Salt- and pH-induced functional changes in protein concentrate of edible green seaweed Enteromorpha species

Abstract

Protein concentrates (PCs) were extracted from three edible green seaweed species of Enteromorpha (E. compressa, E. linza, and E. tubulosa) and were studied for their functional properties with respect to salt and pH. The protein content in the PC was found to be 60.35 ± 2.0, 53.83 ± 0.70, and 33.36 ± 1.04% in E. compressa, E. tubulosa, and E. linza respectively. The minimum nitrogen solubility was observed at pH 4.0 in all three PCs. The water-holding and oil-holding capacities in the three PCs ranged from 1.22 ± 0.06 to 1.53 ± 0.07 ml H 2 O/g PC and from 1.05 ± 0.07 to 1.34 ± 0.10 ml oil/g PC respectively. Foaming capacity and stability were found to be pH-specific. They varied significantly with pH and NaCl concentration (P \ 0.05). The inexpensive source of protein concentrate from Enteromorpha species could be incorporated into value-added food products.

Production of protein extracts from Swedish red, green, and brown seaweeds, Porphyra umbilicalis Kützing, Ulva lactuca Linnaeus, and Saccharina latissima (Linnaeus) J. V. Lamouroux using three different methods

“…In addition, the pH was increased to pH 12 in this study (Wong and Cheung 2001) before ammonium sulfate precipitation was performed, and furthermore the residue was re-extracted five times instead of two, as was done here. Many other studies have examined the extraction of proteins from a variety of seaweed species, beyond those addresses in the present study, using variations of the traditional method (i.e., Wong and Cheung (2001), Kandasamy et al (2012), Suresh Kumar et al (2014) and Garcia-Vaquero et al (2017)). However, since both compositional and structural differences between different seaweed species are substantial, direct comparisons of results are difficult.…”

“…Most reported techniques for extraction of proteins from seaweeds utilize water only (i.e., Galland-Irmouli et al (1999) and Garcia-Vaquero et al (2017)) or a water extraction followed by a second alkaline extraction in the presence of mercaptoethanol (i.e., Wong and Cheung (2001), Kandasamy et al (2012), and Suresh Kumar et al (2014)) followed finally by precipitation with ammonium sulfate. The pH-shift process ( Fig.…”

Seaweed as a protein source for mono-gastric livestock

“…However, the protein fraction has rarely been considered and it will now be important to quantify the effects the solvents have on the extraction of proteins. For example, the by-product of the agar extraction process from Gracilaria potentially represents an underutilised protein resource, however, extraction procedures involve an alkaline extraction using sodium hydroxide (Armisen, 1995) that is critical in solubilising a large proportion of total soluble protein during protein extraction processes for seaweeds (Fleurence, LeCoeur, Mabeau, Maurice, & Landrein, 1995;Kandasamy, Karuppiah, & Rao, 2012;Kumar, Ganesan, Selvaraj, & Rao, 2014;Wong & Cheung, 2001a, 2001b. Although it has not yet been a commercial focus for seaweeds, it is promising that the extraction of soluble polysaccharides with minimal protein losses is routinely done for soybeans, providing a model for seaweeds (Berk, 1992).…”

“…Chemical binding between protein and compounds such as polysaccharides and phenolic compounds limits the solubility of protein and reduces the yield of the soluble protein fraction (Harnedy & FitzGerald, 2011;Jordan & Vilter, 1991;Loomis & Battaile, 1966). Nonetheless, yields of 36.1e48.0% of total protein have been obtained using an initial aqueous extraction followed by an alkaline extraction (Kandasamy et al, 2012;Kumar et al, 2014;Wong & Cheung, 2001a, 2001b. However, these yields are considerably lower than those reported for terrestrial plant sources such as rice (97.4% -Ju, Hettiarachchy, and Rath (2001)) which implies that extraction protocols are not yet optimised for seaweeds.…”

“…The potential therefore exists to optimise protein extraction procedures for seaweeds by incorporating elements of grass and leaf protein extraction protocols that use fresh biomass and have a more mechanical focus (Bals & Dale, 2011;Chiesa & Gnansounou, 2011;Sinclair, 2009). The crude protein (determined using a 6.25 N-to-protein conversion factor) of seaweed protein extracts has been determined in a limited number of studies (range ¼ 33.4e86.3% dw) (Kandasamy et al, 2012;Kumar et al, 2014;Wong & Cheung, 2001a, 2001b. If we calculate the concentration of essential amino acids as a proportion of the extract (for those studies that also determined the quality of protein e amino acids as a proportion of protein), we find that the total essential amino acids, methionine and lysine increase substantially in protein extracts compared to the whole seaweed (Table 3).…”