Seaweed is a collective term for marine algae that are found in various forms worldwide. It is rich in essential nutrients, making it a valuable addition to the human diet. The nutritional composition of seaweed varies depending on the species and environmental conditions. Still, it commonly includes vitamins (e.g., A, C, B-vitamins), minerals (e.g., iodine, calcium, magnesium), dietary fibres, and essential fatty acids (Holdt and Kraan, 2011). Iodine, in particular, is abundant in seaweed and is essential for thyroid function. The presence of these nutrients makes seaweed a nutritious option for vegetarians and vegans.

Moreover, seaweed contains unique compounds such as phycobiliproteins, phycocyanins, and fucoidans with potential health benefits. These bioactive compounds have antioxidant, anti-inflammatory, and antiviral properties (Kumar et al., 2008). The rich nutritional profile of seaweed has sparked interest in its consumption as a superfood, promoting health and well-being.

Seaweed is not only beneficial for human consumption but also for the environment. It plays a significant role in marine ecosystems by providing habitat and food for various marine species. Moreover, seaweed is known for its ability to absorb and store carbon dioxide (CO2) from the atmosphere. This process, called carbon sequestration, helps mitigate the effects of climate change by reducing the concentration of greenhouse gases in the atmosphere (Filbee-Dexter et al., 2023). Seaweed also contributes to biodiversity conservation by acting as a refuge for many marine organisms, including fish, crustaceans, and molluscs.

Seaweed’s versatility extends beyond nutrition and environmental benefits. It has a wide range of applications in various industries, including food, pharmaceuticals, agriculture, and cosmetics. The unique properties of seaweed, such as its gelling ability, bioactive compounds, and texture-enhancing qualities, make it a valuable ingredient in the food industry. Seaweed extracts are used as thickeners, stabilizers, and emulsifiers in a wide array of products, from ice cream to salad dressings and carbonated beverages (Alba and Kontogiorgos, 2019).

Seaweed is also gaining attention in the pharmaceutical and healthcare sectors. Compounds extracted from seaweed, such as fucoidans and carrageenans, have been studied for their potential in drug delivery, wound healing, and as dietary supplements (Neamtu et al., 2022). In agriculture and aquaculture, seaweed is used as a soil conditioner, animal feed, and a means of reducing pollution through bioremediation (Michalak, 2020).

Freeze drying, also known as lyophilization, is a preservation technique that removes moisture from a substance while maintaining its structure, flavour, and nutritional properties. The process involves freezing the material at low temperatures and then subjecting it to a vacuum, allowing the frozen water to sublimate (change directly from a solid to a gas) without passing through the liquid phase. This unique process preserves the integrity of the product, with minimal denaturisation of proteins compared to other drying techniques, making it an attractive option for preserving delicate materials like seaweed (Albers et al., 2021).

The freeze-drying process can be broken down into several key stages:

Freeze drying offers several advantages that make it suitable for preserving seaweed:

One of the primary advantages of using freeze-drying techniques in seaweed preservation is the retention of its nutritional value. Seaweed is renowned for its rich content of vitamins, minerals, and unique bioactive compounds. Traditional drying methods, such as dehydration, sun drying or hot air drying, often lead to the loss of these essential nutrients due to exposure to heat and oxygen. In contrast, freeze drying minimises the damage caused by high temperatures, preserving the seaweed’s nutritional profile (Abdollahi et al., 2019).

Seaweed, in its freeze-dried form, can be a valuable source of dietary iodine, which is essential for thyroid health. Furthermore, the bioactive compounds found in seaweed, like fucoidans and phycocyanins, remain intact during the freeze-drying process, allowing them to retain their potential health benefits (El-Beltagi et al., 2022). This makes freeze-dried seaweed an attractive ingredient for nutraceuticals and dietary supplements.

Another significant benefit of freeze drying is the reduction in weight and volume of the seaweed. The removal of moisture during the freeze-drying process reduces the overall mass of the product, making it more convenient for storage, transportation, and use. This property is particularly important when considering seaweed for culinary applications, as it simplifies logistics and enhances the shelf space efficiency of products containing seaweed (Peñalver et al., 2020).

The extended shelf life of freeze-dried seaweed is a valuable attribute, especially in the context of food products. The removal of water, which is a key factor in microbial growth and enzymatic reactions, significantly reduces the risk of spoilage. This means that freeze-dried seaweed products can remain fresh and safe for consumption for an extended period. This is not only convenient for consumers but also beneficial for the food industry, as it reduces food waste and the need for preservatives or maintenance of a cold chain transport and storage system (Peñalver et al., 2020). A comparative 2023 study on the effect of different drying techniques on phenolic compounds in Australian beach-cast brown seaweeds (Sargassum sp., Ecklonia radiata Cystophora sp.) consistently demonstrated high phenolic and antioxidant properties in freeze dried samples (Subbiah et al., 2023).

Freeze drying is recognized for its environmental advantages when compared to other preservation methods. The energy-efficient nature of the freeze-drying process results in lower greenhouse gas emissions and reduced energy consumption, especially where modern natural refrigerants such as carbon dioxide and heat recovery technologies are embodied in the design of the equipment used. This is particularly relevant in the context of sustainability and environmental responsibility. As the world strives to reduce its carbon footprint, freeze-drying stands out as a method that aligns with these goals (Kaveh et al., 2023). It should be stated that the benefits of freeze-drying are cost effective, when applied to food production, the overall benefits of freeze-drying represent a small contribution to overall energy consumption in global terms.

Freeze-dried seaweed is gaining popularity as a healthy and flavoursome snack. The crispy, lightweight texture of freeze-dried seaweed provides a satisfying alternative to conventional potato chips. These snacks are often seasoned with various flavours, such as sesame, wasabi, or soy sauce, enhancing their appeal to consumers looking for innovative and healthy snacking options. Additionally, freeze-drying retains the umami taste of seaweed, making it an ideal component for flavourful snacks (Coleman et al., 2023).

Examples of commercially available products are detailed below:

Amanofuzu freeze dry seaweed soup: These are seaweed snacks and are available in various flavours like original, wasabi, and onion.

Marukome Freeze Dried Granulated Instant Miso Soup: a seasoned miso seaweed soup available in different flavours.

Wakame Seaweed Flakes (Undaria pinnatifida).

Seaweed extracts and powders, obtained through freeze-drying, have become sought-after ingredients for enhancing the flavour of various dishes. These seaweed-derived seasonings and condiments add a depth of umami and savoury notes to soups, sauces, and marinades. They are a versatile addition to modern cuisines, catering to diverse taste preferences. The convenience and long shelf life of freeze-dried seaweed products make them a valuable resource for culinary innovation Examples include:

Furikake: A Japanese seasoning blend containing seaweed, sesame seeds, and freeze-dried fish flakes, often used to sprinkle over rice or noodles.

Kelp Powder: Ground freeze-dried kelp seaweed that can be used as a seasoning in soups, stews, and sauces to add a savoury flavour.

Seaweed Flakes: Flakes of freeze-dried seaweed that can be used as a seasoning for salads, soups, and stir-fries (Mamat et al., 2013)..

Chefs and food innovators are exploring freeze-dried seaweed’s potential to create new culinary experiences. For instance, it can be rehydrated and used as a wrap for sushi, a topping for salads and seafood dishes, or as a component in fusion cuisine. It can also be rehydrated with an entirely different liquid than the water removed, creating a new novel flavour profile. Freeze-dried seaweed can also be incorporated into baked goods, adding unique flavours and textures to bread, crackers, and pastries. Its adaptability in the kitchen is expanding the horizons of culinary exploration and enriching the world of gastronomy Examples include:

Seaweed Pasta: Pasta made from freeze-dried seaweed or seaweed-infused flour, offering a unique flavour and added nutritional benefits.

Seaweed Butter: Butter infused with freeze-dried seaweed flakes or seaweed extract, adding a savoury umami flavour to dishes.

Seaweed Salsa: Salsa made with seaweed as a primary ingredient, providing a salty and slightly briny flavour profile (Mamat et al., 2013).

Seaweed extracts, such as alginate and carrageenan, have unique properties that make them valuable for wound care and medical dressings. These compounds can absorb exudates from wounds, provide a moist healing environment, and have antimicrobial properties. Freeze drying ensures the stability of these seaweed-derived materials, making them suitable for medical applications. In addition, the porous structure created by freeze-drying allows for the controlled release of active compounds in medical dressings, contributing to improved wound healing (Aderibigbe and Buyana, 2018). An extensive review of alginate dressings is available which discusses freeze-dried seaweed extracts used in alginate wound dressings for their ability to promote wound and burn healing and reduce inflammation (Agarwal et al., 2011).

Seaweed extracts and polysaccharides, when properly processed through freeze drying, can be used in drug delivery systems. These systems allow for the controlled release of drugs or bioactive compounds. The freeze-dried matrices provide a stable environment for drug encapsulation and release, ensuring the drug’s efficacy and safety. This technology can potentially revolutionise pharmaceutical formulations, offering precise control over drug release rates (Klojdová et al., 2023).

The freeze-drying of seaweed extracts and powders facilitates the creation of nutraceutical and dietary supplement products. These supplements provide a convenient way for consumers to access the health benefits of seaweed, such as iodine and bioactive compounds, in a concentrated and easily consumable form. Freeze-dried seaweed supplements ensure the stability of these compounds, preserving their efficacy and health-promoting properties (Lomartire et al., 2021).

Seaweed-based products, derived from freeze-dried seaweed, are used as soil conditioners and fertilizers in agriculture. These products enhance soil structure, water retention, and nutrient availability, improving overall soil health. Freeze-dried seaweed’s low weight and volume are advantageous for transport and application in agriculture, making it an eco-friendly choice for sustainable farming practices (Ali et al., 2021).

Freeze-dried seaweed is a valuable ingredient in animal feed for both terrestrial and aquatic animals. Seaweed contains essential nutrients and bioactive compounds that can improve the health and growth of livestock, poultry, and aquatic species. Its inclusion in animal diets can enhance the quality of meat, eggs, and seafood, while also benefiting the animals’ overall well-being. The ease of handling and storage of freeze-dried seaweed makes it a practical choice for animal feed formulations (Kinley et al., 2020).

Seaweed’s ability to absorb and store pollutants from the environment has led to its use in bioremediation efforts. Freeze-dried seaweed can be employed to remove heavy metals and other contaminants from polluted water bodies. The absorbed pollutants can be recovered from the seaweed, allowing for both environmental clean-up and the potential recycling of valuable resources (Farghali et al., 2023).

Seaweed’s ability to absorb and store carbon dioxide from the atmosphere is a powerful tool for mitigating climate change. As the world seeks to reduce carbon emissions and slow global warming, the cultivation of seaweed for carbon sequestration is gaining attention. Seaweed farms not only help remove CO₂ from the atmosphere but also provide habitat for marine life, promoting biodiversity and ecosystem restoration (Sultana et al., 2023).

Seaweed beds and underwater forests are essential habitats for various marine species, including fish, invertebrates, and algae. By promoting the conservation of these ecosystems, the cultivation and sustainable harvesting of seaweed contribute to biodiversity preservation. Seaweed farms can provide refuge for endangered species and restore damaged marine environments (Xiao et al., 2021). Farghall et al. in 2022 published a wide-ranging and comprehensive review that discusses the roles that seaweeds can play in climate mitigation, wastewater treatment, bioenergy, bioplastic, biochar, food, pharmaceuticals, and cosmetics (Farghali et al., 2023).

The seaweed industry offers economic opportunities to coastal communities and individuals involved in seaweed farming, processing, and product development. These opportunities support livelihoods, reduce poverty, and strengthen local economies. Additionally, the export of seaweed-based products contributes to international trade and economic growth (Rao and Ravishankar, 2022).