Physical characterization and water sorption of freeze dried dulse Palmaria palmata powder

Dulse, Palmaria palmata, is being studied as an alternative source of eicosapentaenoic acid (EPA), an omega-3 fatty acid as it contains > 45 % of total fatty acid as EPA. The physical properties of freeze dried dulse were investigated in terms of bulk and particle density, compressibility, particle size distribution, and moisture sorption properties at 23C. The experimental adsorption isotherm was fitted to two theoretical (BET and CAB) and three empirical models. The model proposed by Iglesias and Chirife (1981) was the most successful. The monolayer moisture content evaluated from GAB parameters was 6.7kg/100 kg dry matter, which was similar to a value corresponding to inflection point of stability isotherm. The powder was highly hygroscopic even at low a(w), a characteristic of gel forming polymers present in dulse.