Trimethylamine and total volatile basic nitrogen determination by flow injection/gas diffusion in Mediterranean hake (Merluccius merluccius).
The reliability of flow injection/gas diffusion (FIGD) methods to determine trimethylamine (TMA-N) and total volatile basic nitrogen (TVB-N) in hake was studied in order to find an alternative and accurate, simple, cheap, and rapid method for non-protein nitrogen determination. FIGD methods involved extracting volatile amines with 7.5% trichloroacetic acid, followed by the injection of the extracts into the FIGD manifold, previously adjusted for TMA-N or TVB-N determinations. Each determination took approximately 2 min. Reliability was satisfactory in linearity, precision, recovery, and sensitivity. There was good correlation (p < 0.001) between FIGD and the classic official methods, for both TMA-N and TVB-N determinations, and also between FIGD and the gas chromatographic procedure described for TMA-N. These results proved that FIGD methods are simpler, cheaper, and faster than current official procedures. To check the suitability of FIGD procedures over a wide range of analyte concentrations, changes of both TMA-N and TVB-N and the P ratio values throughout the ice storage of hake were monitored. The usefulness of each of these potential freshness indicators for hake is discussed.
Baixas-Nogueras
S
S
Departamento de Nutrició i Bromatologia, CeRTA, Facultat de Farmàcia, Universitat de Barcelona, Avinguda Joan XXIII s/n, 08028 Barcelona, Spain.
Bover-Cid
S
S
Vidal-Carou
M C
MC
Veciana-Nogués
M T
MT
Mariné-Font
A
A
D000818:Animals; D004058:Diffusion; D005399:Fishes; D017022:Flow Injection Analysis / Q000379:methods*; D005519:Food Preservation / Q000592:standards; D008744:Methylamines / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis*; D017747:Seafood / Q000032:analysis / Q000592:standards*; D012680:Sensitivity and Specificity; D014835:Volatilization
D008744:Methylamines; C023336:trimethylamine; D009584:Nitrogen