Nutritional value of proteins from edible seaweed Palmaria palmata (Dulse)

Palmaria palmata (Dulse) is a red seaweed that may be a potential protein s ource in the human diet. Its protein content, amino acid composition, and p rotein digestibility were studied with algae collected every month over a 1 -year period. Significant variations in protein content were observed accor ding to the season: The highest protein content (21.9 +/- 3.5%) was found i n the winter-spring period and the lowest (11.9 +/- 2.0%) in the summer-ear ly autumn period. Most of the essential amino acids were present throughout the year. After 6-hour in vitro digestion in a cell dialysis using porcine pepsin and porcine pancreatin, the digestibility of proteins from Palmaria palmata crude powder, represented by dialyzed nitrogen, was estimated at 2 9.52 +/- 1.47%. Relative digestibility was 56%, using casein hydrolysis as 100% reference digestibility. In vitro digestibility of proteins extracted in water was analyzed by sodium dodecylsulfate polyacrylamide gel electroph oresis using either bovine trypsin, bovine chymotrypsin, pronase from Strep tomyces griseus, or human intestinal juice. Dulse proteins were hydrolyzed to a limited extent, which confirmed a rather low digestibility. Hydrolysis rate was higher with trypsin and lower with chymotrypsin compared with the two other enzymatic systems, pronase and intestinal juice, respectively. T he association of algal powder and protein extract to casein and bovine ser um albumin, respectively, produced a significant decrease in the hydrolysis rate of the standard proteins. In conclusion, the digestibility of Palmari a palmata proteins seems to be limited by the algae non-proteic fraction. ( J. Nutr. Biochem. 10:353-359, 1999) (C) Elsevier Science Inc. 1999. All rig hts reserved.