Challenge studies with Clostridium botulinum type E in a value-added surimi product stored under a modified atmosphere

Challenge studies were carried out on raw, cooked, and sterilized surimi nuggets, inoculated with 10(4) spores/g of C. botulinum type E spores. All products were packaged in air and air with an Ageless SS oxygen absorbent and stored at 4, 12 and 25C. Toxin was not detected in any raw product throughout storage (28 days). The absence of toxigenesis was attributed to the low pH (4.1-4.3) due mainly to the growth of lactic acid bacteria (10(7)CFU/g). Toxin was also not detected in any cooked product after 28 days. Product pH did not decrease as previously (due to the absence of LAB), but counts of C. botulinum still decreased throughout storage. In sterile nuggets, C. botulinum counts increased to 10(6) cfu/g at both 12 and 25C, respectively, by 28 days. Lactic acid bacteria and Bacillus spp, were not detected throughout the 28 days storage period. Toxin was detected by days 28 and 14 at 12 and 25C, respectively, and toxigenesis preceded spoilage. The absence of toxin in cooked nuggets was attributed to the anti-botulinal role by Bacillus species, the predominant spoilage bacteria in cooked nuggets.