Nutritional evaluation of some subtropical red and green seaweeds Part II. In vitro protein digestibility and amino acid profiles of protein concentrates

The nutritional values of seaweed protein concentrates (PCs) isolated from two red seaweeds (Hypnea charoides and Hypnea japonica) and one green seaweed (Ulva lactuca) were evaluated by determining their in vitro protein digestibility and amino acid profiles. Both protein extractability and in vitro protein digestibility of the red seaweed PCs (88.7–88.9%) were significantly (P<0.05, ANOVA, Tukey-HSD) higher than those of green seaweed PCs (85.7%). The total amount of essential amino acids (EAAs) in the three seaweed PCs was high (36.2–40.2% of total amino acid content). All three seaweed PCs were rich in leucine, valine and threonine but lacked cystine. However, except for sulphur-containing amino acids and lysine, the levels of all EAAs were higher than those of the FAO WHO requirement pattern. Relationships between total phenolic content in seaweeds and protein extractability as well as those between total phenolic content in seaweed PCs and in vitro protein digestibility are examined.