BACILLUS SPORE CONTAMINATION ASSOCIATED WITH COMMERCIAL BREAD MANUFACTURE

Rope spoilage of bread by Bacillus subtilis and B. licheniformis causes economic losses to the baking industry. The Bacillus spore contamination profile of a typical brown bread manufacturing line in a commercial bakery was assessed by four replicate microbiological surveys to determine numbers, types and sources of Bacillus spores. High Bacillus spore counts were consistently obtained from yeast, crumbs and premix. Food contact surfaces did not contribute noticeably to spore counts. The initial spore count of dough after mixing was 2.6 log cfu g-1 and increased by 0.5 log cfu g-1 before baking. Baking decreased the Bacillus spore count by 1 log cfu g-1. Baked bread stored at 30°C yielded Bacillus counts of c. 107 cfu g-1 after 3 days’ storage. Three hundred randomly selected Bacillus isolates from raw materials, dough, food contact surface and bread samples were characterized as 41.5% B. licheniformis, 38.4% B. subtilis, 12.0% B. megaterium, 3.9% B. pumilis, 2.5% B. laterosporus and 1.1% B. cereus. © 1993 Academic Press Limited.