Seaweeds or macroalgae are a large and diverse group of marine organisms with more than 10,000 different species described to date. Seaweeds have been traditionally used in the food industry as additives (food stabilizers) and as flavouring materials in many Asian countries. Did you know that seaweed is served in approximately 21% of the meals in Japan?

Recently, scientists have turned their attention to new applications of marine ingredients in food, as some proteins and peptides from marine origin have shown heart-protective activities, being especially active in fighting hypertension.

Hypertension or high blood pressure is one of the main, yet controllable, risk factors in cardiovascular diseases. Synthetic drugs against hypertension can come with negative side effects like skin or respiratory problems. There is increased interest in discovering natural products that could be cheaper and easier to include in the lifestyle of the general population through food, and without the negative side effects of the currently used drugs.

This new use of seaweed proteins and peptides against hypertension presents multiple scientific challenges: (1) how to produce proteins and peptides with anti-hypertensive activities and (2) how to incorporate these new ingredients in the food products (food formulation).

(1) Production of anti-hypertensive peptides.

Bioactive peptides are sequences of between 2-30 amino acids in length, which can be generated from various protein sources, including seaweed. These bioactive peptides are inert within their parent protein. This means that the protein source first needs to undergo certain treatments in order to release the peptide. This might happen through enzyme hydrolysis, fermentation, pasteurization and other food processing procedures, or indeed following gastrointestinal digestion. Once released, the peptides may display different beneficial biological activities.

Bioactive peptides have been described as mimic hormones with drug-like activities, and they may alter physiological functions when consumed. Seaweed-derived bioactive peptides identified to date include potent inhibitors of enzymes involved in hypertension, such as renin and angiotensin-I-converting enzyme (ACE-I). Seasonal variations in protein or amino acid profiles in seaweed may also influence the generation of anti-hypertensive peptides. The ACE-I-inhibitory activity of a peptide is influenced by the content of different amino acids (such as tyrosine, phenylalanine, tryptophan, proline, lysine) and the sequence or position of these amino acids in the peptides.

(2) Incorporation of seaweed proteins in food products

The food industry is interested in incorporating bioactive proteins and peptides into various food products such as bread or pasta. This will need to be guided by several factors: the nutritional composition of the peptides, the biological activity of the compounds, and the behaviour of the ingredients in a food matrix, such as the ability of the proteins to create stable structures (i.e. foams).

Recently, protein extracted from the seaweed Himanthalia elongata (Linnaeus) S. F. Gray or seaweed spaghetti showed high levels of essential amino acids, i.e. lysine and methionine. These amino acids cannot be synthesized by the human body and have to be absorbed from the diet. Furthermore, these proteins could be used to create strong foams, following agitation, and stable emulsions when mixed with various vegetable oils. These foaming and emulsifying properties are really appreciated in the food industry, as it allows the new ingredients to be used in a wide variety of food products including bread and pastries, but also sausages and salad dressings.

Clearly, incorporating bioactive peptides into our food is more challenging than simply sprinkling dried seaweed over a salad. However, the discovery, generation and formulation of food products containing bioactive peptides derived from seaweed could be an additional strategy to fight heart attacks using our day-by-day food.