microalge in alimentatie

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Microalgae for Healthy FoodsPossibilities

and ChallengesT.L. Chacon-Lee and G.E. Gonzalez-Marino

Abstract: Microalgae have the potential to become a novel source of bioactive molecules, especially for those whomight wish to enhance the nutritional and functional quality of foods. Spirulina, one of the most popular microalgae, has

been described by the World Health Organization as one of the greatest superfoods on earth serving as an example of the

potential of microalgae. This review provides background on current and future uses of microalgae in the human diet,

lists the most common species of microalgae used to this end, and describes some production methods used in research

and industrial production and recovery. The review also discusses some of the difficulties so far encountered such as low

productivities and recovery rates, as well as challenges in the production of compounds of interest. Many scientists and

engineers in research centers around the globe are currently dedicated to solve these problems as the various capabilitiesof microalgae have caught the attention of the energy, environmental, and agricultural industries, we propose that the

food industry should as well evaluate the potential of microalgae as a novel source of health promoting compounds.

IntroductionMicroalgae are microscopic photosynthetic organisms that are

found in both marine and freshwater environments. Their pho-

tosynthetic mechanism is similar to that of land-based plants.They are generally more efficient in converting solar energy into

biomass, mainly because of their simple cellular structure and being

submerged in an aqueous environment with access to water, CO2,and other nutrients. These organisms constitute a polyphyletic andhighly diverse group of prokaryotic and eukaryotic organisms. The

classification into divisions is based on various properties such aspigmentation, chemical nature of photosynthetic storage prod-

uct, the organization of photosynthetic membranes, and othermorphological features. The most abundant microalgal classesare Cyanophyceae (blue-green algae), Chlorophyceae (green al-

gae), Bacillariophyceae (including the diatoms), and Chryso-phyceae (including golden algae) (Carlsson and others 2007).

Since the end of the Second World War (1945), many pri-

vate and public research groups have dedicated time and effort topresent microalgae to the public as a very important and plen-

tiful source of protein, based on its quality, and as one of thebest to be encountered. Since Tamiya and others (1963), who

under the sponsorship of the Carnegie Inst. reported that the mi-croalgae Chlorella could be cultivated on a large scale, a great

deal of research has been reported regarding these tiny but veryspecial species. In the last 3 decades, there have been numerous

attempts by researchers and profit-seeking companies to commer-

MS 20100409 Submitted 4/14/2010, Accepted 7/3/2010. Authors are with theGrupo de Procesos Agroindustriales at the Faculty of Engineering at the Univ. de

La Sabana, Campus Univ. Puente del Com un, Km 7 Autopista Norte de Bo-got a, ChaCundinamarca, Colombia. Direct inquiries to author Gonzalez-Mari no(E-mail:[email protected]).

cialize production of microalgae and cyanobacteria. Some of thesecompanies have been in business for many years and are success-

fully producing biomass of these organisms and marketing it invarious forms (Gantar and Svircev 2008). Despite this, microalgae

have not become the major source of food that was expected byscientists when their nutritional properties were discovered.

It is important to agree upon common ground regarding whatwe consider as food. According to author Hutton (2002) from the

Royal Society of Chemistry, Food is derived from plants, animals,and microbes which are, in essence, highly organized chemical

systems. Many of the chemicals within food are essential for humanlifeothers just happen to be associated with the material we

actually want to eat. Some (flavor and texture components andcolor) actually persuade us to eat the food. We choose to eat

certain foods because of a combination of the chemicals theycontain that give it a pleasant taste and appearance and those that

we actually need in order to survive.Humans are no strangers to the use of microalgae as a food

source, even if the commercial exploitation of this resource is onlya few decades old, since the early 1950s, when the focus was seton a possible insufficient protein supply due to the rapid increase

of the world population (Spolaore and others 2006). Microalgaeappeared then as a good source of protein and has continued as

such, but with an increased interest due to the unique bioactiveingredients recently found in these small microorganisms, which

gives them great potential as a food source and as a source offunctional molecules.

This review intends to give a critical point of view on thetechnological possibilities of microalgae, an untapped resource

waiting to be exploited by professionals in the food science andtechnology arena. The scope of the review goes beyond the highly

agreed-upon opinions about the use of species such as Chlorella,

Spirulina, Dunaliella, and others as a nutritional supplement and

c 2010 Institute of Food Technologists

doi: 10.1111/j.1541-4337.2010.00132.x Vol. 9, 2010 ComprehensiveReviewsinFoodScienceandFoodSafety 655


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Microalgaepossibilities and challenges . . .

more, and regarding them as a food or as a food ingredient. It pro-vides information regarding the most common production systems

of microalgae biomass, open and closed photo bioreactors, theiradvantages and disadvantages, as well as references of interest for

further research, as well as information regarding biomass recov-ery problems and other downstream processing challenges, thus

highlighting the opportunities for food scientists and engineers toimprove the current technologies in critical areas.

Current Trends in the Market for Healthy FoodsGenerally, the consumer classifies many products, ingredients,

or compounds as healthy or good for you. Their consumption

may benefit, prevent, help, or cure common diseases or gravesickness such as cancer or Alzheimers disease. Those consumers

wishing to fortify their health, and prevent sickness, look for andtry to incorporate into their daily diet these foods, ingredients,

and compounds (Sloan 2008). These are the same consumers wholook for functional foods. The number of them is growing daily,since healthy living, natural products, and better eating habits are

becoming a collective conscience in search of health and wellness

(Kuhn 2008). Among the healthy food sector, we can find variouscategories such as functional foods and nutraceuticals.

Functional foods may be defined as foods that are similar in ap-pearance to conventional foods, are consumed as part of a regulardiet, and can contribute to increase the health condition of a per-

son to a higher degree of that expected from regular nutritionfrom a common food source.

From a similar perspective, nutraceuticals instead are obtainedfrom food, but are not associated with these, they are found in

the form of capsules, tablets, pills, syrups, powders, and such, andare known to benefit the health of the consumer by increasing

the bodys response to infections, disease, and sickness. Generally,these products are commercialized as diet supplements. Nutraceu-

tical and functional foods are concepts not usually used by thenonprofessional, but have started to appear in television commer-

cials and other publicity resources in relation to health products.With the growing trend toward convenience foods, there has

been much consumer pressure in recent years for formulated foodsto be even more nutritious (Pszczola 2008), but reformulated prod-

ucts with higher fiber content, low fat, or low sugar might soonnot be enough. With the emerging and exciting advances occur-

ring in the field of nutrigenomics, customized foods are not faraway from becoming a reality (Fogg-Johnson and Kaput 2003).

Therefore, the food industry is being called upon to match futureconsumer requirements, which will undoubtedly continue to be

sensory satisfaction from all kinds of foods, even foods targetedto protect them from specific diseases and such (Bech-Larson and

Scholderer 2007).This increased demand for healthy foods could find a nontra-

ditional ally in microalgae as a novel source of natural ingredientsand compounds. Microalgae-produced bioactive compounds and

molecules are being actively researched to determine their capa-bilities and potential benefits to consumers, and results so far point

to promising future developments (Shahidi 2004).

Current Uses of Microalgae as FoodMicroalgae are not a new food. They have been part of the

human diet for centuries. For example, Nostochas been used in Asia

andSpirulinaby certain tribes in Africa. Gantar and Svircev (2008)reported interesting and explicit accounts of documented culture

methods and uses of microalgae and cyanobacteria by indigenouspopulations in Mexico and other native populations.

Figure 1Most common presentation forms of microalgae.

During the past decades, microalgae biomass has been usedalmost exclusively in the health food market. Over 75% of the

annual biomass production has been solely dedicated to the man-

ufacture of powders, tablets, and capsules of microalgae production(Figure 1) (Pulz and Gross 2004; Hudson 2008). All of this mi-croalgae biomass and much more could be incorporated into food-

based products, allowing this industry to diversify and grow in wayspreviously unrealized. Liang and others (2004) mention that even

if microalgal tablets are the most popular algal products, it is nec-essary to diversify to other end products to ensure the continuing

development of microalgal biotechnology.Pulz and Gross (2004) pointed out that in order to achieve a

successful algal biotechnology industry, it was necessary to choosethe right alga, one that possesses the relevant properties regarding

culture conditions and products. As evidence of this necessity, agreat deal of research has been performed on a small number of

species. Even though it was a small number of species, much hasbeen learned. The use of this knowledge is sufficient to create a

wider area of influence of microalgae in the food industry. Liangand others (2004) agree with this statement, and report that there

are over a 100 research institutes and manufacturing enterprisesin China alone concerned with the study and development of

microalgae as food. Table 1 provides a reference list of authors thathave carried out research regarding production, extraction, anduse of some compounds of interest found in microalgae.

China is not the only country where microalgae have gained

interest, there have been many investigations regarding the use ofmicroalgae biomass and extracts for human consumption (Toku-soglu and Unal 2003; Becker 2004; Shimamatsu 2004; Sawraj

and Bhushan 2005; Geppert and others 2006; Colla and others2007; Doughman and others 2007; Gouveia and others 2007b;

Valencia and others 2007). The average protein quality of most ofthe algae examined is equal, sometimes even superior, to that of

conventional plant proteins (Becker 2007) (Table 2). Due to thehigh protein content of various species of microalgae, these organ-

isms were initially considered only as an unconventional source ofprotein, but currently protein is no longer the sole argument to

propagate them and promote their utilization as food or as a foodsupplement.

Because all of these compounds are of interest to consumers,Pulz and Gross (2004) make a point on mentioning: There is

an increasing demand for sophisticated products from microal-gae. More importantly, their biomass is known as a natural

656 Comprehensive Reviews in Food Science and Food Safety Vol. 9, 2010 c 2010 Institute of Food Technologists


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Table 1Microalgae classified according to compounds of interest.

Topic of information Microalgae species Reference

Pigments for food and cosmetics, Spirulina platensis Valderrama and others 2003carotenoids: astaxanthin, Wang and others 2007phycocyanine, -carotene Gouveia and others 2008a

Anteloand others 2008Chlorella vulgaris Gouveiaand others 2006, 2007a, 2008a

Bertoldi and others 2006Dunaliella salina Gomez and others 2003

Dufosse and others 2005

Jaime and others 2007Zhu and Jiang 2008Haematococcus pluvialis Kobayashi and others 1997

Lorenz andCysewski 2000Mendes-Pinto and others 2001Olaizola 2003Valderrama and others 2003Brinda andothers 2004Dufosse and others 2005Saradaand others 2006Gouveia and others 2006, 2008a

Porphyridium cruentum Arad and Yaron 1992Bermejo and others 2002

Isochrysis galbana Valenzuela-Espinoza and others 2002Scenedesmus almeriensis Sanchez and others 2007Phaeodactylum tricornutum Sanchez and others 2002

Anabaena Loreto and others 2003Dunaliella bardawil Gomez and others 2003

Various Arad and Yaron 1992Wrolstad 2004van Leeuwe and others 2006del Campo andothers 2007

Antioxidant activity Spirulina platensis Mendiola and others 2005Jaime and others 2005Wang and others 2007Ibanez and others 2008

Chlorella vulgaris Rodriguez-Garcia and Guil-Guerrero 2008Dunaliella salina Jaime and others 2007

Ibanez and others 2008Synechococcus sp. Li and others 2007Nostoc ellipsosporumChlamydomonas nivalisPorphyridium cruentum Rodriguez-Garcia and Guil-Guerrero 2008Phaeodactylum tricornutum

Fatty acids Spirulina platensis Sajilata and others 2008Chlorella vulgaris Bertoldi and others 2006Haematococcus pluvialis Rosa and others 2005

Scenedesmus obliquus Makulla 2000Isochrysis galbana Valenzuela-Espinoza and others 2002Porphyridium cruentum Fabregas and others 1998

Durmaz and others 2007Chlorella minutissima Rosa and others 2005Tetraselmis suecicaVarious Piorreck and others 1984

Geppert and others 2006Nutrient profiles Spirulina platensis Tokusoglu andUnal 2003

Mendiola and others 2007Chlorella vulgaris Tokusoglu andUnal 2003Porphyridium cruentum Rebolloso-Fuentes and others 2000Nannochloropsis Rebolloso-Fuentes and others 2001Isochrysis galbana Valenzuela-Espinoza and others 2002

Tokusoglu andUnal 2003Scenedesmus Becker 1984

Quevedo and others 2008Phaeodactylum tricornutum Sanchez and others 2002Various Becker 2007

Various functional metabolites Spirulina platensis Desmorieux and Hernandez 2004from microalgae Khan and others 2005

Colla and others 2007Mendiola and others 2007, 2008Gouveia and others 2008Ibanez and others 2008

Chlorella vulgaris Quintana and others 1999Mendesand others 2003

Haematococcus pluvialis Garca-Malea and others 2006Dunaliella salina Mendes and others 2003

Ibanez and others 2008

(Continued)

c 2010 Institute of Food Technologists Vol. 9, 2010 Comprehensive Reviews in Food Science and Food Safety 657


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Table 1(Continued)

Topic of information Microalgae species Reference

Scenedesmus almeriensis Sanchez and others 2008Botryococcus braunii Mendes and others 2003

Arthrospira maximaVarious Burja and others 2001

Molina and others 2003Pulz and Gross 2004Singh and others 2005Cardozo and others 2007

Plaza and others 2009Inclusion of microalgae in foods or as food Spirulina platensis Morist and others 2001Desmorieux and Hernandez 2004Gouveia and others 2008a

Chlorella vulgaris Gouveiaand others 2006, 2007a, 2008aAndrade and others 2007

Schizochytrium sp. ANZFA 2002Valencia and others 2007

Haematococcus pluvialis Gouveiaand others 2006, 2008aIsochrysis galbana Valenzuela-Espinoza and others 2002

Gouveia and others 2008bScenedesmus sp. Quevedo and others 2008Anabaena Loreto and others 2003Porphyridium cruentum Guil-Guerrero and others 2004Nannocloropsis spp.Phaeodactylum tricornutum

Spirulina maxima Gouveia and others 2008aDiacronema vlkianum

Various Liang and others 2004Lee 1997

Table 2General composition (N% of dry matter) of different algae and comparison values with traditional sources of food.

Species Protein Carbohydrates Lipids

Spirulina platensis 63 (a) 15 (a) 11 (a)61.32 to 64.43 (d) 15.09 to 15.81 (d) 7.09 to 8.03 (d)

Arthrospira maxima 60 to 71 (a) 13 to 16 (a) 6 to 7 (a)Chlorella vulgaris 51 to 58 (a) 12 to 17 (a) 14 to 22 (a)

47.82 (d) 8.08 (d) 13.32 (d)Chlorella pyreinodosa 57 (a) 26 (a) 2 (a)Dunaliella salina 57 (a) 32 (a) 6 (a)Porphyridium cruentum 28 to 39 (a) 40 to 57 (a) 9 to 14 (a)

34.1 (c) 32.1 (c) 6.53 (c)Scenedesmus obliquus 50 to 56 (a) 10 to 17 (a) 12 to 14 (a)

Aphanizomenon flos-aquae 62 (a) 23 (a) 3 (a)Chlamydomonas rheinhardtii 48 (a) 17 (a) 21 (a)

Anabaena cylindrica 43 to 56 (a) 25 to 30 (a) 4 to 7 (a)Euglena gracilis 39 to 61 (a) 14 to 18 (a) 14 to 20 (a)

Spirogyra sp. 6 to 20 (a) 33 to 64 (a) 11 to 21 (a)Synechococcus sp. 46 to 63 (a) 8 to 14 (a) 4 to 9 (a)Nannocloropsis spp. 28.8 (b) 35.9 (b) 18.36 (b)Haematococcus pluvialis 48 (e) 27 (e) 15 (e)Isochrisis galbana 26.99 (d) 16.98 (d) 17.16 (d)

Conventional foodsBakers yeast 39 (e) 38 (e) 1 (e)Meat 43 (e) 1 (e) 34 (e)Egg 47 (e) 4 (e) 41 (e)Milk 26 (e) 38 (e) 28 (e)Rice 8 (e) 77 (e) 2 (e)Soya 37 (e) 30 (e) 20 (e)

Valuesexpressedas percent drymatter.

(a) Becker 2007.(b) Rebolloso-Fuentesand others2001.(c) Rebolloso-Fuentesand others2000.

(d) Tokusogluand Unal2003.(e)Gouveiaand others2008a.

source of unlimited potent biologically active compounds, such

as carotenoids, phycobilins, fatty acids, polysaccharides, vitamins,and sterols, which all deliver important benefits to the human

consumer (Gouveia and others 2007a).

Micro- and macronutrients found in microalgaeMany analyses of gross chemical composition have been pub-

lished for different strains of microalgae under different growthconditions (Tokusoglu and Unal 2003; Becker 2004; Liang

and others 2004; Shimamatsu 2004; Spolaore and others 2006;

Rodriguez-Garcia and Guil-Guerrero 2008).There are new evaluations of microalgal protein content, such

as the protein efficiency ratio, the apparent biological value, andthe true digestibility value of protein content (Becker 2004). In

all of these tests, microalgae have compared favorably with thereference and other food proteins in the amino acid content and

proportion and availability of amino acids in their protein profile(Table 3).



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Table3Aminoacidcompositionofproteinfrommicroalgae,somecommonlyconsumedfoods,andthedailyrecommendedvalues

accordingtotheWHOandtheFAO.

Amino

Sp

iru

lina

Sp

iru

lina

C

hlore

lla

Duna

lie

lla

Scene

desmus

Scene

desmus

Art

hrosp

ira

Ap

han

izomenon

Whole

acid

platensis

platensis

vu

lgaris

bardaw

il

obliquus

sp.

max

ima

sp.

WHO

FAO

Soy

egg

Wheat

Ile

6.7

(a)

7.2

(c)

3.8

(a)

4.2

(a)

3.6

(a)

42(e)

6.0

(a)

2.9

(a)

4.0

(c)

130(e)

120(e

)

5.8

0(b)

3.8

0(b)

6.8

(d)

4.8

2(b)

Leu

9.8

(a)

5.7

(c)

8.8

(a)

11

.0(a)

7.3

(a)

123(e)

8.0

(a)

5.2

(a)

7.0

(c)

160(e)

170(e

)

9.0

(b)

6.4

0(b)

4.2

(d)

10

.78(b)

Val

7.1

(a)

4.9

(c),(d)

5.5

(a)

5.8

(a)

6.0

(a)

61(e)

6.5

(a)

3.2

(a)

5.0

(c)

140(e)

130(e

)

7.2

0(b)

4.3

0(b)

7.8

6(b)

Lys

4.8

(a)

4.2

(c)

8.4

(a)

7.0

(a)

5.6

(a)

230(e)

4.6

(a)

3.5

(a)

5.5

(c)

110(e)

160(e

)

6.7

0(b)

2.7

0(b)

3.3

(d)

7.7

0(b)

Phe

5.3

(a)

7.4

(c)

5.0

(a)

5.8

(a)

4.8

(a)

174(e)

4.9

(a)

2.5

(a)

6.0

(c)

185(e)

190(e

)

5.3

0(b)

4.6

0(b)

5.9

(d)

6.0

2(b)

Tyr

5.3

(a)

3.4

(a)

3.7

(a)

3.2

(a)

3.9

(a)

(a)

4.3

0(b)

3.2

0(b)

3.0

2(b)

Met

2.5

(a)

1.7

(c)

2.2

(a)

2.3

(a)

1.5

(a)

286(e)

1.4

(a)

0.7

(a)

3.5

(c)

100(e)

60(e

)

3.0

(b)

1.6

0(b)

1.9

(d)

1.5

5(b)

Cys

0.9

(a)

1.4

(a)

1.2

(a)

0.6

(a)

0.4

(a)

0.2

(a)

2.1

0(b)

2.1

0(b)

0.5

(b)

Try

0.3

(a)

3.8

(c)

2.1

(a)

0.7

(a)

0.3

(a)

(e)

1.4

(a)

0.7

(a)

1.0

(c)

15(e)

15(e

)

1.7

0(b)

4.2

(d)

1.1

(b)

Thr

6.2

(a)

3.8

(c)

4.8

(a)

5.4

(a)

5.1

(a)

84(e)

4.6

(a)

3.3

(a)

4.0

(c)

85(e)

85(e

)

5.3

0(b)

2.9

0(b)

4.2

(d)

5.6

(b)

Ala

9.5

(a)

7.9

(a)

7.3

(a)

9.0

(a)

6.8

(a)

4.7

(a)

3.4

0(b)

7.1

8(b)

Arg

7.3

(a)

6.4

(a)

7.3

(a)

7.1

(a)

6.5

(a)

3.8

(a)

6.4

0(b)

4.3

0(b)

7.9

7(b)

Asp

11.8

(a)

9.0

(a)

10

.4(a)

8.4

(a)

8.6

(a)

4.7

(a)

10

.70(b)

5.0

(b)

10

.39(b)

Glu

10.3

(a)

11

.6(a)

12

.7(a)

10

.7(a)

12

.6(a)

7.8

(a)

12

.30(b)

27

.70(b)

11

.6(b)

Gly

5.7

(a)

5.8

(a)

5.5

(a)

7.1

(a)

4.8

(a)

2.9

(a)

3.8

0(b)

3.8

0(b)

5.0

5(b)

His

2.2

(a)

2.0

(a)

1.8

(a)

2.1

(a)

1.8

(a)

0.9

(a)

2.6

0(b)

2.1

0(b)

2.4

0(b)

Pro

4.2

(a)

4.8

(a)

3.3

(a)

3.9

(a)

3.9

(a)

2.9

(a)

4.3

0(b)

10

.10(b)

3.8

8(b)

Ser

5.1

(a)

4.1

(a)

4.6

(a)

4.2

(a)

4.2

(a)

2.9

(a)

7.7

0(b)

4.8

0(b)

3.5

0(b)

(a)Valuesexpressedasg/100gprotein(Becker2007).

(b)Valuesexpressedasg/100gprotein(MorrisQuevedoandothers1999).

(c),(d)Expressedasg/16gN:(c)freeze-driedbiomass,

(d)spray-driedbiomass(Moristandothers2001).

(e)ValuesexpressedasmgAA/gessentialAA(Quevedoa

ndothers2008).



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Microalgae are also a fine source of carbohydrates, found inthe form of starch, cellulose, sugars, and other polysaccharides.

The available carbohydrates have good overall digestibility and,therefore, few limitations on their uses and applications.

The average lipid content in microalgae varies between 1% and40% and, according to growing conditions, can be as high as 85%

of dry weight. Algal lipids are typically composed of glycerol, sug-ars, or bases esterified to fatty acids, with carbon numbers in the

range of C12 to C22. The most important lipids are the essen-

tial polyunsaturated fatty acids such as linoleic, eicosapentaenoic(EPA), and docosahexaenoic (DHA). Probably the most valuablecompounds found in microalgae are the polyunsaturated fatty acids

because they are of great importance to human health (Table 4).They are slightly higher in concentration than in fish oil, have less

chemical contamination than seafood lipids, and may have greaterpurity after extraction (Pulz and Gross 2004). Oil from algae shows

additional benefits as a long-chain PUFA supplier over fish oils,including low taste intensity and off-odor problems (Valencia and

others 2007). Microalgae represent a valuable source of nearly allimportant vitamins, which improve the nutritional value of algal

biomass.Due to their phototrophic life, microalgae are often exposed to

high oxygen and free-radical stresses, which has resulted in theevolution of numerous efficient protective systems against oxida-

tive and radical stressors. Among these protective systems is theproduction of pigments, such as carotenes, chlorophylls, and phy-

cobiliproteins, all having high antioxidant and protective properties(Pulz and Gross 2004).

Many toxicological trials are required for any new food itembefore it can be declared safe for human consumption. Most ofthese investigations are detailed toxicological tests to prove the

harmlessness of the product, like in the case of unconventionalprotein sources, such as microalgae. By considering the available

information on possible toxic properties, or any other adverseeffects of the different algae tested so far, it can be stated that none

of them have shown negative effects. All tests, including humanstudies, have failed to reveal any evidence that would restrict the

utilization of properly processed algal material (Becker 2007).

Commonly utilized microalgal species used for humanconsumption

Microalgae such asSpirulina,Chlorella,Dunaliella,Haematococcus,and Schizochytrium are classified as food sources falling into theGRAS (Generally Regarded as Safe) category by the U.S. Food

and Drug Administration. Consequently, many high-value com-pounds produced by microalgae can be administered as a powder

of dried or freeze-dried biomass with no extraction undertaken(Walker and others 2005).

Among the most used microalgae are Chlorella and Spirulina,

in addition, Dunaliella, Haematococcus, Schizochytrium, Scenedesmus,Aphanizomenon, Odontella, and Porphyridium are gaining acceptancein the food and health-food market. It might be useful to take a

brief look at what makes each of these microalgae special, bothfrom the consumer point of view, and from the point of view of

the food industry (Table 5), since their individual attributes willallow for an adequate selection according to the need at hand.

Spirulina is one of the richest algal sources of-linolenic acid(GLA). GLA is an essential polyunsaturated fatty acid and a po-

tent nutraceuticaI (Sajilata and others 2008). Various studies haveasserted its pharmaceutical value, especially in lowering the low-

density lipoprotein in hypercholesterolemic patients (Ishikawa andothers 1989) and alleviation of symptoms of premenstrual syn-

drome (Horrobin 1983) and atopic eczema (Biagi and others1988). In vitro and in vivo studies have shown GLA to selectively

kill tumor cells without harming normal cells (Reddy and others1998). GLA is also implicated in the amelioration of a number

of diseased states including schizophrenia, multiple sclerosis, der-matitis, diabetes, and rheumatoid arthritis (Ziboh 1989; Sajilata

and others 2008).

Spirulinais an excellent source of phycobiliproteins. These com-

pounds are being studied due to their high free-radical scavenging

capacity, which could make them a potential antitumor and an-ticancer drug (Hu 2004). Spirulina is a good source of vitaminB1 (Desai and Sivakami 2004). Due to the easy bioavailability of

nutrients, including minerals, Spirulinamay be a good choice forwomen during pregnancy and lactation and is also beneficial for

malnourished children. The World Health Organization (WHO)has called Spirulinaas one of the greatest superfoods on earth and

NASA considers it as an excellent compact food for space travel,as a small amount can provide a wide range of nutrients (Khan and

others 2005). Spirulina has been incorporated in noodles, cook-ies, nutritional bars, and other functional food products (Pulz and

Gross 2004). Spirulina also supports digestive functions and helpsto maintain bacteria in the gut.

Chlorellacells contain -1,3-glucan, an active immunostimula-tor, which acts as a free-radical scavenger and as a reducer of blood

lipids (Becker 2004). A polysaccharide also found in Chlorellahasbeen linked to antitumor effects (Iwamoto 2004).Chlorella vulgarisis also a rich source of proteins, 8 essential amino acids, vita-mins (B-complex, ascorbic acid), minerals (potassium, sodium,

magnesium, iron, and calcium), -carotene, chlorophyll, CGF(Chlorella growth factor), as well as other health-promoting sub-stances (Rodriguez-Garcia and Guil-Guerrero 2008).

Dunaliella is known for its capacity to produce high concen-trations of carotenes, especially -carotene. Among the other

carotenoids produced byDunaliellaare lutein, neoxanthin, zeaxan-thin, violaxanthin, cryptoxanthin, and -carotene, which are gen-

erally marketed together as a carotenoid mix (Ben-Amotz 2004).

Haematococcus produces a carotenoid known as astaxanthin.

There is increasing evidence that astaxanthin surpasses -carotene,zeaxanthin, canthaxanthin, vitamin C, and vitamin E regarding an-

tioxidant benefits. Animal studies have shown that astaxanthin canprotect skin from UV radiation effects, protect against chemically

induced cancers, and enhance the immune system (Cysewski andLorenz 2004). It also has antiinflammatory properties, which may

help alleviate arthritis, muscle pain, and carpal tunnel syndrome(Walker and others 2005). Astaxanthin is a product of recent com-

mercialization and is sold under many different names, one ofwhich is BioAstin by Cyanotech Corp. (Kailua-Kona, Hawaii,

U.S.A.).

Porphyridium cruentum contains relatively rare polyunsaturated

fatty acids such as arachidonic acid and EPA, both important inhuman nutrition (Arad and Richmond 2004).

Aphanizomen flos-aquaeis a cyanobacterium with a rather shorthistory of human consumption. Aphanizomenhas many beneficial

health effects such as antiinflammatory, exhaustion relief, assistingdigestion, and general improvement of overall well being (Hu

2004).

Current Biomass Production Systems and DownstreamProcesses

The chemical composition of microalgae is not an intrinsically

constant factor, it varies among strains and batch cultures, andaccording to environmental parameters such as temperature, pH,



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mineral content of water, light exposure, and agitation, all of whichcome down to the type of culturing method used, open or closed,

indoors or outdoors.The factors to be considered in this selection include the biology

of the alga, the cost of land, labor, energy, water, and nutrients,as well as climate (if the culture is outdoors) and the type of final

product desired. These parameters can be controlled in such a waythat the metabolism of the microalgae will favor a high production

of the particular compound of commercial interest, such as fatty

acids or antioxidants among others (Sierra and others 2008).An efficient algal separation process should be able to process

a large volume of broth, yield a product with a high dry weight

percentage, and require modest investment, low consumption ofenergy, and low maintenance cost (Poelman and others 1997).

Currently, recovery of biomass operations from culture broth canaccount up to 20% to 30% of the total cost of production of the

biomass (Molina and others 2003), thus there is need for futureresearch directed to diminish costs and increase efficiencies in this

step of the production. Figure 2 compiles information regardingcommonly used production systems, with the parameters that af-

fect productivity of microalgae and the biomass recovery systemscurrently in use.

Photobioreactor designs for biomass productionMost commercial systems used today are open-air systems. The

4 major types of open-air systems currently in use are shallow

big ponds, tanks, circular ponds, and raceway ponds. Open-pondsystems for microalgae are of easy construction and operation

(Borowitzka 1999), but have been inappropriate when high pro-ductivity is desired. Before the 1990s, most systems for growing

microalgae were open pond and carrousel (circular) types, whichallowed cellular densities of up to 0.7 g cells per liter (Contreras-

Flores and others 2003). An open system usually was a closed-circuit canal about 15 to 20 cm deep, with a paddle rotation

system able to move the culture medium all around the circuit.

It required a large area of land, but was economical to build andoperate (Borowitzka 1999). Unfortunately, productivity of thesesystems seems to have reached its maximum, impairing somewhat

the further development of microalgae biotechnology.Culturing microalgae in open ponds and raceways has been

well developed and is still in use, but only a few species canbe maintained in the traditional open systems, those that control

contamination by using highly alkaline or saline selective envi-ronments (Molina and others 2001). An example of this kind of

system would be a Cyanotech Corp. (www.cyanotech.com) open-pond operation forSpirulinaand Haematococcus in Hawaii, and of

Earthrise Nutritionals (www.earthrise.com) for the production ofcyanobacteria for food in California (Spolaore and others 2006).

Open systems have other disadvantages, such as ease of contam-ination, difficulties with the recovery of biomass, and problems

with temperature control, which all must be taken into accountwhen selecting an outdoor system. These problems have led to the

Figure 2Commonly used production systems, parameters, and recovery operations for the production of microalgae.



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Table 6Processing parameters for the production of microalgae.

Processing parameters Microalgae used Reference

Culture medium Spirulina Soletto and others 2005Oliveira and Vieira Costa 2006Colla and others 2007

Chlorella vulgaris/emersonii Scragg and others 2002Bertoldi and others 2006

Dunaliella salina/Bardawil Gomez and others 2003Zhu and Jiang 2008

Haematococcus pluvialis Kobayashi andothers 1997

Brinda and others 2004Isochrysis galbana Valenzuela-Espinoza and others 2002Scenedesmus obliquus/almeriensis/sp. Becker 1984

Martnez and others 1999Makulla 2000Quevedo and others 2008

Porphyridium cruentum Fabregas and others 1998Anabaena Loreto and others 2003Various Piorreck andothers 1984

Janssen and others 2000Carbon dioxide consumption efficiency Spirulina platensis Grequede Morais andVieiraCosta 2007

Soletto and others 2008Chlorella vulgaris/sp./Buitenzorg Wijanarko and others 2004

Cheng and others 2006Chiu and others 2008

Scenedesmus Grequede Morais andVieiraCosta 2007General Camacho and others 1999

Kurano and Miyachi 2004

Biomass production Spirulina platensis Oliveira and Vieira Costa 2006Oliveira and others 2009

Chlorella vulgaris/emersonii Scragg and others 2002Haematococcus pluvialis Brinda and others 2004

Scenedesmus almeriensis/sp. Sanchez and others 2008Quevedo and others 2008

Isochrysis aff. Galbana Valenzuela-Espinoza and others 2002Phaeodactylum tricornutum Sanchez and others 2002General Grobbelaar 2000

Molina and others 2003Light source/supply/cycle/irradiance Spirulina platensis Wu and others 2005

Soletto and others 2008Chlorella sorokiniana Ugwu and others 2007Haematococcus pluvialis Garca-Malea and others 2006

Scenedesmus almeriensis Sanchez and others 2008Phaeodactylum tricornutum Sanchez and others 2002Chlamydomonas reinhardtii Janssen and others 2000Dunaliella tertiolecta

Anabaena Loreto and others 2003Cyanobacteria Jacob-Lopes and others 2009

Simmer and others 1994General Pulz and others 1995

Molina and others 1999Ogbonna and others 1999Kommareddy and Anderson 2004Grobbelaar 2009

Mass transfer General Thomas and Gibson 1990Molina and others 1999

Dissolved oxygen Chlorella sorokiniana Ugwu and others 2007Phaeodactylum tricornutum Sanchez and others 2004General Camacho and others 1999

Temperature Spirulina platensis Colla and others 2007Chlorella sorokiniana Ugwu and others 2007

Scenedesmus almeriensis/obliquus Martnez and others 1999Sanchez and others 2008

General Hancke and others 2008Biomass recovery and downstream processing Spirulina platensis Morist andothers 2001Desmorieux and Hernandez 2004Oliveira and others 2008

Chlorella vulgaris Hee-Mock and others 2001Dunaliella salina Orset and others 1999

Ben-Amotz 2004Zhu and Jiang 2008

General Bilanovic and Shelef 1988Sukenik and others 1988Chisti andMoo-Young 1991Petrusevski and others 1995Poelman and others 1997Borowitzka 1999Olaizola 2003Molina and others 2003Danquah and others 2009Lee and others 2009



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Table 7Microalgae production vessels commonly used.

Types of photobioreactors Microalgae used in research Authors

Design aspects Spirulina Masojdek and others 2003Cyanobacteria Marxen and others 2005

Nedbal and others 2008General Pulz and Scheibenbogen 1998

Pulz 2001Contreras-Flores and others 2003Janssen and others 2003Sierra and others 2008

Production systems Spirulina spp./platensis Duerr and others 1997Habib and others 2008

Dunaliella salina Hejazi andWijfferls 2004General Borowitzka 1999

Janssen and others 2003Eriksen 2008Grobbelaar 2000, 2009

Tubular Spirulina and Scenedesmus Grequede Morais and Vieira Costa 2007Chlorella vulgaris and C. emersonii Scragg and others 2002Porphyridium cruentum Rebolloso and others 1999Phaeodactylum tricornutum Molina andothers 1994, 2001General Acien and others 1997

Gudin 1983Sastre and others 2007Acien and others 1998Tredici and Zittelli 1998Camacho andothers 1999

Helical Spirulina platensis Soletto and others 2008General Watanabe and Hall 1996

Airlift Phaeodactylum tricornutum Sanchez and others 2002Chlorella Xu and others 2002General Vunjak-Novakovic and others 2005

Acien and others 2001

Bubble colums Phaeodactylum tricornutum Sanchez and others 2002General Sanchez and others 1999

Flat plate Chlorella sp. Doucha and Livansky 1995General Tredici and Zittelli 1998

Pulz and others 1995Tredici and others 1991Samon and Leduy 1985Hu andRichmond 1996Hu and others 1996Sierra and others 2008

Stirred tank Chlamydomonas reinhardtii Janssen and others 2000Dunaliella tertiolecta Janssen and others 2000General Ogbonna and others 1996

Open Scenedesmus obliquus Becker 1984Spirulina platensis/spp. Duerr and others 1997

Shimamatsu 2004General Borowitzka 1999

Molina andothers 2001Contreras-Flores and others 2003

Spirulina platensis, but presents difficulties with the smaller unicel-

lular kind such as Chlorellaand Dunaliella. It has the disadvantagethat tends to be a slower operation than centrifugation. Membrane

microfiltration and ultrafiltration are possible alternatives to con-ventional filtration methods, but their costs are still high, up to the

point that for treatment of large volumes, costs are comparable tothose of centrifugation (Molina and others 2003). The effect of

growth state of the microalgae on the efficiency of tangential flowfiltration has been evaluated by Danquah and others (2009). They

found that a mixed culture ofTetraselmis suecica/Chlorococum sp.(a species of microalgae evaluated for biodiesel production) har-

vested during the low growth rate phase required less energy percubic meter of supernatant removed, and that operation in a fixed

time allowed for a higher concentration of biomass than thosecells harvested during the high growth rate phase. This research

is indicative that the growth state in which a microalgae cultureis at the moment of harvesting might improve the efficiency of

cell recovery and at the same time help diminish operational costs

of biomass recovery, therefore, further studies regarding this phe-

nomenon are necessary for microalgae species of interest for thefood industry.

Gravity-assisted sedimentation is a slow method for dewateringmicroalgae cultures, and therefore one that is not frequently used.

It has the advantage of being a method that has low operationalcost, but with the disadvantage of being time consuming and

not working for all species. If there is no danger of ocurrence ofdecomposition in the microalgae biomass this is an easy method for

dewatering microalgae biomass, and is now commonly used withmicroalgae of larger sized cells or with those that form colonies.

Danquah and others (2009) found that microalgae left to settle ina glass container presented different settling velocities according to

the light condition at which they were left to settle, and accordingto the growth rate at which they were harvested. The microalgae

culture left to settle under dark conditions settled faster than thoseunder daylight conditions, as well as those harvested under low

growth rate phase. The explanation Danquah and others gave



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Figure 3Solar energy operated tubular photobioreactor.

to this observations was that, in the presence of daylight and/orhigh growth rate phase (exponential phase), the microalgal cells

are actively photosynthesizing with a high metabolism rate andunicellular mobility, and this retards their agglomeration rate and

therefore lowers their settling rate. On the other hand, microalgalcells exposed to darkness and/or low growth rate phase (stationary

phase) do not photosynthesize, hence their metabolism rate is lowand this causes the cells to agglomerate and settle f aster.

Flocculationis a method that has gained popularity for dewater-ing microalgae biomass, but with limited applications in the food

industry because of the addition of substances to promote theformation of aggregates or floccules that are not allowed in food

processing, for example multivalent metal salts or cationic poly-mers (Bilanovic and Shelef 1988). Bioflocculation is an interesting

option, but one that has been considered to be unreliable (Bene-mann and Oswald 1996). It is based on the possibility of inducing

the aggregation of cells by environmental stresses such as extremepH, nutrient depletion, or temperature changes. The difficulty of

this method is achieving the desired aggregation of cells withoutmodifying the cell composition. In applications such as biodiesel

production from algal biomass, microbial flocculation has renderedvery good results (Al-Shahwani and others 1986; Noue and others

1992; Hee-Mock and others 2001; Lee and others 2009). Findingmicrobial flocculants safe for human use would be of great interest

for the recovery of microalgal biomass.

Downstream processes for biomass drying and preservationBiomass drying can be achieved using sunlight shining onto heat

trays containing biomass and thus evaporate the residual water;

conventional ovens are used as well. But the most commonly usedmethods are spray-drying and freeze-drying, the latter usually isnot economically feasible.

Desmorieux and Hernandez (2004) compiled information re-garding traditional drying methods of spirulina at an industrial

level, according to their report paper, spray-drying is the com-monly used method at the most important farms. Cyanotechs

patented Ocean Chill method is a process that combines the useof spray-drying with air that has a very low concentration of oxy-gen to protect sensitive nutrients from oxidation by this element.

Hot air is commonly used on semiindustrial farms and artisanalproduction farms where the biomass paste is extruded into small

cylinders, placed on trays, and dried by convective hot air, or di-

rectly by sun exposure. Another method reported by Desmorieux

and Hernandez (2004) is that of adding freshly filtrated spirulinato precooked and dried hot flour, mixed, and dried until a low

moisture content is achieved.Not much information can be found regarding the operational

parameters of these processes, since on a laboratory scale, freeze-drying and oven-drying are commonly used as means of obtaining

dried weight measurements, and preserving the biomass for fur-ther analysis, and these methodologies are not easily scalable or

economically feasible. Once the production of microalgae turns

to commercial and industrial scale, this information is not largelypublished or is even protected by patents, some references can befound in Table 4.

Oliveira and others (2008) characterize the thin-layer dryingofS. platensisutilizing experimental curves to determine the best

condition of drying. A statistical model was applied to analyze theeffects of independent variables (air temperature and solids) on the

response of solubility in acid medium. Desmorieux and Hernan-dez (2004) reported problems encountered while drying spirulina

biomass using conventional drying methods, such as protein andsugar losses occurring in a drying oven that varies according to

the temperature of the air, and they reported a higher loss of sugarcontent (about 30%) compared to proteins (10% to 20%); at a tem-

perature of 60

C there was a higher loss of protein by convectiveor infrared drying.

Desmorieux and Hernandez (2004) also reported that the bestmethod to recover proteins and total sugars was freeze-drying,

but Orset and others (1999) stated that freeze-drying of microal-gae biomass is a time-consuming process that results in a highly

hygroscopic powder and is poorly applicable on a large scale.Morist and others (2001) published a comprehensive research

report on the possibilities of spirulina biomass as an auto-

regenerative biological life support system for men in outerspace.They designed a process for spirulina biomass recovery and fur-

ther treatment to be used as food in 2 forms, liquid and dry.It includes washing, pasteurization, and spray-drying and they

presented discussions on biomass quality regarding potential mi-crobial contamination and changes in composition during the

process.Another of the great controversies surrounding the industrial

production of microalgae is the search for an adequate use forthe used-up spent culture medium that can no longer be reused

or concentrated. A proposal by us is that since these spent mediacontain a high concentration of nutrients and exocellular products,

they could be used as biofertilizers, thus providing added value tothe process and by helping the overall production to be friendlier

to the environment. This alternative should be evaluated beforedrawing any definite conclusion.

Future and Perspective of Microalgae Applicationsin So-Called Health Foods

At the moment,even with all the studies referring to the possiblebenefits of incorporating microalgae in food, such as improving

cardiovascular systems (Khan and others 2005), their slimmingproperties (Lyons and OBrien 2002), energizing properties (Desai

and Sivakami 2004), antioxidant capabilities (Lyons and OBrien2002), and cholesterol and tr iglyceride lowering effects (Geppert

and others 2006), the most popular way to consume microalgaeis as a diet supplement in tablet, capsule, or powder form (Molinaand others 2003).

The incorporation of microalgal biomass into traditional prod-ucts has been found inconvenient in some cases because of its

strong green color, fishy taste, and odor, as well as its powdery

consistency. All these aspects constitute main areas in need of



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improvement. The color effect may be disguised in products sim-ilar to ravioli, but it has not been possible to disguise the taste and

odor of microalgae, therefore, limiting the amount to be used.It must be mentioned that the degree of acceptability of

microalgae-based products seems to depend on the traditional dietof the population where such a product is incorporated. While

Liang and others (2004) point out that in China, traditional prod-ucts that incorporate microalgae are considered a flavorful and

favorable trait, very appreciated by consumers, Becker (2007) has

found that the strong fishy flavor is a negative trait that limits theacceptability of these food products with many people. In Chinaand other Asian countries, the use of microalgae is not a drastic

addition to food, since the traditional cuisine includes algae inmany preparations, and the substitution or addition of microalgae

is not a strong or noticeable change. In Western cultures, the op-posite occurs; algae are not a commonly used ingredient or food;

therefore, microalgae constitute a very new and, in most cases, anunacceptable addition to foods.

A different approach may be that of employing the microalgalbiomass as a source of biomolecules of interest, instead of using

the whole biomass, as was suggested by Gantar and Svircev (2008).Extracting bioactive molecules and compounds such as fatty acids,

pigments, and antioxidants, for use as additives in the food in-dustry, is a reality that is gaining ground and becoming popular

in todays climate, as alternatives to the usual chemical additivesand supplementations. This approach is mainly taken by the cos-

metic and pharmaceutical industries, where the additional cost ofthe extraction might not add significantly to the final price of

the product due to the relatively higher sale prices of those prod-ucts, especially in the case of the newer nutraceutical and cosme-ceutical lines.

With the newly developing increase in demand for more sophis-ticated products, microalgal biomass and extracts are beginning to

position themselves firmly in this new market. In Germany, somecompanies prominent in the production and commercialization of

food products have begun to involve themselves in activities re-garding functional foods with microalgae and cyanobacteria, such

as bread, pasta, noodles, yogurt, and beverages. Pulz and Gross(2004) report similar developments in France, Japan, the United

States, China, and Thailand.In recent years, more and more scientists have begun to study

the feasibility of including microalgal biomass, pigments, and fatsinto foods. To achieve this, creative and innovative solutions are

needed; here is where food scientists and engineers have the op-portunity to create new and diverse products. A study that partially

substituted pork fat with oil fromSchizochytriumspp. hoped to en-rich dry fermented sausages with -3 polyunsaturated fatty acids.

The results showed that a 25% substitution was not acceptable toconsumers, but at 15% supplied 1.30 g/100 g meat of DHA, which

was stable after 30 d storage under vacuum conditions (Valenciaand others 2007).

Spirulina has been a favorite ingredient in shakes and smooth-ies for the so-called health enthusiasts, but these beverages are

not for everyone. Instead, smaller quantities of spirulina combinedwith other ingredients capable of disguising its flavor has allowed

the development of new and exciting products aimed at the massmarket. For example, in New Zealand, it is possible to find Char-

lies Honest Superfood Smoothie Spirulina & Fruit. Coca-ColasOdwalla brand carries an Odwalla Original Superfood Micronu-

trient Fruit Juice Drink label, with a great variety of fruit pureesand superfoods such as spirulina, wheat grass, barley grass, and

wheat sprouts. Naked juice by PepsiCo is a Naked Green Ma-

chine All Natural Superfood 100% Juice Smoothie with Spirulina(Hudson 2008). All of these products tend to appeal to a health-

conscious audience and, more importantly, to children who areoften enticed by the unusual.

Natural colors are a growing segment of the food and cosmeticindustries, as synthetic colors have started to be replaced either

due to consumer request or by government demands. The globalvolume consumption of natural colors increased from over 550000

metric tons in 2002 to over 600000 tons in 2008, with a further

5% increment expected by 2012 (Madden 2009). But there mightbe some difficulties regarding the supply of natural colors, sincethe bulk is derived from fruits and vegetables, always subject to

climate, environmental, and even political fluctuations. Therefore,a shortage of produce will directly affect the availability of natural

colors; as demand becomes higher than supply, then prices willbe driven higher. Since nanotechnology may allow for a higher

bioavailability of pigments and, more interestingly, of those whodouble as functional ingredients, this area of research is sure to

draw great interest among scientists and food technologists.Microalgae can serve as a natural source for pigments, with the

possibility of year-round production in closed photobioreactors.Scientists have studied the effects of solar radiation on pigment

content in microalgae (Wu and others 2005), nutrient effect overpigment production (Ortega and others 2004), as well as supercrit-

ical extraction of pigments (Gouveia and others 2007b) and HPLCanalysis (van Leeuwe and others 2006). All microalgae contain a

large palette of pigments, some ranging from yellow to red, andall the way to blue, many of which double as functional moleculessuch as -carotene, -carotene, astaxanthin, violaxanthin, lutein,

phycocyanin, alloxanthin, neoxanthin, zeaxanthin, cryptoxanthin,monadoxanthin, crocoxanthin, phycoerythrin, and others (Arad

and Yaron 1992; Dufosse and others 2005).Various studies conducted in Portugal (Gouveia and others

2006, 2007a, 2008a, 2008b), have opened real possibilities tothe inclusion of microalgal biomass as a pigment and functional

ingredient in food products. The incorporation of C. vulgarisand Haematococcus pluvialis biomass in oil-in-water pea protein-

stabilized emulsions has resulted in good color stability, addedresistance to oxidation, and a good compromise in sensory qual-

ities. The 2nd paper refers to the use ofC. vulgaris biomass as anatural green pigment source in coloring Christmas cookies, with

good possibilities, as the green tonalities obtained in the study werelong lasting and acceptable to consumers. The 3rd paper also refers

to the possibilities of producing biscuits enriched with microalgalbiomass. In this case, Isochrysis galbana was used due to its content

in PUFA -3. The biscuits presented an enhancement of textureproperties, high stability of color and texture, and a good profile

of polyunsaturated fatty acids.As a result of intensive research and as an example of industrial

application of microalga-based pigments, Nestle Rowntree rein-troduced their blue Smarties back into the market after having

found in blue-green cyanobacteria a natural source of blue color-ing (Crowley 2008). No details are available whether the company

is using whole biomass or a pigment extracted from it.It is interesting to point out that, in spite of the fact that mi-

croalgae were and continue to be promoted as an important sourceof protein, very few companies bank on this benefit to boost their

sales. It could be that the amount of microalgal biomass currentlyincorporated in food products does not constitute a good source of

protein; or it could be that the segment of population in dire needof protein is not able to assume the cost, therefore little effort is

made to promote the concept. This constitutes a new challenge for



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Figure 4Challenges for food scientists and engineers.

food scientists and engineers around the world, shouldering social

responsibility, and helping to achieve popularity and production ofmicroalgal-based foods in such a way that this nutritional product

may adequately reach people of lower incomes, especially preg-nant women, babies, and young children in poverty-stricken areas

around the world.

Suggested approaches to use microalgae in healthy foodsThe situation as described earlier shows a highly favorable

panorama for the development of foods with high nutritional con-

tents and functional properties. It is necessary to take into accountthat to achieve this important goal, many technological challenges

must be surpassed first, especially regarding new technologies infood engineering. Figure 4 displays some of the challenges that

are yet to be surpassed regarding microalgae production and usein foods.

A solution to the strong flavor of microalgae might reside inthe production of exotic-flavored snacks and foods, with microal-

gae incorporated, along with the traditional Asian and Indianspices, which will give the Western consumer a chance to accept

these new tastes along with the new products, instead of forcinga new taste, color, and odor into well loved, everyday foods. Or,

maybe, more technical solutions are needed, such as encapsulationof biomass to provide masking and improved rheological proper-

ties, or identification and removal of odor-producing compounds,allowing an increase of concentration of microalgae in foods. Ul-

timately, it is left in the hands of scientists and food engineers tofind the best solution.

But beside the flavor of microalgae and its impact on prod-

uct acceptability, there are still many other aspects that need tobe resolved from a food engineers point of view, but necessarily

with help from other related disciplines. These aspects regard thestability of the functional compounds found in microalgae and

their bioavailability according to their structure and the food ma-trix where they are included, as well as considerations concerning

preservation, packaging, and shelf life.An additional challenge for the preservation processes of mi-

croalgae biomass is that of effectively entering nonthermic process-ing technologies, which could greatly contribute to a reduction

in costs compared to processes like freeze-frying, while helpingto maintain intact all the properties of the protein and the func-

tional biomolecules of interest. Such technologies would involve

cryoconcentration, microwaves, and high pressures.The industrial production of microalgal biomass also presentsitself with the technical challenges to obtain higher yields, lower

energy consumption rates, higher biomass recoveries, and lowerproduction costs in closed photobioreactors. These challenges are

not new, and many investigators have been, and are, currently atwork to improve microalgal photobioreactor performances andbiomass recovery systems. It is of great importance to also con-

duct studies regarding used-up culture media. Water conservationprograms and agricultural programs might find interest, if the used

culture media can be utilized for irrigation of traditional crops,especially if there are compounds present that might be benefi-

cial for the preservation of the land or the growth and quality ofcrops.



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And last but not least, we are in need of adequate and com-prehensive legislation and regulations regarding microalga-based

products, with the objective to provide guidelines for the foodindustry and to assure consumers of their safety. Microalgae can

be perceived as a novelty food or ingredient, but they have the ca-pability to become a staple food for consumers all over the world.

All that is needed is food scientists and engineers capable of takingon the challenges.

Summary and ConclusionsConsumers around the world are moving toward functional

foods as a way to preserve and improve their well being. They arebeginning to search for not only low-fat and low-sugar products,

but also for foods considered as natural or with ingredients takenfrom natural sources as opposed to synthetically produced ingre-

dients. Consumers are searching for food products that will helpthem prevent and fight diseases, increase their energy and wellness,

and help them live longer, healthier, and productive lives. Withthat in mind, food scientists can find in microalgae a novel source

for wholesome food and bioactive ingredients.Microalgae have been around forever, but only in the last

few decades have been produced and marketed as nutraceuticals

and food supplements. Their potential is so much greater than thecurrent applications. Genera such asSpirulina,Chlorella,Dunaliella,

Haematococcus, Schizochytrium, and Isochyris, have become popular

microalgal sources of protein-rich biomass and compounds, es-pecially carotenoids, pigments, antioxidant extracts, and essential

fatty acids.The acceptance of the use of microalgae biomass or

biomolecules extracted from it has resulted in the developmentof various innovative food products enriched with microalgae or

their subproducts. Up to the moment, very few such products haveappeared in the health and natural sector shelves of stores across

Europe and Asia, therefore, there is still a very large untappedopportunity in this food area.

There are still many and great challenges to be breached, but thepossibilities offered by these minuscule plant entities have many

scientists across the world searching for innovative solutions. Oneof the biggest challenges is achieving energy- and cost-effective

production and recovery systems optimized for microalgae. Thisinvolves achieving higher productivities and better recoveries of

the produced biomass.Currently, the various production systems are either open or

closed photobioreactors. Open ponds or raceways such as those

used by Cyanotech and Earthrise Nutritionals in the United Statesare used for species such as Spirulina that grow in a very se-

lective medium and in latitudes where weather conditions donot vary significantly during the year. In areas where weather

conditions vary to extremes, closed photobioreactors such as

tubular, flat panel, air lift, and bubble column models are pre-ferred, both to achieve a more consistent production of biomassand bioactive compounds and for microalgae species that are

more susceptible to suffer contamination or invasion from othermicroorganisms.

Another difficulty faced in the production of microalgae is theirrecovery and preservation, the low productivity of biomass signi-

fies that the recovery systems need to manage efficiently very largevolumes of medium with a very low concentration of biomass.

This alone constitutes a great challenge to engineers who veryoften need to combine various recovery operations such as sedi-

mentation, flotation, filtration, and centrifugation to recover andthen preserve the microalgae cells produced, so as to maintain the

protein quality of the biomass and the activity of other compoundsof interest to the food industry or others.

The challenges are not only for engineers, food scientists havetheir own hurdles to overcome when it comes to the use of mi-

croalgae as food or as a source of ingredients for foods. Theseinclude the not so attractive taste, odor, and color of microalgae

biomass that very likely will modify the sensory properties of allfoods prepared with them. Another challenge is arriving at a com-

prehensive legislative and regulatory oversight for the use of mi-

croalgae species and extracts obtained from their biomass in foods.Only such governmental oversight will allow for a controlled andsafe expansion of microalgae-based products.

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