Change of thermal inactivation of Clostridium botulinum spores during rice cooking.
Cooked and packed rice (CaPR), a popular rice product in Japan, is distributed with oxygen-absorbing agents and without refrigeration. When the final product was inoculated with spores of several strains of proteolytic Clostridium botulinum at a dose of 10(3) spores per g (2 x 10(5) spores per package) and incubated at 30 degrees C, the bacteria grew and produced neurotoxins in 40 days. To simulate more realistic cases of contamination, the same dose of spores was inoculated before the cooking process. When cooked at 100 degrees C for 30 min, a small number of spores survived and the toxins were detected in some of the samples after incubation for 180 days. However, when cooked at 100 degrees C for 15 min immediately followed by 105 degrees C for 15 min, neither survivors nor the toxins were detected during incubation for 270 days after cooking. Even when inoculated with 10(5) spores per g of one of the most heat-resistant strains, 213B, viable spores were not detected after cooking. The inactivation by these heating conditions in different media indicated that the spores were inactivated >1,000-fold more in rice suspension than in cooked meat medium or phosphate buffer. It was therefore suggested that rice contains component(s) that facilitates thermal inactivation of C. botulinum.
Konagaya
Yukifumi
Y
Department of Food Sciences, Niigata University of Pharmacy and Applied Life Sciences (NUPALS), Akiha-ku, Niigata-shi, Niigata 956-8603, Japan.
Urakami
Hiroshi
H
Hoshino
Jun
J
Kobayashi
Atsushi
A
Sasagawa
Akihiko
A
Yamazaki
Akira
A
Kozaki
Shunji
S
Tanaka
Nobumasa
N
D001905:Botulinum Toxins / Q000032:analysis*; D003014:Clostridium botulinum / Q000254:growth & development / Q000502:physiology*; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D003296:Cooking / Q000379:methods*; D005506:Food Contamination / Q000032:analysis; D005511:Food Handling; D005516:Food Microbiology; D006358:Hot Temperature; D006801:Humans; D012275:Oryza / Q000382:microbiology*; D013171:Spores, Bacterial / Q000254:growth & development
D001905:Botulinum Toxins