Dried and salted roe, obtained from the reproductive organs of female tuna (Thunnus tynnus L.), is a typical fish-based food in the Mediterranean area of Spain. In the present study, we monitored the formation of volatile amines (trimethyamine nitrogen [TMA-N] and total basic volatile nitrogen [TBVN]) and nonvolatile amines (biogenic amines) in dried and salted tuna roe after processing and storage for 8 weeks at 4, 20, and 30°C. The salting and drying process significantly increased the TBVN, cadaverine, tyramine, phenylethylamine, and tryptamine contents, and bacteria with histamine decarboxylase activity were detected both in raw and in dried and salted tuna roes. During storage of tuna roe, TMA-N and TBVN levels increased significantly after the fourth week of storage at 30°C, whereas biogenic amine contents remained more or less constant. However, samples stored at 30°C showed histamine formation after the first week of storage, with a concentration of <50 ppm. The volatile and nonvolatile amine concentrations in tuna roe were below the consumer safety limit, with the exception of the total biogenic amine level in roe stored at 30°C, which exceeded the European Community's recommended limit (300 ppm). These results indicate that in properly stored tuna roe, histamine formation will not represent a serious health risk to consumers unless the tuna roe has previously been mishandled.
Biosynthesis and Secretion of Pullulanase, a Lipoprotein from Klebsiella aerogenes