Submitted by Robert D. Lucas,Ph.D. and CFS, Certified Food Scientist
The Editor
Barbados Underground
Bridgetown, Barbados
West Indies
Dear Sir/Madam,
The following is an overview of the uses of seaweed in the food industry. Suggestions are also proposed for prospective uses of the product.
Seaweeds belong to a group commonly called macro-algae or hydrocolloids in the food industry. The latter name derives from the propensity of the substances to form viscous dispersions and or gels when dispersed in water (colloidal sols) and from the extensive hydroxyl groups with which the substances can form attachments with water molecules.. Hydrocolloids are a heterogeneous group of long chain polymers (polysaccharides{sugars} and proteins). Some of the amino acids in the protein chain contain sulfur (for example; methionine). These are broken down by sulfur using bacteria into hydrogen sulfide and other noxious substances. Hydrocolloids are widely used in the food industry because of their ability to modify the rheology of food systems This include two basic properties of food systems namely, flow behavior (viscosity) and mechanical solid (texture)property (Saha,D.and Bhattacharya,S.(2010) “Hydrocolloids as thickening and gelling agents in food: a critical review.” J. Food Sci.Technol. 47:6: 587-597.).
According to McHugh. J.D. 2003. “A Guide to the Seaweed Industry.” FAO. Fisheries Technical Paper #44:: “The seaweed industry provides a wide variety of products that have an estimated total annual value of US$ 5.5-6 billion. Food products for human consumption contribute about US$ 5 billion of this. Substances that are extracted from seaweeds -hydrocolloids – account for a large part of the remaining billion dollars, while smaller, miscellaneous uses, such as fertilizers and animal feed additives, cosmetics and the manufacture of paper make up the rest.”
Hydrocolloids fall under the heading of functional food additives,. They are widely used in many food formulations to improve quality attributes and shelf-life. The two main uses are as thickening and gelling agents. As thickening agents, they find uses in soups, gravies, salad dressings, sauces and toppings while as gelling agents, they are extensively used in products like jam, jelly, marmalade, restructured foods and low sugar/calorie gels (Saha and Bhattacharya. 2010).
Seaweeds are classified in commerce according to pigmentation as: red(used for agar and carrageenan in the food and microbiology) and brown or green. Sargassum seaweeds (SW) are brown. Brown seaweeds are used for the manufacture of aginlates for the food industry. Apart from being thickeners, alginates have some applications that are not related to either their viscosity or gel properties. They act as stabilizers in ice cream; addition of alginates reduce the formation of ice crystals during freezing, giving a smooth product Alginate gels are used in re-structured or re-formed food products. For example, re-structured meats can be made by taking meat pieces, binding them together and shaping them to resemble usual cuts of meat, such as nuggets, roasts, meat loaves, even steaks.They are also used in the controlled release of medicinal drugs and other chemicals. In some applications, the active ingredient is placed in a calcium alginate bead and slowly released as the bead is exposed in the appropriate environment.
Available information on Sargassum natans and fluitans, the two species of primary concern across the Caribbean, is sparse (Michelle Morrison, CPI and Daniel Gray. The Caribbean Council, Anaerobic Digestion Economic Feasibility Study: Generating energy from waste, sewage and Sargassum Seaweed in the OECS :CPI Report Number: CPI-SP-RP-141(31/01/2017).It was also concluded that it was not economically feasible to generate bio-gas using anaerobic digestion since SW have low biochemical methane potentials (BMP). Anaerobiosis using pure culture techniques were apparently not used. Using pure culture techniques one can swamp the indigeneous microflora of the substrate with the microflora of choice, thereby controlling the rate of the process using continuous anaerobiosis (by using pure cultures other organisms that can divert the production of methane are effectively inhibited. Must also be noted that the carbohydrate content of seaweed as a substrate varies during the course of the season. According to Lenstra and others (.2011).Ocean Seaweed Biomass For large scale bio-fuel production Energy Research Center,Netherlands (ECN) S. natans has the following chemical composition :on a dry weight basis(dw) Proteins;6.59%; Fat 0.54%;Carbohydrate 76.43%; Phosphorus 0.082; Potassium19.56%; Energy (kJ/100g dry matter) 1410.
SW structurely consists of linear polysaccharides made up of 25-30 glucose units linked by(beta) b 1-3 glycosidic bonds. In some cases b1-6 glycosidic bonds occur. Since the cell wall of SW contains cellulose. the biomass must be pretreated and then (1) treated with (hydrolyzed ) cellulase enzyme systems supplemented with β-glucosidase followed by(2) fermentation with Saccharomyces cerevisiae(yeasts). Having stage(1)immediately followed by stage (2), result in what is known as a two-stage process which is economically more expensive. It is better to have stage (1) and (2) operating simultaneous, using continuous fermentation in the production of alcohol This can be done by the use of immobilized enzyme technology. In immobilized enzymes, the enzymes are enmeshed in a membrane (made of aginlate) which facilitates the reuse of the enzymes reducing costs and increasing reaction efficiencies.
SW can be used as an animal feed for ruminants only at present, since poultry do not have the necessary enzyme systems required to handle b glycosidic links. Feed from SW, has a low protein content when compared to soy. To augment the protein content, SW can be used as a substrate for the production of single cell protein. Using continuous fermentation techniques, protein yields as high as 40% on a dry-weight basis can be obtained. Single cell protein can be used in the formulation of non-ruminant rations as I having been advocating for more than twenty years (letters to the Editor, Barbados Advocate). Thinking long term, the gene for the beta glycoside using gene editing techniques can be inserted into a bacterium found normally in the gut microflora of non-ruminants. The edited bacterium with the added gene can then be reinserted into the gut microflora of the non-ruminant by incorporating it into the rations.. The non-ruminant is now able to utilize feeds made from SW. Alternatively, SW itself can be gene edited and the gene for the b condition changed to the a state, making it possible to have feed that can be utilized by both ruminants and non-ruminants directly.
Brown macroalgae, Sargassum ssp., are considered as a potential biomass source for energy production due to their relatively fast growth rates, ease of harvesting, and low pre-production cost. Sargassum fluitans, S. natans, and S. filipendula are three of the most abundant macroalgae species found at Puerto Rico’s coasts. The lipids content of Sargassum spp. ranges between 1.0 and 2.5% (total lipids)Diaz-Vazquez and others (2015) “Demineralization of Sargassum spp. macroalgae biomass: selective hydrothermal liquefaction process for bio-oil production.”Front.Energy Res. 3:6..
If the temperature and pressure of carbon dioxide are both increased to be at or above its critical point ,it can adopt properties midway between a gas and a liquid. More specifically, it behaves as a super critical fluid above its critical temperature 31.10 °C, (87.98 °F) and critical pressure of 72.9 atm, (7.39 MPa, 1,071 psi), expanding to fill its container like a gas but with a density like that of a liquid. Under these conditions carbon dioxide(CO2) acts as a solvent and removes fats/oils from a product. It is commonly used in the food industry in the manufacture of decaffeinated coffee. This method can be used to extract oil from SW without the residual harmful effects of the use of hexane, the solvent currently in wide spread use.
SW is prevalent throughout the earth’s oceans. There has been a lot of noise locally about how to handle the problem. As far as I am concerned, there is no reason why the approach used in the fishing industry should not be adopted. With the use of drones and appropriate algorithms or biosensors one can easily detect the position of SW. Using algorithms, the difference in color of the ocean where the SW is versus where it is absent can be used to pinpoint the product. Alternatively, since S.natans has the ability to fix atmospheric nitrogen( by an associated epiphyte or cyanobacteria), a build up of or a depletion of nitrates can be used to detect SW, since the background levels in the ocean will be different. Similarly,the same should hold good for carbon dioxide(CO2) which is utilized during photosynthesis. Finally, there should be a temperature differential, due to the metabolic processes underway in the developing SW and the ocean’s background temperatures. Lenstra and others (.2011) have outlined measures for fishing and harvesting SW. Recently a Caribbean country purchased two seaweed harvesters. So, instead of waiting for SW to come to Barbados, Barbados should go hunting for it.
Sincerely,
Robert D. Lucas,Ph.D. and CFS
Certified Food Scientist.
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