Semisolid parameters

During the flight of droplets in the spray, the forced convective and radiative heat exchanges with the atomization gas lead to a rapid heat extraction from the droplets. A droplet undergoing cooling and phase change may experience three states (a) fully liquid, (b) semisolid, and (c) fully solid. If the Biot number of a droplet in all three states is smaller than 0.1, the lumped parameter model 1561 can be used for the calculation of droplet temperature. Otherwise, the distributed parameter model 1541 should be used. 

The key parameter for any drug product is its efficacy as demonstrated in controlled clinical trials. The time and expense associated with such trials make them unsuitable as routine quality control methods. Therefore, in vitro surrogate tests are often used to assure that product quality and performance are maintained over time and in the presence of change. A variety of physical and chemical tests commonly performed on semisolid products and their components (e.g., solubility, particle size and crystalline form of the active component, viscosity, and homogeneity of the product) have historically provided reasonable evidence of consistent performance. More recently, in vitro release testing has shown promise as a means to comprehensively assure consistent delivery of the active component(s) from semisolid products. 

Zatz, J.L., Drug Release from Semisolids Effect of Membrane Permeability on Sensitivity to Product Parameters." Pharmaceutical Research 2 787-789, 1995. 

Chu PI, Doyle D. Development and evaluation of a laboratory-scale apparatus to simulate the scale-up of a sterile semisolid and effects of manufacturing parameters on product viscosity. Pharm Dev Technol 1999 4(4) 553-559. 

When a restraining membrane has to be employed, as with suppositories and most semisolids, the retarding properties of the membrane have to be considered and the amount of formulation applied in the test apparatus must be considered before the key parameters, such as particle size of the dmg, are determined. Examples in Fig. 12.9 demonstrate in one test system how the influence of... 

Semisolid foods belong, in general, to a group than can be characterized by viscoelastic parameters. Viscoelasticity is due to the delayed motion and retarded response of a system to a shear resulting from a joint viscous and elastic nature. Jellies and deserts fall into this category. Jams are also included however, some additional measure of elasticity of the product is required. 

All of them are worthy in order to gain knowledge relevant to the processing parameters of non-Newtonian liquid and semisolid food systems, particularly in the following areas ... 

Measurement of C requires more sophisticated and expensive rheometers and more involved experimental procedures. It must be remembered that experiments have to he carried out below the critical strain value (see Sec II), or in [he region of linear viscoelastic behavior. This region is determined by measuring the complex modulus G as a function of the applied strain at a constant oscillation frequency (usually 1 Hz). Up to 7, G does not vary with the strain above Yr, G tends to drop. The evaluation of oscillatory parameters is more often restricted to product formulation studies and research. However, a controlled-fall penetrometer may be used to compare the degree of elasticity between different samples. Creep compliance and creep relaxation experiments may be obtained by means of this type of device. In fact, a penetrometer may be the only way to assess viscoeIa.sticity when the sample does not adhere to solid surfaces, or adheres too well, or cures to become a solid or semisolid. This is the case of many dental products such as fillings, impression putties, sealants, and cements. 

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