Examination of freshness degradation of sourdough bread made with kefir through monitoring the aroma volatile composition during storage

The aroma volatile compositions of sourdough breads containing kefir grains were monitored by SPME GC–MS analysis during a 5-day storage. Breads were made with (A) 20% w/w and (B) 10% w/w (on flour basis) kefir sourdough, and were compared with breads made with 20% w/w commercial sourdough (C) and sourdough prepared in the laboratory (D) without addition of starter culture. A dramatic decrease of volatiles was observed during storage for all samples, but the kefir sourdough breads (A and B) exhibited more complex profiles of volatiles with lower loss rates during storage. Differences in the percentages of esters on total volatiles were also observed (6.2%, 5.0%, 2.8% and 2% in the case of breads A, B, C, and D, respectively). The customer oriented sensory evaluation revealed significant differences among the tested samples, with best results scored in the case of bread A in all days of storage, agreeing with the analytical data.