Semisolid physical state

The choice of the term oil or fat usually is based on tradition and the physical state of the material. Generally, oils are liquid at ambient temperatures, and fats are semisolid mixtures of crystals in oil. Fats often are of animal origin (beef tallow, pork lard, and butter fat) or hardened (hydrogenated, interester-ified, or thermally fractionated) vegetable oils, whereas oils are extracted from plant seeds or tissues or fish. In English-speaking countries outside the United States, oils liquid at room temperature sometimes are called soft oils, and those hard or pasty are called hard oils. Nutritionists generally use fats for solids or liquids. 

Fine-grained soil which contains clay minerals in the presence of water can be remolded. As the amount of water in the soil increases the material moves through various physical states. These states are solid to semisolid to plastic and finally to a liquid state. The Atterberg limits describe the firmness (i.e., consistency) of this remolded soil with varying moisture contents. The transition from semisolid to plastic state is defined as the plastic limit. The point of transition from plastic to liquid state is defined as the liquid limit. Both of these limits are defined in terms of water contents using simple mechanical tests. A third limit defined as the plasticity index is the difference in percent water content between the liquid limit and the plastic limit. The test procedure has been described in detail in ASTM (D4318). 

On the basis of physical state, SNEDDS are categorized into liquid, semisolid, and solid SNEDDS (S-SNEDDS). By employing the technological innovations and functional excipients, semisolid and solid SNEDDS are further subdivided into pellets, spray dried powders, gastroretentive tablets, minicapsules, etc. (Bansal et al., 2008 Singh et al., 2014). The detailed descriptions and applications of the various SNEDDS formulations are discussed below. 

In terms of their physical state (liquid extracts including fluid extracts, tinctures, oil macerates, semisolid preparations called soft extracts, and dry extracts). 

Concern for the physical and chemical integrity of topical systems is no different than for other dosage forms. However, there are some unique and germane dimensions to stability associated with semisolid systems. A short list of some of the factors to be evaluated for semisolids is given in Table 12. All factors must be acceptable initially (within prescribed specifications), and all must remain so over the stated lifetime for the product (the product s shelf life). 

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