Food Guide

 

A Food Guide to Some Edible or Food-Ingredient Seaweed Species

Alaria esculenta

Description

Alaria esculenta is a distinctive kelp with its pronounced yellow mid-rib, a continuation of its rounded stipe. Its colour varies from golden to greenish brown, and often appears damaged, having lost or torn parts of the blade through storm damage. The stipe is short and fleshy, with small ‘leaflets, growing from the base; these are the reproductive structures, known as sporophylls, their protected position at the base means a lesser risk of damage. Normal length for A. esculenta is around 2m, but in locations protected from surf they may reach up to 4m in length. 

Habitat

  1. esculenta is a common kelp of exposed rocky coasts in Europe and North America. It has been recorded at exposed sites around the UK and Ireland, except for some areas of the east coast of each. It is generally found on the extreme low water mark, on rocky substrate. It tends to prefer small gullies and often can be found hanging from sheer surfaces or in the lee of large boulders. It often appears mixed with L. digitata and other low water species.

Food Use

  1. esculenta has a slightly sweet taste, and is often known as Atlantic Wakame. It has been collected for many years in Ireland through hand harvest and sold as a sea vegetable, and to a lesser extent in Scotland and other parts of the UK. It has been used in the past as an additive to animal feed.

Species specific food safety considerations

  • No specific considerations, but as with other kelps there is the risk of active bioaccumulation of heavy metals
  • Alaria esculenta has high levels of Vitamin B6, Vitamin K, Iodine and Bromine – typical protein values range from 9-20%, fat at 1-2% and carbohydrates around 45%

 

 Ascophyllum nodosum

Description

Ascophyllum nodosum, often generally referred to as wrack (the common name for intertidal branched brown seaweeds) is a large, tough, leathery brown seaweed between 30 and 150cm long and up to 1cm wide. The frond branches irregularly, has no midrib and is attached with a disc-shaped holdfast. The frond contains large egg shaped air bladders set at regular intervals. Fronds often have a red seaweed epiphyte, Polysiphonia lanosa, attached. A. nodosum varies in colour from a dark olive green to a golden yellow-brown, with the latter often visible on the upper surfaces of the frond.

Habitat

A widely distributed species around the UK, it is normally found in sheltered water on the mid-intertidal. A. nodosum is often is the dominant species in the littoral zone, and may share an overlap with Fucus vesiculosus and Fucus serratus. Rarely found on exposed shores and when present there will be smaller and liable to damage and scratching, the species requires a solid substrate (bedrock, boulders) for attachment.

Food Use

Alginates, fertilisers and as seaweed meal for animal and human consumption.

Species specific food safety considerations

  • As a long-lived, perennial shore species, A. nodosum may be at greater risk than other species for bioaccumulation of heavy metals. In addition contamination from shore run-off, either from sewage or other freshwater run-off, should be considered, especially as the species is present in many sheltered Loch environments where human habitation and farming are both present.

 

Ascophyllum nodosum contains high levels of nutrients, vitamins and trace elements (i.e. barium, nickel, selenium etc). Protein varies between 5-12%, fat 2-4% and carbohydrate 42-64%.      

Fucus serratus

Description

Fucus serratus is a robust, olive-brown shrubby seaweed.  It can grow in high densities low on the shore, forming dense mats of long ribbons up to 1m long and 2 to 5cm across.  It attaches to rocks via a discoid holdfast about 3 cm in diameter.  Though technically a brown alga, it can vary in colour from olive green through reddish brown (though it often has a greenish tint).  It typically grows up to 70cm but has been recorded at over 2m in length in very sheltered environments.  The flat, strap-like fronds have a forward-pointing serrated edge, a distinct midrib, and grow from a short stipe.  Fucus serratus is similar to F. vesiculosus, but lacks the air bladders which are very visible on thelatter. Fucus serratus is also similar to F. spiralis, but is not spirally twisted.  The frond surface of F. serratus has numerous pin-pricks with clusters of tiny white hairs.

Habitat

It is most commonly found on sheltered, hard, rocky substrata on the lower part of somewhat sheltered coastlines, subject to some degree of disturbance such as from tidal scour.  Its growth rate varies considerably depending on environmental conditions, but can range from 4 to 12cm per year.  F. serratus plants may become detached and lost to winter storms.

Food Use

Limited (due to the high levels of phlorotannins present) which give the species, along with some other wracks, something of a bitter taste. F. serratus, along with F. vesiculosus is used in the production of cosmetics, and on a smaller scale, seaweed baths in Scotland, Ireland and France. It is also collected when stormcast for land fertilisation in Ireland and Scotland.

Species specific food safety considerations

  • As already described with A. nodosum, F. serratus is a comparatively long-lived, perennial shore species which may be at greater risk than other species for bioaccumulation of heavy metals. In addition contamination from shore run-off, either from sewage or other freshwater run-off, should be considered, especially as the species is present in many sheltered loch environments where both human habitation and livestock are present.

 

Fucus serratus contains high levels of many minerals and trace elements, these include iodine, bromine, zinc, potassium and calcium. Protein varies between 5-10%, fat between 0.5-2% and carbohydrate 60-65%.

 
Laminaria digitata

Description

Laminaria digitata is a large, tough, glossy kelp, which can grow from 1 to 3m in size, and up to 4m in optimum conditions.  Its colour ranges from dark brown to golden brown to olive brown to olive green.  The broad frond or blade is large, lacks a midrib, and is shaped like the palm of a hand with a number of more or less regular finger-like segments (hence the Latin name for this seaweed).  The frond digits extend almost to the base of the frond, and vary in number with amount of exposure. In shelter these are few and short, but with increasing exposure, they are more numerous (up to 10 or 12).

 Habitat

Laminaria digitata is found in rock pools and attached to rocks, bedrock or other suitable hard substrata in the lower intertidal and subtidal or sublittoral fringe, down to a maximum depth of 20m in clear waters.  It can be found higher up on the shore in areas of intense wave action. Laminaria digitata clings to the rocks as the full force of the ocean flows through its fingers in heavy waves, swells, and surf, and flourishes in moderately exposed areas or at sites with strong water currents.  L. digitata may be confused with young Laminaria hyperborea plants.  Laminaria digitata is darker, its stipe is oval in cross-section and is very flexible, whereas Laminaria hyperborea is lighter in color, and its stipe is circular, longer, and thicker.

Food Use

Alginate,  Snacks, Seasoning (flakes, powdered, whole), Laminaria digitata is closely related to the five species (Saccharina latissimaSaccharina japonica, Saccharina angustata, Laminaria longissima and Laminaria ochotensis) typically harvested as ‘kombu’ in Japan, and is frequently harvested and sold as kombu in North America.  Many recipes calling for kombu could be made with this form of kelp.

Species specific food safety considerations

  • Both L. digitata and L. hyperborea can live several years, and have greater potential than other kelps (S. latissima and A. esculenta) to bio-accumulate heavy metals
  • Currently alginate extraction, fertilisers and animal feeds are the main industrial uses for L. digitata, but increased use as a dried sea product. L. digitata has high levels of iodine*, calcium and magnesium – its protein content is 14-18%, fat only 1% and carbohydrate around 50%.

 

 

 

 

Laminaria hyperborean

Description

Laminaria hyperborea, very similar to Laminaria digitiata, is a large, tough kelp. The blade of Laminaria hyperborea is large, tough, flat, lacks a midrib, and usually split into from 5 to 20 fingers or straps (digitate).  The stipe is usually up to 1m long but stipes up to 3m long have been recorded.  The blade length varies with season, age of plant and location, but is commonly around 1m, and reaching over 2m in suitable conditions.  Thus, the entire thallus (plant) of Laminaria hyperborea can often exceed an impressive 2m. The stipe is stiff rather than flexible, and can snap when bent by strong waves if it has been cut or nicked.

 Habitat

Laminaria hyperborea can be found on bedrock or other stable substrata in cold temperate waters of the sublittoral zone.  It may also grow on stable boulders, pebbles on large gravel, deeper parts of pontoons and moorings and other man-made structures.  Laminaria hyperborea does not grow in areas subject to sand scouring but can sometimes be found in areas of siltation.  Its depth ranges from the extreme low water mark to depths dependant on light penetration – typically about 8 m depth in turbid coastal waters to 30 or 40 m in very clear coastal waters.  Laminaria hyperborea grows as dense forests under suitable conditions, and thins out in deeper waters.

Food Use

In Europe, Laminaria hyperborea is one of the two kelp species commercially exploited by the hydrocolloid industry, the other being Laminaria digitata.  Laminaria hyperborea is also utilised by the cosmetic and agrochemical industries and for biotechnological applications, and by the food industry for emulsifiers and gelling agents.  Drift kelp has long been collected as an agricultural fertilizer and soil conditioner, and is Laminaria hyperborea is still harvested and used in popular kelp meal fertilizer products.  Laminaria hyperborea is a source of laminarin and mannitol, which are used in industrial and other applications.  Because of its ability to absorb and retain water, Laminaria hyperborea has been used in wound dressings to prevent adhesions, and has also been used to help dilate the cervix during childbirth.

Species specific food safety considerations

  • As with L. digitata, there is the potential to bio-accumulate heavy metals

 

 Osmundea pinnatifida

Description

Osmundea pinnatifida (pepper dulse) is a small seaweed, typically up to 8 to 10cm in length.  It is tough and cartilaginous with branched and flattened fronds growing from a discoid holdfast.  Branching is alternate in a single plane, with branches becoming shorter and more rounded towards the top.  Colour and size of Osmundea pinnatifida varies depending on the overall sunlight available.  Higher shore plants are generally dwarfed and yellow-green to green with strong sunlight, but it ranges from purple to red to reddish brown under shady conditions on the lower shore, and can even be a near-black shade of red.  It can be common on exposed to moderately sheltered middle and lower rocky shores, often covering large areas with a greenish-yellow turf like growth in pools and on rocks but never subtidal.

Habitat

It can be common on exposed to moderately sheltered middle and lower rocky shores, often covering large areas with a greenish-yellow turf like growth in pools and on rocks but never subtidal.

Food Use

A lot of interest has been shown in pepper dulse as a new species for food use – it has a unique flavour, which varies between populations, but includes hints of iodine, pepper and a rounded smokiness. When dried soon after harvest this makes it one of the most richly flavoured species, and ideal as an accompaniment in a variety of cooking. Due to the difficult in harvest (due to size and location) it has not been much used historically as a harvested species.

Species specific food safety considerations

  • As an intertidal species, there may be a risk of contamination from run-off containing human or animal wastes
  • O. pinnatafida is rich in calcium, iron, copper and zinc, and has typical protein levels of 8%, fat of 4% and carbohydrate levels of 45%.

 

Description

Palmaria palmata has colors which range from dark brownish-red, dark red, blood red, purplish red, to a deep purple. Newer growth tends to be lighter in color.  Palmaria palmata is a foliose red algae which grows as a flat blade from a small discoid holdfast and short (5mm) dark red stipe, gradually widening, subdividing, and branching into many small lobed and erect fronds or blades.  The fronds are tough, flat, leathery, lacking a midrib, usually between 10 and 50cm in length but sometimes longer, and have a width from 3 to 8cm.  Younger parts of the blades are more tender, and older parts may have small ‘leaflets’ along the margin, especially where damaged.  Palmaria palmata is a perennial species with new growth every year, whose holdfast could remain for several years.  It grows in the lower littoral and sublittoral or infralittoral to a depth of approximately 20 m in both sheltered and moderately exposed rocky shores.  Where competition for space and light restricts the occurence of Palmaria palmata on rock, the species often grows as an epiphyte on other algae, especially on Laminaria hyperborea stipes.

 Habitat

It grows in the lower littoral and sublittoral or infralittoral to a depth of approximately 20 m in both sheltered and moderately exposed rocky shores.  Where competition for space and light restricts the occurence of Palmaria palmata on rock, the species often grows as an epiphyte on other algae, especially on Laminaria hyperborea stipes.

 Food Use

Widely used historically as a foodstuff in many European cultures. It can be eaten raw, or dried, milled and added as a food supplement. Younger plants and newer fronds from older plants are considered the most tender and edible.

https://seaweedindustry.com/seaweed/type/Palmaria-palmata

Species specific food safety considerations – similar to other intertidal species

  • P. palmata contains high levels of protein, vitamin A and Iron. It’s protein content is between 12-21%, fat between 1-3% and carbohydrate between 45-50%.

 

Pelvetia canaliculata

Description

Pelvetia canaliculata grows attached to hard substrata with a small basal disc on the upper shore, and forms the uppermost zone of algae growing at or above high water mark. It attaches to rocky surfaces by a discoid

holdfast and does not grow larger than 15cm in length. Normally, it is olive brown in colour but it can often appear yellow or a much darker brown or green-brown.  The partially inrolled, downward-facing, channelled fronds help to retain moisture – Pelvetia can withstand long periods of exposure, which accounts for its dominance on the upper shore.

Habitat                                                                                                                

The very upper shoreline, up to normal high water mark, also into the splash zone above. Prefers sheltered or semi-sheltered waters, but can handle limited exposure and current.

Food Use

Pelvetia was commonly harvested for use as animal fodder in Ireland and Scotland. The species is rich in Selenium and Vitamin C, but otherwise has a similar nutritional makeup to Fucus vesiculosus. It has seen an increase in hand harvest for food use, and there is an interest in its ability to stimulate the synthesis of collagens and proteoglycals.

Species specific food safety considerations

  • While not as long lived as the intertidal wrack species (less risk of bioaccumulation of heavy metals), there is still the danger of contamination from shore run-off, either from sewage or other freshwater run-off. Again, this should be considered, as the fact the species is so high on the tidal range, and present with the wrack species, makes it especially susceptible to contamination from human habitation and livestock.

Saccharina latissimi

Description

  1. latissima (which was until recently known as Laminaria saccharina) is an easily recognisable kelp that is present in the low tide zone along with A. esculenta and just above the zone inhabited by L. digitata and L. hyperborea. It has a short stipe, and a long, frilled frond that can extend for up to 4m. There is no mid-rib, the species tending to foul and decay at its furthest end. The stipe is flexible and smooth, with the blade a rich golden brown colour, darkening in the autumn and winter to a deep brown. 

Habitat

A common species, found around Scotland the UK, but less frequent on the east coast. Grows on hard substrate on the lower intertidal and in rock pools, tending to prefer areas with water movement, but not wave action, such as rapid systems. Can be found at depths down to 20m.

Food Use

As with several other species, has been harvested in small quantities as a sea vegetable in the past, but is not recognised as one of the most flavoursome of the kelps due to its high sugar content and naturally occurring monosodium glutamate. Along with other kelp species, it was often used in Scotland and Ireland as a natural fertiliser.

Species specific food safety considerations

  • No specific considerations, but as with other kelps there is the risk of active bioaccumulation of heavy metals
  • S. latissima has high levels of Vitamin B12, Vitamin K, Iodine* and Bromine – typical protein values range from 5-10%, fat at 0.5% and carbohydrates around 60%

 

Ulva lactuca

Description

Ulva lactuca is commonly called sea lettuce.  Its color can range from light yellowish green to darker green, but is most commonly a vivid green underwater.  When exposed at low tide or when washed up on a beach, it is typically darker green.  Out of the water the seaweed looks like a rather slimy lime-green mass but in the water the alga actually does look very much like young lettuce leaves.  Ulva lactuca is vivid green and cellophane thin (only two cell layers thick), and forms light yellowish green to dark green translucent sheets.  The soft frond grows as a single, irregular, but somewhat round shaped blade with slightly ruffled edges which are often torn.  There can be numerous small holes or perforations scattered throughout.  The frond is connected to rocks with a small, almost invisible discoid holdfast, and does not have a stipe.  Ulva lactuca may grow to a diameter of 20 to 30 cm, although it is freqently much smaller, with larger sheets feeling slightly thicker than smaller specimens

Habitat

Ulva lactuca can be found in an array of habitats, but is seen more abundantly in sheltered bays or in protected and semi-protected areas with limited wave action.  It is found in tide pools, rock pools, cobble, boulders, and bedrock in mid- to lower levels of the intertidal zone, and also grows in the sublittoral to a depth of over 20 m.  In very sheltered conditions, plants that have become detached from the substrate can continue to grow, forming extensive floating mats or rafts.  Ulva lactuca tolerates brackish conditions and can be found on suitable substrata in estuaries.  It is present year round, but most abundant in summer and fall.

Food Use

Ulva lactuca is available in different forms from companies in countries which include the UK, Ireland, France, Germany, Vietnam, China, Canada, and the United States.  It is sold both in fresh and dried form, in flakes, powders, and salad mixes.  It is a delicate seaweed with a mild flavour.  It is used as a seasoning by itself and in blends, and can be found in soups and salads.  It is a key ingredient in many cosmetic and personal care items such as soap, lotion, toner, lifting cream, eye cream, lip cream, makeup remover, body polish, bath soaks, anti-aging products, shaving lotion, shampoo, conditioner, and serums.  It is also a component in gardening and fertilizer products.

Species specific food safety considerations

  • As Ulva sp. often grow best in areas of high nutrient availability, care should be taken to ensure that the nutrient source is not from human or animal waste.
  • Ulva contains high levels of iron manganese and magnesium. Typical protein levels are between 15-25%, fat at around 1%, and carbohydrates at 45%.
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