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10 Aquatic Plants and Algae Proteins
accumulation and growth, algae and aquatic plants are much more productive than
land plants. Furthermore, they do not require land for growth which means they do
not compete with space for living and can be grown away from disputed land areas.
Proteins are an important food content and are necessary in maintaining a balanced
diet. FAO estimates that 10.9% of people in the world are undernourished as of 2017
and that figure is said to have been growing in the past two years. The number of
malnourished people in the world rose from 804 million as of 2016 to 821 million
in 2017 (FAO et al. 2018). Alongside carbohydrates and fats, protein forms one of
the macronutrients required by humans for energy and growth.
In many parts of the world, fish serves as a major source of protein. With recent
algal blooms which result in the release of toxins into the water, fish in some parts is
at threat of being unsafe for human consumption. Aquatic plants and algae play two
roles in this aspect. The possible use to clean up water and as alternative sources of
proteins; either directly consumed as food, nutraceuticals or used as ingredients in
food products (Sinha et al. 2019).
An aquatic plant can be regarded as edible if it contains some nutrients which can
be broken down by the enzymes in the body and if it does not contain any toxins.
Recent studies present a protein digestibility of 99.36% for protein extracted from
the blue-green algae Spirulina. This is relatively high compared to that of soybean
which is 85% (Yucetepe et al. 2018). Although this value was derived from in vitro
studies, it indicates that such protein is suitable for food applications and indeed
some Spirulina-based food products are available in the market today. Thousands of
species of macroalgae and microalgae exists, such that the different proteins within
them also largely vary. The digestibility and types of amino acids which make up
the proteins vary for different algae (Boisen and Eggum 1991; Bleakley and Hayes
2017).
When consumed directly as food, algae have relatively low bioavailability. This
is thought to be due to the fact that proteins are usually present alongside other
polysaccharides within the cell wall of the algae. These fibers with which the proteins
are attached are indigestible; for the protein to be available as a nutrient, it must be
released from the fiber and then broken down into forms which can be absorbed
into the body along the alimentary canal. The digestibility therefore depends on the
enzymes present within the body which can break down the protein and free it from
the fibrous structure. Most often, it is therefore necessary to extract these proteins
and then make them into edible preparations as processed foods before they can have
relevant digestibility or bioavailability.
While egg and casein protein have digestibility coefficients of 94.2 and 95.1%,
respectively, microalgae Chlorella sp., Scenedesmus obliquus and Spirulina sp. have
digestibility coefficients of 76.6, 88.0 and 77.6%, respectively (Becker 2007). The
digestibility varies widely among algae species. For example, Undaria pinnatifida
has a bioaccessibility of 87%, Ulva lactuca has a digestibility of about 85.7%, while
P. tenera has a bioavailability of 78%. Some studies report red algae have to be more
digestible than brown algae, digestibility of red algae studied ranged between 83 and
87% while that of the brown algae ranged between 78.7 and 82% (Tibbetts et al.
2016). Much of the digestibilities referred to herein are based on in vitro studies.
10 Aquatic Plants and Algae Proteins
accumulation and growth, algae and aquatic plants are much more productive than
land plants. Furthermore, they do not require land for growth which means they do
not compete with space for living and can be grown away from disputed land areas.
Proteins are an important food content and are necessary in maintaining a balanced
diet. FAO estimates that 10.9% of people in the world are undernourished as of 2017
and that figure is said to have been growing in the past two years. The number of
malnourished people in the world rose from 804 million as of 2016 to 821 million
in 2017 (FAO et al. 2018). Alongside carbohydrates and fats, protein forms one of
the macronutrients required by humans for energy and growth.
In many parts of the world, fish serves as a major source of protein. With recent
algal blooms which result in the release of toxins into the water, fish in some parts is
at threat of being unsafe for human consumption. Aquatic plants and algae play two
roles in this aspect. The possible use to clean up water and as alternative sources of
proteins; either directly consumed as food, nutraceuticals or used as ingredients in
food products (Sinha et al. 2019).
An aquatic plant can be regarded as edible if it contains some nutrients which can
be broken down by the enzymes in the body and if it does not contain any toxins.
Recent studies present a protein digestibility of 99.36% for protein extracted from
the blue-green algae Spirulina. This is relatively high compared to that of soybean
which is 85% (Yucetepe et al. 2018). Although this value was derived from in vitro
studies, it indicates that such protein is suitable for food applications and indeed
some Spirulina-based food products are available in the market today. Thousands of
species of macroalgae and microalgae exists, such that the different proteins within
them also largely vary. The digestibility and types of amino acids which make up
the proteins vary for different algae (Boisen and Eggum 1991; Bleakley and Hayes
2017).
When consumed directly as food, algae have relatively low bioavailability. This
is thought to be due to the fact that proteins are usually present alongside other
polysaccharides within the cell wall of the algae. These fibers with which the proteins
are attached are indigestible; for the protein to be available as a nutrient, it must be
released from the fiber and then broken down into forms which can be absorbed
into the body along the alimentary canal. The digestibility therefore depends on the
enzymes present within the body which can break down the protein and free it from
the fibrous structure. Most often, it is therefore necessary to extract these proteins
and then make them into edible preparations as processed foods before they can have
relevant digestibility or bioavailability.
While egg and casein protein have digestibility coefficients of 94.2 and 95.1%,
respectively, microalgae Chlorella sp., Scenedesmus obliquus and Spirulina sp. have
digestibility coefficients of 76.6, 88.0 and 77.6%, respectively (Becker 2007). The
digestibility varies widely among algae species. For example, Undaria pinnatifida
has a bioaccessibility of 87%, Ulva lactuca has a digestibility of about 85.7%, while
P. tenera has a bioavailability of 78%. Some studies report red algae have to be more
digestible than brown algae, digestibility of red algae studied ranged between 83 and
87% while that of the brown algae ranged between 78.7 and 82% (Tibbetts et al.
2016). Much of the digestibilities referred to herein are based on in vitro studies.