Contamination profiles and characterisation of Bacillus species in wheat bread and raw materials for bread production

The Bacillus counts in white and wholemeal wheat loaves produced without preservatives or sour dough were consistently 106 cfug after two days of storage at ambient summer temperatures (25–30 °C). Identified species were B. subtilis (70%), B. licheniformis (24%), B. pumilus (2%) and B. cereus (2%). The dominance of B. subtilis in bread could be explained by the higher resistance to heat of this species as determined by inoculation studies. Among 14 species isolated from retail bread and wheat grains, B. subtilis was the only species associated with ropiness. Samples of raw materials, particularly bran, seeds and oat products, contained low levels (100–102 cfug) of Bacillus spores, surviving a heat treatment (100 °C, 10 min) corresponding to a baking process. Even low spore levels in raw materials, with the frequently isolated species, B. licheniformis (49%) and B. subtilis (10%), resulted in 107 Bacillus per g bread crumb in two days as determined by test bakings. The results indicate a need for controlling growth of Bacillus in bread.