Studies on tea protein extraction using alkaline and enzyme methods

The extraction of proteins from tea leave pulps, using alkaline and enzyme methods, were investigated in this work. Altogether four enzymes (neutrase, alcalase, protamex and flavourzyme) were examined for tea protein extraction. It was found that an alkaline method produced a high protein yield (56.4% extraction rate). The use of an enzyme alone appeared to be less effective in extracting tea protein (less than 20% extraction rate). However, a combination of two enzymes (for example, alcalase and protamex at a 1:3 weight ratio) became much more capable in extracting protein and led to a much higher extraction rate (as high as 47.8%). Various extraction conditions, such as volume–weight ratio between the extraction solution and the weight of dry tea leave pulps (V/W), the extraction time (t), pH, temperature (T), agent concentration (c) have been investigated for their influences. Optimum combinations of extraction conditions were obtained using the orthogonal analysis technique. The extracted tea protein was further purified for the analysis of molecular weight distribution and amino acid compositions. It was found that tea protein was composed of at least seven different types of proteins and had amino acid composition more or less similar to that of soy protein.