Characterization and growth of Bacillus spp. in heat-treated cream with and without nisin.
OBJECTIVE
To study the germination and growth of both inoculated and naturally occurring Bacillus strains in heat-treated cream with and without nisin.


RESULTS
In heat-treated cream (90 degrees C for 15 min) stored at 8 degrees C, growth was dominated by naturally occurring Bacillus strains such as Bacillus pumilus and B. licheniformis. Only six of the 52 isolated strains were B. cereus/thuringiensis. All of the B. cereus strains, but none of the other strains, produced enterotoxin when tested with the TECRA and reverse passive latex agglutination kits. Bacterial growth during storage of the cream at 8 or 10 degrees C was completely inhibited by low concentrations of nisin.


CONCLUSIONS
The high number of Bacillus strains surviving the heat treatment represent a risk for heat-treated food that contains cream. The safety of the cream, for instance in "ready-to-eat" products, can be improved by the addition of low concentrations of nisin.


CONCLUSIONS
Spores of several Bacillus species may survive heat treatment of cream, but low concentration of nisin with inhibit germination and growth.
Nissen
H
H
MATFORSK, Norwegian Food Research Institute, Oslovn. 1, N-1430 As, Norway. hilde.nissen@matforsk.no
Holo
H
H
Axelsson
L
L
Blom
H
H
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001407:Bacillus / Q000145:classification / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D004768:Enterotoxins / Q000378:metabolism; D006358:Hot Temperature; D007054:Ice Cream / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D009561:Nisin / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D004768:Enterotoxins; D009561:Nisin