Properties of fish protein hydrolysates: comparison of commercial and laboratorymade hydrolysates
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The aim of this work was to examine how addition of fish protein hydrolysates (FPH) influences the functional and antioxidative properties of fish calces. Hydrolysates from cod backbone were prepared in the laboratory and compared to hydrolysates from commercial producers in Denmark, USA and New Zealand. Two batches of hydrolysates were prepared enzymatically by mincing the backbones and digesting them with the endo-protease Protamex for either 20 or 50 minutes at 50°C. A moderate increase in degree of hydrolysis and yield was observed by increasing the time of hydrolysis from 20 to 50 minutes. A decrease in the proportion of large peptides was detected with FPLC. FPH made in the laboratory with 50 minutes time of hydrolysis yielded the highest degree of hydrolysis of all tested powders. Norland had by far the lowest DH tested. FPLC also showed that the molecular weight size distribution of the FPHs made in the laboratory were quite similar to distribution of similarity to the MariPep powders. The Norland and Aroma powders molecular weight distribution were also similar to each other. Variations in frying yield of fish cakes were shown to be caused by differences in fat absorption. Fat absorption of the fish cakes was shown to be depend on the emulsifying properties of the added powder. For the FPH made in the laboratory, higher DH gave lower water holding capacity. Differences in the salt content of the hydrolysates caused the salt concentration of the fish cakes to vary, influencing the functional variables that were analysed.