Physicochemical characterization, emulsifying and antioxidant properties of the polysaccharide conjugates from Chin brick tea (Camellia sinensis).

Tea polysaccharide conjugate fractions (TPCs) with different molecular weights (TPC-40, TPC-60, and TPC-80, MW = 1355 to 204 kDa) were prepared from Chin brick tea using graded alcohol precipitation. The physiochemical and functional properties of TPCs were investigated. Results showed that TPC-80 (204 kDa) had the highest antioxidant activity attributed to its higher phenolic and theabrownin contents. Moreover, this fraction had the highest surface pressure (16.2 ± 0.9 mN/m), but the lowest interfacial dilatational modulus (30.3 ± 2.2 mN/m) than TPC-40 (1355 kDa) and TPC-60 (955 kDa). As a result, TPC-80 had the highest emulsifying activity but the lowest emulsion stabilizing properties due to its fastest adsorption kinetics but the relatively thin interfacial coating on the oil droplets. Overall, our results indicate that the chemical compositions and structural characteristics of TPCs significantly impact their functional attributes. TPCs have the potential to be a novel natural antioxidant emulsifier in food industry.

TiO2 nanoparticles negatively impact the bioavailability and antioxidant activity of tea polyphenols.

This study was to investigate the influence of TiO2 nanoparticles (NPs) on the stability, bioavailability, and antioxidant activity of co-ingested tea polyphenols extract using an in vitro digestion model. The tea polyphenol contents decreased significantly after addition of 0.5 % (w/w) TiO2 NPs. The gallocatechin gallate level decreased the most, changing from 101.9 to 27.2 µg/mL (about 73.3%). The TiO2 NPs also reduced the bioavailability of the tea polyphenols in a dose-dependent manner, which was ascribed to the formation of large polyphenol-TiO2 NP complex aggregates that could not pass through the pores in the dialysis tube used to simulate the gut wall. Additionally, the TiO2 NPs decreased the antioxidant activity of the tea polyphenols within the simulated gastrointestinal tract. In summary, our results show that high levels of TiO2 NPs (but within the current legal limits in many countries) may negatively impact the bioavailability and bioactivity of polyphenols in foods.

Polysaccharide conjugates from Chin brick tea (Camellia sinensis) improve the physicochemical stability and bioaccessibility of ß-carotene in oil-in-water nanoemulsions.

A natural antioxidant emulsifier, tea polysaccharide conjugate (TPC), was isolated from Chin brick tea. The impact of TPC on ß-carotene stability and bioaccessibility in oil-in-water nanoemulsions was assessed. TPC exhibited strong antioxidant activity and could be used to fabricate stable nanoemulsions (d < 140 nm). The extent of lipid digestion was considerably lower for lipid droplets coated by TPC (68%) than Tween 80 (94%) or whey protein isolate (WPI) (89%), probably because TPC formed interfacial layers that hindered the access of lipases to lipids. The chemical stability of ß-carotene in TPC-nanoemulsions was markedly higher than in those formulated with Tween 80 or WPI due to the high antioxidant activity of TPC. The bioaccessibility of ß-carotene (20-30%) was independent of emulsifier type. TPC from Chin brick tea can therefore be used as a dual-purpose functional ingredient in emulsified foods.