Prebiotic effect of dietary fiber from peach pomace and its interaction with probiotics

In the thesis study, the prebiotic activity of dietary fiber produced from peach pulp, which is separated as waste in fruit juice production, was investigated. In the first step of the research, microbiological analyzes of commercial inulin and peach dietary fiber produced in the laboratory were performed. Total yeast-mold, lactic acid bacteria , total mesophilic aerobic bacteria count results of commercial inulin and peach dietary fiber were determined below the countable values. Then, color, water activity, pH, % titration acidity (in terms of malic acid), total dry matter, total phenolic substance and antioxidant capacity analyzes were made in order to determine the physicochemical properties of dietary fiber. Water activity value of dietary fiber 0.461±0.02, pH value 3.98±0.01, titration acidity value 0.115±0.00%, L* color value 65.52±0.26, a* color value +3.92±0.21 and b* color value 35.26±0.09, total dry substance value was 90.79±0.18%, total phenolic substance content was 216.95±3.70 mg/L, and antioxidant capacity content was 250.128±13.18 nM trolox/mL.In the second stage, it was desired to observe how commercial inulin and peach dietary fiber affect the growth of probiotic bacteria in the broth, so Lactobacillus acidophilus and Bifidobacterium animalis ssp lactis were used as test bacteria. Commercial inulin or dietary fiber produced from peach pulp were added at concentrations of 0.2%, 0.5%, 1%, 5% and 10% as a carbon source into the glucose-free MRSB. According to the counting results, significant increases in the number of microorganisms were not observed in both commercial inulin-containing media and dietary fiber-containing media, and it was determined that the microorganisms remained alive for a longer time compared to the control group. While higher count results were obtained in samples containing inulin than samples containing peach pulp fiber, it was determined that samples containing Bifidobacterium animalis ssp lactis contained more bacteria than samples containing Lactobacillus acidophilus. In the third stage of food trials, 0.5%, 1% and 5% concentrations of peach pulp fiber were added to UHT milk and Bifidobacterium animalis ssp lactis and Lactobacillus acidophilus test microorganisms were inoculated. According to the microbiological cultivation results, no significant changes were observed in the count results during the storage period for both test bacteria. Counting results in samples containing Bifidobacterium animalis ssp lactis at day 48 were 8.63±0.20 log cfu/mL for 0.5% concentration, 8.70±0.06 log cfu/mL for 1% concentration, 8.17±0.06 log cfu/mL for 5% concentration, positive control group 8.56±0.16 log cfu/mL for the negative control group and below the countable values for the negative control group. Counting results in samples containing Lactobacillus acidophilus on day 48 were 8.33±0.22 log cfu/mL for 0.5% concentration, 8.27±0.08 log cfu/mL for 1% concentration, 7.91±0.15 log cfu/mL for 5% concentration, for positive control group 8.15 ±0.15 log cfu/mL was calculated as below countable values for the negative control group. When the pH values were examined, it was observed that the pH values decreased and the titration acidity (in terms of lactic acid) values increased as the dietary fiber concentration and storage time increased. This situation was observed in both test bacteria, and it was interpreted that the metabolic activities of the bacteria increased with the increase in the concentration of dietary fiber. When compared with the control groups in both microorganism experiments, it was determined that the number of microorganisms was not affected significantly for 48 days. The pH and % titration acidity values show that the metabolic activities of the microorganisms increased when compared to the control groups. It has been determined that peach pulp dietary fiber does not affect the test bacteria counts in milk, but increases metabolic activities, and it is thought that it can be considered as a prebiotic functional product.