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A biological procedure was devised to evaluate de Ruyter and Brunet's heat transfer computer simulation for sterilizing particulate foods in a swept surface heat exchanger (SSHE). Turkey cubes measuring 12.7 mm were inoculated with spores of Clostridium sporogenes PA3679, using a so‐called “knotted string” method. Inoculated cubes were introduced into a viscous starch medium and thermally processed in a SSHE to a fractional survivor endpoint. Processed product was packaged aseptically, incubated and examined for survivors. Biological sterilization values calculated from the inoculated packs support the validity of the simulation. Also, a novel method was devised to measure particle residence times in hold tubes using electro‐magnetic induction.

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Resistance to heat of spores of marine and terrestrial strains of Clostridium botulinum type C in 0.067 m phosphate buffer ( p H 7.0) was determined. The marine strains were 6812, 6813, 6814, and 6816; the terrestrial strains were 468 and 571. The inoculum level equaled 10 6 spores/tube with 10 replicate tubes for each time-temperature variable. Heating times were run at three or more temperatures to permit survival of some fraction of the inoculum. Survivors were recovered at 85 F (30 C) in beef infusion broth containing 1% glucose, 0.10% l -cysteine hydrochloride, and 0.14% sodium bicarbonate. D values were calculated for each fractional survivor end point after 6 months of incubation. Thermal resistance curves were constructed from the D value data. D 220 (104 C) values for spores of 468 and 571 equaled 0.90 and 0.40 min, respectively. The corresponding values for spores of 6812, 6813, 6814, and 6816 were 0.12, 0.04, 0.02, and 0.08 min. The z values for the thermal resistance curves ranged from 9.0 to 11.5 F (5.0 to 6.2 C).

In inoculated pack experiments on Clostridium botulinum type E, unirradiated and 0.1-Mrad irradiated haddock fillets often gave nonspecific toxicities by the mouse assay test for botulinum toxin. Samples given 0.2-Mrad radiation failed to produce nonspecific reactions. Nonspecific deaths sometimes occurred within 24 hr after injection, although deaths between 24 and 48 hr were more common. The symptoms and the pattern of these deaths suggested a septicemia. Heart-blood cultured from mice showing nonspecific symptoms indicated an infectious process. Among 23 isolates from the blood, eight were identified as Proteus vulgaris, two P. morganii, one P. rettgeri, one Providence subgroup B, two Aerobacter aerogenes, one Actinobacillus, three enterococci, one Alcaligenes marshalli, and four Erysipelothrix insidiosa. The E. insidiosa, Aerobacter, Providence group, and most of the Proteus isolates were infectious for mice when injected by the intraperitoneal route. But the enterococci, Alcaligenes, and Actinobacillus isolates were not infectious and probably represent secondary invaders. The cultural characteristics of the E. insidiosa isolates conform to those described in the literature, with the exception that the four strains grew in the temperature range 50 F (10 C) to 40 F (4.4 C). Nonspecific toxicities were avoided in assays for botulinum toxin by the protection of mice with chloramphenicol and oxytetracycline.