Free Amino Acids Responsible for the Browning of Cooked Scallop Adductor Muscle

Abstract

The free amino acids responsible for the browning of scallop adductor muscle during the cooking process were investigated. Perchloric acid extracts of unfrozen muscle immediately after death, which did not show browning, and those of cold-stored muscle and of frozen-and-thawed muscle, which showed strong browning, were cooked at 110°C for 90 min, then the contents of amino acids in these extracts before and after cooking were determined with HPLC. Scallop adductor muscle contained large amounts of glycine (1600-1900 mg/100 g), taurine (700-1000 mg/100 g), arginine (500-700 mg/100 g) and alanine (100-300 mg/100 g). The total amount of these four amino acids accounted for more than 90% of the total amount of free amino acids in scallop adductor muscle. After 3 days storage at 5°C, alanine and glutamic acid increased, and arginine as well as proline decreased. During freezing-and-thawing glycine and alanine increased, and proline decreased. The extract from unfrozen muscle immediately after death did not show changes in contents of free amino acids after cooking, and those from cold-stored muscle and frozen-and-thawed muscle showed a decrease in the contents of taurine (10-20%) and alanine (25%). Thus, taurine and alanine are thought to be the main amino acids responsible for the browning of cooked scallop adductor muscle.