Food additives data book - wordpres

Polysaccharides 664
NAME: Alginic acid
CATEGORY: Polysaccharides
FOOD USE: All food products, edible films/ Coatings
SYNONYMS: CAS 9005-32-7/ EINECS 232-680-1/ E400/ Polymannuronic acid/ Norgine
FORMULA: Variable, depending on ratio of mannuronic to guluronic acid, and the presence of other substituents
MOLECULAR MASS: Variable
ALTERNATIVE FORMS: Algin; ammonium alginate; calcium alginate; potassium alginate
PROPERTIES AND APPEARANCE: White to yellow powders or hard flakes
SOLUBILITY % AT VARIOUS Solubility in aqueous solution varies with differences in structure, molecular weight, pH and cations.
TEMPERATURE/pH COMBINATIONS: Alginic acid (low pH) is insoluble in water, monovalent salts (sodium, potassium and ammonium) are
also soluble, but divalent salts (including calcium) except magnesium are insoluble in water. Solubility
declines with increasing molecular weight and increasing concentration. Viscosity is not affected in the
pH 5 to 11 range, but increases at lower pHs (due to alginic acid formation)
FUNCTION IN FOODS: Gelling agent; thickening agent; stabiliser; flocculant and bulking agent. It can be used to stabilise
emulsions and to retard ice-crystal formation
ALTERNATIVES: Carrageenans; gelatin; gellan; agar; xanthan; furcellaran (application-dependent)
TECHNOLOGY OF USE IN FOODS: Alginates should be dispersed in cold deionised water and heated for 10 minutes at 80°C to hydrate the
polysaccharide. A high shear mixer will aid dispersion, although prolonged shear of high molecularweight
polymers will reduced the viscosity. Calcium gels can be prepared by addition of alginate
solutions to a calcium solution (e.g. maraschino cherries), addition of calcium to a hot solution of
alginate and then cooling (gel is thermo-irreversible), or by diffusion. Gels can also be formed by
lowering the pH (alginic acid), but this can be technically difficult.
Alginates are composed of blocks of polymannuronic acid, polyguluronic acid and mixed regions.
Ribbon-like structures are formed in solution and alginates with a high percentage of guluronic blocks
can be cross-linked (gelled) by divalent ions (e.g. calcium)