Effects of air drying and freezing and long-term storage on phytochemical composition of brown seaweeds

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Effects of air drying and freezing and long-term storage on phytochemical composition of brown seaweeds Ekaterina Obluchinskaya 1

&

Anna Daurtseva 1

Received: 31 October 2019 / Revised and accepted: 10 August 2020 # Springer Nature B.V. 2020

Abstract The effect of air drying and freezing at − 25 °C on the total phenolic content, fucoidan, alginate, and amino acids of brown algae Fucus vesiculosus, Fucus distichus, and Ascophyllum nodosum was studied over 365 days of storage every 90 days. The levels of total phenols and polysaccharides in frozen algae samples at 365 days of storage were 75–95% of fresh algae and were higher than in air-dried samples by more than 5–15%. The greatest differences between the fresh and dried samples were in the total phenolic contents. A strong correlation was found between the content of total phenolics and polysaccharides and the water content in frozen samples of F. vesiculosus and A. nodosum. The influence of air drying and freezing processing and storage on the total amino acid content is discussed using F. vesiculosus as an example. The total amino acid content in the air-dried samples increased during storage, but on the 365th day, 99% of the initial content in fresh algae remained. In contrast, the content in the frozen samples had decreased to 82% after the same storage duration. The ratio of the sums of the essential to the total amino acids during storage in the dry and frozen samples increased compared with that in fresh algae from 0.43 to 0.51 after 365 days of storage. Air drying and freezing are suitable procedures in terms of the levels of total phenols, polysaccharides, and amino acids, allowing a shelf life of at least 365 days. Keywords Brown algae . Fucoidan . Alginate . Total phenols . Amino acids . Frozen . Dried . Storage

Introduction Seaweed and Fucus spp. in particular are sources of biologically active substances (BAS), making them highly valuable raw materials for the food and medical industries (Pangestuti and Kim 2011; FAO 2018). The most important biologically active substances in Fucus are fucoidan, polyphenols, and alginate. These compounds have antioxidant, anticancer, anticoagulant, anti-inflammatory, and antimicrobial properties (FAO 1976; Cardozo et al. 2007; Cornish and Garbary 2010; Galasso et al. 2017; Lefranc et al. 2019). The amino acid composition of algae is also an important factor that must be considered since particular Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10811-020-02225-x) contains supplementary material, which is available to authorized users. * Ekaterina Obluchinskaya [email protected] 1

Department of Zoobentos, Research Group of Biochemistry and Technology of Seaweeds, Murmansk Marine Biological Institute Russian Academy of Sciences, Vladimirskaya St. 17, Murmansk 183010, Russia

amino acids can positively affect the human body (Catarino et al. 2018). For example, aspartic acid and glycine are responsible for the formation of new tissues and the regulation of the nervous