Physicochemical, Bioactive, Sensory, and Microbial Evaluation of Functional Drinking Yoghurt Fortified With Beetroot and Orange Juice.

This study aimed to formulate and quality-characterize drinking yoghurt with beetroot pulp, abundant in antioxidants, rich in betalains and phenolic compounds and to enhance its nutritional, bioactive, and sensory attributes by adding orange juice. In this study, three different mixtures of beetroot pulp and orange juice were used: Sample A: 240 g yoghurt, 30 g beetroot pulp, and 30 mL orange juice; Sample B: 225 g yoghurt, 45 g beetroot pulp, and 30 mL orange juice; and Sample C: 255 g yoghurt, 15 g beetroot pulp, and 30 mL orange juice. Formulation-dependent differences were observed in the measured bioactive parameters. Sample B showed the highest DPPH radical-scavenging activity at 800 ppm (56.1% ± 2.1%) and the lowest estimated IC50 (429.4 ppm), together with the highest TPC (51.4 ± 1.5 mg GAE/100 g) and TFC (14 ± 1 mg CE/100 g). The sensory analysis showed that sample A achieved the highest mean sensory scores across the evaluated attributes, whereas Sample C received the lowest taste score. During 0-35 days of refrigerated storage, no coliforms or Escherichia coli were detected in any sample, that is, < 1 CFU/mL yoghurt, whereas the pH of all drinking yoghurt samples remained relatively stable, ranging from 4.0 to 4.5, with sample B demonstrating the highest pH and sample C the lowest. The findings demonstrate formulation-dependent differences in sensory and bioactive characteristics and support further investigation of beetroot-orange fortified drinking yoghurt using independently replicated production batches and broader shelf-life assessment.