Free amino acids in muscle of Norway lobster (Nephrops novergicus (L.)) in controlled and modified atmospheres during chilled storage

Changes in free amino acids (FAAs) in relation to freshness were examined in the muscle of Norway lobster during bulk storage in controlled and modified atmospheres containing two different gas mixes (1:60/15/25 and 2:40/40/20, CO2%/O2%/N2%). The essential free amino acids in the highest concentrations were threonine, leucine, valine, lysine and arginine, all over 40 mg/100 g. Threonine, valine, lysine and arginine concentrations decreased significantly (p<0.05) during storage. These decreases were more pronounced in the lots kept in the CO2-rich mix (1) than the lots kept in the O2-rich mix (2) and this was independent of whether the storage was under controlled (C) or modified (M) atmosphere. The dipeptide anserine showed decreases with the same trend. The most abundant non-essential FAAs were glycine, alanine and glutamic acid (57.9, 57.2 and 31.2 mg/100 g, respectively), along with the dipeptide anserine (52.9 mg/100 g). The non-essential FAAs presented differences attributable to the gas mixes used. No differences were detected in any of the FAA groups studied with respect to the different types of atmospheres (C or M). Only ornithine and tryptophan levels increased significantly (p<0.05) in the course of storage. These increases were significantly (p<0.05) different only in the control lot. These FAAs would appear to be suitable as freshness indices for Norway lobster stored in ice. Moreover, the significant (p<0.05) decrease of the dipeptide anserine could be a suitable freshness index for Norway lobster stored in either ice or in atmospheres (C or M). © 2003 Elsevier Ltd. All rights reserved.Peer Reviewe