Characteristics of the emulsion stabilized by polysaccharide conjugates alkali-extracted from green tea residue and its protective effect on catechins

Alkali-extracted tea polysaccharide conjugates, termed TPC-A, are obtained from the residue derived from tea after water extraction. Oil-in-water emulsions stabilized by different concentrations of TPC-A (0.5 wt%, 1.0 wt %, 1.5 wt %, 2.0 wt %, and 3.0 wt%) were prepared using medium chain triglycerides (MCT). The optimal concentrations of TPC-A were 2.0 wt % and 3.0 wt %. We investigated the effects of the storage time of 10 days, pH 2.0-10.0, and metal ions (Na+ and Ca2+ ) on the emulsion stabilized using 2.0 wt % TPC-A at 25 degrees C. During the 10-day storage period, the mean particle diameter (MPD) (d(32)) of the emulsion stabilized using 2.0 wt % TPC-A slightly increased from 0.31 mu m to 0.37 mu m, and the absolute value of the zeta potential increased from 44.9 mV to 41.4 mV. Under neutral or alkaline conditions, the emulsion stabilized using TPC-A had the MPD (d(32)) of less than 0.30 mu m and the absolute value of the zeta potential ranging from 40.52 to 41.53 mV. The MPD (d(32) ) of the emulsion in different Na+ concentrations from 0 mmol/L to 500 mmol/L, increased from 0.30 mu m to 2.80 mu m, and their absolute value of zeta potential decreased from 41.0 mV to 37.7 mV. The emulsion stabilized using TPC-A had a favorable protective effect on EGCG and EGC, and the retention rates of EGCG and EGC during the 10 days were 7 and 6 times higher than those without TPC-A emulsion protection, respectively. TPC-A extracted from tea residue, which is abundantly available and cheap, can be used as a natural emulsifier, in order to develop a milky food or beverage products with excellent health benefits.