Influence of ohmic heating in the composition of extracts from Gracilaria vermiculophylla

Abstract

Electric field-based technologies for extraction processes have been gaining importance due to sustainability concerns. This work aims to assess the potential of ohmic heating as an efficient and feasible tool for the extraction of different biocompounds from Gracilaria vermiculophylla and its effect on the extracts' composition. Different ratios of water/ethanol (0 to 75% ethanol, v/v) were used to target different families of biocompounds. The ohmic heating-based extraction was performed at 82 • C under electric field and frequency of 2-8 V/cm and 25 kHz, respectively. Conventional extractions without the presence of electric field were made keeping a temperature profile identical to the ohmic heating treatments, thus addressing the potential occurrence of electrical (non-thermal) effects. Extraction yields and extracts composition (content in polysaccharides, proteins, phenolic compounds and pigments) were evaluated. Further, as agar is the major commertially exploited compound from Gracilaria spp., the effect of ohmic heating on the extracted agar in terms of yield, carbohydrates' composition, monosaccharides profile, and gelling ability was also envisaged.Overall, significant differences in the extraction of each family of compounds between ohmic and conventional extractions were observed, being more pronounced at the best solvent for each compound (100% water for carbohydrates, 75:25 water/ethanol for proteins, 75:25 and 50:50 water/ethanol for phenolic compounds and 25:75 water/ethanol for pigments). Higher extraction yields were achieved for ohmic heating at 1 h, except for 100% water, probably indicating accelerated extraction kinetics promoted by the presence of electric field effects. Furthermore, the gelling ability of agar and the antioxidant activity were not impaired by the use of moderate electric fields. Therefore, ohmic heating is an interesting alternative, with reduced energy consumption and improved extraction performances, to recover functional ingredients or additives from seaweeds for the food industry.

Research progress in the preparation, structural characterization, bioactivities, and potential applications of sulfated agarans from the genus Gracilaria

“…The DPPH free radical, ABTS, hydroxyl radical, and superoxide radical scavenging activities of the obtained polysaccharides by Sevag method were better than that by trichloroacetic acid method. Pereira et al (2021) separated several compounds based on the principle that mixtures of water and ethanol with different proportions have different affinities to different compounds, and found that 100% water was the best solvent for carbohydrates. Andriamanantoanina et al (2007) obtained homogeneous polysaccharides by sequential extraction method and found that only the polysaccharides extracted by water/ethanol = 60% had low gelling.…”

Three-Dimensional Printing of Red Algae Biopolymers: Effect of Locust Bean Gum on Rheology and Processability

“…Its applications include the food, pharmaceutical, cosmetic, biotechnological, and biomedical sectors, presenting a notable market size valued at 264 million USD in 2022 [ 10 ]. Agar is mainly composed of agarose and agaropectin, the former being the gel-forming component, with a linear chain of repeating units of (1,3)-linked-β-D-galactose and (1,4)-linked-3,6-anhydro-α-L-galactose [ 11 ]. The gelling ability of agar is hindered by the substitution of the hydroxyl groups of l-galactose by sulphate esters, methyl ethers, or pyruvate acid ketals.…”

“…However, these multi-step methods are time-, energy-, water-, and solvent-consuming, generating large amounts of wastewater. Therefore, the search for alternative polysaccharide extraction methods that are eco-friendlier, due to the absence of a strong alkali, and predictably cheaper, as fewer steps are included in the extraction process, has boosted over increasing ecological concerns [ 11 , 13 ]. These include microwave-, ultrasound-, and enzyme-assisted extraction, which are relatively environment-friendly technologies but still rather limited to the laboratory scale [ 14 ].…”

Extraction of bioactives from brown seaweed using sub and supercritical fluids: Influence of the extract on the storage stability of fish oil enrich mayonnaise

“…To mitigate these challenges, several studies have been conducted in recent years on the extraction of bioactive compounds from seaweeds using emerging technologies (Getachew et al, 2020). These technologies include microwave-assisted extraction (Charoensiddhi et al, 2015), ultrasound-assisted extraction (Moreira et al, 2017), pulsed electric field assisted extraction (Robin et al, 2018), ohmic heating (Pereira et al, 2021), deep eutectic and natural deep eutectic solvents (Das et al, 2016;Obluchinskaya et al, 2019), supercritical carbon dioxide extraction (Saravana et al, 2017), and subcritical water (pressurized liquid extraction) (Sumampouw et al, 2021). Among these extraction technologies, extraction with sub and supercritical fluids is getting increasing attention.…”