Reduction of Escherichia coli O157:H7 counts on whole fresh apples by treatment with sanitizers

The objectives of this study were to determine if washing of whole apples with solutions of three different sanitizers (peroxyacetic acid, chlorine dioxide, or a chlorine-phosphate buffer solution) could reduce a contaminating nonpathogenic Escherichia coli O157:H7 population by 5 logs and at what s...

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Bibliographic Details
Published in:	Journal of food protection Vol. 63; no. 6; p. 703
Main Authors:	Wisniewsky, M A, Glatz, B A, Gleason, M L, Reitmeier, C A
Format:	Journal Article
Language:	English
Published:	United States 01-06-2000
Subjects:	Buffers Chlorine Chlorine Compounds Colony Count, Microbial Disinfectants Escherichia coli O157 - isolation & purification Food Handling - methods Oxides Peracetic Acid Phosphates Rosales - microbiology
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Summary:	The objectives of this study were to determine if washing of whole apples with solutions of three different sanitizers (peroxyacetic acid, chlorine dioxide, or a chlorine-phosphate buffer solution) could reduce a contaminating nonpathogenic Escherichia coli O157:H7 population by 5 logs and at what sanitizer concentration and wash time such a reduction could be achieved. Sanitizers were tested at 1, 2, 4, 8, and 16 times the manufacturer's recommended concentration at wash times of 5, 10, and 15 min. Whole, sound Braeburn apples were inoculated with approximately 1 x 108 or 7 x 106 CFU per apple, stored for 24 h, then washed with sterile water (control) or with sanitizers for the prescribed time. Recovered bacteria were enumerated on trypticase soy agar. Washing with water alone reduced the recoverable population by almost 2 logs from the starting population; this can be attributed to physical removal of organisms from the apple surface. No sanitizer, when used at the recommended concentration, reduced the recovered E. coli population by 5 logs under the test conditions. The most effective sanitizer, peroxyacetic acid, achieved a 5-log reduction when used at 2.1 to 14 times its recommended concentration, depending on the length of the wash time. The chlorine-phosphate buffer solution reduced the population by 5 logs when used at 3 to 15 times its recommended concentration, depending on wash time. At no concentration or wash time tested did chlorine dioxide achieve the 5-log reduction.
ISSN:	0362-028X
DOI:	10.4315/0362-028X-63.6.703