Development of High-Protein Functional Yogurt Technology and Its Quality and Safety Evaluation

Abstract This work presents the results of developing a technology for a high-protein, health-oriented yogurt based on buttermilk with the addition of black elderberry (Sambucus nigra) and pear juices. The feasibility of using buttermilk as the principal raw material was demonstrated, as it increases the nutritional and biological value of the product due to its content of complete milk proteins, trace elements, and bioactive compounds. Two technological approaches to increasing protein content in buttermilk were investigated: the addition of whey protein concentrate WPC-UF-80 and partial whey removal after buttermilk fermentation. It was established that the latter method yielded an optimal protein level of 8.20% and, in the finished product, a reduction in lactose to 3.27%, although in the yogurt base the lactose remained at 4.09%. The use of elderberry and pear juices as natural functional ingredients was substantiated; they enrich the product with vitamin C (6.31 mg/100 g), polyphenols, and anthocyanins, imparting antioxidant activity of 1408 arbitrary units and favorable sensory attributes (total score 20.0 on day 1 of storage; attributes assessed: color, taste, odor, and consistency; 5-point scale). During storage (2–6 °C, 21 days), pH decreased from 4.41 to 4.33, titratable acidity increased from 90 to 102 °Th (Thorner units), viscosity decreased from 2.20 to 2.00 Pa·s, and syneresis increased from 2.0% to 3.8%, while acceptable sensory and microbiological indicators were maintained. The developed product is characterized by mass fractions of protein 8.20%, fat 0.47%, lactose 3.27%, and minerals 0.78%, the presence of probiotic cultures (Bifidobacterium spp.; (0.9 ± 0.2) × 10⁹ CFU·cm⁻³ on day 21), and the absence of coliform bacteria throughout the entire storage period. The combination of a buttermilk protein base with functional plant juices ensures structural stability, high consumer acceptability, and promising applicability in preventive nutrition.