56 MARINE INGREDIENTS
Alginates from seaweed for natural textures
Maud Gelebart, Fabien Canivet, Gérard Tilly - Algaia
For some time now, the global awareness surrounding environmental pollution by plastics (micro and macro) and new consumer expectations for naturally derived products have generated growing demand from the cosmetics industry for natural polymers. One of the major challenges is to combine
the naturalness of ingredients while maintaining both a pronounced and standardised reactivity and the sensorial properties expected by consumers. In this ongoing search for innovative natural textures, alginates play a key role, which tends to increase with the development of new scientific knowledge.
Alginates & naturalness Some texturisers of natural origin are well known to formulators, such as xanthan gum or carrageenan, which are cold-soluble and easy to use. Alginates, hydrocolloids extracted from brown macroalgae, have also been used for decades in pharmaceutical (haemostatic dressings, anti-gastric reflux specialities) and cosmetic (self-gelling masks, encapsulation, moulding) applications. Today, they tend to be more widely used in other applications, such as emulsions, lotions and foaming agents. Algaia, the first brown seaweed processor in
France, produces its Satialgine® and Algogel® alginates from fresh laminaria seaweed harvested sustainably on the seabed in the Iroise Sea off the Breton coast. These meet the ISO 16128 standard for natural and organic ingredients. Beyond this, alginates of 100% French origin also demonstrate their potential in cosmetics.
Variable chemical structure Alginate is a hydrocolloid with a wide rheological range, from liquid to gel. In addition, recent evolutions in the production process now make it possible to have transparent alginate solutions. However, there have been some challenges
to their implementation, such as their gelling power, which is difficult to control in the presence of calcium ions; their sensitivity to shearing, which leads to broken or heterogeneous textures; and a limited grip, linked to the development of stiff networks and forming blocks of yoghurt-like appearance. These are all challenges linked to the technical nature of alginates, which, once mastered, can be overcome to exploit the full potential of these natural texturisers. The chemical structure of alginic acid and its salts (alginates) varies, although the molecule
PERSONAL CARE September 2022
is made up of similar elements linked together (monomers). The macromolecule of alginic acid and alginates is made up of mannuronic acid and guluronic acid chains. These are distributed in blocks, forming the backbone of the polysaccharide chain. Their proportion varies according to the species considered, the part of the alga that is processed, its maturity and its harvesting site.
Controlled cold-gelling mechanism Sodium (INCI: Algin) and potassium alginates form more or less viscous colloidal solutions in water. In a solution, the acid functions are fully ionised: monomers carrying numerous COO- carboxylate groups repel each other, resulting in a thickened solution. This is not the case for calcium alginate or alginic acid, which are insoluble in water. The viscosity of an alginate solution depends essentially on the hydrodynamic volume of the polymer chains. Hence, it can vary greatly, depending on the alginate concentration, the average chain length (molar mass) and the operating conditions (solvent, temperature and ionic strength) which influence both the conformation and flexibility of the chains. An increase in the molar mass of alginate implies an increase in the viscosity of the alginate solution.
Toolkit for formulators All this gives formulators a toolbox for adjusting the texture of the products they develop. For instance, when a calcium ion is added, it can link
two COO groups of two adjacent alginate chains, allowing alginate molecules to come closer to one another. At low calcium levels, the viscosity will increase. By adding more calcium, a gel is formed; the
homogeneous blocks of guluronic acid will be able to form egg-box type aggregates, the egg being the calcium. The alginates that are most reactive to calcium and therefore the most gelling ones are those that are richest in homogeneous blocks of guluronic acid (Table 1). In practice, it is important to ensure that the
cross-linking cation can react gradually and homogeneously. Slowly dissolving calcium salt gradually releases calcium, which can react with the alginate to form a homogeneous, heat-stable gel.
By contrast, if the calcium concentration is
too high from the start, it causes the alginate to gel instantly. The gel will be fragmented during the mixing or pumping operations and the final texture, instead of being smooth and homogeneous, will tend to have a grainy appearance. To control the rate of setting (gelling), calcium sequestrants can be used to allow a later release of calcium towards the alginate.
Modular consistency On the market, the gelling property of alginates must be controlled, measured and even limited to obtain textures that comply with emulsion criteria (consistency, thickening, homogeneity (smoothness), handling, linear flow, evanescence, shape memory, etc.). From a rheological point of view, high
www.personalcaremagazine.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104
