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Cold Plasma Reduction of Salmonella and Escherichia coli O157:H7 on Almonds Using Ambient Pressure Gases
Author(s) -
Niemira Brendan A.
Publication year - 2012
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1750-3841.2011.02594.x
Subject(s) - salmonella , chemistry , escherichia coli , food science , antimicrobial , contamination , agar , inoculation , microbiology and biotechnology , bacteria , biology , horticulture , biochemistry , ecology , genetics , gene , organic chemistry
Contamination of raw nuts, including almonds, is a food safety concern. Cold plasma is a novel antimicrobial intervention that can eliminate foodborne pathogens. The objective of this work was to evaluate the efficacy of rapid cold plasma treatments in eliminating Salmonella and Escherichia coli O157:H7 from dry almonds. Three isolates of Salmonella ( S. Anatum F4317, S. Stanley H0558, and S. Enteritidis PT30) and 3 isolates of E. coli O157:H7 (C9490, ATCC 35150, and ATCC 43894) were separately grown and spot‐inoculated (10 μL) onto whole almonds and allowed to dry for 10 min. Inoculated almonds were treated with a cold plasma jet, with treatment variables evaluated in a factorial design for each isolate: time, distance, and feed gas. Treatment time was 0 s (control), 10 s, or 20 s. Distance from the emitter was 2, 4, or 6 cm. Feed gas was dry air or nitrogen. After treatment, the almonds were sampled using swabs. Survivors were enumerated on tryptic soy agar (TSA) plates. Cold plasma significantly reduced both pathogens on almonds. The greatest reduction observed was 1.34 log cfu/mL reduction of E. coli O157:H7 C9490 after 20 s treatment at 6 cm spacing. The interaction of treatment time with distance from plasma emitter head was complex, and isolate‐dependent. Longer duration of treatment did not always result 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 atmospheric pressure cold plasma can significantly reduce Salmonella and E. coli O157:H7 on almonds. Practical Application: Contamination of raw nuts, including almonds, is a food safety concern. Cold plasma is a novel antimicrobial intervention that can eliminate foodborne pathogens. The results of this research show that short pulses of atmospheric pressure cold plasma can significantly reduce Salmonella and E. coli O157:H7 on almonds. A 20 s treatment was sufficient to achieve up to 1.34 log reduction, depending on treatment parameters. This process is a waterless, contact‐less, chemical‐free method of killing hard‐to‐reach pathogens on almonds.