Optimization of Protein Extraction and Decoloration Conditions for Tea Residues

To optimize alkaline method for extracting proteins from tea residue (TR), the effect of extraction conditions on tea protein extraction rate (TPER) was investigated. Single factor experiment showed the extraction temperature 80 °C, extraction time 100 min, pH value 13 and liquid–solid ratio 40:1 as the optimal extraction conditions. The orthogonal test revealed that the maximum TPER reached 29.71% under the following optimal combination of conditions: extraction temperature 70 °C, extraction time 60 min, pH 12 and liquid–solid ratio 50:1. For optimizing the purification of tea residue proteins, isoelectric point precipitation (pI), ammonium sulfate precipitation (aS) and isoelectric point plus ammonium sulfate precipitation (iPAS) were compared. The result showed that the highest protein precipitation rate (PPR) was 89.70% which was generated by using iPAS. Furthermore, powdered activated carbon was chosen as the most suitable decolorant for the extracted proteins.