Thermal Resistance of Spores of Five Strains of Clostridium botulinum Type E in Ground Whitefish Chubs

Abstract

SUMMARY– Thermal death‐time determinations in the temperature range of 165°F (73.9°C) to 185°F (85°C) were made of spores of five strains of Clostridium botulinum type E in tubed fish paste prepared from whole Great Lakes whitefish chubs. Estimated F176 (80°C) values for the destruction of approximately 1×106 spores per gram of fish paste were as follows: for strain Alaska, 34.2 min; Beluga, 17.0 min; 8E, 14.0 min; Iwanai, 12.5 min; and Tenno, 13.2 min. Estimated 95% confidence limits about these F176 values were for strain Alaska, 23.4‐49.5 min; Beluga, 14.2‐20.2 min; 8E, 8.2‐17.7 min; Iwanai, 10.2–15.4 min; and Tenno, 9.3–18.5 min. D176 values calculated from our F176 values by Schmidt's (1957) equation were for strain Alaska, 4.3 min; Beluga, 2.1 min; 8E, 1.8 min; Iwanai, 1.6 min; and Tenno, 1.6 min. Zy values obtained from thermal death‐time determinations were for strain Alaska, 13.2; Beluga, 13.3; 8E, 10.3; Iwanai, 13.6; and Tenno, 13.1°F.

Boticinogeny and Actions of the Bacteriocin

“…Three tubes were sealed with the caps and heated for 30 min while submerged in a 58 C water bath; the other three tubes were left unheated. The particular heat treatment was chosen because it would kill vegetative cells but not type E spores that are of low natural heat resistance (3). The average estimates of most-probable-number of viable spores in the heated and unheated tubes were not significantly different: unheated, 142,000; heated, 134,000.…”

“…Identification of cultures producing boticin E. Type E and E-related cultures were screened by the stab-plate procedure for ability to inhibit growth of the II strains being tested as indicators ( Table 1). LVA in plates was given a stab inoculation with up to six different cultures, covered with 3 ml of uninoculated agar, and incubated for 3 days. An agar overlay seeded with spores of an indicator strain was then poured over the covering agar layer.…”

Thermal Inactivation of Nonproteolytic Clostridium botulinum Type E Spores in Model Fish Media and in Vacuum-Packaged Hot-Smoked Fish Products

“…Lower z values of around 6 to 7°C have been reported for other seafoods, in fish (7,11,32) and in phosphate buffers (34,37). Such z values have been recommended for use in calculating pasteurization values related to heat processing in the production of REPFEDs at temperatures below 90°C (1,17).…”

“…Tests in phosphate buffers have revealed 6 spores of C. botulinum type E strain Beluga in rainbow trout and whitefish media. }, growth observed in rainbow trout medium within 90 days at 30°C, {, no growth observed in rainbow trout medium; F, growth observed in whitefish medium within 90 days at 30°C, E, no growth observed in whitefish medium; ----, 6D heat treatments (i.e., heat treatments proposed to eliminate 10 6 nonproteolytic spores) recommended by the Advisory Committee on the Microbiological Safety of Foods (1); ------, 6D heat treatments recommended by the European Chilled Food Federation (17 (3), and 2.8 min at 95°C (37), as opposed to 0.07 to 6.6 min at 82°C without lysozyme (7,11,27,32,44,47). The heat-resistant spore fraction was estimated to be on the order of 0.1%, while in phosphate buffer percentages of 0.1 to 1.0% and sometimes up to 20% have been reported (37).…”

“…Biphasic survivor curves indicate that from 0.1 to 20% of a spore population is permeable to lysozyme and is more heat resistant than the nonpermeable fraction (37,45). Without the addition of lysozyme to the recovery medium, decimal reduction times (D values) for spores of type E strains of 0.07 to 6.6 min at 82°C, depending on the heating medium, have been reported (7,11,27,32,41,44,47); with lysozyme, higher D values of 48.3, 12.6, and 3.17 min at 85, 90, and 95°C, respectively, have been determined (37).…”