Enhancing Stability of Vitamin-Fortified Protein Beverages: Optimization of Stabilizer Type and Concentration and Screening of Natural Antioxidant Combinations.

This study optimized stabilizer type and concentration, and screened natural antioxidant combinations to enhance the stability of a protein beverage fortified with vitamins A, D2, and D3. Three stabilizers-carrageenan, sodium carboxymethyl cellulose (Na-CMC), and microcrystalline cellulose (MCC)-were evaluated at 0.15-0.45% (w/v) during accelerated storage at 45 °C for 21 days. Stability was assessed using Turbiscan analysis, pH, particle size, Zeta potential, and color. MCC at 0.35% demonstrated the best stabilization, with minimal changes in Turbiscan Stability Index, particle size, and Zeta potential. Five natural antioxidants-dl-α-tocopherol, vitamin C, epigallocatechin gallate (EGCG), tea polyphenols (TP), and pyrroloquinoline quinone (PQQ)-were screened for vitamin protection using HPLC. Although vitamin C exhibited the highest in vitro DPPH radical scavenging activity (IC50 = 3.44 μg/mL), TP and EGCG provided superior protection of vitamins in the emulsion system. A synergistic antioxidant blend of EGCG, TP, and dl-α-tocopherol in a 4:4:2 mass ratio was identified as optimal, significantly prolonging vitamin retention over 21 days and yielding the longest predicted shelf-life (>84 days at 25 °C). These findings provide a practical formulation strategy for enhancing the physical and nutritional stability of functional protein beverages.