FOOD MICROBIOLOGY www.elsevier.nl/locate/jnlabr/yfmic Food Microbiology 21 (2004) 105–110 Inactivation of Escherichia coli O157:H7 by cinnamic aldehyde purified from Cinnamomum cassia shoot H.-O. Kim 1 , S.-W. Park 2 , H.-D. Park* Department of Food Science and Technology, Kyungpook National University, 1370 Sankyuk, Daegu 702-701, South Korea Received 16 October 2002; accepted 16 January 2003 Abstract Escherichia coli O157:H7 is a pathogen, which causes the hemorrhagic colitis, hemolytic uremic syndrome and thrombotic thrombocytopenic purpura in humans. Control of the bacterial cells in foods is an important factor to reduce outbreaks of the foodborne diseases. In this study, cinnamic aldehyde possessing antimicrobial activity against the bacterial cells was purified from the extract of cinnamon (Cinnamomum cassia Blume) shoot by sequential fractionation with various solvents and silica gel column chromatography. When E. coli O157:H7 cells were incubated at 37  C for 12h in the presence of 500 mgml 1 of the purified from cinnamic aldehyde, the viable counts decreased dramatically (from 4.9  10 6 to 1.0  10 2 cfuml 1 ). In the presence of 1000 mgml 1 of the substance, most of the cells were killed after 2h of incubation suggesting that the antimicrobial activity of cinnamic aldehyde is bacteriocidal in E. coli. Scanning electron microscopic observations revealed that the bacterial cells treated with the cinnamic aldehyde suffered from severe damages in their surface structure. Minimal inhibitory concentration of the cinnamic aldehyde was determined to be 250 mgml 1 against E. coli strains O157:H7 and O26 or 500 mgml 1 against strains ATCC11105 and O111. r 2003 Elsevier Ltd. All rights reserved. Keywords: Antimicrobial effect; Bacteriocidal; Cinnamic aldehyde; Cinnamomum cassia; Cinnamon shoot; E. coli; O157:H7 1. Introduction Strains of Escherichia coli reside in the intestine of humans as an integral part of the normal bacterial flora. These commensal strains may perform essential func- tions for the host, but a few strains are pathogenic, which cause distinct diarrhea syndromes. Among them are enteropathogenic, enteroinvasive, enterotoxigenic and enterohemorrhagic E. coli (EHEC). E. coli O157:H7, a strain of EHEC, was first recognized as a human pathogen in 1982 which causes the hemorrhagic colitis, hemolytic uremic syndrome and thrombotic thrombocytopenic purpura in humans (Zottola and Smith, 1991). Although person-to-person transmission of the pathogenic E. coli has been reported in some day- care centers and nursing home outbreaks, its main transmission mode has been reported to be through foods. Many food-associated outbreaks caused by E. coli O157:H7 have occurred from apple cider, ground beef, poultry, milk, hamburger, ham and cheese sandwiches (Zottola and Smith, 1991). Therefore, there have been many studies on the detection and control methods of E. coli O157:H7 in foods (Onoue et al., 1999). Studies on the control of E. coli O157:H7 have been largely focused on the use of chemical additives (Conner and Kotrola, 1995; Zhao et al., 1993; Bari et al., 1999). Various spices have been used for the purpose of food preservation and appetizer promotion as well as medicinal purposes. In particular, extracts from many kinds of oriental spice plants containing their essential oil and essence have been known to possess antimicro- bial effects. Among them are cassia, clove, garlic, sage, oregano, pimento, thyme, rosemary, mint and allspice (Saleem and Ai-Delaimy, 1982; Shelef et al., 1980; Tassou et al., 2000; Yildirim et al., 2000, Zaika and Kissinger, 1981). Oils of cinnamon, clove, bay and thyme (Bullerman et al., 1977; Smith et al., 1998) as well as plant flavanones (Deng et al., 2000) have been reported to exhibit inhibitory effects against many ARTICLE IN PRESS *Corresponding author. Fax: +82-53-950-6772. E-mail address: hpark@knu.ac.kr (H.-D. Park). 1 Present address: Gyeongbuk Agriculture Technology Administra- tion, 189 Dongho, Daegu 702-708, South Korea. 2 Gyeongbuk Institute of Health and Environment, 1149-1 Sankyuk, Daegu 702-702, South Korea. 0740-0020/03/$-see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0740-0020(03)00010-8