Dispersion and hydration

Dispersion and hydration are the first steps in all applications of hydrocolloid thickeners. To achieve the optimum functionality of any hydrocoUoid, it is important to ensure the product is properly hydrated before use. The main factors that affect the hydration of hydrocolloids are dispersion, mixing speed, particle size and the composition of the solvent. As mixing speed is increased the hydration time is reduced. Particle size will have an influence on both dispersion and hydration. As the particle size increases the hydrocolloid becomes easier to disperse but slower to hydrate. In poor solvents the gum will be easier to disperse but slower to hydrate. Generally, high ionic strength or high solids slow down hydration. 

For the hydrocolloid to hydrate efficiently the individual gum particles must be well dispersed in the solvent. Poor dispersion leads to lumping of particles during mixing, which results in the formation of swollen lumps (sometimes referred to as fish eyes ). Severe lumping prevents complete hydration and reduces functionality. Generally, the larger the particle 

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Clays Magnesium aluminum silicate (V eegum) Anionic 0.5-2.5 Disperses and hydrates readily. Hot water increases rate of hydration 3-11 Plastic/ thixotropy Partially flocculated by electrolytes and incompatible with acidic solution [Pg.168]

A D20/lipid ratio of 2 1 (v w) led to easily handled samples and consistent spectroscopic results. Typically, 10 mg of specifically deuterated phospholipid and 20wl D2O were added to a culture tube, which was then sealed and incubated at 55°C for at least 1 hr, with periodic agitation to ensure complete dispersal and hydration. Similar procedures were followed for cholesterol and Gramicidin D-containing samples. Samples were placed between two AgCl windows, and sealed with a 6 pM, spacer. The assembly was wrapped with Teflon tape, as a further seal against dehydration, and inserted into a Harrick cell. Temperature was controlled to + 0.1 C with a Haake circulating water bath and monitored with a thermocouple placed as close as feasible to the point where the IR radiation was focused. 

Moderate and even low reactivity quicklimes can be used in the drum hydration process, because of the pressurised hydration stage (see section 13.2, Fig. 13.3, and Annex 1 for explanations of these terms). The reactivity of quicklimes used for the silo hydration process should be moderate to high , depending on the silo residence time. For both of these processes, the quicklime should be finely ground (e.g., with 90 % less than 75 pm) to ensure efficient dispersion and hydration. 

Other chemical derivatives of xanthan gum would be expected to have altered dispersibility and hydration behavior. 

Factors Affecting Dispersibility and Hydration of Glyoxal-Treated Xanthan Gum... 

Saturated salt mud is primarily used to prevent excessive hole enlargement while drilling massive salt beds. It can also be used to reduce dispersion and hydration of shales and clays (KMC... 

Fig. 6.29 The phase diagram of sodium perfluorodecanoate concentration versus pressure at 55°C. M, S, and C denote the micellar, singly dispersed, and hydrated solid states, respectively Q, a triple point CSP, critical solution pressure. (From Ref. 136. Reproduced by permission of Plenum Publishing.)...

MC, HPC and HPMC are water soluble ethers with good film-forming properties. In order to avoid the formation of agglomerates the dissolution of these nonionic cellulose ethers must be done in two steps dispersion and hydration. Wherever possible, they should be put into solution before other soluble ingredients are added or should be dispersed in water miscible nonsolvent such as glycerol, ethanol or propylene glycol and then add the slurry to water. The solutions of these cellulose ethers are stable at pH 2-11 and are compatible with surfactants, other water-soluble polysaccharides, and with salts. 

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