Kara havuç, kırmızı pancar, nar ve çileğin ekşi maya ekmeklerinde starter kültür kaynağı olarak değerlendirilmesi

In this study, investigations were carried out on the development of sourdough, derived from various fruits and vegetables, for the production of sourdough bread that meets the consumers demand for natural, tasty and healthy food. Strawberry, pomegranate, black carrot and red beet were preferred as starter culture source in preparation of sourdough. Sourdough preparation carried out in three-stage based on traditional procedure. For determining characteristics of sourdough; pH, total titratable acidity, lactic acid bacteria and yeast count analysis were performed. In evaluation of bread properties; bake loss, specific volume, color characteristic, moisture, pH, water activity and textural analysis were achieved. Furthermore, sensory analysis was conducted to determine consumer preferences in choice of bread. pH and total titratable acidity value of preferment used in sourdough preparation, varied according to substrate source (p<0.05). pH value ranged between 3.58 which is average value for pomegranate and 5.08 which is the pH of red beet. Titratable acidity was lowest for red beet (4.53 ml) and highest for black carrot (7.93 ml). Lowest pH value (5.15) for Dough I was measured in pomegranate samples as in used preferment. The titratable acidity of Dough I was found between 2.37 and 4.97 ml for red beet and pomegranate, respectively. Amoung the Dough I samples , the highest yeast counts (6.0*105 cfu/g) were determined for strawberry and the highest count of lactic acid (7.8*104 cfu/g) were obtained in the black carrot while the lowest cell counts were obtained in pomegranate samples. Afterwards refreshments steps, the measured pH and titratable acidity did not vary according to substrate for Sourdough III (p<0.05). pH and titratable acidity values were found between 3.90 (red beet) and 4.08 (pomegranate); 14.07 (strawberry and pomegranate) and 14.83 (red beet), respectively. Among the Sourdough III samples, the highest yeast counts (1.8*106 cfu/g) were determined for strawberry and the highest count of lactic acid (1.4*108 cfu/g) were obtained in the red beet while the lowest cell counts were obtained in black carrot samples. In this study, the addition level of sourdough and type of substrate, used as a starter culture source in sourdough preparation, did not led to significantly variation in bake loss (p<0.05). In wheat bread (control bread) and sourdough bread samples, loss of moisture during baking was found between 14.00 % (20 % strawberry sourdough usage) and 16.07 % (control and 10 % strawberry sourdough usage). For specific volume, sourdough bread samples prepared with 30 % black carrot sourdough had lowest value (6.19 ml/g) while control bread without sourdough application had highest value (7.58 ml/g). Sourdough application provides differentation in color properties of bread crumb and crust. In bread samples, the lighter color of crumb and crust structure was achieved with sourdough utilization. The parameter L* (lightness) value of bread crumb ranged between 71.17 which is average value for % 30 pomegranate sourdough usage and 76.20 which is for control bread. Sourdough breads prepared with pomegranate sourdough had the lowest parameter L* value (73.08). In case for bread crust, the L* parameter value was found between 44.41 (% 10 strawberry sourdough usage) and 54.89 (% 20 strawberry sourdough usage). The source of substrate did not significantly effect the parameter a* (redness) value of bread crumb whereas the addition of sourdough led to significantly increase in the parameter a* value of bread crust (p<0.05). The highest a* value (17.97) was observed in the sample prepared with %30 addition of sourdough originated from black carrot. The parameter b* (yellowness) value ranged from 23.69 (S-10) to 30.91 (RB-10 and S-20) in crust while in crumb from 12.24 (P-20) to 13.39 (BC-30). Moisture content of bread samples on first day was measured between 33.61 % (30 % strawberry sourdough usage) and 34.69 % (10 % strawberry sourdough usage) while afterwards the storage, a decrease in moisture content was observed.The moisture content of bread samples on the end of the storage ranged from 32.48 % (BC-30) to 34.19 % (RB-10). End of the storage black carrot originated sourdough samples exhibited lowest moisture content (33.07 %) in which maximum moisture loss occurred through storage. In terms of sourdough application, the highest moisture content change (2.64 %) observed in bread prepared with 30 % sourdough application. The water activity (aw) of control bread and sourdough bread was found to 0.94 in all samples and did not change throught storage. Fruits and vegetables, used in sourdough preparation, leads to differentiation in pH value of bread and also there was a decline in pH values with incremental sourdough application (p<0.05). The lowest value (5.05) was determined in bread prepared with 30 % red beet sourdough while this value was found in control bread as 5.58. Besides with storage a decrease in pH values was observed. Neither substrate type nor addition level of sourdough leaded to significantly variation in pH change throughout storage (p<0.05) Nevertheless, maximum change (%) was observed within the sourdough breads prepared by %30 application. In consequence of texturel analysis it was determined that firmness of bread was significantly varied depending on origin of sourdough and level of use (p<0.05). Firmer bread crumb was achieved with incremental sourdough application irrespective of sourdough variety. Firmness of bread on first day was determined between 217.90 (g) for control bread and 449.12 (g) for sourdough bread prepared with 30 % black carrot sourdough. Throughout to storage, change in firmness did not significantly vary in terms of utilization ratio or substrate type (p<0.05); yet black carrot-originated sourdough breads exhibited higher firming rate and significantly different from control bread As a result of sensory analysis carried out for bread samples, sourdough bread prepared with 10 % strawberry sourdough application exhibited highest score (41.10). In respect of sourdough addition, %10 sourdough application resulted in higher score (40.10) than control bread. The addition of sourdough provided an increase of the score in several attributes such as taste, odour and color whereas control bread was preferred mainly in respect to texture and appearance.Considering fruits and vegetables, strawberry sourdough breads had the highest score (38.30); followed by pomegranate (37.50), red beet (37.30) and black carrot (36.37). The exquisite flavour of strawberry provided to exhibit prominent taste and odour features in sourdough breads.