desirable tool for producers and processors. Cold plasma is a novel antimicrobial intervention that can eliminate foodborne pathogens on produce. A key consideration for any treatment is the speed of processing. The objective of this work was to evaluate the efficacy of short-pulse cold plasma treatments in eliminating Salmonella and E. coli O157:H7 from dry almonds. Three isolates of Salmonella (S. anatum F4317, S. stanley H0558 and S. enteritidis PT30) and three isolates of E. coli O157:H7 (C9490, ATCC 35150, and ATCC 43894) were separately grown and spot-inoculated (10ul) onto whole almonds. Inoculation spots were allowed to dry for 10 minutes. Inoculated almonds were positioned under a stream of cold plasma generated using a modified Enercon Dyne-A-Mite HP plasma jet emitter. Three treatment variables were evaluated in a factorial design for each isolate: time, distance and feed gas. Treatment time was 0s (control), 10s or 20s. Distance from the emitter was 2, 4 or 6 cm. Feed gas was either dry air or pure nitrogen. After treatment, the almonds were sampled using swabs, and survivors were enumerated on TSA plates. Cold plasma significantly reduced both pathogens on almonds. The greatest reduction observed was 1.34 log cfu reduction of E. coli O157:H7 C9490 after 20s treatment at 6cm spacing. The interaction of treatment time with distance from plasma emitter head was complex, and isolate-dependent. Longer duration of treatment did not always results in enhanced reductions. In general, nitrogen as a feed gas resulted in a reduced antimicrobial efficacy compared to dry air. These results indicate that short pulses of cold plasma can significantly reduce Salmonella and E. coli O157:H7 on almonds. This information will be of value in defining research parameters for improving the application of cold plasma to almonds and other dry nuts.