Saccharina latissima contains high amounts of iodine in comparison to other seaweeds. The present study aimed to decrease the iodine content of S. latissima (sugar kelp) by water blanching and freezing to avoid an excess intake of iodine by consumption of sugar kelp. Various blanching conditions were investigated (temperature; 30, 45, 60 and 80 °C, and duration; 2, 30, 120 and 300 s). Some conditions resulted in a significant decrease in iodine content (≥45 °C and ≥30 s). Non-processed S. latissima contained on average 4605 mg iodine kg⁻¹ dw⁻¹ which significantly decreased following the treatments. The lowest content obtained was 293 mg iodine kg⁻¹·dw⁻¹ by water blanching at 80 °C for 120 s. The study also investigated if other valuable compounds were affected during the processing conditions. No significant changes were observed for total lipid and protein, but significant changes were seen for ash. A significant loss of two non-essential amino acids (glutamic acid and alanine) due to the blanching process was found. This also resulted in a protein quality increase as the essential amino acid to total amino acid ratio changed from 42.01 ± 0.59% in fresh seaweed to 48.0 ± 1.2% in blanched seaweed. Moreover, the proportion of eicosapentaenoic acid, α-linolenic acid, polyunsaturated fatty acids, and omega-3 fatty acids (%FAME), and the omega-3 to omega-6 fatty acids ratio was significantly higher in the samples blanched at 60 °C for 300 s compared to the fresh and samples blanched at 45 °C for 30 s. The total phenolic content (TPC) and the radical scavenging activity were significantly higher in treated samples. The results indicate that the processing did not compromise the valuable compounds in focus in this study for S. latissima; they did, however, result in biomass with an improved profile of health beneficial compounds.

Seaweeds are indiscriminately said to contain significant amounts of vitamin C, but seaweeds are a diverse group, which may limit the ability to generalize. Several studies have been performed on vitamin C in seaweed, and this review covers these findings, and concludes on how much vitamin C is found in seaweeds. A systematic review of vitamin C in 92 seaweed species was conducted followed by analyzing the 132 data entries. The average vitamin C content was 0.773 mg g⁻¹ seaweed in dry weight with a 90th percentile of 2.06 mg g⁻¹ dry weight. The vitamin C content was evaluated based on taxonomical categories of green, brown and red seaweeds (Chlorophyta (phylum), Phaeophyceae (class), and Rhodophyta (phylum)), and no significant differences were found between them. The vitamin C content was compared to other food sources, and this showed that seaweeds can contribute to the daily vitamin C intake, but are not a rich source. Moreover, seasonal variations, analytical methods, and processing impacts were also evaluated.

Sugar kelp (Saccharina latissima) is a native European brown macroalga with the potential to become a vital part of the green transition of the food industry. Knowledge of the sugar kelp shelf-life is essential to designing the food supply chain to ensure safe and high-quality food. Establishing a single-compound quality index (SCQI) of freshness would be useful for the industry. However, information is currently lacking on how different post-harvest treatments affect the shelf-life of sugar kelp, even though it is important knowledge for manufacturers, authorities and consumers. The objective of this study was to establish the shelf-life of refrigerated sugar kelp following five post-harvest treatments and evaluate the effect of these treatments on changes in quality attributes (sensory, microbial, chemical and physical) during storage to select the SCQI. The post-harvest treatments included washing in sea water, washing in potable water, blanching for 2 min in sea water or potable water and untreated sugar kelp. Based on sensory analysis, the refrigerated (+ 2.8°C) shelf-lives for sugar kelp from all treatments were seven to 9 days. The end of the sensory shelf-life correlated with the development of >7 log (CFU g⁻¹) aerobic viable counts, suggesting this attribute can be used as a SCQI to evaluate the shelf-life of sugar kelp. The microbiota was dominated by putative spoilage organisms from the Pseudoalteromonadaceae and Psychromonadaceae families. Untreated and washed sugar kelp continued to respire and consume carbohydrates up to 5 days post-harvest, indicating respiration rates may be used to determine freshness of non-blanched kelp. Favorable organoleptic properties, e.g., sweetness and umami, decreased during storage and coincided with a reduction in water-soluble mannitol and free glutamic acid. Both blanching treatments changed texture and color and reduced iodine and vitamin C contents while retaining components such as fucoxanthin, chlorophyll a and β-carotene. This study provides crucial documentation of quality changes during the post-harvest storage period of sugar kelp, including information about sugar kelp spoilage and nutrient changes, which would facilitate the development of best practices for manufacturers using sugar kelp in their production of food.

Drying is an important post-harvest process to preserve seaweed as they are highly susceptible to spoilage due to their high moisture content. Drying can be performed in multiple ways by changing the temperature, pressure, air flow, and humidity. Therefore, the choice of drying method can affect the quality of the product in terms of sensory, chemical, and physicochemical properties. Seaweeds contain nutrients (protein, lipids, carbohydrates, vitamins, and minerals) and bioactive compounds. The compounds impact properties such as texture, taste, odor, and appearance. However, there is currently limited knowledge about how different drying methods affect the quality of seaweed products. In this paper we demonstrate, how different drying methods: i) convective drying (52 °C), ii) microwave-vacuum drying (-40 to 40 °C at 10 Pa), and iii) freeze-drying (-20 to 20 °C at 20 Pa) influence the food quality of Fucus vesiculosus and Ulva sp. by investigating physico-chemical properties such as water holding capacity, water absorption, and color, the changes in some of the chemical compounds such as macronutrients, fatty acids, amino acids, antioxidants, and pigments, as well as the taste, odor, appearance, and texture within sensory attributes. This study found that different drying methods have a species-dependent influence on the quality of seaweed, with Ulva sp. showing more similarities of using microwave-vacuum and freeze-drying methods, while the drying method for F. vesiculosus should be selected based on the desired food quality due to significant variations between the drying methods.