Moisture Adsorption of Fish Protein Concentrate at Various Relative Humidities and Temperatures

SUMMARY A simple method was used to determine moisture adsorption isotherms of FPC (fish protein concentrate) made from whole fish (red hake and Gulf menhaden) by isopropyl alcohol extraction. The hake was ground to two particle sizes and either nonsteamed or steam stripped to remove residual alchol. Moisture adsorption isotherms were determined at 25°, 35° and 42°C in constant relative humidities ranging from 11–86%. Equilibrium moisture content ranged from about 5% at 11% RH to about 16% and 86% RH. Particle size of the hake‐FPC did not appear to affect the moisture adsorption. Steam‐stripped samples adsorbed slightly more moisture at low relative humidities and slightly less moisture at high relative humldities than did nonsteamed samples. Menhaden‐FPC adsorbed slightly less moisture than comparable hake‐FPC samples. This difference was due to differences in quantitative chemical composition of the two types of FPC's.