Study of kefir grains application in sourdough bread regarding rope spoilage caused by Bacillus spp.

Sourdough breads prepared with kefir grains resulted in appearance of rope spoilage at the 15th day of bread storage, while the control samples (sourdough breads prepared with wild microflora) were spoiled approximately at the 7th day. Denaturing Gradient Gel Electrophoresis (DGGE) analysis confirmed the above macroscopic observation since Bacillus spp. were detected on sourdough breads prepared with kefir grains at the 15th day of bread storage. The content of organic acids that play synergistic role regarding the enhancement of bread self life was also determined. Lactic acid concentration of sourdough breads prepared with kefir grains were approximately 41–82% higher than the control samples, while acetic acid concentration was about 0.5–1-fold higher respectively. The concentration of some other organic acids studied was also found in higher levels (up to 0.06 μg/g) than the control samples. These findings could probably explain the stability of breads prepared with kefir grains against rope spoilage.