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Botanica Marina

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Solar irradiation as an alternative bleaching process for agar extracted from Gracilariopsis heteroclada in Iloilo, Philippines

Leonilo F. EndomaORCID iD: https://orcid.org/0000-0001-7706-0747 / Loda M. Nacional
  • Institute of Fish Processing Technology, College of Fisheries and Ocean Sciences, University of the Philippines Visayas, Miagao, Iloilo 5023, Philippines
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Rovilla J. Luhan
Published Online: 2019-07-30 | DOI: https://doi.org/10.1515/bot-2018-0120


The current industrial practice of using chemical bleach to achieve the pure white colour of agar is deleterious to both human and environmental health. This study evaluates the potential of solar irradiation as an alternative bleaching process for agar extracted from Gracilariopsis heteroclada in Iloilo, Philippines. The physico-chemical properties of agar obtained from alkaline-treated seaweed after exposure to different bleaching conditions (e.g. solar irradiation, hypochlorite solution, and ultraviolet and fluorescent lights) were examined and compared with commercial bacteriological agar. Photobleaching through solar irradiation produced agar with superior gel strength (1038.61 g cm−2), high 3,6-anhydrogalactose content (41.44%) and low total inorganic sulphate content (1.87%) without compromising agar yield (19.37%). Solar irradiation offers very promising results as a simple, low-cost, environmentally friendly alternative to the chlorine bleaching process for agar extraction.

Keywords: agar extraction; chemical bleaching; Gracilariopsis heteroclada; low-cost and environmentally friendly; photobleaching


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About the article

Leonilo F. Endoma

Leonilo F. Endoma Jr. received his BSc in Fisheries in 2013 and MSc in Fisheries (Major in Fish Processing Technology) in 2016 at University of the Philippines Visayas. His interest is in utilisation and product development of seaweeds and other fishery commodity, and food biochemistry.

Loda M. Nacional

Loda M. Nacional is an Assistant Professor at the Institute of Fish Processing Technology, College of Fisheries and Ocean Sciences, University of the Philippines Visayas. Her research interests cover marine natural products, fish preservation, product development, food composition and utilisation of seaweeds.

Rovilla J. Luhan

Maria Rovilla J. Luhan is an Associate Scientist and Head of the FSES, SEAFDEC/AQD. Her interest is in mariculture of seaweeds, mainly Kappaphycus and Gracilaria. Recent work is on micropropagation, seed/spore production and nursery of seaweeds. This includes seaweed strain improvement and management of inland- and sea-based seaweed nurseries. Currently, she is the seaweed commodity team leader of SEAFDEC/AQD and a lecturer at the University of the Philippines Visayas.

Received: 2019-01-23

Accepted: 2019-06-28

Published Online: 2019-07-30

Citation Information: Botanica Marina, 20180120, ISSN (Online) 1437-4323, ISSN (Print) 0006-8055, DOI: https://doi.org/10.1515/bot-2018-0120.

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