Contribución al estudio de las conservas de atún en aceite. II. Distribución de los componentes nitrogenados

In this study, several nitrogen compounds [total nitrogen (TN), nitrogen non-protein (NPN), total volatile basic nitrogen (TVBN), trimethylamine (TMA)] and others nitrogen fractions [ammoniacal nitrogen (N-NH 3 ) and nitrogen non diffusible (NDN)] has been experimentally determined in canned tuna fish with vegetable oil and white tuna (Thunnus alalunga) with olive oil. The mean total value was 4417 mg/100 g in canned tuna fish with vegetable oil, and 4541 mg/100 g in canned albacore with olive oil. The TN of canned tuna fish with vegetable oil was distributed as follows: nitrogen non-protein, 16.87%; the nitrogen non diffusible fraction, 16.00%; total volatile basic nitrogen, 0.87%; the ammoniacal nitrogen fraction, 0.86%. (The highest content found in nitrogen of trimethylamine was 1.82 mg/100 g). The TN of canned albacore with olive oil was distributed as follows: nitrogen nonprotein, 13,63%; the nitrogen non diffusible fraction, 12,87%; total volatile basic nitrogen, 0,76%; the ammoniacal nitrogen fraction, 0.75%. (The highest content in nitrogen of trimethylamine was 1.80 mg/100 g). The TN and NPN values obtained were in the range of the ones found by other authors for fresh, frozen and canned fish. The values of the volatile bases (TVBN and TMA) which indicate the deterioration grade of the fish, were lightly higher than those considerate for fresh fish. This was probably due to the long storage of the raw material and the heat treatment intensity.