Production of unpurified agar-based extracts from red seaweed Gelidium sesquipedale by means of simplified extraction protocols

Abstract

This work reports on the production and characterization of agar-based extracts from the seaweed Gelidium sesquipedale by means of simple protocols based on hot-water and sonication treatments. The combination of sonication with the hot-water treatment reduced 4-fold the extraction time without significantly affecting the extraction yield (ca. 10-12%) and the extracts' properties. Apart from agar, the extracts contained proteins, polyphenols and minerals, which conferred them high antioxidant capacity and led to the production of brownish softer gels. The application of an alkali pre-treatment yielded almost pure agars, with higher molecular weights and crystallinities than commercial agar, resulting in stiffer gels. However, the partial digestion of agar by the alkali led to low extraction yields (ca. 2-3%). These results show the efficiency of the combined heat and sonication method to generate cost-effective agar-based extracts with potential applications within the food industry.

Superabsorbent food packaging bioactive cellulose-based aerogels from Arundo donax waste biomass

“…10 serum albumin (BSA)/g extract. The total carbohydrate content was determined after sulphuric acid hydrolysis, following the method described in (Martínez-Abad, Giummarella, Lawoko, & Vilaplana, 2018) A detailed description of these protocols can be found elsewhere (Martínez-Sanz et al, 2019). All the determinations were carried out in triplicate.…”

Integral Utilization of Red Seaweed for Bioactive Production

“…The high electronegative charge density from their sulfated esters favors the electrostatic interactions with specific proteins, determining their biological effects, which are also closely related to the structural features [20,26,27,28]. Proteins, minerals and lipids also confer red seaweed important structural value [29].…”

“…Generally, the alkali-treatment was most effective for obtaining more galactose-rich hydrocolloids [24]. However, agar degradation and diffusion towards the aqueous medium could occur, reducing the extraction yield [29,55], although in some cases, no reduction was observed [24]. Alkaline pretreatment variables, such as alkaly type and concentration or heating time and temperature affected the yield and quality of the agar.…”

Structural Features and Rheological Properties of a Sulfated Xylogalactan-Rich Fraction Isolated from Tunisian Red Seaweed Jania adhaerens

“…The flow characteristics of JSP were described by the Ostwald model. always belongs to the d-series, while the former (α-Gal) can occur as d-(carrageenans) or l-(agarans) series [4][5][6][7]. The main backbone can be substituted by pyruvic acid ketals, sulfate, O-glycosyl and/or methyl groups and also by side chains, giving rise to great structural changes along the galactan chain.…”

“…These structural changes affect the physicochemical and rheological behaviors of these polymers. So far, it has been reported that sulfated galactans exhibit numerous biological properties, including antioxidant, anticoagulant, antinociceptive, immunomodulatory, anticancer, gastroprotective, anti-inflammatory, antithrombotic and antiproliferative [1,[6][7][8][9][10][11][12][13][14]. Marine seaweed (Phaeophyceae and Rhodophyceae) cell wall polysaccharides also hold great promise as a raw material for feed, food, and biofuel production.…”