Volatile amines as criteria for chemical quality assessment. Seafoodplus Traceability

• Main Author: Etienne, Monique
• Format: Report
• Language: English
• Published: 2005
• Subjects: Fishing Ground; Hake; Atlantic salmon
• Online Access: https://archimer.ifremer.fr/doc/2005/rapport-6486.pdf; https://archimer.ifremer.fr/doc/00000/6486/

Volatile amines are the characteristic molecules responsible for the fishy odour and flavour present in fish several days after the catch and they are commonly used as criteria for assessing the fish quality. The nature and the formation of the volatile amines are discussed. Ammonia is present in freshly caught fish, during chilled storage it is formed by endogenous and bacterial enzymes, it is a poor indicator of fish freshness and cannot be considered as an effective marker of fish spoilage. DMA is present at very low concentration in freshly caught, about 0.2 mg/100g, it is formed from TMAO, under TMAO-ase action, an endogenous enzyme which is mainly present in gadoids; DMA-N can be considered as an effective marker of fish freshness of many white fish and it can be used to monitor the quality of frozen-stored gadoid fish. In a very fresh fish the amount of TMA-N is low, ≤ 2 mg/100g, it arises from the bacterial reduction of TMAO. TMA-N is an excellent indicator for the spoilage of gadoid fish, it is useful as a rapid means of objectively measuring the eating quality of many demersal fish specially on the medium-later phases of spoilage but it cannot be used as an freshness indicator (constant level during the first days of iced storage). TVB represents the sum of ammonia, DMA, TMA and others basic nitrogenous compounds volatile under the analysis conditions. In freshly caught fish its content is generally superior to 10 mg/100g and does not exceed 15 mg/100g except for pelagic fish. TVB-N is an indicator of spoilage of some fish species such as red fish, flat fish, gadoids, hake and Atlantic salmon, legal requirements in directive 91/493/EEC have been established for the limits of this indicator in the fish muscle for several species. However TVB-N cannot be used as an freshness indicator (constant level during the first days of iced storage) and des not reflect the mode of spoilage. The volatile amines being essentially formed by degradation of TMAO, their production is linked to the initial concentration of TMAO in the muscle which depends on the species, season, fishing ground and depth of living. The influence of processing such as chilling, ice storage, slurry ice, freezing, cooking, canning and packaging including modified atmosphere packaging is discussed. The methods of determination of volatile amines are presented, the first one are specific methods which are used by many laboratories. Some more recent techniques are used in research laboratories and many new rapid methods have been described or are under development. About the methods two main conclusions can be withdrawn : 1) With regard to quality control methods of spoilage, as the volatile amines are produced by enzymatic reaction, their level increases in the chain, even under chilling condition, so it is important to perform the analysis very quickly after the sampling and the analysis result should be express clearly, i.e. TVB in mgN/100g, with the reference of the used method and details about the sampling (nature, date, place); 2 ) With the regard to the validation methodology: In the fish commercialisation chain, it is important to have the possibility of checking quickly the quality, however classical laboratory methods, that cannot be considered as rapid techniques, are still used in Europe. For TVB, the AOAC Official method "Volatile bases in fish, ammonia ion selective electrode method" which is more rapid and easier to perform than our reference method could be compare to the EU official procedure in the aim to facilitate the controls in the chain. For TMA-N, specific sensors and probes recently developed and others being developed in other European projects, based on the selective identification of this molecule, must be validated to assess the possibility of having them as quality control tools for the fish industry.