Effects of type and concentration of dry matter and final pH of fermentation on biochemical, microbial and sensory properties of probiotic dough

Introduction: Recently, the demand for functional foods consumption is growing rapidly due to the increased awareness of the consumers from the impact of these foods on health. The aim of this study was to assess microbiological, biochemical and sensory aspects of probiotic Doogh. Materials and Methods: In this research, the effects of type (skim milk power and whey protein) and percents of dry matters and final pH of fermentation (4 and 4.4) on biochemical viability of probiotics and sensory properties of probiotic Doogh during fermentation and 21 days in refrigerated storage were studied. In this way, pH and redox potential values were measured by pH-meter. Titrable acidity value was determined by titration with 0.1 N NaOH. Probiotic bacteria were enumerated using MRS-bile agar medium. Results: Treatment with 4% skim milk power and 1% whey protein at pH of 4.4 (6 WP-1) -4.4) showed the highest viability of both probiotic bacteria after fermentation and during refrigerated storage. Treatments 4% skim milk power at pH of 4.0 (4 SMP-4.0), 3% skim milk power with 1% whey protein concentrate at pH of 4.4 (4 WPC-1) -4.4), 6% skim milk power at pH of 4.4 (6-SMP-4.4), 6% skim milk power at pH of 4.0 (6 SMP-4.0) and 5% skim milk power with 1% whey protein (6 WP-1) in both final pH 4.4 and 4.0 had the highest level of organoleptic acceptance. However, they have more economic considerations than 6% of dry matter. Conclusion: Overall, whey protein can be used as part of the dry matter Doogh without changes of organoleptic properties and viability of probiotic Doogh.