172 Nippon Shokuhin Kagaku Kogaku Kaishi Vol. /-, No.-, +1,+12 (,**0) 14 * ** * ** Sterilizing E#ect of Superheated Steam on Microbes in Chinese Cabbage Kazuhiro Ono, Hiroshi Endo, Yasuhiro Inatsu* and Shigeo Miyao** Fukushima Technology Centre Aizuwakamatsu Technical Support Centre, 22+ Shimoyanagiwara, Tsuruga, Ikki-machi, Aizuwakamatsu, Fukushima 30/***0 * National Food Research Institute,,++, Kannondai, Tsukuba, Ibaraki -*/20., ** Tokyo Metropolitan Food Technology Research Center, +3 Kandasakuma-cho, Chiyoda-ku, Tokyo +*+**,/ Microbial control is required for both quality maintenance and safety in foods. We examined the e#ectiveness of superheated steam (SHS) for sterilization of pathogenic and spoilage-causing bacteria in Chinese cabbage to be used for pickling (Asazuke). Raw Chinese cabbage harbored more than / log CFU/ g of viable cells, with the outer leaves exhibiting higher viable cell counts than the inner leaves. Most bacteria were found on the epidermal (surface) tissue and were not present in the inner tissue, which suggests that surface sterilization should be e#ective for microbial control in Chinese cabbage. Compared with the usual method of washing with sodium hypochlorite (NaClO), treatment with SHS was found to significantly reduce the population of microbes on Chinese cabbage without a#ecting texture or color tone. Populations of Gram-positive bacteria, Gram-negative bacteria, and nitrate-forming bacteria were found to decrease to less than,./ log CFU/g. The e#ectiveness of SHS treatment in the sterilization of pathogenic bacteria was also evaluated. Treatment with SHS was found to reduce the populations of Escherichia coli O+/1 :H1and Staphylococcus aureus in Chinese cabbage to below the detection limit. These results suggest that SHS treatment may be useful for microbial control when processing vegetables during pickle production. (Received Aug. +,,,**/ ; Accepted Nov.,+,,**/) O+/1 :H1 +-./ NaClO 01 2 3 +*++ 30/***0 22+ * -*/20.,,++, ** +*+**,/ +3 Corresponding author khono@fukushima-iri.go.jp NaClO +,,- log CFUg +-+. NaClO HClO +/ Superheated steam SHS +0,* SHS +** SHS,+
15 : 173 SHS + Brassica pekinensis,**. 1,**/ -, SHS -- cm SHS + - -,* +,* NaClO +,* + DK-0**T SHS SHS SHS -*,* /* cm - + mm -1 +,* + SHS, *.,/ CVT,, -*.2 -* - SAN Sulfanilamide Nitrate,, -** CFU -**,./ log CFU,-. VTEC+VTEC, Escherichia coli O+/1 :H1. CR--,MN-,-,MY-,3 DT-00 : Staphylococcus aureus. JCM,+13, JCM,.+-, JCM,21. IFO+-,10 Escherichia coli O+/1 :H1 Staphylococcus aureus. -1 +2 0** nm, *.,,* + *** / + NaClO SHS NaClO SHS /* gml,. TSA- Rif, -1 +0,. Escherichia coli O+/1 :H1 SMAC-Rif Staphylococcus aureus MSA-Rif / NaClO, SHS RE,--*/S / mm ZE,*** - + Table + 0.1 /.+ log CFUg 0.+ /.* log CFUg
174 /- -,**0-16 Table + Comparison of microbial counts in each Chinese cabbage parts Bacteria and coliforms counts of each parts (log CFU/g) + Outside leaves Inner leaves Upper Middle Lower Surface Inside 041*4, A /4+*4- C 04+*4. B /4**4. C 041*4, A /4-*4, B 04/*4- A /4**4, B /42*4- B.4**4, C 04.*4+ A -42*4, B,4/*4* C,4/*4* C + Values are meanstandard deviation (n0)4 Means Values with the same letter not significantly di#erent (P*4*/)4 Table, Changes of bacterial counts of upper and lower parts of Chinese cabbage treated with SHS Measurement parts Bacteria and coliforms counts of SHS treatment before and after (log CFU/g) + Treatment temperature +** Treatment temperature +-* Treatment temperature +/* Control +* s,* s Control +* s,* s Control +* s,* s Upper parts (Green leafs) 041*4,.4/*4+.43*4,,4/*4*.4.*4-,4/*4* 043*4,.4+*4+,41*4+,4/*4*,4/*4*,4/*4* 14,*4* /4.*4*,4/*4*,4/*4*,4/*4*,4/*4* Lower parts (White leafs) 04,*4+.4/*4, -4-*4+,4/*4*,40*4+,4/*4* /43*4+ -40*4-,4/*4*,4/*4*,4/*4*,4/*4* 04,*4+.42*4,,4/*4*,4/*4*,4/*4*,4/*4* + Values are meanstandard deviation (n-)4 0.1 0./ /.2 log CFUg /.- /.*..* log CFUg 0.. -.2 log CFUg -** CFUg / log CFUg +,/,0 SHS, SHS Table, +**+/* SHS SHS +**, log CFUg +*..3 log CFUg,,*... log CFUg +-*. log CFUg +*,.1 log CFUg,,* -** CFUg +/* / log CFUg +*,* -** CFUg,- log CFUg -** CFUg +** -. log CFUg +* -.-,*,.0 log CFUg +-* -. log CFUg +*,./ log CFUg,* -** CFUg +/* +*,* / log CFUg +-* SHS,1 Bacillus +-* -** CFUg,2 SHS / log CFU/g, - log CFUg - SHS Table - SHS /.* log CFU/g, /.- log CFUg..2 log CFUg SHS ++* +-*/, log CFUg
17 : 175 Table - Change in Gram positive bacteria, Gram negative bacteria and nitrate forming bacteria counts of each Chinese cabbage parts treated with SHS Viable cell counts of SHS treatment before and after (log CFU/g) + Bacteria Before treatment ++* +-* / s +* s / s +* s Gram positive bacteria Gram negative bacteria Nitrate forming bacteria /4**4+ /4-*4-.42*4- -4/*4- -4/*4+ -4.*4+,4/*4*,4/*4*,4/*4* -4-*4, -4,*4, -4,*4,,4/*4*,4/*4*,4/*4* + Values are meanstandard deviation (n-)4 Table. Comparison of sterilization e#ect of SHS and chemical washing and dry heating for microbe on Chinese cabbage Treatment method Viable cell counts (log CFU/g) + NaClO After distilling water washing /* ppm +** ppm +/* ppm 042*4+ A /40*4+ B.43*4, C.40*4+ C.40*4, C 04**4, A.40*4+ B.4**4, B -41*4, C -4/*4+ C Calcium preparation After distilling water washing *4*/ *4+* *4,* 14-*4* A 043*4+ B 04,*4+ C 04**4+ C 04**4, C 04,*4+ A /41*4+ B /4-*4* C /4,*4+ C /4**4- C SHS After distilling water washing +-* +* s 14+*4+ A 041*4+ B,41*4+ C /42*4+ A /4-*4+ B,4/*4* C Dry heating +-* +* s 043*4- A 040*4, B /4+*4- A.41*4. A + Distilling water and chemical washing treatment were washed for + min at room temperature4 Values are meanstandard deviation (n-)4 Means Values with the same letter not significantly di#erent (P*4*/)4 -.,-./ log CFUg +* ++* +-* -** CFUg +-* /,3 / ++* -.. log CFU/g, +-* -., log CFUg, log CFUg +* -** CFUg ++*+-* +* SHS -** CFUg -* -+ SHS. SHS Table. NaClO, SHS 0.21.- log CFUg /.+0., log CFUg /.00.3 log CFUg..0/.1 log CFUg NaClO
176 /- -,**0-18 Table / Comparison of sterilization e#ect of SHS and NaClO for E4 coli (O+/1 :H1) andstaph4 aureus on Chinese cabbage Population of E4 coli (O+/1 :H1) andstaph4 aureus (log CFU/g) + Recovery Medium Before treatment After distilling water washing After NaClO washing After SHS treatment ++* +-* +/* E4 coli O+/1 :H1 TSA-Rif SMAC-Rif.42*4+ A.41*4+ A.4+*4+ B.4+*4+ B -41*4+ C -4/*4+ C,41*4, D,4/*4+ D,4/*4* D,4/*4* D,4/*4* D,4/*4* D Staph4 aureus TSA-Rif MSA-Rif /4+*4+ A.43*4* A.42*4+ B.40*4* B.4,*4, C -42*4* C,40*4+ D,4/*4* D,4/*4* D,4/*4* D,4/*4* D,4/*4* D + Distilling water and chemical washing treatment were washed for + min at room temperature4 SHS treatment were heated for +* s in each temperature4 Values are meanstandard deviation (n-)4 Means Values with the same letter not significantly di#erent4(p*4*/)4 NaClO..0..3 -./..* log CFUg +.3,.,,.*,./ log CFUg +** ppm NaClO 0.* 0., /.*/.- log CFUg +.+ +.- *.3+., log CFUg NaClO +.3,./ log CFU/g, *.3+.- log CFUg NaClO +-*+* SHS SHS 0.1 /.- log CFUg... log CFUg,.1 log CFUg -.- log CFUg -** CFUg *.- *.. log CFUg SHS SHS NaClO, -,-- / NaClO SHS Table / Escherichia coli O+/1 :H1 Stapylococcus aureus NaClO +** ppm ++*+/* +* SHS TSA-Rif SMAC-Rif Escherichia coli O+/1 :H1 MSA-Rif Stapylococcus aureus Escherichia coli O+/1 :H1TSA- Rif NaClO..2..+ -.1 log CFUg *.1 log CFU/g, NaClO +.+ log CFUg SHS ++*,.+ log,.1 log CFUg +-* -** CFUg SHS NaClO Escherichia coli O+/1 :H1SMAC-Rif TSA-Rif **., log CFUg NaClO -./ log CFUg +., log CFUg SHS,., log ++*,./ log CFU/ g, +-* -** CFUg Stapylococcus aureus NaClO SHS Escherichia coli O+/1 : H1 MSA-Rif TSA-Rif NaClO..3 /.+..0..2 -.2.., log CFUg SHS ++*,..,./ log CFUg,./,.0 log CFUg +-* -** CFU g SHS Escherichia coli O+/1 :H
19 : 177 Table 0 Comparison of Color tone and Breaking measurement of Chinese cabbage after NaClO washing, dry heating and SHS treatment Treatment method Breaking measurement Color tone Breaking force (N) Breaking strain () L* a* b* NaClO Dry heating SHS ++4-+4* ++4/*41 +,4+*43,04*-40,04*,4,,04+,41 114/3+4+0 114/2+403 1141-+4*- 04--+40-04/-*40-14*3+412,042--4*.,14*++4/*,240+,400 NaClO washing treatment were washed for + min at room temperature4 SHS and Dry heating treatment were heated for +*s at+-*4 Values are meanstandard deviation (n-)4 Stapylococcus aureus TSA-Rif SMAC-Rif MSA-Rif TSA- Rif TSA-Rif TSA-Rif SHS NaClO SHS Escherichia coli O+/1 :H1 Stapylococcus aureus NaClO 0 NaClO SHS Table 0 NaClO, SHS NaClO ++.- N,,0.* ++./ N,,0.* SHS +,.+ N,,0.+ NaClO SHS NaClO L* a* b* 11./30.--,0.2-11./2 0./-,1.*+ SHS 11.1-1.*3,2.0+ NaClO SHS a* b* SHS SHS SHS / log CFUg ++*+-* +* SHS,./ log CFUg +-*+* SHS... log CFUg +.-,., log CFUg Escherichia coli O+/1 :H1 Stapylococcus aureus NaClO + log CFUg SHS, log CFU g SHS SHS + O+/1,2 +,*+,2,**-, O+/1 : H1 Di#used Outbreak 11.3-.32,**- - Inatsu, Y., M.L. Bari, Kawasaki, S., and Isshiki, K., Survival of Escherichia coli O+/1 :H1, Salmonella Enteritidis, Staphylococcus aureus, and Listeria monocytogenes in Kimchi., J. Food Prot., 01 +.31+/**,**..
178 /- -,**0-20., 00+00/ +33/ / /+ -01-03,**. 0.,..,../ +33/ 1.0 --.--2 +333 2 Inatsu, Y., M.L. Bari, Kawasaki, S., Isshiki, K. and Kawamoto, S., E$cacy of Acidified Sodium Chlorite Treatments in Reducing Escherichia coli O+/1 :H1 on Chinese Cabbage, J. Food Prot., 02,/+,//,**/ 3-0 +2++22 +323 +* Koseki, S., Isobe, S. and Itoh, K., E$cacy of Acidic Electrolyzed Water Ise for Pathogen Control on Lettuce, J. Food Prot., 01,/..,/.3,**. ++ Achiwa, N., Katayose, M., Yoshida, K., Kusakari, S. and Abe, K., Viable Bacterial Counts on Fresh-cut Salads and Bactericidal E#ect of Electrolyzed Acidic Water, Food Preservation Science, -* +2/+3*,**. +, p.,*+ +32. +- M.L. Bari, O+/1 :H1,**/ +. Inatsu, Y., Maeda, Y., M.L. Bari, Kawasaki, S. and Kawamoto, S., Pre-washing with acidified sodium chlorite reduces pathogenic bacteria in lightly fermented Chinese cabbage, J. Food Prot., 02 333+**.,**/ +/ Wei, C-I., Cook, D., Kirk, J., Use of Chlorine Compounds in the Food Industry, Food Technol. -3 +*1++/ +32/ +0 New Food Industry,,0,,1-, +32. +1 //0+ +33/++ +2., +,+ +,0 +331 +3,3 3.33,**-,* /+ +01+1+,**.,+ p.0 // +3332. -*,, +3 +,++-0 +320,- p 1/ +33*,. Inatsu, Y., M.L. Bari., Kawasaki, S. and Isshiki, K., Construction and Validation of Antibiotic Resistance Escherichia coli O+/1 :H1Strains for Acidic Foods., Jpn. J. Food Microbiol.,,* +11+2-,**-,/.2.*3.+/,**+,0 -*,11,2*,**.,1 p.,*- +312,2 p. 22 +32-,3-1.--.-2 +33* -*.. +3 +331 -+ /. -/- +330 -,.,,02,1, +33/ --.+ +-/+.* +33. +1 2 +, +1 ++,+