Total number of essential amino acid among the given list of amino acids is _______ Arginine, Phenylalanine, Aspartic acid, Cysteine, Histidine, Valine, Proline

Essential amino acids are those that cannot be synthesized by the human body and must be obtained from diet.

The essential amino acids (mnemonic: PVT TIM HALL) are: Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine, Leucine, Lysine.

From the given list:

- Arginine: Essential ✓ (semi-essential/conditionally essential, but generally counted)

- Phenylalanine: Essential ✓

- Aspartic acid: Non-essential ✗

- Cysteine: Non-essential (conditionally essential) ✗

- Histidine: Essential ✓

- Valine: Essential ✓

- Proline: Non-essential ✗

Total essential amino acids = 4 (Arginine, Phenylalanine, Histidine, Valine).

The answer is $$\boxed{4}$$.