Marine nutrition

Exploiting marine resources from around its coastline could help Ireland become a major player in the world’s functional foods market. Lou Reade reports

The world's second most abundant natural substance could help Ireland to become a major player in the functional foods market. The substance in question is chitin: the hard material that makes up the shells of crabs and other crustaceans. Scientists in a pan-Irish research project, NutraMara, are looking to identify, isolate and exploit bio-active compounds from chitin and other marine resources such as seaweed.

"Chitin is the most abundant compound in nature after cellulose," says Bahar Bojlul, a researcher at University College Dublin (UCD) and one of 30-plus scientists involved in NutraMara. "We've identified some bio-active compounds in it that could be used to treat obesity."

Chitin is a hard, inert substance a polymerised carbohydrate. But treating it with strong acid or alkali can produce chitosans: a range of compounds that are potentially far more useful.

Chitosans are polymers of glucosamine which is known to be bioactive. Bojlul says that chitosans are believed to have similar if not stronger bioactive properties, and have been proven to have 'anti-obesity' properties. "Most of the bio-activity is because of the amino group," says Bojlul. "But this activity is reduced by the presence of an acetyl group."

The acid/alkali treatment is used to remove acetyl groups from the chitosan, but this is never 100% effective. An ongoing research effort will try to improve this process to boost bioactivity.

Bojlul began by analysing five commercially available chitosans and screening these in cell cultures to determine their bioactivity. "I'm now clear as to which chitosans I should be asking our research partners to isolate," he says.

Understanding the mechanism

While some of the compounds identified will be absolutely new, many will be well-known. The novelty is that they will have been isolated from a previously untapped source. But even if strongly bioactive compounds can be isolated, there are still other problems to solve. "Chitosan is hard to dissolve in neutral media, and needs an acid environment," says Bojlul. "That means that, if it could be taken up in the bloodstream, it would precipitate."

The answer which many others are also trying is to modify chitosan so that it will dissolve at a neutral pH. The fact that chitosan prevents fat being absorbed in the gut is well known, he says. But his research will try to understand the mechanism of action behind this. "I want to know if chitosan can get into cells and do anything at the biochemical or molecular level."

For now, he is conducting feeding trials in pigs, and says that chitosan has had some effect on body weight. Detailed results will be published soon. After two similar trials, he hopes to be able to move to a human study in late 2011. "The advantage of working with chitosan is that it's already been approved as a safe compound."

UCD is only one of seven Irish research centres and universities involved in NutraMara. Each will use its own area of expertise to move the project forwards. "Our aim is to identify novel marine ingredients for the functional foods market," says scientific project manager Maria Hayes of Teagasc, the Irish agriculture and food development authority. Researchers will look for these compounds in natural marine resources including: seaweeds; waste from fish processing such as crab shells; and fish that are abundant in Irish waters but not traditionally eaten.

"An example is the blue whiting," says Hayes. "It's often caught when fishermen are trawling for other fish, but it's thrown back because it's too small for filleting. It might be a good source of peptides."

The quest to find high-value, bioactive ingredients in fish waste is also attractive. Waste products from the fish industry such as crab shells and fish heads are generally inedible, and can be difficult to dispose of. Teagasc manages the project, which is split into a number of 'work practices. Stage one, led by the University of Galway, assesses the feasibility of the project. Stage two will discover and generate bioactives such as antioxidants, pigments, peptides, fatty acids, amino acids and carotenoids, mainly through the universities of Dublin and Limerick. "The aim is to develop optimised technologies for extraction and characterisation of these compounds," says Hayes.

A range of techniques including solvent extraction and fermentation are used to isolate the compounds. Teagasc also has expertise in scaling up the production of any promising compounds. "If we demonstrate we can upscale, this would make it a more attractive proposition for commercialisation," she says. "We're already looking at that for chitosan."

In stage three, the compounds are put through in-vitro and animal trials to further assess their bioactivity. In stage four, a team led by University College Cork will study how compounds might be incorporated into foods. "Right now, we are between stages two, three and four," says Hayes.

The final stage of the research phase is a human dietary study led by the University of Ulster in Coleraine, Northern Ireland.

"Here we'll be measuring biological end-points for conditions such as cardiovascular disease and creating a databas e that will capture the knowledge of species, active compounds and extraction techniques in a single place. It will be an inventory of all the exploitable material that we discover," she says.

Seaweed as protein source

At the University of Limerick, researchers are looking for bioactive proteins from the many types of seaweed that are found around Ireland's shoreline. "Seaweed is commonly used as a source of carbohydrate compounds, such as carrageenan and agar," says Padraigin Harnedy, of the department of life sciences. "But we've seen very little focus on using seaweed as a source of protein."

There are three main types red, brown and green which could prove to be sources of "biofunctional peptides" that can improve health by blocking certain chemical pathways in the body such as laying down cholesterol in blood vessels. They could also kill bacteria, reduce hypertension and prevent thrombosis.

"We've seen that one particular species of seaweed has different proteins according to when you harvest it," she says. "By sampling at different times of the year, we could increase our chances of finding something new."

Head of department Dick FitzGerald says that seaweed is a "major untapped resource" in the search for functional ingredients. By using smart enzymes to 'snip' the proteins into different length, the team may be able to find new peptides or at the very least some established compounds from a new source. These could be incorporated into a range of functional food products from beverages to snack bars.

"We're interested in those compounds that have an effect on metabolic conditions such as cardiovascular diseases and obesity," he comments.