Separation, identification, and quantification of low molecular weight nitrogen containing compounds in fish byproducts

Abstract

There is interest by the fish processing industry in the identification and eventual extraction of higher valued low molecular weight nitrogen compounds from fish byproducts such as stickwater, hydrolysates, fish tissues, and other byproducts. A hydrophilic interaction liquid chromatography (HILIC) method was developed for the separation and quantification of amino acids, small nitrogenous acids and bases, as well as, other nitrogen containing metabolites. The HILIC method developed is a robust and non-derivatizing method for the analyses of aqueous compounds found in freeze dried red salmon whole fish and red salmon byproducts (pretreated stickwater, post-treated stickwater, and fishmeal). Triplicate samples of all byproducts were obtained from commercial processors in Kodiak, AK. Byproduct samples were extracted and centrifugally filtered through 3000 MW membranes. The identification of low molecular weight compounds in different fractions of fish byproduct showed the partitioning of unbound components during fishmeal processing. Several aqueous nitrogen containing compounds were quantified and comparisons were made of these components in different fish byproduct fractions. This study suggests that creative, creatinine, taurine, and hypoxanthine are found in elevated concentrations in stickwater and are preferentially partitioned into the stickwater fraction.