Formulation and characterization of functional yogurt fortified with red beetroot peel polyphenols and color pigments encapsulated in water-in-oil-in-water emulsions

Abstract

This study was conducted to examine the storage and quality characteristics of yogurt encapsulated with red beetroot peel extract to promote waste valorization. The beetroot peel extraction was performed with the ultrasonically assisted extraction. The water-in-oil-in-water (W/O/W) emulsions were prepared with 3% (w/w) whey protein isolates. The yogurt was formulated with 0 mL (To), 10 mL (T1), 20 mL (T2), and 30 mL (T3) of the W/O/W emulsions. The yogurts were studied in terms of pH, titratable acidity, syneresis, water holding capacity, phytochemical profile, hardness, and sensory evaluation for 1, 3, 7, 10, 15, and 30 days of storage at 4 °C. All the treatments showed a significant increase in titratable acidity, syneresis, and hardness, while a decrease in pH, water holding capacity, and phytochemicals, except color, which showed non-significant changes after 30 days. The polyphenolic content for To, T1, T2, and T3 decreased to 1.2 mg/g, 5.5 mg/g, 8 mg/g, and 15.9 mg/g, respectively, after 30 days. However, the optimal ranges for pH (4.0–4.4), titratable acidity (0.7–1.2%), and hardness (3–7 × 103 N/m2) are required for the quality characteristics of yogurt, consistent with current research findings of over a month of storage. Moreover, T2 received the best sensory hedonic and just about right scores due to the beetroot earthy and emulsion oily flavor being the negative drivers for the acceptance of T3. Overall, significant differences were observed for phytochemicals in yogurt treatments in contrast to the control, making the beetroot peel extract a promising ingredient for functional effects in yogurt.

Keywords: Beetroot peel extract, Ultrasonicated-assisted extraction, W/O/W emulsions, Whey proteins, Yogurt formulation.