Impact of thermal processing on the nutrients, phytochemicals, and metal contaminants in edible algae

Algae-derived compounds: Bioactivity, allergenicity and technologies enhancing their values

As a rapidly growing source of human nutrients, algae biosynthesize diverse metabolites which have promising bioactivities. However, the potential allergenicity of algal components hinder their widespread adoption. This review provides a comprehensive review of various macro and micronutrients derived from algal biomass, with particular focus on bioactive compounds, including peptides, polyphenols, carotenoids, omega-3 fatty acids and phycocyanins. The approaches used to produce algal bioactive compounds and their health benefits (antioxidant, antidiabetic, cardioprotective, anti-inflammatory and immunomodulatory) are summarised. This review particularly focuses on the state-of-the-art of precision fermentation, encapsulation, cold plasma, high-pressure processing, pulsed electric field, and subcritical water to reduce the allergenicity of algal compounds while increasing their bioactivity and bioavailability. By providing insights into current challenges of algae-derived compounds and opportunities for advancement, this review contributes to the ongoing discourse on maximizing their application potential in the food nutraceuticals, and pharmaceuticals industries.

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.

Determination of the Nutrient and Toxic Element Content of Wild-Collected and Cultivated Seaweeds from Hawai'i

For centuries, Hawaiians have gathered seaweed for food, medicine, and ceremonial purposes. Seaweed contains nutrients, but some varieties can accumulate toxic elements. We measured target macrominerals (Na, Mg, P, K, Ca), microminerals (B, V, Mn, Co, Cu, Zn, Mo), and nonessential/toxic elements (As, Sr, Cd, Sn, Hg, Pb, and U) in a sample of wild-collected and cultivated seaweeds from Hawai'i. The samples consisted of brown (Sargassum aquifolium, Sargassum echinocarpum), red (Gracilaria parvispora, Halymenia formosa, Halymenia hawaiiana), and green (Ulva ohnoi) seaweed. Elemental composition was determined by inductively coupled plasma (ICP)-atomic emission spectroscopy and ICP-mass spectrometry (MS). Speciation of As was conducted by using liquid chromatography-ICP-MS. S. echinocarpum per 80 g serving was high in Ca (~37% daily value [DV]), U. ohnoi was high in Mg (~40%DV), H. formosa was high in Fe (~40%DV), and G. parvispora was high in Mn (~128%DV). In this study, the highest amounts of toxic elements were observed in S. aquifolium and S. echinocarpum (27.6 mg inorganic As/kg fdw), G. parvispora (43.3 mg Pb/kg fdw) and H. formosa (46.6 mg Pb/kg fdw). These results indicate that although seaweeds from Hawai'i contain a variety of nutrients, some species can accumulate high amounts of toxic elements.

Role of Algal-derived Bioactive Compounds in Human Health

Algae is emerging as a bioresource with high biological potential. Various algal strains have been used in traditional medicines and human diets worldwide. They are a rich source of bioactive compounds like ascorbic acid, riboflavin, pantothenate, biotin, folic acid, nicotinic acid, phycocyanins, gamma-linolenic acid (GLA), adrenic acid (ARA), docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), etc. Beta-carotene, astaxanthin, and phycobiliproteins are different classes of pigments that are found in algae. They possess antioxidant, anti-inflammatory and anticancer properties. The sulfur-coated polysaccharides in algae have been used as an anticancer, antibacterial, and antiviral agent. Scientists have exploited algal-derived bioactive compounds for developing lead molecules against several diseases. Due to the surge in research on bioactive molecules from algae, industries have started showing interest in patenting for the large-scale production of bioactive compounds having applications in sectors like pharmaceuticals, food, and beverage. In the food industry, algae are used as a thickening, gelling, and stabilizing agent. Due to their gelling and thickening characteristics, the most valuable algae products are macroalgal polysaccharides such as agar, alginates, and carrageenan. The high protein, lipid, and nutrient content in microalgae makes it a superfood for aquaculture. The present review aims at describing various non-energy-based applications of algae in pharmaceuticals, food and beverage, cosmetics, and nutraceuticals. This review attempts to analyze information on algal-derived drugs that have shown better potential and reached clinical trials.

Impact of thermal processing on dietary flavonoids

Flavonoids are a class of polyphenols which are widely distributed in natural products and foods. They have diverse bioactivities, including anti-inflammatory, anti-aging, and antioxidant activities. Generally, the foods rich in flavonoids are usually consumed after thermal processing. However, thermal stability of flavonoids is usually low, and thermal processing could cause either positive or negative influences on their stability and bioactivities. In this review, the effects of thermal processing on thermal stability and bioactivity of dietary flavonoids from different food sources are summarized. Then, strategies to improve thermal stability of dietary flavonoids are discussed and the effect of some promising thermal technologies are also preliminary clarified. The promising thermal technologies may be alternative to conventional thermal processing technologies.

Physicochemical characterization and cosmetic application of kelp blanching water polysaccharides

Seaweeds account for half of global mariculture and have become a key player in bio-based industries. Seaweed process typically starts with hot water blanching that helps reduce postharvest quality deterioration but also generates large amounts of hydrothermal waste. This study aims to explore the feasibility of isolating water-soluble biopolymers from seaweed hydrothermal waste and their potential applications. Using Saccharina japonica (formerly Laminaria japonica) blanching water as example, 2.9 g/L of polymeric substances were efficiently isolated by ultrafiltration, implying biopolymer coproduction potential of ~5.8 kt from blanching wastewater of current kelp industry. Physicochemical characterizations revealed polysaccharidic nature of the biopolymers, with high contents of fucose, uronic acids and sulfate, showing distinct but also overlapping structural features with hot water-extracted kelp polysaccharides. The main fraction of the blanching water polymers after anion exchange chromatography was acidic polysaccharide, the major backbone residues of which were (1-4) linked mannopyranose, (1-4) linked gulopyranose and (1-2) linked fucopyranose while the branched residues were primarily 1,3,4-, 1,2,4- and 1,4,6-linked hexoses but also 1,3,4-fucopyranose. Furthermore, the polysaccharides were found to have a good compatibility in cosmetic creams with added cohesiveness and freshness, demonstrating the application potential of such natural biopolymers from currently underexplored seaweed blanching water.

A Blend Consisting of Agaran from Seaweed Gracilaria birdiae and Chromium Picolinate Is a Better Antioxidant Agent than These Two Compounds Alone

A blend refers to the combination of two or more components to achieve properties that are superior to those found in the individual products used for their production. Gracilaria birdiae agaran (SPGb) and chromium picolinate (ChrPic) are both antioxidant agents. However, there is no documentation of blends that incorporate agarans and ChrPic. Hence, the objective of this study was to generate blends containing SPGb and ChrPic that exhibit enhanced antioxidant activity compared to SPGb or ChrPic alone. ChrPic was commercially acquired, while SPGb was extracted from the seaweed. Five blends (B1; B2; B3; B4; B5) were produced, and tests indicated B5 as the best antioxidant blend. B5 was not cytotoxic or genotoxic. H₂O₂ (0.6 mM) induced toxicity in fibroblasts (3T3), and this effect was abolished by B5 (0.05 mg·mL^-1); neither ChrPic nor SPGb showed this effect. The cells also showed no signs of toxicity when exposed to H₂O₂ after being incubated with B5 and ChrPic for 24 h. In another experiment, cells were incubated with H₂O₂ and later exposed to SPGb, ChrPic, or B5. Again, SPGb was not effective, while cells exposed to ChrPic and B5 reduced MTT by 100%. The data demonstrated that B5 has activity superior to SPGb and ChrPic and points to B5 as a product to be used in future in vivo tests to confirm its antioxidant action. It may also be indicated as a possible nutraceutical agent.

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.

Recent Advances in Natural Polyphenol Research

Polyphenols are secondary metabolites produced by plants, which contribute to the plant's defense against abiotic stress conditions (e.g., UV radiation and precipitation), the aggression of herbivores, and plant pathogens. Epidemiological studies suggest that long-term consumption of plant polyphenols protects against cardiovascular disease, cancer, osteoporosis, diabetes, and neurodegenerative diseases. Their structural diversity has fascinated and confronted analytical chemists on how to carry out unambiguous identification, exhaustive recovery from plants and organic waste, and define their nutritional and biological potential. The food, cosmetic, and pharmaceutical industries employ polyphenols from fruits and vegetables to produce additives, additional foods, and supplements. In some cases, nanocarriers have been used to protect polyphenols during food processing, to solve the issues related to low water solubility, to transport them to the site of action, and improve their bioavailability. This review summarizes the structure-bioactivity relationships, processing parameters that impact polyphenol stability and bioavailability, the research progress in nanocarrier delivery, and the most innovative methodologies for the exhaustive recovery of polyphenols from plant and agri-waste materials.

Algal biorefinery culminating multiple value-added products: recent advances, emerging trends, opportunities, and challenges

Algal biorefinery is rising as a prominent solution to economically fulfill the escalating global requirement for nutrition, feed, fuel, and medicines. In recent years, scientific productiveness associated with microalgae-based studies has elaborated in multiplied aspects, while translation to the commercial level continues to be missing. The present microalgal biorefinery has a challenge in long-term viability due to escalated market price of algal-mediated biofuels and bioproducts. Advancements are required in a few aspects like improvement in algae processing, energy investment, and cost analysis of microalgae biorefinery. Therefore, it is essential to recognize the modern work by understanding the knowledge gaps and hotspots driving business scale up. The microalgae biorefinery integrated with energy-based products, bioactive and green compounds, focusing on a circular bioeconomy, is urgently needed. A detailed investigation of techno-economic analysis (TEA) and life cycle assessment (LCA) is important to increase the market value of algal products. This review discusses the valorization of algal biomass for the value-added application that holds a sustainable approach and cost-competitive algal biorefinery. The current industries, policies, technology transfer trends, challenges, and future economic outlook are discussed. This study is an overview through scientometric investigation attempt to describe the research development contributing to this rising field.

Association of Mushrooms and Algae Consumption with Mortality among Chinese Older Adults: A Prospective Cohort Study

Mushrooms and algae are important sources of dietary bioactive compounds, but their associations with mortality remain unclear. We examined the association of mushrooms and algae consumption with subsequent risk of all-cause mortality among older adults. This study included 13,156 older adults aged 65 years and above in the Chinese Longitudinal Healthy Longevity Survey (2008-2018). Consumption of mushrooms and algae at baseline and age of 60 were assessed using a simplified food frequency questionnaire (FFQ). We used Cox proportional hazards models to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs). During 74,976 person-years of follow-up, a total of 8937 death cases were documented. After adjustment for demographic, lifestyle, and other dietary factors, participants who consumed mushrooms and algae at least once per week had a lower risk of all-cause mortality than rare consumers (0-1 time per year) (HR = 0.86; 95% CI: 0.80-0.93). Compared to participants with rare intake at both age 60 and the study baseline (average age of 87), those who maintained regular consumptions over time had the lowest hazard of mortality (HR = 0.86; 95% CI: 0.76-0.98). Our findings supported the potential beneficial role of long-term consumption of mushrooms and algae in reducing all-cause mortality among older adults. Further studies are warranted to evaluate the health benefit for longevity of specific types of mushrooms and algae.

Metal Contamination of Oman Sea Seaweed and Its Associated Public Health Risks

Oman Sea region is a major gateway for international and local shipping. Metal pollution of aquatic environment is primarily caused by such shipping and industrial activities. Agricultural runoffs are also of concern. Seaweed contamination with heavy metals in this area is therefore a distinct possibility. We examined seaweed of Oman Sea for heavy metal content and potential risk of its consumption to the public. During winter of 2019, water, sediment, and seaweed were collected along twelve stations on the coast of Oman Sea. Triplicates of each sample were analyzed for metal content by atomic absorption spectroscopy. Biomarkers of metals in seaweed (metallothionein and phytochelatin) were also analyzed. A significant positive correlation exists among levels of Zn, Ni, Pb, Cr, Cu, and Fe in water, sediment, and seaweed (P < 0.05). Cadmium correlations were weak. The highest levels of metallothionein and phytochelatin were found in brown and red seaweed (118.6 µg/g wet weight, 16.4 amol/cell; 111.4 µg/g ww, 12.1 amol/cell), respectively. For nickel and lead, human consumption of red, brown, and green seaweed was associated with "some health hazard," with a target hazard quotient of > 1. We conclude that concerns over heavy metal contamination of some parts of Oman Sea are valid, and we invite policy makers to implement measures for protection of public and environment from metal toxic effects in the region.

Seaweed Value Chain Stakeholder Perspectives for Food and Environmental Safety Hazards

With a world population estimated at 10 billion people by 2050, the challenge to secure healthy and safe food is evident. Seaweed is a potential answer to this challenge. Expanding the use of seaweed in food systems requires an emphasis on safe practices to avoid adverse human health effects after consumption and irreversible damage to marine ecosystems. This study aims to evaluate relevant food safety and environmental safety hazards, monitoring measures, and mitigation strategies in the seaweed sector. For this study, a literature review, survey (n = 36), and interviews (n = 12) were conducted to identify hazards. The review and interviews aimed at pinpointing monitoring measures and mitigation strategies applied, while the survey revealed data gaps and further actions needed for the sector. Relevant food safety hazards include (inorganic) arsenic, iodine, and heavy metals, among others, such as pathogenic bacteria, while environmental hazards include environmental pathogens and parasites introduced into the ecosystem by domesticated seaweed, among others. Measures applied aim at preventing or mitigating hazards through good hygienic or manufacturing practices, food safety procedures or protocols, or pre-site farm selection. Although the future needs of the seaweed sector vary, for some, harmonized advice and protocols that align with a changing food system and hazard knowledge development as well as information on the benefits of seaweed and regulating climate and water quality may help.

Microbiological Food Safety of Seaweeds

The use of seaweeds in the human diet has a long history in Asia and has now been increasing also in the western world. Concurrent with this trend, there is a corresponding increase in cultivation and harvesting for commercial production. Edible seaweed is a heterogenous product category including species within the green, red, and brown macroalgae. Moreover, the species are utilized on their own or in combinatorial food products, eaten fresh or processed by a variety of technologies. The present review summarizes available literature with respect to microbiological food safety and quality of seaweed food products, including processing and other factors controlling these parameters, and emerging trends to improve on the safety, utilization, quality, and storability of seaweeds. The over- or misuse of antimicrobials and the concurrent development of antimicrobial resistance (AMR) in bacteria is a current worldwide health concern. The role of seaweeds in the development of AMR and the spread of antimicrobial resistance genes is an underexplored field of research and is discussed in that context. Legislation and guidelines relevant to edible seaweed are also discussed.

An Investigation of Toxic Metal Levels (Pb, Cd, Cr, As, Hg) in Dried Porphyra and Laminaria Collected from Coastal Cities, China

This investigation was aimed at determining the concentration levels of five toxic heavy metals (lead, cadmium, chromium, arsenic, and mercury) in dried Porphyra and Laminaria samples from coastal city of China. Inductively coupled plasma-mass spectrometry (ICP-MS) was used for determination of lead, cadmium and total arsenic. Atomic fluorescence spectrometry was used for mercury, and liquid chromatography coupled with ICP-MS was used for arsenic speciation. The mean concentrations of lead, cadmium, chromium, total arsenic, and mercury were 0.96 ± 0.03 mg/kg, 2.62 ± 0.07 mg/kg, 1.64 ± 0.08 mg/kg, 36.67 ± 0.53 mg/kg, and 7.56 ± 0.42 μg/kg for Porphyra samples and 0.61 ± 0.03 mg/kg, 0.48 ± 0.02 mg/kg, 3.78 ± 0.56 mg/kg, 43.85 ± 1.42 mg/kg, and 46.61 ± 2.02 μg/kg for Laminaria samples. The results were comparable with previous similar research. The potential health risk assessment was conducted by comparing the calculated weekly intakes of toxic metals from Porphyra and Laminaria with provisional tolerable weekly intake. Consumption of these seaweeds does not seem to pose a risk for the consumers' health regarding their content of heavy metals. However, the potential health risk of cadmium should not be overlooked for consumers with high intake of Porphyra.

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.

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.

A survey of arsenic, mercury, cadmium, and lead residues in seafood (fish, crustaceans, and cephalopods) from the south-eastern Mediterranean Sea

Seafood is capable of bioaccumulating heavy metals (HM), making it a potentially major dietary source of HM for humans. Presently, little data exists on seafood from the eastern-most boundary of the Mediterranean Sea. This study aims to provide exposure insight of the Israeli population to HM through the consumption of locally caught seafood by assessing the levels of arsenic, mercury, cadmium, and lead in raw tissues of seafood. A wide survey of local fisheries was conducted providing 296 samples from 11 different species, including seven fish, two crustacean, and two cephalopod species. Total arsenic, cadmium, and lead were analyzed by graphite-furnace atomic absorption. Total mercury was measured by cold-vapor mercury analyzer. Arsenic speciation was performed by anion chromatography-inductively coupled plasma sector field mass spectrometry. Results suggested that the total arsenic concentrations were significantly higher in crustaceans and cephalopods than fish. Arsenic speciation revealed two samples that exceed 1 mg/kg of inorganic arsenic, whereas methylated arsenic was below the detection limit. Elevated mercury levels were detected in the commercial benthic species Mullus barbatus (red mullet), cadmium was detected in one-third of the samples, and lead detected in eight samples. Comparing the results to health guidelines, 99.4% of seafood tested in this study abide with acceptable levels of heavy metals in seafood, as defined by both Israeli and European Union guidelines.