Effect of calcium alginate/collagen hydrolysates beads encapsulating high-content tea polyphenols on quality characteristics of set yogurt during cold storage

High-content tea polyphenols (TPs) are necessary for the functional and health-related properties, but precipitate milk proteins to prevent milk from fermenting into yogurt. In this study, calcium alginate/collagen hydrolysates beads encapsulating high-content TPs (CA/CHBs-e-HCTPs) were prepared and added at 0 (control), 5, 10 or 15 (g/100 g) to milk to produce fortified set yogurt and stored at 4 °C for 7 days. The results showed the encapsulation efficiency of TPs in CA/CHBs-e-HCTPs was 91.58 % (103 mg TP/g beads), resulting in a maximum TPs content of 1545 mg/100 g of set yogurt that still gave yogurt stable rheological properties and good water holding capacity, as well as significantly enhancement in antioxidant properties during cold storage when the addition of CA/CHBs-e-HCTPs increased from 0 to 15 (g/100 g). Moreover, after fermentation and storage, CA/CHBs-e-HCTPs swelled by 10% that equipped with stable texture, and TPs released from CA/CHBs-e-HCTPs was <6.42%. FTIR and SEM results revealed the stable intertwined interactions between TPs and wall materials. In conclusion, the CA/CHBs-e-HCTPs could effectively alleviate the precipitate of milk proteins to ferment into fortified set yogurt and played an important role in enhancing the nutritional and functional values of yogurt by high-content TPs.