Losses of nitrogen fractions from herring to brine during marinating

► Total nitrogen loss from meat to brine amounted 6–27% of raw herring. ► Higher nitrogen content in herring did not influence nitrogen loss. ► The main factors affecting amount of losses are herring type and marinating time. ► Other factors are dressing, freezing, salt and acid concentration in brine. Fish meat is characterized by a high content of valuable nutrients. During the marinating process, however, the process of proteins diffusion and other nitrogen fractions from fish to the surrounding brine is commonly observed. It was determined that the total nitrogen loss from herring meat of industrial maturity (4–5day) amounted to 6–19% of raw material nitrogen. Extension of the marinating time to 16–18days increases nitrogen losses even to 18–27%. Less loss was observed during marinating of fresh than of frozen herring and during marinating of carcasses, as opposite to fillets. Higher nitrogen content in fish was not proved to influence higher nitrogen losses in a brine. The majority of loss consisted of nitrogen fractions soluble in TCA, of which one third was formed by α-amine nitrogen. Nitrogen contained in brine suspension accounted for only 1.5–4% of total nitrogen losses. With increasing salt or acid concentration the amount of total nitrogen loss was lower from fresh herring and higher from frozen one. Higher salt concentration significantly reduced the amount of non-protein nitrogen and all its fractions during marinating of fresh and frozen herring. In case of acetic acid, the influence of its concentration was diverse and depended on type of herring and its dressing.