Effect of Oven-Drying on the Recovery of Valuable Compounds from Ulva rigida, Gracilaria sp. and Fucus vesiculosus

Abstract

The effect of oven-drying at 25, 40 and 60 °C was evaluated on three macroalgae of relevance in Europe, namely Ulva rigida, Gracilaria sp. and Fucus vesiculosus, with respect to quality aspects, including their potential to be exploited as a source of valuable compounds. Notably, as compared to freeze-drying, oven-drying at 25 °C promoted the extraction of chlorophylls and carotenoids from U. rigida, as well as those of phycoerythrin and chlorophyll a from Gracilaria sp., while 40 °C favored the recovery of fucoxanthin and pheophytin a from F. vesiculosus. On the other hand, the use of oven-drying had a negative impact on the extraction of phenolic compounds from this alga, also diminishing the antioxidant activity of the resulting extracts. Instead, the impact of oven-drying of raw material on the recovery of specific polysaccharides differed among the macroalgae. While the amounts of ulvans and fucoidans obtained from macroalgae dried at higher temperatures tended to be superior, the recovery of agar was not affected with the drying temperatures applied to Gracilaria sp. The overall results showed that oven-drying might serve as a good alternative to stabilize Ulva rigida, Gracilaria sp. and Fucus vesiculosus, especially if extraction of pigments and polysaccharides is aimed, thought the appropriate temperature applied must be adapted for each macroalgae.

Physicochemical Changes of Air-Dried and Salt-Processed Ulva rigida over Storage Time

“…Moreover, as expected, the total color difference parameter (calculated on the basis of a*, b*, and L* coordinates) confirmed that changes in colors during the storage time were particularly evident in salt-treated samples, probably due to superior changes in the cells’ structures, which might contribute to additional losses/changes in pigments. In fact, this is partially supported by the results of Figure 1, which show higher levels of extracted chlorophylls and total carotenoids (presumably lutein as shown in our previous work [15]) in air-dried U. rigida at t180, when compared to salt-treated samples.…”

“…from Chile, together with changes in the levels of phytochemicals and the profile of amino acids and fatty acids. Moreover, our group has recently evidenced the effect of distinct oven-drying temperatures (25, 40 and 60 °C) on quality parameters and recovery yield of valuable compounds (pigments, phenolic compounds, and polysaccharides) from U. rigida , as compared to freeze-drying [15].…”

The effect of different drying methods on certain nutritionally important chemical constituents in edible brown seaweeds

“…For example, phenolic compounds (capable of acting as antioxidants) are often depleted when using certain drying methods, which may then result in reduced antioxidant activity (Ling et al 2015;Cruces et al 2016). Other valuable biomolecules such as amino acids, proteins, lipids, fatty acids and other bioactive compounds in seaweeds can also be affected by drying procedures (Chan et al 1997;Le Lann et al 2008;Ling et al 2015;Cruces et al 2016;Neoh et al 2016;Hamid et al 2018;Sappati and Nayak 2018;Silva et al 2019). These studies have demonstrated the value of selecting appropriate drying treatments in order to preserve important bioactive compounds within seaweeds that are destined for use as functional foods.…”

Effect of different post-harvest treatments on free amino acid content in Fucus vesiculosus

“…The results of the study showed that, apart from iodine, other chemical components did not change under the influence of drying. In a recent study Silva et al [23] compared the chemical composition of Ulva rigida, Gracilaria sp. and F.vesiculosus seaweed tallomes dried in an oven (25, 40 and 60 ∘ C) compared to fresh seaweed, and showed that the extraction of polyphenols and their activity are significantly influenced by the drying method.…”