Leaf protein extraction process optimization and analysis of amino acids contents of Helianthus tuberosus

The extraction process of fresh leaf protein concentrate (LPC) of Helianthus tuberosus was studied. Four kinds of extraction agents were evaluated based on the extraction rate of LPC, protein content of LPC and extraction rate of crude protein and the result suggested that sodium metabisulfite was optimal for protein extraction. In order to optimize the extraction process of LPC, the solid-liquid proportion, dosage of salt, temperature and pH were optimized by single factor and orthogonal test. The optimal LPC extraction process conditions were solid-liquid proportion of 1∶7, salt dosage of 0.5%, temperature at 90 ℃ and pH 2.0. The amino acid content analysis suggested the LPC was rich in all kinds of amino acid with harmonious proportion. The total content of amino acid was 42.07%, the ratio of essential amino acids and total amino acids (E/T) was 40.55% and the ratio of essential amino acids and non-essential amino (E/N) was 0.68.