Factors influencing the amino acid and protein content

Very common seaweeds, which are used as human food, are species of red algae Porphyra (nori), brown algae Laminaria (kombu), and Undaria (wakame) (FAO, 2002). USDA (2010) shows that the raw seaweed Undaria spp. contains approximately 3.0% of proteins and, with regard to 80% moisture content, it has about 15.2% of protein of dry matter. Admittedly, protein values range from 5% to 47% according to the species, environmental conditions, habitats, maturity, and applied methods used for protein and amino acid determination (Ito and Hori, 1989).

Seaweed proteins contain all amino acids, which significantly depend on the seasonal period (Fleurence, 1999a; Galland-Irmouli et al., 1999). Generally, the highest protein value has been found during the period of winter-early spring and the lowest during summer-early autumn (Galland-Irmouli et al., 1999). According to Denis et al. (2010), in red algae Grateloupia turuturu, the maximal concentration of protein was observed from January to April and the lowest amount of protein from July to August. The minimum of protein value in summer could be connected with the destruction of phycobiliproteins (Galland-Irmouli et al., 1999). In contrary to the other compounds (ash or dietary fiber), proteins were put through large changes within the year. Moreover, it was reported that different protein levels depend on the specific areas, too. For example, Yaich et al. (2011) mentions that Ultrica lactuca, which come from the littoral area of Tunisia, contains almost by 50% higher amount of protein than the same species from Philippines. From the data gained by Renaud and Luong-Van (2006), it is evident that the highest concentration of protein was found in red algae collected in summer (4.8-12.8%), while it was significantly lower during winter.

Protein concentration varied especially within the same species among populations (McDermid and Stuercke, 2003). Generally, the protein amount of brown seaweeds is low. It has been reported that it is lower than 15% (Fleurence, 1999a). On the contrary, red seaweeds contain a high quantity of protein, and this value is often comparable with the amount of other foods such as soybean or eggs. There were established some differences in the protein value between red and green seaweeds. In agreement with Qasim (1991), in brown seaweeds, there was determined the interval of 21-28%, in green 14-26%, and in red seaweeds 11-24%. Roslin (2003) found a minimum of protein at the level of 1.5% in green algae. It was observed that red alga Gracilaria changii contains a relatively high amount of protein, approximately 34% of dry weight (Norziah and Ching, 2000), which is comparable with the value of protein in green peas (USDA, 2010). Nevertheless, protein quantity is very changeable in dependence on different species, for example, red alga Corallina officinalis provided a very low protein content, approximately 7% (Marsham et al., 2007). Generally, the protein content decreases in the order of the seaweed group: red > green > brown. In Tables 24.3 and 24.4, there are presented protein content of some seaweed demonstrating their variability.

Many researchers have assessed protein content by measuring nitrogen content and multiplying it by different conversion factors. In the case of seaweed, the nitrogen-to-protein factor ranges from 3.75 to 5.72 (Lorenco et al., 2002); therefore, the traditional value might overestimate the protein content. However, nitrogen in seaweeds is a component of many types of molecules in addition to protein, such as DNA, ATP, etc. High amount of polysaccharides could limit the accessibility of protein

TABLE 24.3 Protein content (%, dry matter) of red seaweed

Red seaweed

Protein

Methods

References

Ahnfeltiopsis concinna

5.7

Lowry

McDermid and Stuercke (2003)

Amansia multifida

25.6

Kjeldahl

Ramos et al. (2000)

Asparagopsis taxiformis

6.1

Lowry

McDermid and Stuercke (2003)

Bryothamnion seaforthii

17.3

Kjeldahl

Ramos et al. (2000)

Bryothamnion

11.8

Kjeldahl

Ramos et al. (2000)

triquertrum

Corallina officinalis

6.9

Kjeldahl

Marsham et al. (2007)

Corallina officinalis

2.3

Kjeldahl

Ramos et al. (2000)

Digenea simplex

15.6

Kjeldahl

Ramos et al. (2000)

Enantiocladia duperreyi

19.5

Kjeldahl

Ramos et al. (2000)

Eucheuma cottonii

9.8

Kjeldahl

Matanjun et al. (2009)

Eucheuma

4.9

Lowry

McDermid and Stuercke (2003)

denticulatum

Gelidiella acerosa

31.1

Biuret

Manivannan et al. (2009)

Gracilaria birdiae

7.1

Bradford

Gressler et al. (2010)

Gracilaria domingensis

6.2

Bradford

Gressler et al. (2010)

Gracilaria folifera

7.0

Biuret

Manivannan et al. (2008)

Gracilaria changgi

34.5

Kjeldahl

Norziah and Ching (2000)

Gracilaria

7.7

Kjeldahl

Ramos et al. (2000)

lemaneiformis

Gracilaria salicornia

5.6

Lowry

McDermid and Stuercke (2003)

Grateloupia turuturu

22.9

Kjeldahl

Denis et al. (2010)

Halymenia formousa

21.2

Lowry

McDermid and Stuercke (2003)

Hypnea charoides

18.4

Kjeldahl

Wong and Cheung (2000)

Hypnea japonica

19.1

Kjeldahl

Wong and Cheung (2000)

Hypnea valentiae

8.3

Biuret

Manivannan et al. (2008)

Chondrus ocellatus

8.3

Lowry

McDermid and Stuercke (2003)

Laurencia filiformis

18.3

Bradford

Gressler et al. (2010)

Laurencia intricata

4.6

Bradford

Gressler et al. (2010)

Laurencia nidifica

3.2

Lowry

McDermid and Stuercke, 2003

Ochtodes secundiramea

10.1

Bradford

Gressler et al. (2011)

Palmaria palmata

18.3

Kjeldahl

Galland-Irmouli et al. (1999)

Plocamium brasiliense

15.7

Bradford

Gressler et al. (2011)

Porphyra sp.

31.3

Kjeldahl

Dawczynski et al. (2007)

Porphyra sp.

44.0

Kjeldahl

Marsham et al. (2007)

Porphyra vietnamensis

16.5

Lowry

McDermid and Stuercke (2003)

Solieria filiformis

21.3

Kjeldahl

Ramos et al. (2000)

Vidalia obtusiloba

18.1

Kjeldahl

Ramos et al. (2000)

TABLE 24.4 Protein content (%, dry matter) of green and brown seaweed

Protein Methods References

Protein Methods References

TABLE 24.4 Protein content (%, dry matter) of green and brown seaweed

Green seaweed

Caulerpa lentillifera

9.7

Lowry

McDermid and Stuercke (2003)

Caulerpa lentillifera

10.4

Kjeldahl

Matanjun et al. (2009)

Caulerpa sertularioides

20.0

Kjeldahl

Ramos et al. (2000)

Cladophora glomerata

20.4

Biuret

Manivannan et al. (2009)

Cladophora glomerata

14.1

Kjeldahl

Akkoz et al. (2011)

Codium reediae

7.0

Lowry

McDermid and Stuercke (2003)

Codium tomentosum

6.1

Biuret

Manivannan et al. (2008)

Enteromorpha

12.3

Biuret

Manivannan et al. (2009)

compressa

Enteromorpha flexuosa

7.9

Lowry

McDermid and Stuercke (2003)

Enteromorpha

15.2

Kjeldahl

Akkoz et al. (2011)

intestinalis

Enteromorpha

16.4

Biuret

Manivannan et al. (2008)

intestinalis

Halimeda macroloba

28.9

Biuret

Manivannan et al. (2009)

Halimeda tuna

23.1

Biuret

Manivannan et al. (2009)

Monostroma

9.6

Lowry

McDermid and Stuercke (2003)

oxyspermum

Ulva fasciata

8.8

Lowry

McDermid and Stuercke (2003)

Ulva fasciata

6.3

Kjeldahl

Ramos et al. (2000)

Ulva lactuca

7.1

Kjeldahl

Wong and Cheung (2000)

Ulva lactuca

27.2

Kjeldahl

Ortiz et al. (2006)

Ulva lactuca

3.3

Biuret

Manivannan et al. (2008)

Ulva lactuca

8.5

Kjeldahl

Yaich et al. (2011)

Ulva reticulata

13.5

Biuret

Manivannan et al. (2009)

Ulva reticulata

20.0

Biuret

Shanmugam and Palpandi

(2008)

Brown seaweed

Dictyota acutiloba

12.0

Lowry

McDermid and Stuercke (2003)

Dictyota sadvicensis

6.4

Lowry

McDermid and Stuercke (2003)

Durvillaea antartica

10.4

Kjeldahl

Ortiz et al. (2006)

(leaves)

Durvillaea antartica

11.6

Kjeldahl

Ortiz et al. (2006)

(stem)

Hizikia fusiforme

11.6

Kjeldahl

Dawczynski et al. (2007)

Laminaria sp.

7.5

Kjeldahl

Dawczynski et al. (2007)

Padina gymnospora

17.1

Biuret

Manivannan et al. (2008)

Padina gymnospora

11.2

Kjeldahl

Ramos et al. (2000)

Padina pavonica

13.6

Biuret

Manivannan et al. (2009)

TABLE 24.4 (continued)

Protein

Methods References

Sargassum

10.3

Lowry McDermid and Stuercke (2003)

echinocarpum

Sargassum fluitans

12.8

Kjeldahl Ramos et al. (2000)

Sargassum

13.0

Lowry McDermid and Stuercke (2003)

obtusifolium

Sargassum polycystum

5.4

Kjeldahl Matanjun et al. (2009)

Sargassum tenerimum

12.4

Biuret Manivannan et al. (2008)

Sargassum vulgare

16.3

Kjeldahl Ramos et al. (2000)

Undaria pinnatifida

19.8

Kjeldahl Dawczynski et al. (2007)

Kjeldahl method based on the nitrogen-to-protein factor 6.25.

Kjeldahl method based on the nitrogen-to-protein factor 6.25.

(Fleurence, 1999b). For example, McDermid and Stuercke (2003) used Lowry's method (Lowry et al., 1951), which is specific for protein. Another method used for the estimation of protein is Biuret method (Manivannan et al., 2008). Gressler et al. (2011) reported that the value of soluble protein obtained by Bradford's method (with bovine serum albumin as a standard) was quite similar to that determined by the method based on the nitrogen-to-protein factor 4.43.

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