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Porphyra
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| Porphyra | |
|---|---|
| Porphyra umbilicalis (right) and Porphyra purpurea (front), in Heligoland | |
| Scientific classification | |
| Domain: | Eukaryota |
| Clade: | Archaeplastida |
| Division: | Rhodophyta |
| Class: | Bangiophyceae |
| Order: | Bangiales |
| Family: | Bangiaceae |
| Genus: | Porphyra C.Agardh 1824 |
| Species[1] | |
| Synonyms[1] | |
Porphyra is a genus of coldwater seaweeds that grow in cold, shallow seawater. More specifically, it belongs to red algae phylum of laver species (from which comes laverbread), comprising approximately 70 species.[2] It grows in the intertidal zone, typically between the upper intertidal zone and the splash zone in cold waters of temperate oceans. In East Asia, it is used to produce the sea vegetable products nori (in Japan) and gim (in Korea). There are considered to be 60–70 species of Porphyra worldwide[3] and seven around Britain and Ireland, where it has been traditionally used to produce edible sea vegetables on the Irish Sea coast.[4] The species Porphyra purpurea has one of the largest plastid genomes known, with 251 genes.[5]
Life cycle
[edit]Porphyra displays a heteromorphic alternation of generations.[6] The thallus we see is the haploid generation; it can reproduce asexually by forming spores which grow to replicate the original thallus. It can also reproduce sexually. Both male and female gametes are formed on the one thallus. The female gametes while still on the thallus are fertilized by the released male gametes, which are non-motile. The fertilized, now diploid, carposporangia after mitosis produce spores (carpospores) which settle, then bore into shells, germinate and form a filamentous stage. This stage was originally thought to be a different species of alga, and was referred to as Conchocelis rosea. That Conchocelis was the diploid stage of Porphyra was discovered in 1949 by the British phycologist Kathleen Mary Drew-Baker for the European species Porphyra umbilicalis.[7] It was later shown for species from other regions as well.[2][8]
Food
[edit]Most human cultures with access to Porphyra use it as a food or somehow in the diet, making it perhaps the most domesticated of the marine algae,[9] known as laver, rong biển (Vietnamese), nori (Japanese:海苔), amanori (Japanese),[10] zakai, gim (Korean:김),[10] zǐcài (Chinese:紫菜),[10] karengo, sloke or slukos.[3] The marine red alga Porphyra has been cultivated extensively in many Asian countries as an edible seaweed used to wrap the rice and fish that compose the Japanese food sushi and the Korean food gimbap. In Japan, the annual production of Porphyra species is valued at 100 billion yen (US$1 billion).[11]
P. umbilicalis is harvested from the coasts of Great Britain and Ireland, where it has a variety of culinary uses, including laverbread.[12] In Hawaii, "the species P. atropurpurea is considered a delicacy, called Limu luau".[12] Porphyra was also harvested by the Southern Kwakiutl, Haida, Seechelt, Squawmish, Nuu-chah-nulth, Nuxalk, Tsimshian, and Tlingit peoples of the North American Pacific coast.[12]
Vitamin B12
[edit]Porphyra contains vitamin B12 and one study suggests that it is the most suitable non-meat source of this essential vitamin.[13] In the view of the Academy of Nutrition and Dietetics, however, it may not provide an adequate source of B12 for vegans.[14]
Species
[edit]Porphyra currently contains 57 confirmed species and 14 unconfirmed species.[15]
Confirmed
[edit]- Porphyra akasakae A.Miura, 1977
- Porphyra angusta Okamura & Ueda, 1932
- Porphyra argentinensis M.L.Piriz, 1981
- Porphyra atropurpurea (Olivi) De Toni, 1897
- Porphyra augustinae Kützing, 1843
- Porphyra autumnalis Zanardini, 1860
- Porphyra bulbopes (Yendo) Ueda, 1932
- Porphyra capensis Kützing, 1843
- Porphyra ceylanica J.Agardh, 1883
- Porphyra chauhanii C.Anil Kumar & M.V.N.Panikkar, 1995
- Porphyra coccinea J.Agardh
- Porphyra corallicola H.Kucera & G.W. Saunders, 2012
- Porphyra delicatula Welwitsch
- Porphyra dentimarginata Chu Chia-yen & Wang Su-chuan, 1960
- Porphyra dioica J.Brodie & L.M.Irvine, 1997
- Porphyra fujianensis Zhang & Wang, 1993
- Porphyra grateloupicola P.L.Crouan & H.M.Crouan, 1878
- Porphyra guangdongensis C.K.Tseng & T.J.Chang, 1978
- Porphyra inaequicrassa Perestenko, 1980
- Porphyra indica V.Krishnamurthy & M.Baluswami, 1984
- Porphyra ionae R.W.Ricker, 1987
- Porphyra irregularis E.Fukuhara, 1968
- Porphyra kanyakumariensis V.Krishnamurthy & M.Baluswami, 1984
- Porphyra ledermannii Pilger, 1911
- Porphyra linearis Greville, 1830
- Porphyra longissima A.Meynard, M.E.Ramírez & L.Contreras-Porcia, 2018
- Porphyra lucasii Levring, 1953
- Porphyra luchea A.Meynard, M.E.Ramírez & L.Contreras-Porcia, 2018
- Porphyra malvanensis Anilkumar & P.S.N.Rao, 2005
- Porphyra marcosii P.A.Cordero, 1976
- Porphyra marginata C.K.Tseng & T.J.Chang, 1958
- Porphyra microphylla Zanardini, 1860
- Porphyra monosporangia S.Wang & J.Zhang, 1980
- Porphyra mumfordii S.C.Lindstrom & K.M.Cole, 1992
- Porphyra njordii P.M.Pedersen, 2011
- Porphyra ochotensis Nagai, 1941
- Porphyra okamurae Ueda, 1932
- Porphyra okhaensis H.V.Joshi, R.M.Oza & A.Tewari, 1992
- Porphyra oligospermatangia C.K.Tseng & B.F.Zheng, 1981
- Porphyra plocamiestris R.W.Ricker, 1987
- Porphyra pujalsiae Coll & E.C.Oliveira, 1976
- Porphyra punctata Y.Yamada & H.Mikami, 1956
- Porphyra purpurea (Roth) C.Agardh, 1824
- Porphyra qingdaoensi C.K.Tseng & B.F.Zheng, 1988
- Porphyra ramosissima Pan & Wang, 1982
- Porphyra rizzinii Coll & E.C.Oliveira, 1976
- Porphyra roseana M.Howe, 1928
- Porphyra schistothallus B.F.Zheng & J.Li
- Porphyra segregata (Setchell & Hus) V.Krishnamurthy, 1972
- Porphyra subtumens J.Agardh
- Porphyra tanakae Pham Hoang-Ho, 1985
- Porphyra tenuis B.F.Zheng & J.Li
- Porphyra tristanensis Baardseth, 1941
- Porphyra umbilicalis Kützing, 1843
- Porphyra violacea J.Agardh, 1899
- Porphyra vulgaris Kützing, 1843
- Porphyra woolhouseae Harvey, 1863
Unconfirmed
[edit]- Porphyra carnea Grunow, 1889
- Porphyra cordata Meneghini, 1844
- Porphyra cucullata De Notaris, 1865
- Porphyra grayana Reinsch, 1875
- Porphyra hospitans Zanardini, 1855
- Porphyra livida De Notaris, 1846
- Porphyra microphylla Reinsch, 1878
- Porphyra minor Zanardini, 1847
- Porphyra nobilis De Notaris, 1846 or J.Agardh, 1883
- Porphyra reniformis Meneghini, 1849
- Porphyra sericea (Wulfen) J.Agardh, 1883
- Porphyra subtumens J.Agardh ex R.M.Laing, 1928
- Porphyra tenuissima C.Agardh ex Frauenfeld, 1855
Following a major reassessment of the genus in 2011, many species previously included in Porphyra have been transferred to Pyropia: for example Pyropia tenera, Pyropia yezoensis, and the species from New Zealand Pyropia rakiura and Pyropia virididentata, leaving only five species out of seventy still within Porphyra itself.[16]
See also
[edit]References
[edit]- ^ a b Guiry, Michael D. (2012). Porphyra. In: Guiry, M.D. & Guiry, G.M. (2017). AlgaeBase. World-wide electronic publication, National University of Ireland, Galway (taxonomic information republished from AlgaeBase with permission of M.D. Guiry). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=143808 on 2017-09-06
- ^ a b Brodie, J.A. and Irvine, L.M. 2003. Seaweeds of the British Isles. Volume 1 Part 3b. The Natural History Museum, London.ISBN 1 898298 87 4
- ^ a b Kain, J.M. 1991. Cultivation of attached seaweeds. in Guiry, M.D. and Blunden, G. 1992. Seaweed Resources in Europe: Uses and Potential. John Wiley and Sons, Chichester ISBN 0-471-92947-6
- ^ Hardy, F.G. and Guiry, M.D. 2006. A Check-list and Atlas of the Seaweeds of Britain and Ireland. British Phycological Society, London. ISBN 3-906166-35-X
- ^ The Chlamydomonas Sourcebook: Organellar and Metabolic Processes Volum 2
- ^ Porphyra life cycle Archived 2007-04-11 at the Wayback Machine
- ^ Drew, Kathleen M. (1949). "Conchocelis-phase in the life-history of Porphyra umbilicalis (L.) Kütz". Nature. 164 (4174): 748–749. Bibcode:1949Natur.164..748D. doi:10.1038/164748a0. S2CID 4134419.
- ^ Thomas, D. 2002. Seaweeds. The Natural History Museum, London. ISBN 0-565-09175-1
- ^ Mumford, T.F. and Miura, A. 4.Porphyra as food: cultivation and economics. in Lembi, C.A. and Waaland, J.R. 1988. Algae and Human Affairs. Cambridge University Press, Cambridge. ISBN 0-521-32115-8
- ^ a b c Abbott, Isabella A (1989). Lembi, Carole A.; Waaland, J. Robert (eds.). Algae and human affairs (Food and food products from seaweeds). Cambridge University Press, Phycological Society of America. p. 141. ISBN 978-0-521-32115-0.
- ^ Aoki, Y. and Kamei, Y. 2006 Preparation of recombinant polysaccharide-degrading enzymes from the marine bacterium, Pseudomonas sp. ND137 for the production of protoplasts of Porphyra yezoensis Eur. J. Phycol. 41: 321-328.
- ^ a b c "Laver Seaweed – A Foraging Guide to Its Food, Medicine and Other Uses". eatweeds.co.uk. 30 August 2018. Retrieved 22 March 2021.
- ^ Watanabe F, Yabuta Y, Bito T, Teng F (May 2014). "Vitamin B₁₂-containing plant food sources for vegetarians". Nutrients. 6 (5): 1861–73. doi:10.3390/nu6051861. PMC 4042564. PMID 24803097.
A nutritional analysis of six vegan children who had consumed vegan diets including brown rice and dried purple laver (nori) for 4–10 years suggested that the consumption of nori may prevent Vitamin B12 deficiency in vegans.
- ^ Melina V, Craig W, Levin S (2016). "Position of the Academy of Nutrition and Dietetics: Vegetarian Diets". J Acad Nutr Diet. 116 (12): 1970–1980. doi:10.1016/j.jand.2016.09.025. PMID 27886704. S2CID 4984228.
Fermented foods (such as tempeh), nori, spirulina, chlorella algae, and unfortified nutritional yeast cannot be relied upon as adequate or practical sources of B-12.39,40 Vegans must regularly consume reliable sources— meaning B-12 fortified foods or B-12 containing supplements—or they could become deficient, as shown in case studies of vegan infants, children, and adults.
- ^ Michael D. Guiry (2024). "Porphyra C.Agardh, 1824". WoRMS. World Register of Marine Species. Retrieved 17 April 2024.
- ^ Sutherland; et al. (October 2011). "A New Look at an Ancient Order: Generic Revision of the Bangiales (Rhodophyta)". J. Phycol. 47 (5): 1131–1151. doi:10.1111/j.1529-8817.2011.01052.x. PMID 27020195. S2CID 2779596.
External links
[edit]
Media related to Porphyra at Wikimedia Commons
Data related to Porphyra at Wikispecies- Video footage of Laverbread or Bara Lawr
Porphyra
View on GrokipediaBiology
Morphology and Habitat
Porphyra species exhibit a distinctive thin, sheet-like thallus in their macroscopic gametophyte phase, consisting of a monostromatic blade typically one to two cells thick and measuring 20–150 μm in thickness.[6][7] These blades can reach up to 1 meter in length, though they are commonly 10–20 cm long, with irregular, ruffled or undulate edges that enhance surface area for nutrient absorption.[7][8] The thallus color varies from olive green in juveniles to red-purple in mature forms, influenced by environmental light levels and the presence of pigments such as phycoerythrin, which dominates under higher irradiance and imparts the characteristic reddish hue.[7][6] The thallus attaches to substrates via a small holdfast composed of branched rhizoids extending from basal cells, anchoring the alga firmly to rocky surfaces.[8][7] Porphyra thrives in intertidal and upper subtidal zones, where it endures periodic emersion, tolerating desiccation by losing 85–95% of cellular water content without irreversible damage, as well as temperature fluctuations from -2°C to 30°C and salinity variations between 30–38 PSU.[9][7] These adaptations include the production of mucilage, such as porphyran in the outer cell wall matrix (comprising up to 30% of its dry weight), which helps retain moisture and resist drying during low tides.[6][7] Porphyra has a cosmopolitan distribution in cold-temperate and tropical coastal waters, predominantly on rocky substrates in regions like the northeastern Atlantic, Pacific coasts, and upwelling systems such as the Benguela Current.[9][10] In these environments, it often forms dense, monospecific stands, serving as a primary producer that supports intertidal community productivity and provides habitat and forage for herbivores, including limpets that graze on the blades.[7] The species also demonstrates rapid growth in nutrient-enriched waters, such as those from coastal upwelling, where elevated nitrogen levels enhance thallus expansion and biomass accumulation.[11][12]Life Cycle
Porphyra exhibits a heteromorphic diplohaplontic life cycle, characterized by an alternation of generations between a macroscopic haploid gametophyte phase, which forms the edible sheet-like thallus, and a microscopic diploid sporophyte phase known as the Conchocelis, consisting of branched filamentous structures that grow endophytically within calcium carbonate substrates such as mollusk shells.[3][6] In sexual reproduction, male and female gametophytes develop reproductive structures on their thalli; males release biflagellate spermatia, while females produce carpogonia with trichogynes that receive the spermatia for fertilization, leading to the formation of a carposporophyte that bears carposporangia.[3] These carposporangia release diploid carpospores, which germinate into the Conchocelis phase.[13] The Conchocelis then undergoes meiosis in specialized conchocelis sporangia to produce haploid conchospores, which settle on substrates and develop into new gametophytic thalli.[3] Asexual reproduction occurs primarily through neutral spores released directly from the gametophyte thallus in certain species, such as Porphyra umbilicalis, where these spores germinate to form identical new thalli without involving the sporophyte phase.[6] This mode allows for rapid propagation and is observed year-round in some populations.[1] The Conchocelis phase was discovered in 1949 by Kathleen M. Drew, who identified it as the missing diploid stage in the life history of Porphyra umbilicalis, linking carpospore germination to filamentous growth that eventually regenerates the leafy thallus and resolving long-standing uncertainties about the cycle's completion.[13] This breakthrough connected wild populations with cultivated forms, revolutionizing the Japanese nori industry by enabling controlled cultivation of Conchocelis on oyster shells to produce conchospores for seeding.[3] Spore release is triggered by environmental cues, including temperatures of 20–28°C, increased light intensity, and specific photoperiods, with conchospores typically liberated in autumn.[3] The annual cycle aligns with seasonal conditions: the gametophyte phase dominates in cooler winter and spring months for growth, while the Conchocelis phase persists through warmer summer periods, often cultured from May to October before spore release in early to mid-October.[3]Taxonomy
Classification History
The genus Porphyra was established by Carl Adolf Agardh in 1824 within his Systema Algarum, initially encompassing three species: P. laciniata, P. purpurea, and P. miniata, based on their foliose, red-pigmented thalli previously classified under Ulva.[14] This foundational description emphasized macroscopic features such as blade shape and color, setting the stage for subsequent taxonomic expansions.[1] Porphyra is classified within the phylum Rhodophyta, order Bangiales, and family Bangiaceae, a placement rooted in its red algal characteristics like phycoerythrin pigmentation and the complex life cycle involving macroscopic gametophytes and microscopic sporophytes.[2] Early classifications relied heavily on morphological traits such as thallus margin undulation, cell arrangement, and reproductive structure visibility, which proved insufficient for resolving variability; by the 1990s, over 130 species had been described worldwide, many later deemed synonyms due to overlapping forms across geographic ranges.[15] A pivotal molecular phylogenetic revision in 2011 by Sutherland et al. restructured the genus using rbcL gene sequences alongside morphological data, restricting Porphyra sensu stricto to five described species and a number of undescribed species, while reassigning other foliose taxa previously placed in Porphyra to seven additional genera, including the resurrected Pyropia which received the majority of the economically important species such as P. yezoensis (now Pyropia yezoensis).[16] This split addressed polyphyly in the original broad Porphyra, highlighting genetic divergences not evident from morphology alone. Ongoing refinements continue, with the World Register of Marine Species (WoRMS) as of 2025 accepting 58 species in Porphyra, incorporating DNA barcoding to tackle cryptic diversity where morphologically similar entities reveal hidden lineages through markers like COI and rbcL; this represents an increase from 57 species accepted in 2024, reflecting continued descriptions of new taxa.[2][17] Prior to 2011, the expansive Porphyra genus encompassed most cultivated laver species used in nori production, underscoring its economic prominence; the post-revision framework now better reflects underlying genetic diversity, aiding targeted conservation and aquaculture efforts.[16]Species
The genus Porphyra currently comprises 58 accepted species in the strict sense, a reduction from the broader circumscription prior to the 2011 taxonomic revision that transferred numerous taxa to the genus Pyropia and other genera.[2][16] Approximately 14 additional names remain unconfirmed or are treated as synonyms pending further resolution.[2] Notable species include P. purpurea, the type species of the genus, which occurs in the North Atlantic and is harvested as edible laver; P. dioica, found in the intertidal zones of the Mediterranean Sea; and P. mumfordii, a Northeast Pacific species ranging from British Columbia to California.[2] These examples illustrate the genus's focus on foliose red algae adapted to marine environments, with P. purpurea serving as a model for traditional utilization.[18] Species of Porphyra exhibit a predominantly temperate to polar distribution, with the highest diversity concentrated in the Northern Hemisphere, particularly over 20 species documented in the Pacific Northwest region encompassing Oregon, Washington, British Columbia, and southeast Alaska.[19] Regional endemics contribute to this pattern, such as P. mumfordii in the California Current region.[2] Identification of Porphyra species is complicated by morphological similarities among thalli, which often overlap in blade shape, color, and size; these challenges are largely overcome through molecular markers, including internal transcribed spacer (ITS) sequences of ribosomal DNA, enabling precise delineation of cryptic taxa.[20]| Species | Habitat/Distribution | Notes on Edibility |
|---|---|---|
| P. purpurea | North Atlantic, intertidal rock | Edible as traditional laver |
| P. dioica | Mediterranean Sea, intertidal | Not commonly harvested |
| P. mumfordii | Northeast Pacific (BC to CA), high intertidal | Potentially edible, limited use |
| P. capensis | Southern Africa, intertidal | Local consumption in some regions |
| P. umbilicalis | North Atlantic, intertidal to shallow subtidal | Edible, used in some cuisines |
Cultivation
Methods
Cultivation of Porphyra species, commonly known as nori, relies on controlled manipulation of its heteromorphic life cycle to produce viable seedlings for commercial farming. The microscopic Conchocelis phase serves as the foundational stage for seeding, allowing growers to bypass reliance on wild spores and ensure consistent production. This approach was revolutionized following the 1949 discovery of the Conchocelis phase by Kathleen Drew, which enabled the transition from opportunistic wild harvesting to systematic lab-to-sea propagation starting in the 1950s in Japan.[13][22] In the Conchocelis cultivation phase, sporophytes are grown indoors in shallow tanks filled with sterilized seawater enriched with nutrients like nitrogen and phosphorus. Substrates typically include oyster shells, mussel shells, or synthetic alternatives such as transparent vinyl films coated with calcite granules to mimic natural colonization sites. Inoculation involves spraying carpospores or zygotospores onto these substrates, with cultures maintained at temperatures between 15-25°C under low light intensities of 500-2000 lux to promote filament formation and growth.[23][22][24] This phase, lasting 4-6 months, is timed for spring initiation (March-April in temperate regions) to align with seasonal spore release induction by lowering temperatures to 18-23°C and adjusting photoperiods to 8-10 hours of daylight.[22][24] Once mature, Conchocelis filaments produce conchospores, which are released and used for net seeding. In controlled indoor or outdoor nursery systems, nets (typically 15-20 cm mesh, 18-20 m long) are submerged in tanks or calm bays where spores settle evenly, often facilitated by rotating drums at 2-3 rpm for 20-60 minutes to achieve uniform distribution at densities of 50,000-100,000 spores per net. About 10 shells of cultured Conchocelis can seed one net effectively. Seeded nets are then outplanted in coastal farms using vertical long-line systems, floating rafts, or fixed pole arrays, predominantly in sheltered bays of Japan and China where water currents of 20-30 cm/s promote nutrient uptake without excessive turbulence.[23][22][24] Outplanting occurs in autumn (September-October) when seawater temperatures drop to 18-20°C, triggering thallus germination and rapid growth in nutrient-rich winter waters.[22] The thalli phase involves multiple harvesting cycles, with blades reaching harvestable size (15-20 cm) in 40-50 days and subsequent regrowth allowing 10-20 cuts per season every 10-15 days. Growth rates of 5-10 cm per week are achieved in cold waters (3-10°C) with high nitrogen levels (100-200 mg/m³) and light intensities of 5000-8000 lux, as the algae's broad blades maximize photosynthesis. Harvesting is done manually or mechanically by cutting blades at the base, followed by immediate processing to prevent degradation.[23][22] Successful cultivation requires specific environmental conditions, including seawater salinity of 25-35 ppt, pH 7.5-8.5, and avoidance of polluted sites to minimize toxin accumulation. Seasonal timing is critical, with seeding in autumn and growth peaking in winter to exploit natural nutrient upwelling. Challenges include diseases like "green spot" rot caused by bacteria such as Vibrio and Pseudomonas species, which manifest as green lesions and can devastate crops; control measures involve reducing net density, periodic air-drying, temperature adjustments to 20-25°C, and UV sterilization of water in hatcheries to suppress pathogens.[22][25][26] Innovations address these issues through selective breeding of hybrid strains, such as crosses between Porphyra yezoensis and P. pseudolinearis, which exhibit 20-30% faster growth rates (up to 8-9% day⁻¹ for Conchocelis) and improved disease resistance, enabling higher yields and quality in commercial settings.[27][28][29]Production and Economics
Global production of Porphyra (now classified under Pyropia) reached approximately 2.83 million tonnes (wet weight) in 2023, primarily from aquaculture, with an estimated value of around US$2.7 billion based on earlier trends.[30][31] This output reflects stable growth since the 2000s, driven by demand for nori in food products.[32] The leading producers are China, accounting for about 74% of global farmed Pyropia production, followed by South Korea at 19% and Japan at 7%.[33] These countries have shifted nearly entirely to aquaculture, with over 95% of Porphyra supply from farming by 2010, up from significant wild harvesting in prior decades.[34] It bolsters local economies through integrated systems combining seaweed with shellfish aquaculture, which absorb excess nutrients and help reduce coastal eutrophication.[35] Recent trends include expansion beyond Asia, with pilot projects in Europe (e.g., Ireland) and [North America](/page/North America) (e.g., Maine) exploring offshore cultivation to diversify supply.[3] However, climate change poses challenges, as warmer waters have reduced yields in traditional growing areas by stressing thalli growth and increasing disease susceptibility.[36] Sustainability is a key strength of Porphyra farming, which requires no chemical fertilizers or freshwater inputs, minimizing environmental footprint.[37] Additionally, these farms contribute to carbon sequestration, capturing 1-2 tonnes of CO₂ equivalent per hectare annually through biomass growth and sediment storage.[38]Uses
Culinary
Species in the genera Porphyra and Pyropia, commonly known as nori when processed, is a staple in various global cuisines, particularly in East Asia, where it is harvested and transformed into versatile food products.[39] The seaweed is typically processed by washing, chopping, and pressing the fresh fronds into thin sheets, which are then dried and roasted to enhance flavor and texture. This method yields the familiar nori sheets used in wrapping sushi and onigiri, while alternative forms include ao-nori flakes, made by grinding and drying without pressing, or fresh laver served raw in salads. In Wales, fresh Porphyra is boiled and puréed to create laverbread, a traditional dish often mixed with oats and served on toast with bacon. Key dishes highlight Porphyra's adaptability across cultures. In Japanese cuisine, nori sheets are essential for maki rolls and temaki, where they encase rice, fish, and vegetables, providing a crisp, salty contrast. Korean gim, similar to nori but often seasoned with oil and salt, is roasted into snacks or crumbled over rice bowls like bibimbap. Chinese preparations feature zicai, or dried Porphyra, in hot and sour soups or stir-fries, adding a subtle oceanic depth. These uses underscore Porphyra's role in enhancing everyday meals with its mild, briny taste. Historically, Porphyra's culinary significance dates back over a millennium in Japan, with references to its consumption appearing in the 8th-century Kojiki, an ancient text describing it as a valued food source. Its global popularity surged post-World War II, spreading through Asian diaspora communities in the United States and Europe, where it transitioned from niche import to mainstream ingredient in fusion foods. Today, modern innovations include nori chips seasoned with wasabi or chili, and nori strips used as vegan bacon alternatives in plant-based recipes, reflecting its versatility in both savory and sweet applications. The umami flavor of Porphyra derives from its high glutamate content, which intensifies when roasted, making it a natural seasoning in broths and snacks. Quality grading for nori sheets, primarily conducted in Japan, evaluates factors such as color uniformity (preferring deep green to black), thickness for even texture, and flavor intensity, with premium grades commanding higher prices. Japan produces approximately 80% of the world's nori supply, supporting its dominant role in international culinary markets. Briefly, incorporating Porphyra into dishes can add essential vitamins like B12, enriching meals nutritionally.Nutrition
Porphyra species exhibit a nutrient-dense profile on a dry weight basis, with macronutrients comprising 25–50% protein, 1–5% lipids, and 40–50% carbohydrates, the latter including the sulfated polysaccharide porphyran that contributes to its structural integrity and potential prebiotic effects.[40][41] Dietary fiber content is notably high at 25–50%, supporting digestive health and satiety.[42] These proportions vary by species and environmental factors, such as Pyropia yezoensis (formerly Porphyra yezoensis) often showing higher protein levels around 35–40%.[43][44] Micronutrients in Porphyra are abundant, particularly iodine at levels up to 0.4 mg/g dry weight, alongside vitamins A, C, and E, and minerals including iron (up to 100 mg/100 g) and calcium (around 200 mg/100 g).[45] The caloric density is moderate for a dried seaweed, approximately 250–350 kcal per 100 g dry weight, making it a low-volume, nutrient-rich option.[46] These elements position Porphyra as a valuable source for addressing common deficiencies in iodine and iron, though consumption should account for variability across species.[47] A distinctive feature of Porphyra is its vitamin B12 content, ranging from 0.2–0.6 µg/g dry weight, encompassing both true cobalamin and pseudovitamin B12 forms.[48] This exceeds levels in most plant foods, which typically contain none, but its reliability as a vegan source remains debated; a 2014 review highlighted dried purple laver (Porphyra spp.) as suitable for vegetarians due to bioactive forms, yet bioavailability varies by species, processing, and individual absorption, with some studies indicating it may not suffice long-term without supplementation.[49] A 2022 systematic review confirmed partial efficacy in preventing deficiency when incorporated into varied seaweed diets, particularly for Porphyra/nori at 1–2.7 µg per typical serving.[50] Health benefits of Porphyra include antioxidant effects from phycobiliproteins like phycoerythrin, which scavenge free radicals and protect against oxidative stress in cellular models.[41] Potential anti-inflammatory properties arise from polysaccharides and peptides that modulate immune responses and reduce pro-inflammatory cytokines in vitro and animal studies.[51] However, risks exist with excessive intake, as high iodine levels may lead to thyroid dysfunction, including hyper- or hypothyroidism, particularly in iodine-sensitive individuals; moderation to 5–10 g dry weight daily is recommended. Dried nori forms retain most of these nutrients, preserving bioavailability for culinary integration.[53]References
- https://pubmed.ncbi.nlm.nih.gov/15588380/