effect of microbial biopolymers on extensographic properties of wheat dough and shelf life of raised bread

kefiran is an exogenous microbial metabolite produced mainly by bacteria and fungi during growth. the present study investigated the effects of the addition of 3% kefiran and 3% xanthan on the extensographic characteristics of wheat dough and the shelf life of raised bread. kefir grain was cultivated in a shaking incubator and kefiran extraction was carried using a centrifugal refrigerator. the physicochemical properties of sardari and parsi wheat and their respective flours were analyzed using an inframatic analyzer. the rheological properties of the wheat dough were measured using an extensograph and the shelf life was recorded from samples preserved in an incobatore. sardari wheat recorded lower values for 1000-seed weight, falling number, zeleny index, protein, water absorption and rigidity, but higher gluten and hectoliter weights than for parsi wheat. the addition of 3% xanthan significantly decreased (p < 0.05) wheat dough extensibility and significantly increased resistance-to-extension and energy. the addition of 3% kefiran to sardari dough significantly increased (p < 0.05) resistance-to-extension (each period) and energy (in periods of 45 and 90 min) over the parsi wheat and significantly decreased (p < 0.05) extensibility in both wheat doughs. the results of staling tests done at 24, 48 and 72 h showed that the addition of 3% kefiran and 3% xanthan significantly decreased crumb staling (p < 0.05). the addition of 3% xanthan decreased staling and increased hardness over the control samples. the addition of 3% kefiran and 3% xanthan extended the shelf life of parsi wheat bread by 13 and 11 d, respectively, and the shelf life of sardari wheat bread by 12 and 10 d, respectively.