Essential Amino Acids

Contents 17.1 Introduction 287 17.2 Sample Preparation for the Analysis of Seafood Essential Amino Acids 28817.2.1 Sample Preparation for Free Essential Amino Acid Analysis 288 17.2.2 Sample Preparation for Total or Hydrolyzed Essential AminoAcid Analysis 289 17.3 Seafood Essential Amino Acid Analysis 29017.3.1 High-Performance Liquid Chromatographic Methods 291 17.3.1.1 Cation Exchange Chromatography 291 17.3.1.2 Reversed-Phase High-Performance Liquid Chromatography 29217.3.2 Gas Liquid Chromatographic Methods 298 17.3.3 Capillary Zone Electrophoretic Methods 298 17.3.4 Mass Spectrometry 29917.4 Conclusions 300 References 30017.1 Introduction Amino acids are the basic components of the muscle protein structure of seafood. However, not all proteins have the same nutritional value, because protein quality strongly depends on its amino acid composition and digestibility.1 Fish and, in general, seafood proteins are considered as highquality proteins because of their balanced content in amino acids, especially in all the essential amino acids necessary for physical and mental well-being. Amino acids may also be found in free form, which contribute to sh taste and indirectly to aroma 2,3 by generation of volatilecompounds through Maillard reactions and Strecker degradations.4 Branched-chain essential amino acids (valine, isoleucine, and leucine), sulfur-containing amino acids (methionine and cystine/cysteine), and aromatic amino acids (phenylalanine and tyrosine) are the most important from this point of view. Free amino acids initiate important changes at early postmortem and during storage and can be very useful as quality indices of processing and storage.5-10us, the analysis of essential amino acids in seafood is important for the evaluation of both the nutritive value and the sensory quality of seafood.