Improvement of the digestibility of the proteins of the red alga Palmaria palmata by physical processes and fermentation

Abstract

Palmaria palmata (dulse) is an edible red alga constituting a potential protein source in human diet. However, previous studies showed that the digestibility of dulse proteins is bad because of the cell-wall encapsulating cytoplasmic proteins and the presence of fibers. The water-soluble xylan, present in high proportions in dulse, could be involved to explain the weak digestibility of proteins. To limit the influence of fibers and to improve the nutritional quality of these proteins, we have treated dulse by physical processes or by fermentation by moulds. After a 30 min predigestion by pepsin followed by a 6 h digestion into a cell dialysis containing porcine pancreatin, the corrected in vitro digestibility of crude dulse was very low (about 1.5% after correction by digestibility blank). The in vitro protein digestibility was estimated to 58% of that of casein for dulse samples obtained after washing in demineralized water and grinding in liquid nitrogen. The in vitro protein digestibility of fermented samples was 45%-65% of that of casein. After physical treatment, the digestibility improvement was related to the elimination of soluble molecules such as xylan and mineral salts. The improvement observed after fermentations seemed due to the degradation of insoluble fibers.

Seasonal Variability of the Biochemical Composition and Antioxidant Properties of Fucus spiralis at Two Azorean Islands

“…Increasing the bioavailability by using physical processes or fermentation to break down the fibers and release the protein has been investigated [26]. Overall, macroalgae have been favorably reviewed as sources of proteins for nutritional purposes [27].…”

Algal Proteins: Extraction, Application, and Challenges Concerning Production

“…acanthophora , Sargassum vulgare , and Ulva fasciata following immersion in ultra-pure water (Table 1) [68]. Alternatively, osmotic stress has also been reported to improve extraction of algal proteins efficiency [45,75]. Osmotic shock was reported to yield a significantly higher concentration of water soluble proteins from P. palmata (1.02 ± 0.07 g/100 g) compared to high shear force with an Ultra-turrax ® T25 Basic tool (IKA ® , Staufen, Germany) (0.74 ± 0.02 g/100 g) [73].…”

Algae as nutritional and functional food sources: revisiting our understanding

“…In general, protein in most algae is digested less completely than reference proteins such as casein (a milk protein) in in vitro model systems containing digestive enzymes such as pepsin, pronase, and pancreatin, with evidence that this is due especially to inhibitory soluble fibers (e.g., Fujiwara-Arasaki et al 1984; Fleurence 1999a; Urbano and Goni 2002; Marrion et al 2003, 2005; Wong and Cheung 2003; De Marco et al 2014). Inclusion of pre-analytical steps such as freezing, milling, digestion of crude sample with polysaccharide-digesting enzymes, and/or osmotic rupture of cells to free intracellular compounds is an active area of research (e.g., Harnedy and FitzGerald 2013; Safi et al 2014; Ursu et al 2014; and references therein).…”