Green extraction of proteins, umami and other free amino acids from brown macroalgae Ascophyllum nodosum and Fucus vesiculosus

Abstract

Seaweeds are a valuable potential source of protein, as well as free amino acids (FAAs) with umami flavour which are in high demand by the food industry. The most commonly used flavouring agents in the food industry are chemically synthesised and therefore are subject to concerns regarding their safety and associated consumer resistance. This study focuses on the effects of extraction time (1 and 2 h) and solvents (0.1 M HCl, 1% citric acid and deionised water) on the extraction of protein and FAAs including umami FAAs from Irish brown seaweeds (Ascophyllum nodosum and Fucus vesiculosus). Extraction yields were influenced by both the extraction solvent and time, and also varied according to the seaweed used. Both seaweeds investigated were found to be good sources of protein, FAAs including umami FAAs, demonstrating potential application as flavouring agents in the food industry. Overall, the use of green solvents (deionised water and citric acid) resulted in higher recoveries of compounds compared to HCl. The results of this study will facilitate the use of more sustainable solvents in industry for the extraction of proteins and flavouring agents from seaweed.

Keywords: Algae; Flavour industry; Flavouring agents; Free amino acids; Green solvents; Phaeophyta; Umami.

Fig. 1

Bar chart representing the effect of solvent type (deionised water, 0.1 M HCl and citric acid (1% w/v)) and extraction time (1 and 2 h) on the yields of protein (g protein per 100 g seaweed biomass or %) extracted from A. nodosum and F. vesiculosus. Results are expressed as average ± standard deviation of the mean. Different letters indicate statistical differences (P < 0.05) between the different extraction treatments using different solvents either 1 h (upper case letters) or 2 h (lower case letters). The statistical differences between 1 and 2 h treatments when using the same solvents are represented on the top of the bars either by ns (non-significant) or * (P < 0.05)

Fig. 2

Bar charts representing the influence of solvent type (deionised water, 0.1 M HCl and 1% citric acid) and extraction time (1 and 2 h) on the % umami FAAs extracted from A. nodosum and F. vesiculosus. Results are expressed as average ± standard deviation of the mean. Different letters indicate statistical differences in the % of umami FAAs extracted using multiple solvents during 1 h (uppercase letters) or 2 h (lowercase letters). The statistical differences in the % of umami amino acids extracted by using different times of extraction and the same solvent are represented as: *P < 0.05, **P < 0.01 and ***P < 0.001

Fig. 3

PCA scatter plot representing the scores for the recovery of umami FAAs and protein from A. nodosum (AN) and F. vesiculosus (FV). The solvents of extraction were abbreviated in the figure as follows: DW (deionised water), HCl (0.1 M HCl) and CA (1% citric acid)