Optimization of tea‐leaf saponins water extraction and relationships between their contents and tea (Camellia sinensis) tree varieties

Resulting from the year‐on‐year increase in tea plantations and the saturated consumption of tea leaves, the relative overcapacity in China's tea‐leaf production appears. Discovering the new utilization of tea leaves is helpful to alleviate this phenomenon. The feasibility of extracting saponins from aged tea leaves was investigated and confirmed; three major variables in water extraction were optimized by Box‐Behnken designs. The significant variable found in Box‐Behnken designs, liquid–solid ratio, was went through single‐variable experiments for a more accurate optimization. Seventy‐five ml/g, 1 hr, and 80°C were optimal values and tea‐leaf saponins yield of tea tree variety Longjing 43 reached 12.19% ± 0.0030% after optimizations, higher than the yield of tea‐seed saponins from Camellia oleifera seed meals using the same extraction method (water extraction based on optimizations). According to correlation analyses, tea tree's leaf type and germination stage affected tea‐leaf saponins contents positively, indicating tea trees with larger leaves and later germination stage would have a higher content of tea‐leaf saponins with a higher yield of tea‐leaf saponins under the same extraction method.