Effect of prebiotic addition used at different ratios on physicchemical, microbiological characteristics and shelf life of probiotic yogurts

In this study, physicochemical and microbiological properties of probiotic yogurts produced using different prebiotics (carrot fiber, pea fiber, inulin and quinoa flour) add different concentrations (0% (control), 0.5%, 1.0%, 3.0%, 5.0%) were investigated on the 1st, 7th, 10th, 14th, 21st, 28th, 35th, 42nd and 50th days. In this study, the quality criteria of probiotic added yogurt enriched with various prebiotic sources were examined and the effect on the shelf life of this newly developed functional yoghurt was determined by its microbiological quality. In this thesis study, total mesophilic aerobic bacteria (TMAB), mold yeast (M&Y) and lactic acid bacteria (LAB) analyzes were performed to determine the initial microflora. As a result of the microbiological analyzes, sample types and different concentrations before fermentation had no effect on the number of TMAB and M&Y. As a result of the physico-chemical analyzes of probiotic yoghurts with carrot fiber, pea fiber, inulin and quinoa flour before fermentation; pH values were between 5.13±0.00 and 5.56±0.01, respectively; color values were between for L* values 80.98±0.44 and 85.87±0.95, for a* values (-3.89±0.04) and (-1.24±0.03); aw values were between 0.990±0.00 and 0.994±0.00 in all samples, and titratable acidity % (lactic acid) was determined in the range of 0.22±0.01 and 0.31±0.01 , respectively. The results of the LAB counts after fermentation in probiotic yogurts supplemented with carrot fiber, pea fiber, inulin and quinoa flour were between 3.60±0.01 and 9.14±0.03 log cfu/g, 4.76±0.05 and 9.29±0.08 log cfu/g, 4.69±0.04 and 9.66±0.02 cfu/g, 4.84±0.03 and 9.69±0.05 log cfu/g, respectively. As a result of the physico-chemical analyzes of probiotic yogurts with carrot fiber, pea fiber, inulin and quinoa flour added, after fermentation, pH: 3.98±0.00 and 4.65±0.00, 4.07±0.01 and 4.64±0.00, 3.95±0.00 and 4.66±0.01, 3.83±0.00 and 4.68±0.01; titratable acidity % (lactic acid): 0.72±0.00% to 1.25±0.00, 0.72±0.00% to 0.98±0.00, 0.70±0.00% to 0.88±0.00, 0.72±0.00% to 1.23±0.00; color values: L* 77.00±1.09 to 87.66±0.42, 77.51±0.28 to 86.89±0.35, 78.41±0.19 to 86.61±0.30, 76.36±0.94 to 86.97±0.07; a* (-4.84±0.04) to (3.79±0.15), (-5.68±0.28) to (-2.36±0.33), (-5.24±0.08) to (-2.21±0.02), (-4.39±0.09) to (-1.61±0.99); b* 8.25±0.15 to 10.36±0.02, 8.53±0.38 to 11.50±0.05, 8.89±0.34 to 11.30±0.12, 9.09±0.01 to 12.74±0.13; aw values ranged from 0.971±0.00 to 0.975±0.00, 0.970±0.00 to 0.975±0.00, 0.969±0.00 to 0.977±0.00, 0.967±0.00 to 0.978±0.00, respectively. As a result, according to the data obtained, it was determined that the microbiological and physicochemical properties of probiotic yogurts produced using prebiotics were constructive and it contributed to the shelf life.