Reducing the High Iodine Content of Saccharina latissima and Improving the Profile of Other Valuable Compounds by Water Blanching

The green seaweed Ulva: tomorrow's "wheat of the sea" in foods, feeds, nutrition, and biomaterials

Ulva, a genus of green macroalgae commonly known as sea lettuce, has long been recognized for its nutritional benefits for food and feed. As the demand for sustainable food and feed sources continues to grow, so does the interest in alternative, plant-based protein sources. With its abundance along coastal waters and high protein content, Ulva spp. have emerged as promising candidates. While the use of Ulva in food and feed has its challenges, the utilization of Ulva in other industries, including in biomaterials, biostimulants, and biorefineries, has been growing. This review aims to provide a comprehensive overview of the current status, challenges and opportunities associated with using Ulva in food, feed, and beyond. Drawing on the expertise of leading researchers and industry professionals, it explores the latest knowledge on Ulva's nutritional value, processing methods, and potential benefits for human nutrition, aquaculture feeds, terrestrial feeds, biomaterials, biostimulants and biorefineries. In addition, it examines the economic feasibility of incorporating Ulva into aquafeed. Through its comprehensive and insightful analysis, including a critical review of the challenges and future research needs, this review will be a valuable resource for anyone interested in sustainable aquaculture and Ulva's role in food, feed, biomaterials, biostimulants and beyond.

Brown seaweed as a food ingredient contributing to an adequate but not excessive amount of iodine in the European diet. A case study with bread

BACKGROUND

The large amounts of iodine in brown seaweeds may contribute towards an adequate iodine intake, but also pose a food safety risk. In the current work we estimate the maximum amount of the cultivated brown seaweeds Saccharina latissima and Alaria esculenta (blanched and non-blanched) that can be added to white loaf-type wheat-bread so European consumers are protected against excessive chronic intakes. We use data for high-level consumers of bread with special ingredients added from the EFSA comprehensive European food consumption database to construct a conservative risk management model. We bake prototype seaweed bread and use the output from the model to assess exposure to iodine and trace metals. We also assess some bread quality parameters such as sensory characteristics, crumb firmness and specific volume.

RESULTS

The maximum level of iodine in bread that would mitigate the European consumer from excess intakes was 857 μg I kg-1 bread. Assuming a typical 60% wheat flour per kilogram of bread, a maximum amount of 11.3 g of dried blanched A. esculenta (115 mg I kg-1 dry weight) could be incorporated per kilogram of wheat flour into the bread recipe whilst for non-blanched S. latissima, which contained 3500 mg I kg-1 dry weight, only a minuscule 350 mg of seaweed was the limit. For prototype breads, seaweed addition had no significant impact on the specific volume and crumb firmness. Levels of cadmium and arsenic in the bread were also of low toxicological concern.

CONCLUSION

A maximum 1-2% brown seaweed of total flour weight could be added to bread to contribute towards European consumers' adequate iodine intake without overexposure. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Emerging green cell disruption techniques to obtain valuable compounds from macro and microalgae: a review

In the modern era, macro-microalgae attract a strong interest across scientific disciplines, owing to the wide application of these cost-effective valuable bioresources in food, fuel, nutraceuticals, and pharmaceuticals etc. The practice of eco-friendly extraction techniques has led scientists to create alternative processes to the conventional methods, to enhance the extraction of the key valuable compounds from macro-microalgae. This review narrates the possible use of novel cell disruption techniques, including use of ionic liquid, deep eutectic solvent, surfactant, switchable solvents, high voltage electrical discharge, explosive decompression, compressional-puffing, plasma, and ozonation, which can enable the recovery of value added substances from macro-microalgae, complying with the principles of green chemistry and sustainability. The above-mentioned innovative techniques are reviewed with respect to their working principles, benefits, and possible applications for macro-microalgae bioactive compound recovery and biofuel. The benefits of these techniques compared to conventional extraction methods include shorter extraction time, improved yield, and reduced cost. Furthermore, various combinations of these innovative technologies are used for the extraction of thermolabile bioactive compounds. The challenges and prospects of the innovative extraction processes for the forthcoming improvement of environmentally and cost-effective macro-microalgal biorefineries are also explained in this review.

High spatial and temporal variation in biomass composition of the novel aquaculture target Ecklonia radiata

The biomass composition of kelp varies within species both spatially and temporally. However, this variation in biomass quality has not yet been investigated for the native kelp Ecklonia radiata within New Zealand, where the kelp is a target for the emerging seaweed aquaculture industry. In this study we quantified spatial and temporal variation in the composition of E. radiata biomass, collected from 12 sites around the North Island of New Zealand and from 12 months across a full year at a single site (n = 138). High spatial variation was detected for most components, including alginate (range: 16.6 - 22.7% DW, n = 12), fucoidan (range: 1.2 - 1.6% DW, n = 12), phlorotannins (range: 4.8 - 9.3% DW, n = 72), and glucose (range: 9.3 - 22.6% DW, n = 12). The biomass composition of E. radiata varied significantly among sites but with no clear patterns among regions, indicating that geographic differences were mostly local rather than regional, possibly due to site-specific environmental conditions. Significant temporal variation (measured by positive autocorrelation between months) was detected in the content of lipids, proteins, glucose, guluronic acid, nitrogen, phosphorous, iodine, arsenic, and mercury, and for the mannuronic to guluronic acid (M:G) ratio. Overall, E. radiata had comparable biomass composition to that of commercially grown northern hemisphere species but with substantially higher phlorotannin content. These results demonstrate that E. radiata could be a viable southern hemisphere alternative for a broad range of commercial applications.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10811-023-02969-2.

Variation of the Nutritional Composition and Bioactive Potential in Edible Macroalga Saccharina latissima Cultivated from Atlantic Canada Subjected to Different Growth and Processing Conditions

Macroalgae are a new food source in the Western world. The purpose of this study was to evaluate the impact of harvest months and food processing on cultivated Saccharina latissima (S. latissima) from Quebec. Seaweeds were harvested in May and June 2019 and processed by blanching, steaming, and drying with a frozen control condition. The chemical (lipids, proteins, ash, carbohydrates, fibers) and mineral (I, K, Na, Ca, Mg, Fe) compositions, the potential bioactive compounds (alginates, fucoidans, laminarans, carotenoids, polyphenols) and in vitro antioxidant potential were investigated. The results showed that May specimens were significantly the richest in proteins, ash, I, Fe, and carotenoids, while June macroalgae contained more carbohydrates. The antioxidant potential of water-soluble extracts (Oxygen Radical Absorbance Capacity [ORAC] analysis-625 µg/mL) showed the highest potential in June samples. Interactions between harvested months and processing were demonstrated. The drying process applied in May specimens appeared to preserve more S. latissima quality, whereas blanching and steaming resulted in a leaching of minerals. Losses of carotenoids and polyphenols were observed with heating treatments. Water-soluble extracts of dried May samples showed the highest antioxidant potential (ORAC analysis) compared to other methods. Thus, the drying process used to treat S. latissima harvested in May seems to be the best that should be selected.

Mild blanching prior to pH-shift processing of Saccharina latissima retains protein extraction yields and amino acid levels of extracts while minimizing iodine content

The seaweed Saccharina latissima is often blanched to lower iodine levels, however, it is not known how blanching affects protein extraction. We assessed the effect of blanching or soaking (80/45/12 °C, 2 min) on protein yield and protein extract characteristics after pH-shift processing of S. latissima. Average protein yields and extract amino acid levels ranked treatments as follows: blanching-45 °C ∼ control > soaking ∼ blanching-80 °C. Although blanching-45 °C decreased protein solubilization yield at pH 12, it increased isoelectric protein precipitation yield at pH 2 (p < 0.05). The former could be explained by a higher ratio of large peptides/proteins in the blanched biomass as shown by HP-SEC, whereas the latter by blanching-induced lowering of ionic strength, as verified by a dialysis model. Moreover, blanching-45 °C yielded a protein extract with 49 % less iodine compared with the control extract. We recommend blanching-45 °C since it is effective at removing iodine and does not compromise total protein extraction yield.

Biomolecules from Macroalgae-Nutritional Profile and Bioactives for Novel Food Product Development

Seaweed is in the spotlight as a promising source of nutrition for humans as the search for sustainable food production systems continues. Seaweed has a well-documented rich nutritional profile containing compounds such as polyphenols, carotenoids and polysaccharides as well as proteins, fatty acids and minerals. Seaweed processing for the extraction of functional ingredients such as alginate, agar, and carrageenan is well-established. Novel pretreatments such as ultrasound assisted extraction or high-pressure processing can be incorporated to more efficiently extract these targeted ingredients. The scope of products that can be created using seaweed are wide ranging: from bread and noodles to yoghurt and milk and even as an ingredient to enhance the nutritional profile and stability of meat products. There are opportunities for food producers in this area to develop novel food products using seaweed. This review paper discusses the unique properties of seaweed as a food, the processes involved in seaweed aquaculture, and the products that can be developed from this marine biomass. Challenges facing the industry such as consumer hesitation around seaweed products, the safety of seaweed, and processing hurdles will also be discussed.

Dietary exposure to heavy metals and iodine intake via consumption of seaweeds and halophytes in the European population

EFSA assessed the relevance of seaweed and halophyte consumption to the dietary exposure to heavy metals (arsenic, cadmium, lead and mercury) and the iodine intake in the European population. Based on sampling years 2011-2021, there were 2,093 analytical data available on cadmium, 1,988 on lead, 1,934 on total arsenic, 920 on inorganic arsenic (iAs), 1,499 on total mercury and 1,002 on iodine. A total of 697 eating occasions on halophytes, seaweeds and seaweed-related products were identified in the EFSA Comprehensive European Food Consumption Database (468 subjects, 19 European countries). From seaweed consumption, exposure estimates for cadmium in adult 'consumers only' are within the range of previous exposure estimates considering the whole diet, while for iAs and lead the exposure estimates represent between 10% and 30% of previous exposures from the whole diet for the adult population. Seaweeds were also identified as important sources of total arsenic that mainly refers, with some exceptions, to organic arsenic. As regards iodine, from seaweed consumption, mean intakes above 20 μg/kg body weight per day were identified among 'consumers only' of Kombu and Laver algae. The impact of a future increase in seaweed consumption ('per capita') on the dietary exposure to heavy metals and on iodine intake will strongly depend on the seaweeds consumed. The exposure estimates of heavy metals and iodine intakes in 'consumers only' of seaweeds were similar to those estimated in a replacement scenario with selected seaweed-based foods in the whole population. These results underline the relevance of the current consumption of seaweeds in the overall exposure to different heavy metals and in the intake of iodine. Recommendations are provided for further work needed on different areas to better understand the relationship between seaweed consumption and exposure to heavy metals and iodine intake.

Iodine from brown algae in human nutrition, with an emphasis on bioaccessibility, bioavailability, chemistry, and effects of processing: A systematic review

Brown algae are becoming increasingly popular as a food source and dietary supplement in Europe and other Western countries. As they are highly rich in iodine, they represent a potential new dietary iodine source. Iodine deficiency has been re-emerging in Europe, and it is important to ensure adequate intake through one's diet. However, macroalgae, and especially brown algae, may contain very high amounts of iodine, and both iodine deficiency and excessive iodine may increase the risk of negative health effects. The iodine content of algae or foods containing algae is currently not regulated in the European Union. The aim of this paper is to review the literature to determine the chemical species of iodine in brown algae, the loss of iodine during processing, and the bioavailability and bioaccessibility of iodine. A systematic search of the literature was performed in April 2021, via the databases Web of Science and PubMed. The review includes studies of iodine in brown macroalgae in relation to bioavailability, bioaccessibility, processing and speciation. A meta-analysis was conducted in relation to the following topics: (i) the correlation between total iodine and iodide (I- ) content in brown algae; (ii) the correlation between the loss of iodine during processing and the I- content; and (iii) the correlation between bioavailability and the I- content. The bioavailability of iodine from brown algae was generally high, with in vivo bioavailability ranging from 31% to 90%. The in vitro bioavailability of iodine (2%-28%) was systematically lower than in vivo bioavailability (31%-90%), indicating an inadequate in vitro methodology. Processing may reduce the iodine content of brown algae, and a higher I- content was positively correlated with increased iodine loss during processing. Although processing strategies may reduce the iodine content of brown algae significantly, the iodine content may still be high after processing. These findings may be used in food safety evaluations of brown algae as well as in the development of macroalgae-containing foods with iodine contents suitable for human consumption. Further research on processing techniques to reduce the iodine content in brown macroalgae are warranted.

Sustainable resource production for manufacturing bioactives from micro- and macroalgae: Examples from harvesting and cultivation in the Nordic region

Micro- and macroalgae are a great and important source of raw material for manufacturing of bioactives and ingredients for food, feed, cosmetics, or pharmaceuticals. Macroalgae (or seaweeds) have been harvested locally from wild stocks in smaller volumes for a long time, and a production chain based on cultivated seaweed for the harvest of considerably larger amounts is in progress for several species. Microalgae and cyanobacteria such as Spirulina have been produced in "backyard ponds" for use in food and feed also for a long time, and now we see the establishment of large production plants to control the cultivation process and increase the production yields. There is also a shift from harvesting or cultivation centered in warmer, sunnier areas to increasing exploitation of natural resources in temperate to boreal regions. In locations with strong seasonal variations in solar irradiance and temperatures, we need to develop procedures to maximize the biomass production in the productive seasons and ensure efficient stabilization of the biomass for year-round processing and product manufacturing. Industrialized biomass production and large-scale manufacturing of bioactives also mean that we must employ sustainable, cost-effective, and environmentally friendly processing methods, including stabilization and extraction methods such as ensiling and subcritical water extraction (SWE) and advanced analytic tools to characterize the products. These topics are focus areas of the Nordic Centre of Excellence (NCoE) NordAqua, and here we present a review of current activities in the field of micro- and macroalgae biomass production sectors illustrated with some of our experiences from the NordAqua consortium.

Impact of Blanching, Freezing, and Fermentation on Physicochemical, Microbial, and Sensory Quality of Sugar Kelp (Saccharina latissima)

Low seaweed consumption in the West is due to lack of availability and consumer familiarity. In this study, the effects of preservation processes on quality aspects of Saccharina latissima products were assessed. First, a blanching (100 °C for 1 or 3 min) treatment was used to produce seaweed salad. In a second study, effects of blanching, freezing, and fermentation on kelp quality were assessed and processed kelp was used to produce sauerkraut. Blanching significantly decreased (p ≤ 0.05) the instrumental kelp a* value and firmness. The a* value negatively correlated with overall liking of salads. To prepare sauerkraut, raw, raw/frozen (-20 °C), blanched (100 °C, 1 min), or blanched/frozen kelp were mixed with cabbage, salted, inoculated with starter cultures and fermented. Inconsistent trends in L* values, firmness, and fungi enumeration were observed after fermentation. Consumers evaluated kelp salad (n = 100) and sauerkraut (n = 80) for acceptability. Blanched kelp salad had higher hedonic scores than raw kelp salad. A 100% cabbage sauerkraut control and blanched kelp/cabbage blends were compared; kelp blends were similar to control for appearance, color, and texture but were lower for overall acceptability. Results suggest improved quality and enhanced consumer acceptability of seaweed products with use of minimal processing.

Effects of Heat Treatment Processes: Health Benefits and Risks to the Consumer

Macroalgae are a biological group that has mainly been used in Asian countries; however, the interest shown by Western society is recent, its application in the industrial sector having increased in the last few decades. Seaweeds are filled with properties which are beneficial to our health. To use them as food and enhance these properties, heat has been used on them. This process alters the bioactive compounds. If we study the levels of moisture, they can vary according to the drying methods used. High values of moisture can lead to a short shelf life due to oxidation, microbial or enzyme activity, so controlling these values is highly recommended. Heat causes enzymatic activity as well as oxidation, which leads to degradation of phenolic compounds in comparison with freeze-drying, which causes fewer losses of these components. Due to the same occurrences, lipid content can also vary, modifying the bioactive compounds and their benefits. Pigments are some of the components most affected by heat, since, through this process, seaweeds or seaweed products can suffer a change in color. Iodine in macroalgae can decrease drastically; on the other hand, protein yield can be greatly enhanced. Some studies showed that the amount of arsenic in raw seaweeds was higher than when they were heat processed, and that arsenic values varied when different heat treatments were applied. Additionally, another study showed that heat can alter protein yield in specific species and have a different effect on other species.

Seaweeds rehydration and boiling: Impact on iodine, sodium, potassium, selenium, and total arsenic contents and health benefits for consumption

Considering the importance of seaweeds for the development of sustainable and innovative food products, this study aimed to characterize the impact of hydrothermal processing on iodine, sodium, potassium, selenium, and arsenic concentrations of four seaweed species (S. latissima, L. digitata, U. pinnatifida, and C. crispus) and on the associated health risks-benefits for consumers. These elements revealed a common pattern for leachable fractions of iodine, total arsenic, and selenium: L. digitata ≥ S. latissima > C. crispus > U. pinnatifida after rehydration and boiling during different periods. The behavior for sodium was: S. latissima > L. digitata > C. crispus > U. pinnatifida, and for potassium: U. pinnatifida > L. digitata > S. latissima > C. crispus. Generally, the species that attained more significant losses were S. latissima and L. digitata. A health-relevant sodium/potassium ratio below 0.7 was found for all species except for U. pinnatifida. In some species, the risk-benefit analysis revealed that high iodine and arsenic levels might promote risks for consumption, even after 20 min boiling, but 5 g of processed U. pinnatifida could contribute to adequate iodine, sodium, potassium, and selenium intakes for all population groups. Standardized processing treatments of seaweeds can open new opportunities for the sector.

Saccharina latissima Cultivated in Northern Norway: Reduction of Potentially Toxic Elements during Processing in Relation to Cultivation Depth

There is an increasing interest in the use of Saccharina latissima (sugar kelp) as food, but the high iodine content in raw sugar kelp limits the daily recommended intake to relatively low levels. Processing strategies for iodine reduction are therefore needed. Boiling may reduce the iodine content effectively, but not predictably, since reductions from 38-94% have been reported. Thus, more information on which factors affect the reduction of iodine are needed. In this paper, sugar kelp cultivated at different depths were rinsed and boiled, to assess the effect of cultivation depth on the removal efficacy of potentially toxic elements (PTEs), especially iodine, cadmium, and arsenic, during processing. Raw kelp cultivated at 9 m contained significantly more iodine than kelp cultivated at 1 m, but the difference disappeared after processing. Furthermore, the content of cadmium and arsenic was not significantly affected by cultivation depth. The average reduction during rinsing and boiling was 85% for iodine and 43% for arsenic, but no significant amount of cadmium, lead, or mercury was removed. Cultivation depths determined the relative effect of processing on the iodine content, with a higher reduction for kelp cultivated at 9 m (87%) compared to 1 m (82%). When not taken into consideration, cultivation depth could mask small reductions in iodine content during rinsing or washing. Furthermore, since the final content of PTEs was not dependent on the cultivation depth, the type and extent of processing determines whether cultivation depth should be considered as a factor in cultivation infrastructure design and implementation, or alternatively, in product segmentation.

Commercially available kelp and seaweed products - valuable iodine source or risk of excess intake?

BACKGROUND

Seaweeds and kelps, also known as macroalgae, have long been common in the East-Asian diet. During recent years, macroalgae have entered the global food market, and a variety of macroalgae products are now available for consumers. Some macroalgae species are known to be particularly rich in iodine, but little data regarding the iodine content of macroalgae-containing foods exists.

OBJECTIVE

The aim of this research study was to analyse the iodine content in a large variety of commercially available macroalgae-containing foods and supplements and to evaluate whether such products are sources of adequate dietary iodine.

DESIGN

Ninety-six different products were collected after surveying the Norwegian market for commercially available macroalgae products, collected from three categories: 1) wholefood macroalgae products (n = 43), 2) macroalgae-containing foods (n = 39), and 3) dietary supplements containing macroalgae (n = 14). All products were analysed for iodine content by inductively coupled plasma-mass spectrometry (ICP-MS).

RESULTS

The iodine content in one portion of wholefood macroalgae products ranged from 128 to 62,400 μg. In macroalgae-containing foods, the iodine content ranged from 30 to 25,300 μg per portion, and in supplements it ranged from 5 to 5,600 μg per daily dose. The species with the highest analysed iodine content were oarweed, sugarkelp and kombu, with mean iodine levels of 7,800, 4,469 and 2,276 μg/g, respectively. For 54 products, the intake of one portion or dose would exceed the tolerable upper intake level (UL) for iodine.

DISCUSSION AND CONCLUSION

The iodine content in the included products was variable and for most products high, exceeding the tolerable upper intake level (UL) if consumed as a serving or portion size. The labelling of macroalgae species included, and declaration of iodine content, were inadequate or inaccurate for several products. As macroalgae-containing products are unreliable iodine sources, inclusion of such products in the diet may pose a risk of consuming excessive amounts of iodine.

Innovative Ultrasound-Assisted Approaches towards Reduction of Heavy Metals and Iodine in Macroalgal Biomass

The aim of this work was to evaluate the potential of ultrasound (US), alone or in combination with mild heating and/or EDTA towards reduction of As, Cd, I, and Hg content of Laminaria hyperborea. Concentrations of As, Cd, I, and Hg of 56.29, 0.596, 7340, and <0.01 mg kg⁻¹ of dry weight, respectively, were found in L. hyperborea blades. Treatment with US at 50 °C increased approx. 2-fold the amount of As released, although did not affect significantly the content of Cd or I, as compared to control (no US) samples. Reducing the temperature to 8 °C significantly decreased the effect of US, but heating at 80 °C did not cause a significant effect as compared to treatments at 50 °C. On the other hand, treatment with 0.1 N EDTA at 50 °C enhanced the percentage of Cd released by approximately 7-fold, regardless of sonication. In the present work, the combination of US and EDTA at 50 °C for 5 min led to a significant reduction of the As (32%), Cd (52%) and I (31%) content in L. hyperborea, thus improving the product’s safety for consumers.

Characterisation and chemometric evaluation of 17 elements in ten seaweed species from Greenland

Several Greenland seaweed species have potential as foods or food ingredients, both for local consumption and export. However, knowledge regarding their content of beneficial and deleterious elements on a species specific and geographical basis is lacking. This study investigated the content of 17 elements (As, Ca, Cd, Cr, Cu, Fe, Hg, I, K, Mg, Mn, Na, Ni, P, Pb, Se and Zn) in 77 samples of ten species (Agarum clathratum, Alaria esculenta, Ascophyllum nodosum, Fucus distichus, Fucus vesiculosus, Hedophyllum nigripes, Laminaria solidungula, Palmaria palmata, Saccharina latissima and Saccharina longicruris). Element profiles differed between species but showed similar patterns within the same family. For five species, different thallus parts were investigated separately, and showed different element profiles. A geographic origin comparison of Fucus species indicated regional differences. The seaweeds investigated were especially good sources of macrominerals (K > Na > Ca > Mg) and trace minerals, such as Fe. Iodine contents were high, especially in macroalgae of the family Laminariaceae. None of the samples exceeded the EU maximum levels for Cd, Hg or Pb, but some exceeded the stricter French regulations, especially for Cd and I. In conclusion, these ten species are promising food items.