Polysaccharides in Selenium-Enriched Tea: Extraction Performance under Innovative Technologies and Antioxidant Activities

Pulsed electric fields (PEF) and ultrasonic-assisted extraction (UE) were applied to improve the extraction performance of selenium-enriched tea polysaccharides (Se-TPSs) in mild conditions. Two combined extraction processes were investigated: (1) PEF strength at 10 kV/cm followed by conventional extraction (CE) at 50 °C for 60 min and (2) PEF+UE (PEF strength at 10 kV/cm followed by UE at 400 W for 60 min). The optimal extraction yields, and energy consumption rates were obtained at 36.86% and 41.53% and 78.78 kJ/mg and 133.91 kJ/mg, respectively. The Se-TPSs were analyzed and characterized by GPC, UV, and FT-IR, which evidenced the structural stability of the Se-TPSs during the extraction processes. It was found that PEF and UE could reduce the particle size diameter of the Se-TPS extract, as well as the proportion of uronic acid. Moreover, PEF could increase the selenium content in the Se-TPS extract by 160.14% due to a lower extraction temperature compared to conventional extraction. The antioxidant activities of the Se-TPSs in vitro were investigated using OH, O2-, and ABTS+ scavenging experiments, as well as a total antioxidant ability evaluation. It was found that the antioxidant activity of the Se-TPSs obtained using PEF2+CE2 was relatively high due to the potential synergistic effect between the selenium and polysaccharides. Based on these results, we speculate that PEF2+CE2 was the best extraction process for the Se-TPSs. Furthermore, this research indicates the application of selenium-enriched tea for functional food production.