Advancements in ulvan valorization from Ulva rigida: Unveiling a combined approach of electric fields and subcritical water extraction☆

abstract

Ulvan is the sulphated polysaccharide present in the cell wall of the green seaweed Ulva sp., exhibiting some rheological and biological features. The traditional recovery of this polysaccharide has certain drawbacks, including high energy and time consumption and the use of chemicals generating dangerous residues in the environment. Green alternative processing technologies have drawn attention due to their sharp processing with a decrease in solvents, energy and environmental impact. This study aims to evaluate the effect of moderate electric fields, subcritical water extraction, combination of both and benchmark with conventional extraction, on ulvan-rich fraction recovery from Ulva rigida. The combined technology increased the extraction efficiency (9-17 %), proving to be a time-saving process by inducing the rupture of cell walls. Also, a decrease in molecular weight was observed for the treatment at 170 degrees C (92 kDa), and an increase in rhamnose (159 mg/g extract) and xylose (23 mg/g extract) was recorded at 150 degrees C. All the ulvan-rich fraction samples used in this work were considered to be weak gels and/or highly viscous liquids. According to FTIR analysis, the three different methods were capable of maintaining the intrinsic properties of the ulvan-rich fraction samples without causing structural changes. Hence, the combination of high temperature and pressure together with the passage of an electric field current, where the heating is more effective with a reduced energy consumption, is a more feasible, innovative and sustainable approach to extract seaweeds' polysaccharides.

keywords

ASSISTED EXTRACTION; ANTIOXIDANT; LACTUCA; IMPACT

subject category

Food Science & Technology

authors

Pereira, SG; Pereira, RN; Ferreira, S; Nunes, C; Teixeira, JA; Rocha, CMR

Groups

G4 - Renewable Materials and Circular Economy

Projects

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

acknowledgements

The work was supported by Portuguese Foundation for Science and Technology FCT under the scope of the strategic funding of UID/BIO/04469/2020 unit and by LABBELS-Associate Laboratory in Biotechnology, Bioengineering and Microelectromechanical Systems, LA/P/0029/2020. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 (DOI 10.544 99/UIDB/50011/2020) , UIDP/50011/2020 (DOI 10.54499/UIDP/50011/2020) & LA/P/0006/2020 (DOI 10.54499/LA/P/0006/2020), financed by national funds through the FCT/MCTES (PIDDAC). Sara G. Pereira acknowledges FCT for the scholarship 2021.07623.BD. Ricardo N. Pereira acknowledges FCT for its Assistant Research program under the scope of Scientific Stimulus Employment with reference CEECIND/02903/2017.